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(* some parts (AdjustBalance...) of this unit are based on the AVLTree unit *)
(* TODO: Implement node.eof / node.bof *)
unit SynEditFoldedView;

{$mode objfpc}{$H+}
{$IFDEF CPUPOWERPC} {$INLINE OFF} {$ENDIF} (* Workaround for bug 12576 (fpc) see bugs.freepascal.org/view.php?id=12576 *)

{$IFOPT C+}
  {$DEFINE SynAssertFold}
{$ENDIF}
{$IFDEF SynAssert}
  {$DEFINE SynAssertFold}
{$ENDIF}

{$IFDEF SynFoldDebug}
  {$DEFINE SynDebug}
  {$DEFINE SynFoldSaveDebug}
{$ENDIF}
{$IFDEF SynFoldSaveDebug}
  {$DEFINE SynDebug}
{$ENDIF}

interface

uses
  Classes, SysUtils,
  // LCL
  Graphics, LCLType,
  // LazUtils
  LazLoggerBase, LazMethodList,
  // SynEdit
  LazSynEditText, SynEditTypes, SynEditMiscClasses, SynEditMiscProcs,
  SynEditPointClasses, SynEditHighlighter, SynEditHighlighterFoldBase,
  SynEditKeyCmds;

type

  TFoldNodeClassification = (
    fncInvalid,
    fncHighlighter,     // Fold provided by HL
    fncHighlighterEx,   // Fold originally provided by HL, but no longer exists in HL (text edited)
    fncBlockSelection
  );
  TFoldNodeClassifications = set of TFoldNodeClassification;

  { TSynTextFoldAVLNodeData }

  TSynTextFoldAVLNodeData = class(TSynSizedDifferentialAVLNode)
  protected
    function Left: TSynTextFoldAVLNodeData;
    function Parent: TSynTextFoldAVLNodeData;
    function Right: TSynTextFoldAVLNodeData;
    procedure FreeAllChildrenAndNested;
  public    (* Position / Size *)
    (* FullCount:  Amount of lines in source for this fold only
                   (excluding overlaps) *)
    FullCount : Integer;
    (* LineOffset: Line-Number Offset to parent node
                   All line numbers are stored as offsets,
                   for faster updates if lines are inserted/deleted *)
    property LineOffset: Integer read FPositionOffset write FPositionOffset;
    (* LeftCount:  Lines folded in left tree.
                   Used to calculate how many lines are folded up to a specified line *)
    property LeftCount: Integer read FLeftSizeSum write FLeftSizeSum;
    (* MergedLineCount: Amount of lines folded away by this fold,
                        FullCount + Lines covered by overlaps *)
    property MergedLineCount: Integer read FSize write FSize;
  public
    (* Sub-Tree  *)
    Nested : TSynTextFoldAVLNodeData; (* Nested folds (folds within this fold) do not need to be part of the searchable tree
                             They will be restored, if the outer fold (this fold) is unfolded
                             Nested points to a standalone tree, the root node in the nested tree, does *not* point back to this node *)


    (* Source Info *)
    FoldIndex: Integer;    (* Index of fold in line; if a line has more than one fold starting *)
    FoldColumn, FoldColumnLen: Integer; (* The column (1-based) and len of the keywordm which starts this fold *)
    FoldTypeCompatible: Pointer; (* help identifying in FixFolding *)
    Classification: TFoldNodeClassification;
    VisibleLines: Integer; (* Visible Source lines, containing the "fold keyword"
                              0: Hiden block (the fold-keyword is inside the fold)
                              1: Normal fold (There is *1* visible line with the fold-keyword)
                            *)


    function RecursiveFoldCount : Integer; (* Amount of lines covered by this and all child nodes *)
    function Precessor : TSynTextFoldAVLNodeData; reintroduce;
    function Successor : TSynTextFoldAVLNodeData; reintroduce;
    function Precessor(var aStartPosition, aSizesBeforeSum : Integer) : TSynTextFoldAVLNodeData; reintroduce;
    function Successor(var aStartPosition, aSizesBeforeSum : Integer) : TSynTextFoldAVLNodeData; reintroduce;
  end;

  { TSynTextFoldAVLNode }

  TSynTextFoldAVLNode = object
  private
    function GetClassification: TFoldNodeClassification;
    function GetFoldColumn: Integer;
    function GetFoldColumnLen: Integer;
    function GetFoldIndex: Integer;
    function GetMergedLineCount : Integer;
    function GetFullCount : Integer;
    function GetSourceLine: integer;
    function GetSourceLineOffset: integer;
    procedure SetFoldColumn(const AValue: Integer);
  protected
    fData : TSynTextFoldAVLNodeData; // nil if unfolded
    fStartLine : Integer;            // start of folded
    fFoldedBefore : Integer;
  public
    procedure Init(aData : TSynTextFoldAVLNodeData; aStartLine, aFoldedBefore: Integer);
    function IsInFold : Boolean;
    function Next : TSynTextFoldAVLNode;
    function Prev : TSynTextFoldAVLNode;

    property MergedLineCount: Integer read GetMergedLineCount; // Zero, if Not in a fold
    property FullCount: Integer read GetFullCount; // Zero, if Not in a fold
    property StartLine: Integer read fStartLine;   // 1st Line of Current Fold
    property FoldedBefore: Integer read fFoldedBefore;  // Count of Lines folded before Startline

    function IsHide: Boolean;
    property FoldIndex: Integer read GetFoldIndex;
    property FoldColumn: Integer read GetFoldColumn write SetFoldColumn;
    property FoldColumnLen: Integer read GetFoldColumnLen;
    property SourceLine: integer read GetSourceLine;    // The SourceLine with the fold-keyword
    property SourceLineOffset: integer read GetSourceLineOffset;    // The SourceLine with the fold-keyword
    property Classification: TFoldNodeClassification read GetClassification;
  end;

  { TSynTextFoldAVLNodeNestedIterator:
    Iterates included nested nodes
    FoldedBefore is not valid in nested nodes
  }

  TSynTextFoldAVLNodeNestedIterator = class
  private
    FCurrentNode: TSynTextFoldAVLNode;
    FOuterNodes: Array of TSynTextFoldAVLNode;
  public
    constructor Create(ANode: TSynTextFoldAVLNode);
    destructor Destroy; override;
    function Next: TSynTextFoldAVLNode;
    function Prev: TSynTextFoldAVLNode;
    function EOF: Boolean;
    function BOF: Boolean;
    function IsInFold: Boolean;
    property Node: TSynTextFoldAVLNode read FCurrentNode;
  end;

  { TSynTextFoldAVLTree
    - Nodes in the tree cover the folded lines only.
      The (visible) cfCollapsed line at the start of a fold, is *not* part of a node.
    - In the public methods "ALine" indicates the first invisible/hidden line
    - TSynEditFoldedView uses this with 1-based lines (ToDo: make 0-based)
  }

  TSynTextFoldAVLTree = class(TSynSizedDifferentialAVLTree)
  protected
    fNestParent: TSynTextFoldAVLNodeData;
    fNestedNodesTree: TSynTextFoldAVLTree; // FlyWeight Tree used for any nested subtree.

    function NewNode : TSynTextFoldAVLNodeData; inline;
    Function RemoveFoldForNodeAtLine(ANode: TSynTextFoldAVLNode;
                                     ALine : Integer) : Integer; overload; // Line is for Nested Nodes

    // SetRoot, does not obbey fRootOffset => use SetRoot(node, -fRootOffset)
    procedure SetRoot(ANode : TSynSizedDifferentialAVLNode); overload; override;
    procedure SetRoot(ANode : TSynSizedDifferentialAVLNode; anAdjustChildLineOffset : Integer); overload; override;

    Function  InsertNode(ANode : TSynTextFoldAVLNodeData) : Integer; reintroduce; // returns FoldedBefore // ANode may not have children
    function TreeForNestedNode(ANode: TSynTextFoldAVLNodeData; aOffset : Integer) : TSynTextFoldAVLTree;
  public
    constructor Create;
    destructor Destroy; override;
    procedure Clear; override;

    (* Find Fold by Line in Real Text *)
    Function FindFoldForLine(ALine : Integer; FindNextNode : Boolean = False) : TSynTextFoldAVLNode;
    (* Find Fold by Line in Folded Text // always returns unfolded, unless next=true *)
    Function FindFoldForFoldedLine(ALine : Integer; FindNextNode: Boolean = False) : TSynTextFoldAVLNode;
    Function InsertNewFold(ALine, AFoldIndex, AColumn, AColumnLen, ACount, AVisibleLines: Integer;
                           AClassification: TFoldNodeClassification;
                           AFoldTypeCompatible: Pointer
                          ) : TSynTextFoldAVLNode;
    (* This will unfold the block which either contains tALine, or has Aline as its cgColapsed line
       If IgnoreFirst, the cfCollapsed will *not* unfold => Hint: IgnoreFirst = Make folded visible
       Returns the pos(1-based) of the cfCollapsed Line that was expanded; or ALine, if nothing was done
    *)
    Function RemoveFoldForLine(ALine : Integer; OnlyCol: Integer = -1) : Integer; overload;
    Procedure AdjustForLinesInserted(AStartLine, ALineCount, ABytePos: Integer);
    Procedure AdjustForLinesDeleted(AStartLine, ALineCount, ABytePos: Integer);
    procedure AdjustColumn(ALine, ABytePos, ACount: Integer; InLineBreak: boolean = False);
    Function FindLastFold : TSynTextFoldAVLNode;
    Function FindFirstFold : TSynTextFoldAVLNode;
    Function LastFoldedLine : integer; // The actual line; LastNode.StartLine + LastNode.LineCount - 1
    {$IFDEF SynDebug}
    procedure Debug; reintroduce;
    {$ENDIF}
  end;

  { TSynFoldNodeInfoHelper }

  TSynFoldNodeInfoHelper = class
    FCurInfo: TSynFoldNodeInfo;
    FActions: TSynFoldActions;
    FHighlighter: TSynCustomFoldHighlighter;
  protected
    procedure Invalidate;
  public
    constructor Create(AHighlighter: TSynCustomFoldHighlighter);

    function FirstOpen: TSynFoldNodeInfo;
    function Next: TSynFoldNodeInfo;
    function Prev: TSynFoldNodeInfo;
    function FindClose: TSynFoldNodeInfo;
    function GotoOpenPos(aLineIdx, aNodeIdx: integer): TSynFoldNodeInfo;
    function GotoOpenAtChar(aLineIdx, aXPos: integer): TSynFoldNodeInfo;
    function GotoNodeOpenPos(ANode : TSynTextFoldAVLNode): TSynFoldNodeInfo;
    function GotoNodeClosePos(ANode : TSynTextFoldAVLNode): TSynFoldNodeInfo;
    function IsAtNodeOpenPos(ANode : TSynTextFoldAVLNode): Boolean;
    function IsValid: Boolean;
    function Equals(AnInfo: TSynFoldNodeInfo): Boolean;
    function Equals(AHelper: TSynFoldNodeInfoHelper): Boolean;

    property Info: TSynFoldNodeInfo read FCurInfo write FCurInfo;
    property Actions: TSynFoldActions read FActions write FActions;
  end;

  TFoldChangedEvent = procedure(aLine: Integer) of object;
  TInvalidateLineProc = procedure(FirstLine, LastLine: integer) of object;

  TFoldViewNodeInfo = record
    HNode: TSynFoldNodeInfo;    // Highlighter Node
    IsFold, IsHide: Boolean;
    Text, Keyword: String;
    LineNum, ColIndex: Integer;
    OpenCount: Integer; // Highlighter-Nodes opening on this line (limited to the FoldGroup requested)
  end;

  TSynEditFoldLineCapability = (
    // Capabilities of Line
    cfFoldStart, cfHideStart,
    cfFoldBody,
    cfFoldEnd,
    // State indicators
    cfCollapsedFold,
    cfCollapsedHide,   // lines hidden, after this line
    // Special flags
    cfSingleLineHide,
    cfNone
  );
  TSynEditFoldLineCapabilities = set of TSynEditFoldLineCapability;
  TSynEditFoldType = (scftOpen, scftFold, scftHide, scftAll, scftInvalid);

  TSynEditFoldLineMapInfo = record
    Capability: TSynEditFoldLineCapabilities;
    Classifications :TFoldNodeClassifications;
  end;

  {$IFDEF SynFoldSaveDebug}
const
  SynEditFoldTypeNames: Array [TSynEditFoldType] of string =
    ('scftOpen', 'scftFold', 'scftHide', 'scftAll', 'scftInvalid');
type
  {$ENDIF}

  { TSynEditFoldProvider }
  TSynEditFoldProviderNodeInfo = record
    LineCount: Integer;
    Column, ColumnLen: Integer;
    DefaultCollapsed: Boolean;
    FoldTypeCompatible: Pointer;  // eg begin, var, procedure
    FoldGroup: Integer; // eg.: pas, region, ifdef
    Classification: TFoldNodeClassification;
  end;

  TSynEditFoldProviderNodeInfoList = array of TSynEditFoldProviderNodeInfo;
  TSynEditFoldProvider = class;

  TSynEditFoldProvider = class
  private
    FEnabled: boolean;
    FHighlighter: TSynCustomFoldHighlighter;
    FLines : TSynEditStrings;
    FEdit: TSynEditBase;
    FNestedFoldsList: TLazSynEditNestedFoldsList;
    function GetFoldsAvailable: Boolean;
    function GetHighLighterWithLines: TSynCustomFoldHighlighter;
    function GetLineCapabilities(ALineIdx: Integer): TSynEditFoldLineCapabilities;
    function GetLineClassification(ALineIdx: Integer): TFoldNodeClassifications;
    function GetNestedFoldsList: TLazSynEditNestedFoldsList;
    procedure SetHighLighter(const AValue: TSynCustomFoldHighlighter);
    procedure SetLines(AValue: TSynEditStrings);
  protected
    property HighLighterWithLines: TSynCustomFoldHighlighter read GetHighLighterWithLines;
  public
    constructor Create;
    destructor Destroy; override;

    // Info about Folds opening on ALineIdx
    function  FoldOpenCount(ALineIdx: Integer; AType: Integer = 0): Integer;
    function  FoldOpenInfo(ALineIdx, AFoldIdx: Integer; AType: Integer = 0): TSynFoldNodeInfo;
    //property FoldOpenInfo[ALineIdx, AColumnIdx: Integer]: Integer read GetFoldOpenInfo;

    function  FoldLineLength(ALine, AFoldIndex: Integer): integer;
    function  InfoForFoldAtTextIndex(ALine, AFoldIndex : Integer;
                                     HideLen: Boolean = False;
                                     NeedLen: Boolean = True): TSynEditFoldProviderNodeInfo;
    function  InfoListForFoldsAtTextIndex(ALine: Integer; NeedLen: Boolean = False): TSynEditFoldProviderNodeInfoList;

    property LineCapabilities[ALineIdx: Integer]: TSynEditFoldLineCapabilities
             read GetLineCapabilities;
    property LineClassification[ALineIdx: Integer]: TFoldNodeClassifications
             read GetLineClassification;
    property Lines: TSynEditStrings read FLines write SetLines;
    property HighLighter: TSynCustomFoldHighlighter read FHighlighter write SetHighLighter;
    property FoldsAvailable: Boolean read GetFoldsAvailable;
    property NestedFoldsList: TLazSynEditNestedFoldsList read GetNestedFoldsList;
    property Enabled: boolean read FEnabled write FEnabled;
  end;

  { TFoldChangedHandlerList }

  TFoldChangedHandlerList = class(TMethodList)
  public
    procedure CallFoldChangedEvents(AnIndex: Integer);
  end;

  TSynEditFoldedView = class;

  { TLazSynDisplayFold }

  TLazSynDisplayFold = class(TLazSynDisplayViewEx)
  private
    FFoldView: TSynEditFoldedView;
    FLineState: integer;
    FTokenAttr: TSynHighlighterAttributesModifier;
    FMarkupLine: TSynSelectedColorMergeResult;
    FLineFlags, FLineFlags2: TSynEditFoldLineCapabilities;
  public
    constructor Create(AFoldView: TSynEditFoldedView);
    destructor Destroy; override;
    procedure SetHighlighterTokensLine(ALine: TLineIdx; out ARealLine: TLineIdx; out AStartBytePos, ALineByteLen: Integer); override;
    function GetNextHighlighterToken(out ATokenInfo: TLazSynDisplayTokenInfo): Boolean; override;
    function GetLinesCount: Integer; override;

    function TextToViewIndex(ATextIndex: TLineIdx): TLineRange; override;
    function ViewToTextIndex(AViewIndex: TLineIdx): TLineIdx; override;
    function ViewToTextIndexEx(AViewIndex: TLineIdx; out AViewRange: TLineRange): TLineIdx; override;
  end;

  { TSynTextFoldedView
      *Line      = Line (0-based) on Screen (except TopLine which should be TopViewPos)
      *ViewPos   = Line (1-based) in the array of viewable/visible lines
      *TextIndex = Line (0-based) in the complete text(folded and unfolded)
  }

  TSynEditFoldedViewFlag = (fvfNeedCaretCheck, fvfNeedCalcMaps);
  TSynEditFoldedViewFlags = set of TSynEditFoldedViewFlag;

  { TSynEditFoldedView }

  TSynEditFoldedView = class(TSynEditStringsLinked)
  private
    FOwner: TSynEditBase;
    fCaret: TSynEditCaret;
    FFoldProvider: TSynEditFoldProvider;
    fFoldTree : TSynTextFoldAVLTree;   // Folds are stored 1-based (the 1st line is 1)
    FMarkupInfoFoldedCode: TSynSelectedColor;
    FMarkupInfoFoldedCodeLine: TSynSelectedColor;
    FMarkupInfoHiddenCodeLine: TSynSelectedColor;
    fTopLine : Integer;
    fLinesInWindow : Integer;          // there may be an additional part visible line
    fTextIndexList : Array of integer;   (* Map each Screen line into a line in textbuffer *)
    fFoldTypeList : Array of TSynEditFoldLineMapInfo;
    fLockCount : Integer;
    fNeedFixFrom, fNeedFixMinEnd : Integer;
    FFlags: TSynEditFoldedViewFlags;
    FInTopLineChanged: Boolean;
    FDisplayView: TLazSynDisplayFold;

    function GetFoldClasifications(index : Integer): TFoldNodeClassifications;
    function GetHighLighter: TSynCustomHighlighter;
    function GetDisplayNumber(index : Integer) : Integer;
    function GetTextIndex(index : Integer) : Integer;
    function GetFoldType(index : Integer) : TSynEditFoldLineCapabilities;
    function IsFolded(index : integer) : Boolean;  // TextIndex
    procedure ProcessMySynCommand(Sender: TObject; AfterProcessing: boolean;
      var Handled: boolean; var Command: TSynEditorCommand;
      var AChar: TUTF8Char; Data: pointer; HandlerData: pointer);
    procedure SetHighLighter(AValue: TSynCustomHighlighter);
    procedure SetTopLine(const ALine : integer);
    function  GetTopTextIndex : integer;
    procedure SetTopTextIndex(const AIndex : integer);
    procedure SetLinesInWindow(const AValue : integer);
    procedure DoFoldChanged(AnIndex: Integer);
    function TextIndexAddLines(aTextIndex, LineOffset : Integer) : Integer;     (* Add/Sub to/from TextIndex (0-based) skipping folded *)
  protected
    procedure SetManager(AManager: TSynTextViewsManager); override;
    procedure SetSynStrings(AValue: TSynEditStrings); override;
    function GetViewedLines(index : Integer) : String; override;
    function GetViewedCount: integer; override;
    function GetDisplayView: TLazSynDisplayView; override;
    procedure InternalGetInfoForViewedXY(AViewedXY: TPhysPoint;
      AFlags: TViewedXYInfoFlags; out AViewedXYInfo: TViewedXYInfo;
      ALogPhysConvertor: TSynLogicalPhysicalConvertor); override;
    procedure DoBlockSelChanged(Sender: TObject; Changes: TSynStatusChanges);
    Procedure CalculateMaps;
    function  FoldNodeAtTextIndex(AStartIndex, ColIndex: Integer): TSynTextFoldAVLNode; (* Returns xth Fold at nth TextIndex (all lines in buffer) / 1-based *)
    function  FixFolding(AStart : Integer; AMinEnd : Integer; aFoldTree : TSynTextFoldAVLTree) : Boolean;

    procedure DoCaretChanged(Sender : TObject);
    Procedure LineCountChanged(Sender: TSynEditStrings; AIndex, ACount : Integer);
    Procedure LinesCleared(Sender: TObject);
    Procedure LineEdited(Sender: TSynEditStrings; aLinePos, aBytePos, aCount,
                            aLineBrkCnt: Integer; aText: String);
    Procedure LinesInsertedAtTextIndex(AStartIndex, ALineCount, ABytePos: Integer;
                                       SkipFixFolding : Boolean = False);
    //Procedure LinesInsertedAtViewPos(AStartPos, ALineCount : Integer;
    //                                 SkipFixFolding : Boolean = False);
    Procedure LinesDeletedAtTextIndex(AStartIndex, ALineCount, ABytePos: Integer;
                                      SkipFixFolding : Boolean = False);
    //Procedure LinesDeletedAtViewPos(AStartPos, ALineCount : Integer;
    //                                SkipFixFolding : Boolean = False);
    property FoldTree: TSynTextFoldAVLTree read fFoldTree;
  public
    constructor Create(AOwner: TSynEditBase; ACaret: TSynEditCaret);
    destructor Destroy; override;
    
    // Converting between Folded and Unfolded Lines/Indexes
    function TextToViewIndex(aTextIndex : TLineIdx) : TLineIdx; override;   (* Convert TextIndex (0-based) to ViewPos (1-based) *)
    function ViewToTextIndex(aViewIndex : TLineIdx) : TLineIdx; override;     (* Convert ViewPos (1-based) to TextIndex (0-based) *)
    function TextXYToViewXY(APhysTextXY: TPhysPoint): TPhysPoint; override;
    function ViewXYToTextXY(APhysViewXY: TPhysPoint): TPhysPoint; override;

    function InternTextToViewIndex(aTextIndex : TLineIdx) : TLineIdx;           (* Convert TextIndex (0-based) to ViewPos (1-based) *)
    function InternViewToTextIndex(aViewIndex : TLineIdx) : TLineIdx;             (* Convert ViewPos (1-based) to TextIndex (0-based) *)

    function TextIndexToScreenLine(aTextIndex : Integer) : Integer; (* Convert TextIndex (0-based) to Screen (0-based) *)
    function ScreenLineToTextIndex(aLine : Integer) : Integer;      (* Convert Screen (0-based) to TextIndex (0-based) *)

    function AddVisibleOffsetToTextIndex(aTextIndex: TLineIdx; LineOffset: Integer): TLineIdx; override;
    function IsTextIdxVisible(aTextIndex: TLineIdx): Boolean; override;

    // Attributes for Visible-Lines-On-screen
    property DisplayNumber[index : Integer] : Integer   (* LineNumber for display in Gutter / result is 1-based *)
      read GetDisplayNumber;
    property FoldType[index : Integer] : TSynEditFoldLineCapabilities (* FoldIcon / State *)
      read GetFoldType;
    property FoldClasifications[index : Integer] : TFoldNodeClassifications (* FoldIcon / State *)
      read GetFoldClasifications;
    property TextIndex[index : Integer] : Integer       (* Position in SynTextBuffer / result is 0-based *)
      read GetTextIndex; // maybe writable

    // Define Visible Area
    property TopLine : integer                          (* refers to visible (unfolded) lines / 1-based *)
      read fTopLine write SetTopLine;
    property TopTextIndex : integer                     (* refers to TextIndex (folded + unfolded lines) / 1-based *)
      read GetTopTextIndex write SetTopTextIndex;
    property LinesInWindow : integer                    (* Fully Visible lines in Window; There may be one half visible line *)
      read fLinesInWindow write SetLinesInWindow;

    property MarkupInfoFoldedCode: TSynSelectedColor read FMarkupInfoFoldedCode;
    property MarkupInfoFoldedCodeLine: TSynSelectedColor read FMarkupInfoFoldedCodeLine;
    property MarkupInfoHiddenCodeLine: TSynSelectedColor read FMarkupInfoHiddenCodeLine;
  public
    procedure Lock;
    procedure UnLock;
    {$IFDEF SynDebug}
    procedure debug;
    {$ENDIF}
    (* Arguments for (Un)FoldAt* (Line, ViewPos, TextIndex):
       - ColumnIndex (0-based)
           Can be negative, to access the highest(-1) available, 2nd highest(-2) ...
           If negative, count points downward
       - ColCount = 0 => all
       - Skip => Do not count nodes that are already in the desired state
           (or can not archive the desired state: e.g. can not hide)
       - AVisibleLines: 0 = Hide / 1 = Fold
    *)
    procedure FoldAtLine(AStartLine: Integer; ColIndex : Integer = -1;          (* Folds at ScreenLine / 0-based *)
                         ColCount : Integer = 1; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure FoldAtViewPos(AStartPos: Integer; ColIndex : Integer = -1;        (* Folds at nth visible/unfolded Line / 1-based *)
                            ColCount : Integer = 1; Skip: Boolean = False;
                            AVisibleLines: Integer = 1);
    procedure FoldAtTextIndex(AStartIndex: Integer; ColIndex : Integer = -1;    (* Folds at nth TextIndex (all lines in buffer) / 1-based *)
                              ColCount : Integer = 1; Skip: Boolean = False;
                              AVisibleLines: Integer = 1);
    procedure UnFoldAtLine(AStartLine: Integer; ColIndex : Integer = -1;        (* UnFolds at ScreenLine / 0-based *)
                         ColCount : Integer = 0; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure UnFoldAtViewPos(AStartPos: Integer; ColIndex : Integer = -1;      (* UnFolds at nth visible/unfolded Line / 1-based *)
                         ColCount : Integer = 0; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure UnFoldAtTextIndex(AStartIndex: Integer; ColIndex : Integer = -1;  (* UnFolds at nth TextIndex (all lines in buffer) / 1-based *)
                         ColCount : Integer = 0; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure UnFoldAtTextIndexCollapsed(AStartIndex: Integer);   (* UnFolds only if Index is in the fold, ignores cfcollapsed line, if unfolded / 1-based *)

    function LogicalPosToNodeIndex(AStartIndex: Integer; LogX: Integer;         (* Returns the index of the node, at the logical char pos *)
                                   Previous: Boolean = False): Integer;

    procedure CollapseDefaultFolds;
    // Load/Save folds to string
    // AStartIndex, AEndIndex: (0 based) First/last line (EndIndex = -1 = open end)
    // AStartCol, AEndCol: (1 based) Logical text pos in Line. (AEndCol = -1 = full line)
    function  GetFoldDescription(AStartIndex, AStartCol, AEndIndex,
                                 AEndCol: Integer; AsText: Boolean = False;
                                 Extended: Boolean = False) :String;
    procedure ApplyFoldDescription(AStartIndex, AStartCol, AEndIndex,
                                   AEndCol: Integer; FoldDesc: PChar;
                                   FoldDescLen: Integer; IsText: Boolean = False);

    procedure UnfoldAll;
    procedure FoldAll(StartLevel : Integer = 0; IgnoreNested : Boolean = False);
    procedure FixFoldingAtTextIndex(AStartIndex: Integer; AMinEndLine: Integer = 0); // Real/All lines
  public
    function OpenFoldCount(aStartIndex: Integer; AType: Integer = 0): Integer;
    function OpenFoldInfo(aStartIndex, ColIndex: Integer; AType: Integer = 0): TFoldViewNodeInfo;

  public
    // Find the visible first line of the fold at ALine. Returns -1 if Aline is not folded
    function CollapsedLineForFoldAtLine(ALine : Integer) : Integer;
    function ExpandedLineForBlockAtLine(ALine : Integer; HalfExpanded: Boolean = True) : Integer;

    function GetPhysicalCharWidths(Index: Integer): TPhysicalCharWidths;

    function  IsFoldedAtTextIndex(AStartIndex, ColIndex: Integer): Boolean;      (* Checks xth Fold at nth TextIndex (all lines in buffer) / 1-based *)
    property FoldedAtTextIndex [index : integer] : Boolean read IsFolded;

    property HighLighter: TSynCustomHighlighter read GetHighLighter
                                                write SetHighLighter;
    property FoldProvider: TSynEditFoldProvider read FFoldProvider;
  end;

function dbgs(AClassification: TFoldNodeClassification): String; overload;
function dbgs(AFoldLineCapability: TSynEditFoldLineCapability): String; overload;

implementation

//var
//  SYN_FOLD_DEBUG: PLazLoggerLogGroup;

type
  TFoldExportEntry = Record
    // Lines and Pos (o 1st line) are relative to Scan-Start
    Line, LogX, LogX2: Integer;     // StartLine and Pos
    ELine, ELogX, ELogX2: Integer;  // EndLine and pos
    FType: Integer;                 // e.g ord(cfbtBeginEnd)
    LinesFolded: Integer;          // Lines Folded according to AVL-Node
  end;

  { TSynEditFoldExportStream }

  TSynEditFoldExportStream = class
  private
    FData: String;
    FLen, FPos: Integer;
    FMem: PChar;
    function  GetLen: Integer;
    procedure SetLen(const AValue: Integer);
    function  GetMem: PChar;
    procedure SetMem(const AValue: PChar);
    function  GetText: String;
    procedure SetText(const AValue: String);
  protected
    function GrowData(AppendSize: Integer): PChar;
    function EncodeIntEx(Anum: Integer): String;  // base 43, with leading continue bit
    function EncodeIntEx2(Anum: Integer): String; // for numbers expected below 467; specially 0..80
    function InternalReadNum(var APos: Integer): Integer;
    function InternalReadNumEx(var APos: Integer): Integer;
  public
    constructor Create;
    procedure Compress;
    procedure Decompress;

    procedure AddChecksum;
    function  VerifyChecksum: Boolean;

    // see notes for Compression
    Procedure AppendMem(AMem: Pointer; ALen: Integer);
    Procedure AppendString(ATxt: String);
    Procedure AppendNum(ANum: Integer);
    Procedure AppendNumEx(ANum: Integer);

    Procedure Reset;
    Procedure Clear;
    function ReadMem(AMem: Pointer; ALen: Integer): Boolean;
    function PeakString(ALen: Integer): String;
    function FindChar(AChar: Char): Integer; // 0 based
    function ReadString(ALen: Integer): String;
    function ReadNum: Integer;
    function ReadNumEx: Integer;
    function EOF: Boolean;

    property Text: String read GetText write SetText;
    property Mem: PChar read GetMem write SetMem;
    property Len: Integer read GetLen write SetLen;
    property Pos: Integer read FPos;
  end;

  TSynEditFoldExportCoderEntry = record
    aX, aY, aLen: Integer;
    aFoldType: TSynEditFoldType;
  end;
  TSynEditFoldExportCoderStates =
    (sfecAtBegin, sfecAtPoint, sfecInRepeatCount, sfecInvalid, sfecAtEOF);
  {$IFDEF SynFoldSaveDebug}
const
  SynEditFoldExportCoderStates: Array [TSynEditFoldExportCoderStates] of String =
    ('sfecAtBegin', 'sfecAtPoint', 'sfecInRepeatCount', 'sfecInvalid', 'sfecAtEOF');
type
  {$ENDIF}

  { TSynEditFoldExportCoder }

  TSynEditFoldExportCoder = class
  private
    FExportStream: TSynEditFoldExportStream;
    FFoldType: Pointer;

    FReadY, FReadLastY, FReadX, FReadSumLen, FReadCount: Integer;
    FReadType: TSynEditFoldType;
    FReadDefaultType: TSynEditFoldType;
    FReadState: TSynEditFoldExportCoderStates;

    FWriteCache: Array of TSynEditFoldExportCoderEntry;
    FWriteCacheLen: Integer;
    FWriteCacheTypes: set of TSynEditFoldType;
    function GetReadIsValid: Boolean;
  public
    constructor Create(AFoldType: Pointer);
    constructor Create(AStream: TSynEditFoldExportStream);
    destructor Destroy; override;

    procedure AddNode(aX, aY, aLen: Integer; aFoldType: TSynEditFoldType);
    procedure Finish;

    function ReadNode(aX, aY: Integer; aLen: Integer): TSynEditFoldType;
    function EOF: Boolean;
    procedure Reset;
    property ReadIsValid: Boolean read GetReadIsValid;

    property FoldType: Pointer read FFoldType;
    property Stream: TSynEditFoldExportStream read FExportStream;
  end;

const
  // use only xml encode-able ascii
  // do not use [ or ], they are reserved for compression
  // space can be used a special indicator
  NumEncode86Chars: string[86] = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-+;:,.@=*/\!?$%()''^{}~_#';

  NumEncodeAsOneMax = 80;                        // Maximum Value to encode as 1 char
  NumEncodeAsTwoMax = 81 + 4*86 + 43;            // =  467; Maximum Value to encode as 2 char
  NumEncodeAsThreeMax = 81 + 4*86 + 43 * 43 - 1; // = 2273  Maximum Value to encode as 3 char


  SEQMaxNodeCount     = 75;  // New Full entry at least every 75 folds
  SEQMaxLineDistEach  = 500;  //  New Full entry, if folds startlines are more than 500 appart
  SEQMaxLineDistTotal = 2500; // New Full entry at least every 2500; check position

var
  NumEncode86Values: Array [Char] of integer;

procedure InitNumEncodeValues;
var
  i: integer;
  c : Char;
begin
  for c := low(Char) to high(Char) do begin
    NumEncode86Values[c] := -1;
  end;
  for i := 1 to length(NumEncode86Chars) do
    NumEncode86Values[NumEncode86Chars[i]] := i - 1;
end;

{ TFoldChangedHandlerList }

procedure TFoldChangedHandlerList.CallFoldChangedEvents(AnIndex: Integer);
var
  i: LongInt;
begin
  i:=Count;
  while NextDownIndex(i) do
    TFoldChangedEvent(Items[i])(AnIndex);
end;

{ TLazSynDisplayFold }

constructor TLazSynDisplayFold.Create(AFoldView: TSynEditFoldedView);
begin
  inherited Create;
  FFoldView := AFoldView;
  FTokenAttr := TSynHighlighterAttributesModifier.Create(nil);
  FMarkupLine := TSynSelectedColorMergeResult.Create(nil);
end;

destructor TLazSynDisplayFold.Destroy;
begin
  FreeAndNil(FTokenAttr);
  FreeAndNil(FMarkupLine);
  inherited Destroy;
end;

procedure TLazSynDisplayFold.SetHighlighterTokensLine(ALine: TLineIdx; out
  ARealLine: TLineIdx; out AStartBytePos, ALineByteLen: Integer);
begin
  FLineState := 0;
  CurrentTokenLine := ALine;
  FLineFlags := FFoldView.FoldType[CurrentTokenLine + 1 - FFoldView.TopLine] * [cfCollapsedFold, cfCollapsedHide];
  FLineFlags2 := FLineFlags;

  if not FFoldView.MarkupInfoFoldedCodeLine.IsEnabled then
    Exclude(FLineFlags2, cfCollapsedFold);
  if not FFoldView.MarkupInfoHiddenCodeLine.IsEnabled then
    Exclude(FLineFlags2, cfCollapsedHide);

  if (FLineFlags2 <> []) then begin
    FFoldView.MarkupInfoFoldedCodeLine.SetFrameBoundsLog(1, MaxInt, 0);
    FFoldView.MarkupInfoHiddenCodeLine.SetFrameBoundsLog(1, MaxInt, 0);
  end;

  inherited SetHighlighterTokensLine(FFoldView.InternViewToTextIndex(ALine), ARealLine, AStartBytePos, ALineByteLen);
end;

function TLazSynDisplayFold.GetNextHighlighterToken(out ATokenInfo: TLazSynDisplayTokenInfo): Boolean;
const
  MarkSpaces: string = '   ';
  MarkDots: string = '...';
  LSTATE_BOL       = 0; // at BOL
  LSTATE_TEXT      = 1; // in text
  LSTATE_BOL_GAP   = 2; // BOL and in Gap (empty line)         // must be LSTATE_BOL + 2
  LSTATE_GAP       = 3; // In Gap betwen txt and dots          // must be LSTATE_TEXT + 2
  LSTATE_DOTS      = 4; // In Dots
  LSTATE_EOL       = 5; // at start of EOL
var
  EolAttr: TSynHighlighterAttributes;
  MergeStartX, MergeEndX: TLazSynDisplayTokenBound;
begin
  case FLineState of
    LSTATE_BOL, LSTATE_TEXT: begin
        Result := inherited GetNextHighlighterToken(ATokenInfo);
        if ( (not Result) or (ATokenInfo.TokenStart = nil)) and (FLineFlags <> [])
        then begin
          inc(FLineState, 2); // LSTATE_BOL_GAP(2), if was at bol // LSTATE_GAP(3) otherwise
          ATokenInfo.TokenStart := PChar(MarkSpaces);
          ATokenInfo.TokenLength := 3;
          if Assigned(CurrentTokenHighlighter)
          then EolAttr := CurrentTokenHighlighter.GetEndOfLineAttribute
          else EolAttr := nil;
          if EolAttr <> nil then begin
            FTokenAttr.Assign(EolAttr);
            ATokenInfo.TokenAttr := FTokenAttr;
          end
          else begin
            ATokenInfo.TokenAttr := nil;
          end;
          Result := True;
        end;
      end;
    LSTATE_GAP: begin
        FLineState := LSTATE_DOTS;
        FTokenAttr.Assign(FFoldView.MarkupInfoFoldedCode);
        FTokenAttr.SetAllPriorities(MaxInt);
        ATokenInfo.TokenStart := PChar(MarkDots);
        ATokenInfo.TokenLength := 3;
        ATokenInfo.TokenAttr := FTokenAttr;
        Result := True;
      end;
    else begin
      Result := inherited GetNextHighlighterToken(ATokenInfo);
    end;
  end;

  if (FLineFlags2 <> []) then begin
    FMarkupLine.Clear;
    if ATokenInfo.TokenAttr = nil then begin
      // Text Area does not expect StartX/Endx
      // So we must merge, to eliminate unwanted borders
      //  if (cfCollapsedFold in FLineFlags2)
      //  then ATokenInfo.TokenAttr := FFoldView.MarkupInfoFoldedCodeLine
      //  else ATokenInfo.TokenAttr := FFoldView.MarkupInfoHiddenCodeLine;
      //  exit;
      FMarkupLine.Clear;
    end //;
    else
      FMarkupLine.Assign(ATokenInfo.TokenAttr);

    MergeStartX.Physical := -1;
    MergeStartX.Logical := -1;
    MergeEndX.Physical := -1;
    MergeEndX.Logical := -1;
    if FLineState in [LSTATE_BOL, LSTATE_BOL_GAP] then
      MergeStartX := FFoldView.MarkupInfoFoldedCodeLine.StartX;
    if FLineState = LSTATE_EOL then // LSTATE_GAP; // or result := true
      MergeEndX := FFoldView.MarkupInfoFoldedCodeLine.EndX;

    // fully expand all frames
    //FMarkupLine.SetFrameBoundsLog(0,0,0);
    //FMarkupLine.CurrentStartX := FMarkupLine.StartX;
    //FMarkupLine.CurrentEndX := FMarkupLine.EndX;

    if (cfCollapsedFold in FLineFlags2) then
      FMarkupLine.Merge(FFoldView.MarkupInfoFoldedCodeLine, MergeStartX, MergeEndX)
    else
      FMarkupLine.Merge(FFoldView.MarkupInfoHiddenCodeLine, MergeStartX, MergeEndX);

    ATokenInfo.TokenAttr := FMarkupLine;
  end;

  if FLineState in [LSTATE_BOL, LSTATE_BOL_GAP, LSTATE_DOTS, LSTATE_EOL] then
    inc(FLineState);
end;

function TLazSynDisplayFold.GetLinesCount: Integer;
begin
  Result := FFoldView.ViewedCount;
end;

function TLazSynDisplayFold.TextToViewIndex(ATextIndex: TLineIdx): TLineRange;
begin
// TODO: inherited AFTER fold mapping?
  Result := inherited TextToViewIndex(ATextIndex);
  if Result.Top = Result.Bottom then begin
    Result.Top    := FFoldView.InternTextToViewIndex(Result.Top);
    Result.Bottom := Result.Top;
  end
  else begin
    Result.Top    := FFoldView.InternTextToViewIndex(Result.Top);
    Result.Bottom := FFoldView.InternTextToViewIndex(Result.Bottom);
  end;
end;

function TLazSynDisplayFold.ViewToTextIndex(AViewIndex: TLineIdx): TLineIdx;
begin
  Result := FFoldView.InternViewToTextIndex(inherited ViewToTextIndex(AViewIndex));
end;

function TLazSynDisplayFold.ViewToTextIndexEx(AViewIndex: TLineIdx; out
  AViewRange: TLineRange): TLineIdx;
begin
  Result := FFoldView.InternViewToTextIndex(inherited ViewToTextIndexEx(AViewIndex, AViewRange));
end;

{ TSynEditFoldExportStream }

constructor TSynEditFoldExportStream.Create;
begin
  inherited;
  FPos := 0;
  FLen := 0;
  FMem := nil;
end;


function TSynEditFoldExportStream.GetLen: Integer;
begin
  Result := FLen;
end;

procedure TSynEditFoldExportStream.SetLen(const AValue: Integer);
begin
  FPos := 0;
  FLen:= AValue;
end;

function TSynEditFoldExportStream.GetMem: PChar;
begin
  if FData <> '' then
    Result := @FData[1]
  else
    Result := FMem;
end;

procedure TSynEditFoldExportStream.SetMem(const AValue: PChar);
begin
  FData := '';
  FMem := AValue;
  FPos := 0;
end;

function TSynEditFoldExportStream.GetText: String;
begin
  // only valid for FData
  SetLength(FData, FLen);
  Result := FData;
end;

procedure TSynEditFoldExportStream.SetText(const AValue: String);
begin
  FData := AValue;
  FMem := nil;
  FPos := 0;
end;

function TSynEditFoldExportStream.GrowData(AppendSize: Integer): PChar;
var
  l: integer;
begin
  l := length(FData);
  if l < FLen + AppendSize then
    SetLength(FData, l + AppendSize + Max((l+AppendSize) div 4, 1024));
  Result := @FData[FLen + 1];
  inc(FLen, AppendSize);
end;

function TSynEditFoldExportStream.EncodeIntEx(Anum: Integer): String;
var
  n: integer;
begin
  //    0 -   42 => 1 byte
  //   43 - 1848 => 2 byte
  // 1849 - .... => 3 and more
  Result := '';
  if ANum = 0 then Result := NumEncode86Chars[1];
  n := 0;
  while ANum > 0 do begin
    Result := NumEncode86Chars[1 + (Anum mod 43) + n] + Result;
    ANum := ANum div 43;
    n := 43;
  end;
end;

function TSynEditFoldExportStream.EncodeIntEx2(Anum: Integer): String;
var
  n: Integer;
begin
  //   0 -   80 => 1 char
  //  81 -  424 => 2 char   (80 + 4 * 86)
  // 425 -  467 => 2 char (len(EncodeIntEx) = 1)
  // 468 - 2272 => 3 and more char
  //2273 - .... => 4 and more char
  Result := '';
  if Anum <= 80 then
    Result := NumEncode86Chars[1 + Anum]
  else
  begin
    n := (Anum-81) div 86;
    if n <= 3 then
      Result := NumEncode86Chars[1 + 81 + n] + NumEncode86Chars[1 + (Anum - 81) mod 86]
    else
      Result := NumEncode86Chars[1 + 85] + EncodeIntEx(Anum - 81 - 4*86);
  end;
end;

function TSynEditFoldExportStream.InternalReadNum(var APos: Integer): Integer;
var
  n: Integer;
begin
  Result := 0;
  while True do begin
    if FPos >= FLen then exit(-1);
    n := NumEncode86Values[(FMem + APos)^];
    if n < 43 then break;
    dec(n, 43);
    Result := Result * 43 + n;
    inc(APos);
  end;
  Result := Result * 43 + n;
  inc(APos);
end;

function TSynEditFoldExportStream.InternalReadNumEx(var APos: Integer): Integer;
begin
  if FPos >= FLen then exit(-1);
  Result := NumEncode86Values[(FMem + APos)^];
  inc(APos);
  if Result <= 80 then
    exit;
  if FPos >= FLen then exit(-1);
  if Result < 85 then begin
    Result := 81 + (Result-81)*86 +  NumEncode86Values[(FMem + APos)^];
    inc(APos);
    exit;
  end;
  Result := 81 + 4*86 + InternalReadNum(APos);
end;

procedure TSynEditFoldExportStream.Compress;
(* Known Sequences: XX = Enc64Num (copy sequence from XX chars before)
                    NN = ENc22 Num / n = enc22digit (copy n bytes)
     [XXn     (up to 21 bytes, from up to 64*64 back)
     [NNXX[   (more then 21 bytes, from up to 64*64 back)
     ]X       (3 bytes from max 64 back)
     ]nx      ( reocurring space,x times, ever n pos)
const
  max_single_len = 22 - 1;
  *)
var
  CurPos, EndPos, SearchPos: Integer;
  FndLen, FndPos, FndPos2: Integer;
  BestLen, BestPos, BestPos2: Integer;
  s: string;
begin
  AppendString(#0);
  dec(FLen);

  EndPos := FLen;
  CurPos := FLen - 3;
  while CurPos >= 4 do begin
    SearchPos := CurPos - 3;
    BestLen := 0;
    while (SearchPos >= 1) do begin
      if CompareMem(@FData[CurPos], @FData[SearchPos], 3) then begin
        FndLen := 3;
        FndPos := SearchPos;
        FndPos2 := CurPos;
        while (SearchPos + FndLen < FndPos2) and
              (FndPos2 + FndLen < EndPos - 1) and
              (FData[SearchPos + FndLen] = FData[CurPos + FndLen])
        do
          inc(FndLen);
        while (FndPos > 1) and (FndPos + FndLen < FndPos2) and
              (FData[FndPos - 1] = FData[FndPos2 - 1]) do
        begin
          dec(FndPos);
          dec(FndPos2);
          inc(FndLen);
        end;

        if (FndLen > BestLen) and
           ((FndPos2 - FndPos <= NumEncodeAsOneMax) or (FndLen >= 4)) and
           ((FndPos2 - FndPos <= NumEncodeAsTwoMax) or (FndLen >= 5)) and
           ((FndPos2 - FndPos <= NumEncodeAsThreeMax) or (FndLen >= 6))
        then begin
          BestLen := FndLen;
          BestPos := FndPos;
          BestPos2 := FndPos2;
        end;
      end;
      dec(SearchPos);
    end;

    s := '';
    if (BestLen >= 4) then
      s := '[' + EncodeIntEx2(BestPos2 - BestPos) + EncodeIntEx2(BestLen)
    else
    if (BestLen = 3) and (BestPos2 - BestPos <= NumEncodeAsOneMax) then
      s := ']' + EncodeIntEx2(BestPos2 - BestPos);
    if (s<>'') and (length(s) < BestLen) then begin
      System.Move(s[1], FData[BestPos2], length(s));
      System.Move(FData[BestPos2 + BestLen], FData[BestPos2 + length(s)], FLen + 1 - (BestPos2 + BestLen));
      dec(FLen, BestLen - length(s));
      EndPos := BestPos;
      CurPos := BestPos2 - 3;
    end
    else
      dec(CurPos);
  end;
end;

procedure TSynEditFoldExportStream.Decompress;
var
  i, j, n: Integer;
  p, p2: PChar;
  NewLen: Integer;
begin
  // curently assumes that FMem points NOT at FData
  if FLen = 0 then
    exit;
  NewLen := 0;
  i := 0;
  while i < Flen do begin
    case (FMem+i)^ of
      '[' :
        begin
          inc(i);
          j := InternalReadNumEx(i);
          n := InternalReadNumEx(i);
          if (j < n) or (j > NewLen) then raise ESynEditError.Create('fold format error');
          inc(NewLen, n);
        end;
      ']' :
        begin
          inc(i, 1);
          j := InternalReadNumEx(i);
          if (j < 3) or (j > NewLen) then raise ESynEditError.Create('fold format error');
          inc(NewLen, 3);
        end;
      else
        begin
          inc(NewLen);
          inc(i);
        end;
    end;
  end;
  SetLength(FData, NewLen);

  i := 0;
  p := PChar(FData);
  while i < Flen do begin
    case (FMem+i)^ of
      '[' :
        begin
          inc(i);
          j := InternalReadNumEx(i);
          n := InternalReadNumEx(i);
          p2 := p;
          while n > 0 do begin
            p^ := (p2 - j)^;
            inc(p);
            dec(j);
            dec(n);
          end;
        end;
      ']' :
        begin
          inc(i);
          j := InternalReadNumEx(i);
          p2 := p;
          for n := 0 to 2 do begin
            p^ := (p2 - j)^;
            inc(p);
            dec(j);
          end;
        end;
      else
        begin
          p^ := (FMem + i)^;
          inc(p);
          inc(i);
        end;
    end;
  end;

  FLen := NewLen;
  FMem := PChar(FData);
  FPos := 0;
end;

procedure TSynEditFoldExportStream.AddChecksum;
var
  i, c: Integer;
begin
  if FLen = 0 then
    exit;
  if FMem = nil then
    FMem := @FData[1];
  c := 0;
  for i := 0 to FLen - 1 do
    c := c xor (ord((FMem + i)^) * (i+1));
  c := (c mod 256) xor ((c div 256) mod 256) xor ((c div 65536) mod 256);
  AppendString(NumEncode86Chars[1 + (c mod 86)]);
end;

function TSynEditFoldExportStream.VerifyChecksum: Boolean;
var
  i, c: Integer;
begin
  if FLen = 0 then
    exit(True);
  if FMem = nil then
    FMem := @FData[1];
  dec(Flen);
  c := 0;
  for i := 0 to FLen - 1 do
    c := c xor (ord((FMem + i)^) * (i+1));
  c := (c mod 256) xor ((c div 256) mod 256) xor ((c div 65536) mod 256);
  Result := (FMem + FLen)^ = NumEncode86Chars[1 + (c mod 86)];
end;

procedure TSynEditFoldExportStream.AppendMem(AMem: Pointer; ALen: Integer);
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendMem len=', ALen]);
  {$ENDIF}
  FMem := nil;
  if ALen > 0 then
    System.Move(AMem^, GrowData(ALen)^, ALen);
end;

procedure TSynEditFoldExportStream.AppendString(ATxt: String);
var
  l: Integer;
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendString ', ATxt]);
  {$ENDIF}
  FMem := nil;
  l := length(ATxt);
  if l > 0 then
    System.Move(ATxt[1], GrowData(l)^, l);
end;

procedure TSynEditFoldExportStream.AppendNum(ANum: Integer);
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendNum ', ANum]);
  {$ENDIF}
  FMem := nil;
  AppendString(EncodeIntEx(ANum));
end;

procedure TSynEditFoldExportStream.AppendNumEx(ANum: Integer);
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendNumEx ', ANum]);
  {$ENDIF}
  FMem := nil;
  AppendString(EncodeIntEx2(ANum));
end;

procedure TSynEditFoldExportStream.Reset;
begin
  FPos := 0;
  if (FMem = nil) and (FData <> '') then
    FMem := @FData[1];
end;

procedure TSynEditFoldExportStream.Clear;
begin
  FLen := 0;
  FMem := nil;
  FPos := 0;
  SetLength(FData, 0);
end;

function TSynEditFoldExportStream.ReadMem(AMem: Pointer; ALen: Integer): Boolean;
begin
  Result := FPos+ ALen <= FLen;
  If not Result then
    exit;
  System.Move((FMem + FPos)^, AMem^, ALen);
  inc(FPos, ALen);
end;

function TSynEditFoldExportStream.PeakString(ALen: Integer): String;
begin
  If not(FPos+ ALen <= FLen) then
    exit('');
  SetLength(Result, ALen);
  if ALen > 0 then
    System.Move((FMem + FPos)^, Result[1], ALen);
end;

function TSynEditFoldExportStream.FindChar(AChar: Char): Integer;
begin
  Result := 0;
  While (FPos + Result < FLen) and ((FMem + FPos + Result)^ <> AChar) do
    inc(Result);
  if FPos + Result = FLen then
    Result := -1;
end;

function TSynEditFoldExportStream.ReadString(ALen: Integer): String;
begin
  If not(FPos+ ALen <= FLen) then
    exit('');
  SetLength(Result, ALen);
  if ALen > 0 then
    System.Move((FMem + FPos)^, Result[1], ALen);
  inc(FPos, ALen);
end;

function TSynEditFoldExportStream.ReadNum: Integer;
begin
  Result := InternalReadNum(FPos);
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.ReadNum ', Result]);
  {$ENDIF}
end;

function TSynEditFoldExportStream.ReadNumEx: Integer;
begin
  Result := InternalReadNumEx(FPos);
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.ReadNumEx ', Result]);
  {$ENDIF}
end;

function TSynEditFoldExportStream.EOF: Boolean;
begin
  Result := FPos >= FLen;
end;

{ TSynEditFoldExportCoder }

function TSynEditFoldExportCoder.GetReadIsValid: Boolean;
begin
  Result := FReadState <> sfecInvalid;
end;

constructor TSynEditFoldExportCoder.Create(AFoldType: Pointer);
begin
  inherited Create;
  FExportStream := TSynEditFoldExportStream.Create;
  FExportStream.AppendString(' T');                // Type Marker
  FExportStream.AppendNum(PtrUInt(AFoldType));
  FFoldType := AFoldType;
  FWriteCacheLen := 0;
  FWriteCache := nil;
  FWriteCacheTypes := [];
end;

constructor TSynEditFoldExportCoder.Create(AStream: TSynEditFoldExportStream);
var
  i: Integer;
begin
  inherited Create;
  FExportStream := TSynEditFoldExportStream.Create;
  FReadState := sfecInvalid;
  if AStream.PeakString(2) <> ' T' then exit;

  AStream.ReadString(2);

  FFoldType := Pointer(PtrUInt(AStream.ReadNum));
  while(true) do begin
    i := AStream.FindChar(' ');
    if i < 0 then i := AStream.Len - AStream.Pos;
    FExportStream.AppendString(AStream.ReadString(i));
    if AStream.EOF or (AStream.PeakString(2) = ' T') then
      break;
    FExportStream.AppendString(AStream.ReadString(2));
  end;
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportCoder.Create(<from input-stream> FType=', dbgs(FFoldType), '  txtLen=', FExportStream.Len, ' Txt="', FExportStream.Text, '"']);
  {$ENDIF}
  Reset;
end;

destructor TSynEditFoldExportCoder.Destroy;
begin
  FreeAndNil(FExportStream);
  Inherited;
end;

procedure TSynEditFoldExportCoder.AddNode(aX, aY, aLen: Integer; aFoldType: TSynEditFoldType);
(* Format:  [Num] <NumEX>
  ' T' [type] [yo] <X> <len> ( <c>* ' p' [sum]  [yo] <X> <len> )* <c>* (' P' [sum] [yo] <X> <len>)?

  //////////////////////////
  // Version info
  V1 - no entries
  V2  July 2010  0.9.29
     - added fold-hide <HideInfo>

  //////////////////////////

  <Stream> = { <TypeStream> };

  <TypeStream> = " T" <TypeId>  <TypeData>;        [* Stores all folds for the given type (eg cfbtBeginEnd) *]

  <TypeId>   = ord(cfbtBeginEnd) or similar
  <TypeData> = [<HideInfo>],
               <NodePos>,
               [ [<FoldList>,]  [{ <FoldListEndCont>, <NodePos>, [<FoldList>] }] ],
               [ <FoldListEnd> ];


  <FoldList> = [{ <ConsecutiveFoldedCount>,  <ConsecutiveUnFoldedCount> }],
               <ConsecutiveFoldedCount>,
               ;
  [* NodePos: is the  position of a folded node (of the type matching the current stream)
     ConsecutiveFoldedCount: more folded nodes of the same type, without any
                             unfolded node (of this type) inbetween.
     ConsecutiveUnFoldedCount: amount of unfolded nodes (of this type) before the next folded node.
  *]

  <NodePos> =  <YOffset> <XPos> <len>;
  <YOffset>                  = <Number>
  <XPos>                     = <ExNumber>
  <len>                      = <ExNumber>
  <ConsecutiveFoldedCount>   = <ExNumber>
  <ConsecutiveUnFoldedCount> = <ExNumber>

  <FoldListEndCont> = ' p', <SumFoldedLines>;
    [* FoldListEndCont is mandotory, if another block of <NodePos>, <FoldList> is coming *]
  <FoldListEnd>     = ' P'  <SumFoldedLines>, <EndY>, <EndX>;
    [* FoldListEnd is optional. It is expected if the previous <FoldList> has more than 10 folded lines*]

  <SumFoldedLines> = <Number>
  [* The sum of all lines folded by folds in <ConsecutiveFoldedCount>.
     Not including the fold in <NodePos>, which has it's own len.
  *]

  <Number> = bigger numbers
  <ExNumber> = for numbers expected below 467; specially 0..80

  <HideInfo> = ' h' | ' H'
    not present: all folds, no hides (default)
    ' H': all hides, no folds
    ' h': mixed hides and folds
      For mixed lists the following applies:
      - XPos is doubled; bit 0 (odd <number>) indicates the first node is a hide
      - ConsecutiveFoldedCount, ConsecutiveUnFoldedCount are doubled;
        bit 0 indicates:
          If last was fold: 1-odd = hide  /  0-even = open
          If last was hide: 1-odd = fold  /  0-even = open
          If last was open: 1-odd = hide  /  0-even = fold
        In the first <ConsecutiveFoldedCount> after <NodePos> the bit is unused, since nodepos is continued.
*)
begin
  {$IFDEF SynFoldSaveDebug}
  debugln(['TSynEditFoldExportCoder.AddNode FType=', dbgs(FFoldType),'   X=', aX, ' Y=', aY, 'Len=', aLen, 'FType=', SynEditFoldTypeNames[aFoldType], ' WCacheLen=', FWriteCacheLen]);
  {$ENDIF}
  if (FWriteCacheLen = 0) and (aFoldType = scftOpen) then
    exit;
  if FWriteCacheLen >= length(FWriteCache) then
    SetLength(FWriteCache, Max(1000, FWriteCacheLen*2));
  FWriteCache[FWriteCacheLen].aY := aY;
  FWriteCache[FWriteCacheLen].aX := aX;
  FWriteCache[FWriteCacheLen].aLen := aLen;
  FWriteCache[FWriteCacheLen].aFoldType := aFoldType;
  inc(FWriteCacheLen);
  include(FWriteCacheTypes, aFoldType);
end;

procedure TSynEditFoldExportCoder.Finish;
var
  FirstLine, HideFactor, HideBit: Integer;
  CntSum, LinesSum: Integer;
  LastFoldType: TSynEditFoldType;

  procedure WriteCachedNode(AIndex: Integer);
  begin
    HideBit := 0;
    LastFoldType := FWriteCache[AIndex].aFoldType;
    if (HideFactor = 2) and (LastFoldType = scftHide) then
      HideBit := 1;
    FExportStream.AppendNum  (FWriteCache[AIndex].aY - FirstLine);
    FExportStream.AppendNumEx(FWriteCache[AIndex].aX * HideFactor + HideBit);
    FExportStream.AppendNumEx(FWriteCache[AIndex].aLen);
    FirstLine := FWriteCache[AIndex].aY;
  end;

  function CountConsecutiveNodes(var AStartIndex: Integer; out ACount, ALines: Integer;
    ASkipFirst: Boolean = True): Boolean;
  var l1, l2: Integer;
      t: TSynEditFoldType;
  begin
    // reset counters for following <FoldList>
    CntSum := 0;

    HideBit := 0;;
    case LastFoldType of
      scftOpen: if scftHide = FWriteCache[AStartIndex].aFoldType then HideBit := 1;
      scftFold: if scftHide = FWriteCache[AStartIndex].aFoldType then HideBit := 1;
      scftHide: if scftFold = FWriteCache[AStartIndex].aFoldType then HideBit := 1;
    end;
    LastFoldType := FWriteCache[AStartIndex].aFoldType;

    Result := False;
    ACount := 0;
    ALines := 0;

    l2 := FirstLine;
    t := FWriteCache[AStartIndex].aFoldType;
    Repeat
      if (AStartIndex >= FWriteCacheLen) then
        exit;
      l1 := FWriteCache[AStartIndex].aY;
      if (ACount         > SEQMaxNodeCount) or
         (ALines         > SEQMaxNodeCount) or  // TODO should this be SEQMaxLineDistEach ?
         (l1 - l2        > SEQMaxLineDistEach) or
         (l1 - FirstLine > SEQMaxLineDistTotal)
      then
        exit;

      if not ASkipFirst then begin
        ALines := ALines + FWriteCache[AStartIndex].aLen;
        inc(ACount);
      end;
      inc(AStartIndex);
      l2 := l1;
      ASkipFirst := False;
    until FWriteCache[AStartIndex].aFoldType <> t;
    Result := True;
  end;

  var DeferredZero: Boolean;
  procedure WriteNodeCount(ACount, ALines: Integer; AState: TSynEditFoldType);
  begin
    inc(CntSum, ACount);
    inc(LinesSum, ALines); // non folds are always 0
    if ACount = 0 then begin
      DeferredZero := True;
      exit;
    end;
    if DeferredZero then
      FExportStream.AppendNumEx(0);
    DeferredZero := False;
    FExportStream.AppendNumEx(ACount * HideFactor + HideBit);
  end;

  function ScanForFold(var AIndex: Integer): Boolean;
  begin
    Result := True;
    while AIndex < FWriteCacheLen do begin
      if FWriteCache[AIndex].aFoldType in [scftFold, scftHide] then exit;
      inc(AIndex);
    end;
    Result := False;
  end;
var
  i, i2, CntF, CntNF, LinesF, LinesNF: Integer;
  r: boolean;
begin
  if (FWriteCacheLen = 0) or (FWriteCacheTypes * [scftFold, scftHide] = []) then begin
    FExportStream.Clear;
    exit;
  end;
  {$IFDEF SynFoldSaveDebug}
  DebugLnEnter(['TSynEditFoldExportCoder.Finish FType=', dbgs(FFoldType)]);
  {$ENDIF}

  FirstLine := 0;
  if (FWriteCacheTypes * [scftFold, scftHide] = [scftFold, scftHide]) then begin
    HideFactor := 2;
    FExportStream.AppendString(' h');
  end
  else begin
    HideFactor := 1; // no bit for hide/fold differentation needed
    if scftHide in FWriteCacheTypes then
      FExportStream.AppendString(' H');
  end;
  i := 0;
  while i < FWriteCacheLen do begin
    LinesSum := 0;
    WriteCachedNode(i);

    DeferredZero := False;   // special case at start, there may be 0 more folded nodes
    r := CountConsecutiveNodes(i, cntF, linesF, True);
    WriteNodeCount(CntF, LinesF, scftFold); // or hide, no matter here
    while r do begin
      r := CountConsecutiveNodes(i, cntNF, linesNF, False);
      if not r then break;
      r := CountConsecutiveNodes(i, cntF, linesF, False);
      WriteNodeCount(CntNF, LinesNF, scftOpen);
      WriteNodeCount(CntF, LinesF, scftFold); // or hide, no matter here
    end;

    i2 := i;
    ScanForFold(i);
    if (i < FWriteCacheLen) then begin
      // another node will follow, must insert ' p' marker
      FExportStream.AppendString(' p');      // point marker (no marker needed for first entry)
      FExportStream.AppendNum(LinesSum);   // Start with sum from last sequence
    end;
  end;

  if LinesSum > 10 then begin
    // end of data; write ' P' marker if needed
    FExportStream.AppendString(' P');      // point marker (no marker needed for first entry)
    FExportStream.AppendNum  (LinesSum);   // Start with sum from last sequence
    FExportStream.AppendNum  (FWriteCache[i2-1].aY - FirstLine);  // Last folded Coords
    FExportStream.AppendNumEx(FWriteCache[i2-1].aX);
  end;
  {$IFDEF SynFoldSaveDebug}
  DebugLnExit(['TSynEditFoldExportCoder.Finish FType=', dbgs(FFoldType), '  txtLen=', FExportStream.Len, ' Txt="', FExportStream.Text, '"']);
  {$ENDIF}
end;

function TSynEditFoldExportCoder.ReadNode(aX, aY: Integer; aLen: Integer): TSynEditFoldType;
(* Format:  [Num] <NumEX>
  ' T' [type]
   [yo] <X> <len> ( <c>* ' p' [sum]  [yo] <X> <len> )* <c>* (' P' [sum] [yo] <X>)?
*)
  function GetCommand: Char;
  begin
    Result := #0;
    if (FExportStream.PeakString(1) = ' ') and (FExportStream.Len > FExportStream.Pos+1) then
      Result := FExportStream.ReadString(2)[2];
  end;

  function Invalidate: TSynEditFoldType;
  begin
    {$IFDEF SynFoldSaveDebug}
    DebugLn(['Invalidate']);
    {$ENDIF}
    FReadState := sfecInvalid;
    Result := scftInvalid;
  end;

var
  i: Integer;
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLnEnter(['TSynEditFoldExportCoder.Readnode  X=', aX, ' Y=', aY, ' Len=',aLen,
                '   ReadState=',SynEditFoldExportCoderStates[FReadState],
                ' FReadCount=', FReadCount, ' FReadY=', FReadY, ' FReadX=', FReadX,
                ' FReadSumLen=', FReadSumLen, ' FReadType=', SynEditFoldTypeNames[FReadType]
                 ]);
  try
  {$ENDIF}
  Result := scftInvalid;
  case FReadState of
    sfecAtBegin, sfecAtPoint:
      begin
        if (FReadState = sfecAtBegin) then begin
          case GetCommand of
            'H': begin
                FReadDefaultType := scftHide;
                FReadType := scftHide;
              end;
            'h': begin
                FReadDefaultType := scftAll;
              end;
          end;
          FReadState := sfecAtPoint;
        end;

        if FReadCount = 0 then begin
          FReadCount  := 1;
          FReadY      := FExportStream.ReadNum + FReadLastY;
          FReadX      := FExportStream.ReadNumEx;
          FReadSumLen := FExportStream.ReadNumEx;
          if FReadSumLen < 0 then exit(Invalidate);

          if FReadDefaultType = scftAll then begin
            if (FReadX and 1) = 1 then
              FReadType := scftHide
            else
              FReadType := scftFold;
            FReadX := FReadX div 2;
          end
          else
            FReadType := FReadDefaultType;
        end;

        // ax may be off by one, since pas highlighter changed to include $ in $IFDEF
        if ((aY < FReadY) or ((aY = FReadY) and (aX+1 < FReadX))) then
          exit(scftOpen);  // actually, read before point

        i := 0;
        if FReadType = scftHide then i := 1; // fold one more than len
        if (aY <> FReadY) or (abs(aX - FReadX) > 1) or (aLen + i <> FReadSumLen) then
          exit(Invalidate);

        FReadLastY := FReadY;
        FReadSumLen := 0; // was len of current fold, no len remaining => prepare for counting consecutive folds
        Result := FReadType;

        if FExportStream.EOF then
          FReadState := sfecAtEOF
        else case GetCommand of
          'p':
            begin
              FExportStream.ReadNum;  // skip len (must be 0) since there was no <ConsecutiveFoldedCount>
              FReadCount := 0;
              FReadState := sfecAtPoint;
            end;
          'P':
            begin
              // end marker isnt expected? there were no <ConsecutiveFoldedCount>
              FReadState := sfecAtEOF;
            end;
          else
            begin
              FReadState := sfecInRepeatCount;
              FReadCount := FExportStream.ReadNumEx;  // count up and check at end
            end;
        end;
      end;

    sfecInRepeatCount:
      begin
        if FReadCount = 0 then begin
          if FExportStream.EOF then begin
            FReadState := sfecAtEOF;
            exit(scftOpen);
          end
          else case GetCommand of
            'p':
              begin
                if FReadSumLen <> FExportStream.ReadNum then
                  exit(Invalidate);
                FReadCount := 0;
                FReadState := sfecAtPoint;
                exit(ReadNode(aX, aY, aLen));
              end;
            'P':
              begin
                if (FReadSumLen <> FExportStream.ReadNum) or
                   (FReadY <> FExportStream.ReadNum + FReadLastY) or
                   (FReadX <> FExportStream.ReadNumEx)
                then
                  exit(Invalidate);
                FReadState := sfecAtEOF;
                exit(scftOpen);
              end;
            else
              begin
                FReadCount := FExportStream.ReadNumEx;  // count up and check at end
                if FReadDefaultType = scftAll then begin
                  if (FReadCount and 1) = 1 then begin
                    case FReadType of
                      scftOpen: FReadType := scftHide;
                      scftFold: FReadType := scftHide;
                      scftHide: FReadType := scftFold;
                    end;
                  end else begin
                    case FReadType of
                      scftOpen: FReadType := scftFold;
                      scftFold: FReadType := scftOpen;
                      scftHide: FReadType := scftOpen;
                    end;
                  end;
                  FReadCount := FReadCount div 2;
                end
                else begin
                  if FReadType = scftOpen then
                    FReadType := FReadDefaultType
                  else
                    FReadType := scftOpen;
                end;
              end;
          end;
        end;
        dec(FReadCount);
        if FReadType <> scftOpen then
          inc(FReadSumLen, aLen);
        Result := FReadType;
      end;

    sfecAtEOF:
      begin
        exit(scftOpen);
      end;
    sfecInvalid:
      begin
        exit(scftInvalid);
      end;
  end;
  {$IFDEF SynFoldSaveDebug}
  finally
    DebugLnExit(['TSynEditFoldExportCoder.Readnode << ']);
  end;
  {$ENDIF}
end;

function TSynEditFoldExportCoder.EOF: Boolean;
begin
  Result := FExportStream.EOF;
end;

procedure TSynEditFoldExportCoder.Reset;
begin
  FExportStream.Reset;
  FReadY := -1;
  FReadX := -1;
  FReadLastY := 0;
  FReadCount := 0;
  FReadSumLen := 0;
  FReadState := sfecAtBegin;
  if FExportStream.Len = 0 then
    FReadState := sfecInvalid;
  FReadDefaultType := scftFold;
  FReadType := scftFold;
end;

{ TSynTextFoldAVLNodeData }

function TSynTextFoldAVLNodeData.Left: TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData(FLeft);
end;

function TSynTextFoldAVLNodeData.Parent: TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData(FParent);
end;

function TSynTextFoldAVLNodeData.Right: TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData(FRight);
end;

procedure TSynTextFoldAVLNodeData.FreeAllChildrenAndNested;
begin
  if FLeft <> nil then begin
    Left.FreeAllChildrenAndNested;
    FreeAndNil(FLeft);
  end;

  if FRight <> nil then begin
    Right.FreeAllChildrenAndNested;
    FreeAndNil(FRight);
  end;

  if Nested <> nil then begin
    Nested.FreeAllChildrenAndNested;
    FreeAndNil(Nested);
  end;
end;

function TSynTextFoldAVLNodeData.RecursiveFoldCount : Integer;
var
  ANode: TSynTextFoldAVLNodeData;
begin
  Result := 0;
  ANode := self;
  while ANode <> nil do begin
    Result := Result + ANode.MergedLineCount + ANode.LeftCount;
    ANode := ANode.Right;
  end;
end;

function TSynTextFoldAVLNodeData.Precessor: TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData(inherited Precessor);
end;

function TSynTextFoldAVLNodeData.Successor: TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData(inherited Successor);
end;

function TSynTextFoldAVLNodeData.Precessor(var aStartPosition,
  aSizesBeforeSum: Integer): TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData(inherited Precessor(aStartPosition, aSizesBeforeSum));
end;

function TSynTextFoldAVLNodeData.Successor(var aStartPosition,
  aSizesBeforeSum: Integer): TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData(inherited Successor(aStartPosition, aSizesBeforeSum));
end;

{ TSynTextFoldAVLNode }

function TSynTextFoldAVLNode.GetClassification: TFoldNodeClassification;
begin
  if fData = nil
  then Result := fncInvalid
  else Result := fData.Classification;
end;

function TSynTextFoldAVLNode.GetFoldColumn: Integer;
begin
  if fData = nil
  then Result := -1
  else Result := fData.FoldColumn;
end;

function TSynTextFoldAVLNode.GetFoldColumnLen: Integer;
begin
  if fData = nil
  then Result := -1
  else Result := fData.FoldColumnLen;
end;

function TSynTextFoldAVLNode.GetFoldIndex: Integer;
begin
  if fData = nil
  then Result := -1
  else Result := fData.FoldIndex;
end;

function TSynTextFoldAVLNode.GetMergedLineCount : Integer;
begin
  if fData = nil
  then Result := 0
  else Result := fData.MergedLineCount;
end;

function TSynTextFoldAVLNode.GetFullCount: Integer;
begin
  if fData = nil
  then Result := -1
  else Result := fData.FullCount;
end;

function TSynTextFoldAVLNode.GetSourceLine: integer;
begin
  if fData = nil then
    Result := -1
  else
    Result := StartLine - fData.VisibleLines;
end;

function TSynTextFoldAVLNode.GetSourceLineOffset: integer;
begin
  if fData = nil then
    Result := 0
  else
    Result := fData.VisibleLines;
end;

procedure TSynTextFoldAVLNode.SetFoldColumn(const AValue: Integer);
begin
  if fData <> nil then
    fData.FoldColumn :=  AValue;
end;

procedure TSynTextFoldAVLNode.Init(aData: TSynTextFoldAVLNodeData; aStartLine,
  aFoldedBefore: Integer);
begin
  fData := aData;
  fStartLine :=  aStartLine;
  fFoldedBefore := aFoldedBefore;
end;

function TSynTextFoldAVLNode.IsInFold : Boolean;
begin
  Result := fData <> nil;
end;

function TSynTextFoldAVLNode.Next : TSynTextFoldAVLNode;
var aStart, aBefore : Integer;
begin
  if fData <> nil then begin
    aStart := StartLine;
    aBefore := FoldedBefore;
    Result.fData := fData.Successor(aStart, aBefore);
    Result.fStartLine := aStart;
    Result.fFoldedBefore := aBefore;
  end
  else Result.fData := nil;
end;

function TSynTextFoldAVLNode.Prev : TSynTextFoldAVLNode;
var aStart, aBefore : Integer;
begin
  if fData <> nil then begin
    aStart := StartLine;
    aBefore := FoldedBefore;
    Result.fData := fData.Precessor(aStart, aBefore);
    Result.fStartLine := aStart;
    Result.fFoldedBefore := aBefore;
  end
  else Result.fData := nil;
end;

function TSynTextFoldAVLNode.IsHide: Boolean;
begin
  Result := (fData <> nil) and (fData.VisibleLines = 0);
end;

{ TSynTextFoldAVLNodeNestedIterator }

constructor TSynTextFoldAVLNodeNestedIterator.Create(ANode: TSynTextFoldAVLNode);
begin
  SetLength(FOuterNodes, 0);
  FCurrentNode := ANode;
end;

destructor TSynTextFoldAVLNodeNestedIterator.Destroy;
begin
  SetLength(FOuterNodes, 0);
  inherited Destroy;
end;

function TSynTextFoldAVLNodeNestedIterator.Next: TSynTextFoldAVLNode;
var
  NewData: TSynTextFoldAVLNodeData;
  i: Integer;
  PNode: TSynTextFoldAVLNode;
begin
  i := length(FOuterNodes);
  if FCurrentNode.fData.Nested = nil then begin
    FCurrentNode := FCurrentNode.Next;
    while (not FCurrentNode.IsInFold) and (i > 0) do begin
      dec(i);
      FCurrentNode := FOuterNodes[i];
      SetLength(FOuterNodes, i);
      FCurrentNode := FCurrentNode.Next;
    end;
  end else begin
    SetLength(FOuterNodes, i + 1);
    FOuterNodes[i] := FCurrentNode;
    NewData := FCurrentNode.fData.Nested;
    FCurrentNode.fData := NewData;
    FCurrentNode.FStartLine := FCurrentNode.FStartLine + NewData.LineOffset;

    PNode := FCurrentNode.Prev;
    while PNode.IsInFold do begin
      FCurrentNode := PNode;
      PNode := FCurrentNode.Prev;
    end;
  end;
  Result := FCurrentNode;
end;

function TSynTextFoldAVLNodeNestedIterator.Prev: TSynTextFoldAVLNode;
var
  i: Integer;
  NewData: TSynTextFoldAVLNodeData;
  PNode: TSynTextFoldAVLNode;
begin
  FCurrentNode := FCurrentNode.Prev;
  i := length(FOuterNodes);
  if FCurrentNode.IsInFold then begin
    while (FCurrentNode.fData.Nested <> nil) do begin
      SetLength(FOuterNodes, i + 1);
      FOuterNodes[i] := FCurrentNode;
      NewData := FCurrentNode.fData.Nested;
      FCurrentNode.fData := NewData;
      FCurrentNode.FStartLine := FCurrentNode.FStartLine + NewData.LineOffset;

      PNode := FCurrentNode.Next;
      while PNode.IsInFold do begin
        FCurrentNode := PNode;
        PNode := FCurrentNode.Next;
      end;
    end;
  end
  else // not IsInFold
  if (i > 0) then begin
    dec(i);
    FCurrentNode := FOuterNodes[i];
    SetLength(FOuterNodes, i);
  end;
  Result := FCurrentNode;
end;

function TSynTextFoldAVLNodeNestedIterator.EOF: Boolean;
begin
  Result := not FCurrentNode.Next.IsInFold;
end;

function TSynTextFoldAVLNodeNestedIterator.BOF: Boolean;
begin
  Result := not FCurrentNode.Prev.IsInFold;
end;

function TSynTextFoldAVLNodeNestedIterator.IsInFold: Boolean;
begin
  Result := FCurrentNode.IsInFold;
end;

{ TSynFoldNodeInfoHelper }

constructor TSynFoldNodeInfoHelper.Create(AHighlighter: TSynCustomFoldHighlighter);
begin
  inherited Create;
  FHighlighter := AHighlighter;
  Invalidate;
end;

function TSynFoldNodeInfoHelper.FirstOpen: TSynFoldNodeInfo;
begin
  FActions := [sfaOpen, sfaFold];
  FCurInfo.NodeIndex := -1;
  FCurInfo.LineIndex := 0;
  Result := Next;
end;

procedure TSynFoldNodeInfoHelper.Invalidate;
begin
  FCurInfo.FoldAction := [sfaInvalid];
end;

function TSynFoldNodeInfoHelper.Next: TSynFoldNodeInfo;
var
  Cnt, Line, Idx: LongInt;
begin
  Idx := FCurInfo.NodeIndex + 1;
  Line := FCurInfo.LineIndex;
  Cnt := FHighlighter.FoldNodeInfo[Line].CountEx(FActions);
  if Idx >= Cnt then begin
    Idx := 0;
    inc(Line);
    while (Line < FHighlighter.CurrentLines.Count) and
          (FHighlighter.FoldNodeInfo[Line].CountEx(FActions) = 0)
    do
      inc(Line);
  end;
  if (Line < FHighlighter.CurrentLines.Count) then
    FCurInfo := FHighlighter.FoldNodeInfo[Line].NodeInfoEx(Idx, FActions)
  else
    Invalidate;
  Result := FCurInfo;
end;

function TSynFoldNodeInfoHelper.Prev: TSynFoldNodeInfo;
var
  Line, Idx: LongInt;
begin
  Idx := FCurInfo.NodeIndex - 1;
  Line := FCurInfo.LineIndex;
  if Idx < 0 then begin
    dec(Line);
    while (Line >= 0) and
          (FHighlighter.FoldNodeInfo[Line].CountEx(FActions) = 0)
    do
      dec(Line);
    Idx := FHighlighter.FoldNodeInfo[Line].CountEx(FActions) - 1;
  end;
  if (Line >= 0) then
    FCurInfo := FHighlighter.FoldNodeInfo[Line].NodeInfoEx(Idx, FActions)
  else
    Invalidate;
  Result := FCurInfo;
end;

function TSynFoldNodeInfoHelper.FindClose: TSynFoldNodeInfo;
var
  Line, EndLine, Cnt: Integer;
  NdInfo: TSynFoldNodeInfo;
begin
  Line := FCurInfo.LineIndex;
  EndLine := FHighlighter.FoldEndLine(Line, FCurInfo.NodeIndex);
  FActions := [sfaClose, sfaFold];
  Cnt := FHighlighter.FoldNodeInfo[EndLine].CountEx(FActions) - 1;
  while Cnt >= 0 do begin
    NdInfo := FHighlighter.FoldNodeInfo[EndLine].NodeInfoEx(Cnt, FActions);
    if (NdInfo.FoldLvlStart = FCurInfo.FoldLvlEnd) and
       (NdInfo.FoldType = FCurInfo.FoldType)
    then
      break;
    dec(Cnt);
  end;
  if Cnt < 0 then
    Invalidate
  else
    FCurInfo := NdInfo;
  Result := FCurInfo;
end;

function TSynFoldNodeInfoHelper.GotoOpenPos(aLineIdx, aNodeIdx: integer): TSynFoldNodeInfo;
begin
  FActions := [sfaOpen, sfaFold];
  FCurInfo := FHighlighter.FoldNodeInfo[aLineIdx].NodeInfoEx(aNodeIdx, FActions);
  Result := FCurInfo;
end;

function TSynFoldNodeInfoHelper.GotoOpenAtChar(aLineIdx, aXPos: integer): TSynFoldNodeInfo;
var
  Cnt: Integer;
begin
  FActions := [sfaOpen, sfaFold];
  Cnt := FHighlighter.FoldNodeInfo[aLineIdx].CountEx(FActions) - 1;
  while Cnt >= 0 do begin
    FCurInfo := FHighlighter.FoldNodeInfo[aLineIdx].NodeInfoEx(Cnt, FActions);
    if FCurInfo.LogXStart = aXPos then break;
    dec(Cnt);
  end;
  if Cnt < 0 then
    Invalidate;
  Result := FCurInfo;
end;

function TSynFoldNodeInfoHelper.GotoNodeOpenPos(ANode: TSynTextFoldAVLNode): TSynFoldNodeInfo;
begin
  FActions := [sfaOpen, sfaFold];
  FCurInfo := FHighlighter.FoldNodeInfo[ANode.StartLine - ANode.SourceLineOffset - 1]
              .NodeInfoEx(ANode.FoldIndex, FActions);
  Result := FCurInfo;
end;

function TSynFoldNodeInfoHelper.GotoNodeClosePos(ANode: TSynTextFoldAVLNode): TSynFoldNodeInfo;
var
  NdInfo, NdInfo2: TSynFoldNodeInfo;
  Cnt, EndCol, EndLineIdx: Integer;
begin
  FActions := [sfaClose, sfaFold];
  NdInfo := FHighlighter.FoldNodeInfo[ANode.StartLine - ANode.SourceLineOffset - 1]
            .NodeInfoEx(ANode.FoldIndex, [sfaOpen, sfaFold]);
  if sfaInvalid in NdInfo.FoldAction then exit(NdInfo);

  EndLineIdx := FHighlighter.FoldEndLine(ANode.StartLine - ANode.SourceLineOffset - 1,
                                        ANode.FoldIndex);
  {$IFDEF SynAssertFold}
  SynAssert(EndLineIdx >= 0, 'TSynFoldNodeInfoHelper.GotoNodeClosePos: Bad EndLineIdx=%d # Anode: StartLine=%d SrcLOffs=%d ColIdx=%d FoldCol=%d', [EndLineIdx, ANode.StartLine, ANode.SourceLineOffset, ANode.FoldIndex, ANode.FoldColumn]);
  {$ENDIF}
  Cnt := FHighlighter.FoldNodeInfo[EndLineIdx].CountEx([sfaClose, sfaFold]);
  EndCol := 0;
  while EndCol < Cnt do begin
    NdInfo2 := FHighlighter.FoldNodeInfo[EndLineIdx].NodeInfoEx(EndCol, [sfaClose, sfaFold]);
    if (NdInfo2.FoldLvlStart = NdInfo.FoldLvlEnd) and
       (NdInfo2.FoldType = NdInfo.FoldType) then break;
    inc(EndCol);
  end;
  if (EndCol = Cnt) or (sfaInvalid in NdInfo2.FoldAction) then
    Invalidate
  else
    FCurInfo := NdInfo2;
  Result := FCurInfo;
end;

function TSynFoldNodeInfoHelper.IsAtNodeOpenPos(ANode: TSynTextFoldAVLNode): Boolean;
begin
  Result := (not (sfaInvalid in FCurInfo.FoldAction)) and
            (ANode.IsInFold) and
            (FCurInfo.LineIndex = ANode.StartLine - ANode.SourceLineOffset - 1) and
            (FCurInfo.NodeIndex = ANode.FoldIndex);
end;

function TSynFoldNodeInfoHelper.IsValid: Boolean;
begin
  Result := (not (sfaInvalid in FCurInfo.FoldAction));
end;

function TSynFoldNodeInfoHelper.Equals(AnInfo: TSynFoldNodeInfo): Boolean;
begin
  Result := (FCurInfo.LineIndex = AnInfo.LineIndex) and
            (FCurInfo.NodeIndex = AnInfo.NodeIndex) and
            (FCurInfo.LogXStart = AnInfo.LogXStart) and
            (FCurInfo.LogXEnd   = AnInfo.LogXEnd) and
            (FCurInfo.FoldLvlStart = AnInfo.FoldLvlStart) and
            (FCurInfo.FoldLvlEnd   = AnInfo.FoldLvlEnd) and
            (FCurInfo.FoldAction = AnInfo.FoldAction) and
            (FCurInfo.FoldType   = AnInfo.FoldType) and
            (FCurInfo.FoldGroup  = AnInfo.FoldGroup);
end;

function TSynFoldNodeInfoHelper.Equals(AHelper: TSynFoldNodeInfoHelper): Boolean;
begin
  Result := Equals(AHelper.Info);
end;

{ TSynTextFoldAVLTree }

function TSynTextFoldAVLTree.NewNode : TSynTextFoldAVLNodeData;
begin
  Result := TSynTextFoldAVLNodeData.Create;
end;

destructor TSynTextFoldAVLTree.Destroy;
begin
  Clear;
  if fNestedNodesTree <> nil then begin
    fNestedNodesTree.fRoot := nil; //was freed in self.Clear
    fNestedNodesTree.fNestParent := nil; // Or Destroy will access invalid memory
    fNestedNodesTree.Free;
  end;
  inherited Destroy;
end;

procedure TSynTextFoldAVLTree.Clear;
  procedure DeleteNode({var} ANode: TSynTextFoldAVLNodeData);
  begin
    if ANode.Left <>nil   then DeleteNode(ANode.Left);
    if ANode.Right <>nil  then DeleteNode(ANode.Right);
    if ANode.Nested <>nil then DeleteNode(ANode.Nested);
    DisposeNode(TSynSizedDifferentialAVLNode(ANode));
  end;
begin
  if fRoot <> nil then DeleteNode(TSynTextFoldAVLNodeData(fRoot));
  SetRoot(nil);
end;

procedure TSynTextFoldAVLTree.SetRoot(ANode : TSynSizedDifferentialAVLNode);
begin
  inherited;;
  if fNestParent <> nil then fNestParent.Nested := TSynTextFoldAVLNodeData(ANode);
end;

procedure TSynTextFoldAVLTree.SetRoot(ANode : TSynSizedDifferentialAVLNode; anAdjustChildLineOffset : Integer);
begin
  inherited;;
  if fNestParent <> nil then fNestParent.Nested := TSynTextFoldAVLNodeData(ANode);
end;

(* Find Fold by Line in Real Text *)
function TSynTextFoldAVLTree.FindFoldForLine(ALine : Integer;
  FindNextNode : Boolean = False) : TSynTextFoldAVLNode;
var
  r : TSynTextFoldAVLNodeData;
  rStartLine : Integer;
  rFoldedBefore : Integer;
begin
  r := TSynTextFoldAVLNodeData(fRoot);
  rStartLine := fRootOffset;
  rFoldedBefore := 0;
  while (r <> nil) do begin
    rStartLine := rStartLine + r.LineOffset;

    if ALine < rStartLine then begin
      if FindNextNode and (r.Left = nil) then break;
      r := r.Left; // rStartLine points to r, so if r.Left is nil then it is pointing to the next fold;
      continue;
    end;

    rFoldedBefore := rFoldedBefore + r.LeftCount;
    if ALine < rStartLine + r.MergedLineCount
    then break;

    if FindNextNode and (r.Right = nil) then begin
      r := r.Successor(rStartLine, rFoldedBefore);
      break;
    end;

    rFoldedBefore := rFoldedBefore + r.MergedLineCount;
    r := r.Right; // rStartLine points to r, which now is the start of the previous fold;
  end;

  Result{%H-}.Init(r, rStartLine, rFoldedBefore);
end;

(* Find Fold by Line in Folded Text // always returns unfolded, unless next=true *)
function TSynTextFoldAVLTree.FindFoldForFoldedLine(ALine : Integer;
  FindNextNode : Boolean) : TSynTextFoldAVLNode;
var
  r : TSynTextFoldAVLNodeData;
  rStartLine : Integer;
  rFoldedBefore : Integer;
begin
  r := TSynTextFoldAVLNodeData(fRoot);
  rStartLine := fRootOffset;
  rFoldedBefore := 0;
  while (r <> nil) do begin
    rStartLine := rStartLine + r.LineOffset;

    // r.LeftCount => "FoldedBefore"
    if ALine + r.LeftCount < rStartLine then begin
      if FindNextNode and (r.Left = nil) then break;
      r := r.Left; // rStartLine points to r, so if r.Left is nil then it is pointing to the next fold;
      continue;
    end;

    ALine := ALine + r.LeftCount + r.MergedLineCount;
    rFoldedBefore := rFoldedBefore + r.LeftCount;

    if FindNextNode and (r.Right = nil) then begin
      r := r.Successor(rStartLine, rFoldedBefore);
      break;
    end;

    rFoldedBefore := rFoldedBefore + r.MergedLineCount;
    r := r.Right; // rStartLine points to r, which now is the start of the previous fold;
  end;

  Result{%H-}.Init(r, rStartLine, rFoldedBefore);
end;

procedure TSynTextFoldAVLTree.AdjustForLinesInserted(AStartLine, ALineCount, ABytePos: Integer);
  Procedure DoAdjustForLinesInserted(Current : TSynTextFoldAVLNodeData;
    CurrentLine : Integer);
  var
    t: LongInt;
  begin
    while (Current <> nil) do begin
      CurrentLine := CurrentLine + Current.LineOffset;

      if (AStartLine <= CurrentLine - Current.VisibleLines) or
         ( (AStartLine - 1 = CurrentLine - Current.VisibleLines) and
           (ABytePos <= Current.FoldColumn) )
      then begin
        // move current node
        Current.LineOffset := Current.LineOffset + ALineCount;
        CurrentLine := CurrentLine + ALineCount;
        if Current.Left <> nil then
          Current.Left.LineOffset := Current.Left.LineOffset - ALineCount;
        Current := Current.Left;
      end
      else if AStartLine > CurrentLine + Current.MergedLineCount- 1 then begin
        // The new lines are entirly behind the current node
        Current := Current.Right;
      end
      else begin
        // grow current node (there is only one node one the line, the others are nested)
        // CurrentLine <= AStartLine  <= CurrentLine + Current.FullCount - 1
        t := Current.FullCount;
        if AStartLine <= CurrentLine + t - 1 then
          Current.FullCount := t + ALineCount;
        Current.MergedLineCount:= Current.MergedLineCount+ ALineCount;
        Current.AdjustParentLeftCount(ALineCount);
        TreeForNestedNode(Current, CurrentLine).AdjustForLinesInserted(AStartLine, ALineCount, ABytePos);

        if Current.Right <> nil then // and move entire right
          Current.Right.LineOffset := Current.Right.LineOffset + ALineCount;
        break;
      end;
    end;
  end;

begin
  {$IFDEF SynFoldDebug}debugln(['FOLD-- AdjustForLinesInsertedAStartLine:=', AStartLine, ' ALineCount=',ALineCount, '  ABytePos=',ABytePos ]); {$ENDIF}
  DoAdjustForLinesInserted(TSynTextFoldAVLNodeData(fRoot), fRootOffset);
  AdjustColumn(AStartLine+ALineCount-1, ABytePos, -ABytePos+1, True);
end;

procedure TSynTextFoldAVLTree.AdjustForLinesDeleted(AStartLine,
  ALineCount, ABytePos: Integer);
  Procedure AdjustNodeForLinesDeleted(Current : TSynTextFoldAVLNodeData;
    CurrentLine, FirstLineToDelete, CountLinesToDelete : Integer);
  var
    LastLineToDelete, LinesBefore, LinesInside, LinesAfter, t : Integer;
  begin
    LastLineToDelete := FirstLineToDelete + CountLinesToDelete - 1; // only valid for delete; CountLinesToDelete < 0

    while (Current <> nil) do begin
      CurrentLine := CurrentLine + Current.LineOffset;

      if FirstLineToDelete <= CurrentLine - Current.VisibleLines then begin
        // move current node
        if LastLineToDelete > CurrentLine  - Current.VisibleLines then begin
          // overlap => shrink
          LinesBefore := CurrentLine - FirstLineToDelete;
          LinesInside := CountLinesToDelete - LinesBefore;
          // shrink
          t := Current.MergedLineCount;
          Current.FullCount := Max(Current.FullCount - LinesInside, -1);
          Current.MergedLineCount := Max(Current.MergedLineCount - LinesInside, 0);
          Current.AdjustParentLeftCount(Current.MergedLineCount - t); // If LineCount = -1; LeftCount will be correctd on delete node
          TreeForNestedNode(Current, CurrentLine).AdjustForLinesDeleted(CurrentLine, LinesInside, ABytePos);

          if (Current.Right <> nil) then begin
            // move right // Calculate from the new curent.LineOffset, as below
            AdjustNodeForLinesDeleted(Current.Right, CurrentLine - LinesBefore,
                                      FirstLineToDelete, LinesInside);
          end;
        end
        else LinesBefore := CountLinesToDelete;

        // move current node (includes right subtree / left subtree needs eval)
        Current.LineOffset := Current.LineOffset - LinesBefore;
        CurrentLine := CurrentLine - LinesBefore;
        //if AStartLine = CurrentLine then begin
        //  Current.FoldColumn := Current.FoldColumn + ABytePos-1;
        //  TreeForNestedNode(Current, CurrentLine).AdjustColumn(CurrentLine, 1, ABytePos-1);
        //end;
        if Current.Left <> nil then
          Current.Left.LineOffset := Current.Left.LineOffset + LinesBefore;
        Current := Current.Left;
      end
      else if FirstLineToDelete > CurrentLine + Current.MergedLineCount - 1 then begin
        // The deleted lines are entirly behind the current node
        Current := Current.Right;
      end
      else begin
        // (FirstLineToDelete >= CurrentLine) AND (FirstLineToDelete < CurrentLine + Current.LineCount);
        LinesAfter  := LastLineToDelete - (CurrentLine + Current.MergedLineCount - 1);
        if LinesAfter < 0 then LinesAfter := 0;
        LinesInside := CountLinesToDelete - LinesAfter;

        // shrink current node
        t := Current.MergedLineCount;
        Current.MergedLineCount := Current.MergedLineCount- LinesInside;
        if Current.FullCount > Current.MergedLineCount then
          Current.FullCount := Current.MergedLineCount;
        Current.AdjustParentLeftCount(Current.MergedLineCount - t); // If MergedLineCount = -1; LeftCount will be correctd on delete node

        TreeForNestedNode(Current, CurrentLine).AdjustForLinesDeleted(FirstLineToDelete, LinesInside, ABytePos);
        Current := Current.Right;
      end;

    end;
  end;

begin
  {$IFDEF SynFoldDebug}debugln(['FOLD-- AdjustForLinesDeleted AStartLine:=', AStartLine, ' ALineCount=',ALineCount, '  ABytePos=',ABytePos ]); {$ENDIF}
  if ABytePos > 1 then
    AdjustColumn(AStartLine+ALineCount-1, 1, ABytePos-1);
  AdjustNodeForLinesDeleted(TSynTextFoldAVLNodeData(fRoot), fRootOffset, AStartLine, ALineCount);
end;

procedure TSynTextFoldAVLTree.AdjustColumn(ALine, ABytePos, ACount: Integer;
  InLineBreak: boolean = False);
var
  Node: TSynTextFoldAVLNode;
begin
  Node := FindFoldForLine(ALine, True);
  {$IFDEF SynFoldDebug}debugln(['FOLD-- AdjustColumn ALine:=', ALine, '  ABytePos=',ABytePos, ' ACount=',ACount, ' // node.srcline=',Node.SourceLine, '  StartLine=', node.StartLine, 'column=',Node.FoldColumn ]); {$ENDIF}
  if (not Node.IsInFold) or (Node.SourceLine > ALine) then exit;
  if (Node.SourceLine = ALine) and (node.FoldColumn >= ABytePos) then begin
    node.FoldColumn := Node.FoldColumn + ACount;
    if (not InLineBreak) and (node.FoldColumn < ABytePos) then node.FoldColumn := ABytePos;
  end;
  TreeForNestedNode(Node.fData, node.StartLine).AdjustColumn(ALine, ABytePos, ACount);
end;

function TSynTextFoldAVLTree.FindLastFold : TSynTextFoldAVLNode;
var
  r : TSynTextFoldAVLNodeData;
  rStartLine : Integer;
  rFoldedBefore : Integer;
begin
  r := TSynTextFoldAVLNodeData(fRoot);
  rStartLine := fRootOffset;
  rFoldedBefore := 0;
  while (r <> nil) do begin
    rStartLine := rStartLine + r.LineOffset;
    rFoldedBefore := rFoldedBefore + r.LeftCount + r.MergedLineCount;
    if r.Right = nil then break;
    r := r.Right; // rStartLine points to r, which now is the start of the previous fold;
  end;

  Result{%H-}.Init(r, rStartLine, rFoldedBefore);
end;

function TSynTextFoldAVLTree.FindFirstFold : TSynTextFoldAVLNode;
var
  r : TSynTextFoldAVLNodeData;
  rStartLine : Integer;
begin
  r := TSynTextFoldAVLNodeData(fRoot);
  rStartLine := fRootOffset;
  while (r <> nil) do begin
    rStartLine := rStartLine + r.LineOffset;
    if r.Left = nil then break;
    r := r.Left;
  end;

  Result{%H-}.Init(r, rStartLine, 0);
end;

function TSynTextFoldAVLTree.LastFoldedLine: integer;
var
  n: TSynTextFoldAVLNode;
begin
  n := FindFirstFold;
  if not n.IsInFold then exit(0);
  Result := n.StartLine + n.MergedLineCount - 1;
end;

{$IFDEF SynDebug}
procedure TSynTextFoldAVLTree.debug;
  function debug2(ind, typ : String; ANode, AParent : TSynTextFoldAVLNodeData; offset : integer) :integer;
  begin
    result := 0;
    if ANode = nil then exit;
    with ANode do
      DebugLn([Format('Lines=%3d-%3d (e=%3d / idx=%d) %2d:%d;  Lcnt=%2d / Fcnt=%2d  | ',
                      [offset + ANode.LineOffset, offset + ANode.LineOffset + ANode.FullCount -1,
                       offset + ANode.LineOffset + ANode.MergedLineCount-1, ANode.FoldIndex,
					   ANode.FoldColumn, ANode.FoldColumnLen,
                       MergedLineCount, FullCount]),
               ind, typ, ' (',LineOffset, ')  LeftCount: ', LeftCount,
               '     Balance: ',FBalance]);
    if ANode.Parent <> AParent then DebugLn([ind,'* Bad parent']);
    Result := debug2(ind+'   ', 'L', ANode.Left, ANode, offset+ANode.LineOffset);
    If Result <> ANode.LeftCount then  debugln([ind,'   ***** Leftcount was ',Result, ' but should be ', ANode.LeftCount]);
    Result := Result + debug2(ind+'   ', 'R', ANode.Right, ANode, offset+ANode.LineOffset);
    debug2(ind+'  #', 'N', ANode.Nested, nil, offset+ANode.LineOffset);
    Result := Result + ANode.MergedLineCount;
  end;
begin
  debugln('StartLine, EndLine (MergedEnd, FoldIndex) - Column:Len; MergedLineCnt / FullCCnt | .. (LineOffset) ...');
  debug2('', ' -', TSynTextFoldAVLNodeData(fRoot), nil, 0);
end;
{$ENDIF}

function TSynTextFoldAVLTree.InsertNewFold(ALine, AFoldIndex, AColumn, AColumnLen,
   ACount, AVisibleLines: Integer; AClassification: TFoldNodeClassification;
   AFoldTypeCompatible: Pointer) : TSynTextFoldAVLNode;
var
  r : TSynTextFoldAVLNodeData;
begin
  {$IFDEF SynFoldDebug}debugln(['FOLD-- InsertNewFold ALine:=', ALine, '  AFoldIndex=', AFoldIndex]);{$ENDIF}
  r := NewNode;
  r.LineOffset := ALine; // 1-based
  r.FoldIndex := AFoldIndex;
  r.FoldColumn := AColumn;
  r.FoldColumnLen := AColumnLen;
  r.MergedLineCount := ACount;
  r.FullCount  := ACount;
  r.LeftCount  := 0;
  r.VisibleLines := AVisibleLines;
  r.Classification := AClassification;
  r.FoldTypeCompatible := AFoldTypeCompatible;

  Result{%H-}.Init(r, ALine, 0);
  Result.fFoldedBefore := InsertNode(r);
end;

function TSynTextFoldAVLTree.RemoveFoldForLine(ALine : Integer;
  OnlyCol: Integer = -1) : Integer;
var
  OldFold : TSynTextFoldAVLNode;
  lcount: Integer;
begin
  {$IFDEF SynFoldDebug}debugln(['FOLD-- RemoveFoldForLine ALine:=', ALine, '  OnlyCol=',OnlyCol]);{$ENDIF}
  Result := ALine; // - 1; // Return index
  OldFold := FindFoldForLine(ALine, False);
  if OldFold.StartLine < Result then
    Result := OldFold.StartLine;

  if (not OldFold.IsInFold) then exit;

  if OnlyCol < 0 then
    RemoveFoldForNodeAtLine(OldFold, ALine)
  else
  if OldFold.FoldIndex = OnlyCol then
    RemoveFoldForNodeAtLine(OldFold, -1)
  else
  if OldFold.fData.Nested <> nil then begin
    TreeForNestedNode(OldFold.fData, OldFold.StartLine).RemoveFoldForLine
      (ALine, OnlyCol);
    lcount := max(OldFold.FullCount,
                  TreeForNestedNode(OldFold.fData, 0).LastFoldedLine + 1);
    if lcount <> OldFold.MergedLineCount then begin
      OldFold.fData.MergedLineCount := lcount;
      OldFold.fData.AdjustParentLeftCount(OldFold.MergedLineCount - lcount);
    end;
  end;
end;

function TSynTextFoldAVLTree.RemoveFoldForNodeAtLine(ANode : TSynTextFoldAVLNode;
  ALine : Integer) : Integer;
var
  NestedNode, MergeNode : TSynTextFoldAVLNodeData;
  NestedLine, offs, lcount : Integer;
  OnlyNested: Boolean;
  Nested: TSynTextFoldAVLNode;
begin
  {$IFDEF SynFoldDebug}debugln(['FOLD-- RemoveFoldForNodeAtLine: ALine:=', ALine, ' ANode.StartLine=', ANode.StartLine]);{$ENDIF}
  OnlyNested := ALine >= ANode.StartLine + ANode.FullCount;
  // The cfCollapsed line is one line before the fold
  Result := ANode.StartLine-1;  // Return the cfcollapsed that was unfolded
  if not OnlyNested then
    RemoveNode(ANode.fData);

  NestedLine := 0;
  If ANode.fData.Nested <> nil then
  begin
    (*Todo: should we mark the tree as NO balancing needed ???*)
    TreeForNestedNode(ANode.fData, ANode.StartLine).RemoveFoldForLine(ALine);

    if OnlyNested then begin
      NestedLine := ANode.StartLine + ANode.FullCount;
      Nested := TreeForNestedNode(ANode.fData, ANode.StartLine).FindLastFold;
      while Nested.IsInFold and (Nested.StartLine >= NestedLine) do begin
        NestedNode := Nested.fData;
        offs := Nested.StartLine;
        Nested := Nested.Prev;

        lcount := ANode.fData.MergedLineCount;
        ANode.fData.MergedLineCount := max(ANode.FullCount,
                         Nested.StartLine + Nested.MergedLineCount - ANode.StartLine);
        ANode.fData.AdjustParentLeftCount(ANode.MergedLineCount - lcount);

        TreeForNestedNode(ANode.fData, ANode.StartLine).RemoveNode(NestedNode);
        NestedNode.LineOffset := offs;
        InsertNode(NestedNode);
      end;
      lcount := max(ANode.FullCount,
                TreeForNestedNode(ANode.fData, ANode.StartLine).LastFoldedLine
                - ANode.StartLine + 1);
      if lcount <> ANode.MergedLineCount then begin
        ANode.fData.MergedLineCount := lcount;
        ANode.fData.AdjustParentLeftCount(ANode.MergedLineCount - lcount);
      end;
    end
    else begin
      // merge the remaining nested into current
      NestedNode := ANode.fData.Nested;
      if NestedNode <> nil
      then NestedLine := ANode.fStartLine + NestedNode.LineOffset;

      while NestedNode <> nil do begin
        while NestedNode.Left <> nil do begin
          NestedNode := NestedNode.Left;
          NestedLine := NestedLine + NestedNode.LineOffset;
        end;

        if NestedNode.Right <> nil then begin
          NestedNode := NestedNode.Right;
          NestedLine := NestedLine + NestedNode.LineOffset;
          continue;
        end;

        // leaf node
        // Anything that is still nested (MergeNode.Nested), will stay nested
        MergeNode := NestedNode;

        NestedLine := NestedLine - NestedNode.LineOffset;
        NestedNode := NestedNode.Parent;

        MergeNode.LineOffset := MergeNode.LineOffset + NestedLine;
        if NestedNode <> nil then begin
          NestedNode.ReplaceChild(MergeNode, nil);
          MergeNode.FParent := nil;
        end;
        MergeNode.LeftCount := 0;
        MergeNode.FBalance   := 0;
        if MergeNode.FullCount <= 0 then begin
          MergeNode.FreeAllChildrenAndNested;
          MergeNode.Free;
        end
        else
          InsertNode(MergeNode);
      end;
    end;

  end;

  if not OnlyNested then
    DisposeNode(TSynSizedDifferentialAVLNode(ANode.fData));
end;

function TSynTextFoldAVLTree.InsertNode(ANode : TSynTextFoldAVLNodeData) : Integer;
var
  rStartLine, NestStartLine : Integer;
  rFoldedBefore, NestFoldedBefore : Integer;

  current, Nest : TSynTextFoldAVLNodeData;
  ALine, AEnd, ACount : Integer;

  (* ANode.StartLine < Current.StartLine // ANode goes into tree  *)
  procedure NestCurrentIntoNewBlock; inline;
  var
    diff, start2, before2 : Integer;
    p : TSynTextFoldAVLNodeData;
  begin
    current.AdjustParentLeftCount(ACount-current.MergedLineCount); // -RecursiveFoldCount(current));
    rStartLine := rStartLine - current.LineOffset;  // rStarteLine is now current.Parent
    p := current.Parent;
    if p <> nil
    then p.ReplaceChild(current, ANode, -rStartLine)
    else SetRoot(ANode, -rStartLine);

    diff := current.LineOffset - ANode.LineOffset;
    ANode.Nested  := current;
    ANode.FBalance := current.FBalance;
    current.LineOffset := diff; // offset to ANode (via Nested)
    current.FParent := nil;
    current.FBalance := 0;
    
    ANode.SetLeftChild(current.Left, diff, current.LeftCount);
    current.FLeft := nil;
    current.LeftCount := 0;
    ANode.SetRightChild(current.Right, diff);
    current.FRight := nil;

    start2 := ALine; before2 := rFoldedBefore;
    p := ANode.Successor(start2, before2);
    while (p <> nil) and (start2 <= AEnd) do begin
      RemoveNode(p);
      p.LineOffset := start2- ALine;
      TreeForNestedNode(Anode, 0).InsertNode(p);

      start2 := ALine; before2 := rFoldedBefore;
      p := ANode.Successor(start2, before2);
    end;
    // check only after loop, if we gre, we did so by existing nodes, so no new overlaps
    start2 := TreeForNestedNode(Anode, 0).LastFoldedLine;
    if start2 > ANode.FullCount - 1 then begin
      ANode.AdjustParentLeftCount(start2 + 1 - ANode.MergedLineCount);
      ANode.MergedLineCount := start2 + 1;
    end;
  end;

  (* ANode.StartLine > Current.StartLine // Current remains in tree  *)
  procedure NestNewBlockIntoCurrent; //inline;
  var
    end2, start2, before2: Integer;
    p: TSynTextFoldAVLNodeData;
  begin
    // Check if current.LineCount needs extension
    ANode.LineOffset := ALine - rStartLine;
    if current.Nested <> nil
    then TreeForNestedNode(current, 0).InsertNode(ANode)
    else current.Nested := ANode;

    end2 := TreeForNestedNode(current, 0).LastFoldedLine;
    if end2 > current.FullCount -1 then begin
      end2 := rStartLine + end2;

      start2 := rStartLine; before2 := rFoldedBefore;
      p := current.Successor(start2, before2);
      while (p <> nil) and (start2 <= end2) do begin
        RemoveNode(p);
        p.LineOffset := start2 - rStartLine;
        TreeForNestedNode(current, 0).InsertNode(p);

        start2 := rStartLine; before2 := rFoldedBefore;
        p := current.Successor(start2, before2);
      end;
      end2 := TreeForNestedNode(current, 0).LastFoldedLine;
      if end2 > current.FullCount -1 then begin
        current.AdjustParentLeftCount(end2 + 1 - current.MergedLineCount);
        current.MergedLineCount := end2 + 1;
      end;
    end;
  end;

begin
  Result := 0;
  if fRoot = nil then begin
    SetRoot(ANode, -fRootOffset);
    exit;
  end;
  ALine := ANode.LineOffset;
  ACount := ANode.MergedLineCount;
  AEnd := ALine + ACount - 1;
  current := TSynTextFoldAVLNodeData(fRoot);
  rStartLine := fRootOffset;
  rFoldedBefore := 0;
  Nest := nil;
  NestFoldedBefore := 0;
  NestStartLine := 0;

  while (current <> nil) do begin
    rStartLine := rStartLine + current.LineOffset;
    
    if ALine < rStartLine then begin
      (* *** New block goes to the left *** *)
      // remember possible nesting, continue scan for nesting with precessor
      if (AEnd >= rStartLine) then begin
        Nest := current;
        NestFoldedBefore := rFoldedBefore;
        NestStartLine := rStartLine;
      end;

      if current.Left <> nil Then begin
        current := current.Left;
        continue;
      end
      else if Nest = nil then begin // insert as Left - no nesting
        current.AdjustParentLeftCount(ACount);
        current.SetLeftChild(ANode, -rStartLine, ANode.MergedLineCount);
        BalanceAfterInsert(ANode);
      end
      else begin // nest
        current := Nest;
        rStartLine := NestStartLine;
        rFoldedBefore := NestFoldedBefore;
        NestCurrentIntoNewBlock;
      end;
      break;
    end;

    rFoldedBefore := rFoldedBefore + current.LeftCount;
    if ALine = rStartLine then begin
      if ANode.FoldIndex > current.FoldIndex then
        (* *** New Block will be nested in current *** *)
        NestNewBlockIntoCurrent
      else
      if ANode.FoldIndex < current.FoldIndex then
        (* *** current will be nested in New Block *** *)
        NestCurrentIntoNewBlock
      else begin
        debugln(['Droping Foldnode / Already exists. Startline=', rStartLine,' LineCount=',ACount]);
        FreeAndNil(ANode);
      end;
    end
    else begin
      If ALine <= rStartLine + current.MergedLineCount - 1
      (* *** New Block will be nested in current *** *)
      then NestNewBlockIntoCurrent
      (* *** New block goes to the right *** *)
      else begin
        rFoldedBefore := rFoldedBefore + current.MergedLineCount;
        if current.Right <> nil then begin
          current := current.Right;
          continue;
        end
        else  if Nest=nil then Begin  // insert to the right - no nesting
          current.AdjustParentLeftCount(ACount);
          current.SetRightChild(ANode, -rStartLine);
          BalanceAfterInsert(ANode);
        end
        else begin // nest
          current := Nest;
          rStartLine := NestStartLine;
          rFoldedBefore := NestFoldedBefore;
          NestCurrentIntoNewBlock;
        end;

      end;
    end;
    
    break;
  end; // while

  Result := rFoldedBefore;
end;

function TSynTextFoldAVLTree.TreeForNestedNode(ANode: TSynTextFoldAVLNodeData; aOffset : Integer) : TSynTextFoldAVLTree;
begin
  if fNestedNodesTree = nil then fNestedNodesTree := TSynTextFoldAVLTree.Create;
  Result := fNestedNodesTree;
  Result.fRoot := ANode.Nested;
  Result.fNestParent := ANode; // TODO: this is dangerous, this is never cleaned up, even if ANode is Destroyed
  Result.fRootOffset := aOffset;
end;

constructor TSynTextFoldAVLTree.Create;
begin
  inherited;
  fNestParent := nil;
  fNestedNodesTree := nil;
end;

{ TSynEditFoldProvider }

function TSynEditFoldProvider.GetLineCapabilities(ALineIdx: Integer): TSynEditFoldLineCapabilities;
var
  c: Integer;
begin
  Result := [];
  if not FEnabled then
    exit;
  if (FEdit <> nil) and (FEdit.SelAvail) then begin
    if (FEdit.BlockBegin.Y < ALineIdx+1) and
       (FEdit.BlockEnd.Y  > ALineIdx+1)
    then Result := [cfFoldBody];
    if (FEdit.BlockEnd.Y  = ALineIdx+1) then Result := [cfFoldEnd];
    if (FEdit.BlockBegin.Y = ALineIdx+1) then Result := [cfHideStart];
    if (FEdit.BlockBegin.Y = ALineIdx+1) and
       (FEdit.BlockEnd.Y  = ALineIdx+1) then Result := [cfHideStart, cfSingleLineHide];
  end;
  if (FHighlighter = nil) or (ALineIdx < 0) then
    exit;

  FHighlighter.CurrentLines := FLines;
  if FHighlighter.FoldBlockEndLevel(ALineIdx - 1) > 0 then Result := Result + [cfFoldBody];
  if FHighlighter.FoldBlockClosingCount(ALineIdx) > 0    then Result := Result + [cfFoldEnd, cfFoldBody];

  c := FHighlighter.FoldNodeInfo[ALineIdx].CountEx([]);
  if c > 0 then begin
    c := FHighlighter.FoldNodeInfo[ALineIdx].CountEx([sfaOpenFold, sfaFoldFold]);
    if c > 0 then
      include(Result, cfFoldStart);
    c := FHighlighter.FoldNodeInfo[ALineIdx].CountEx([sfaOpenFold, sfaFoldHide]);
    if c > 0 then
      include(Result, cfHideStart);
    c := FHighlighter.FoldNodeInfo[ALineIdx].CountEx([sfaOneLineOpen, sfaFoldHide]); // TODO: Include scftFoldEnd ?
    // Todo: cfSingleLineHide only, if there is no other hide
    if c > 0 then
      Result := Result + [cfHideStart, cfSingleLineHide];
  end
  else
    if FHighlighter.FoldBlockOpeningCount(ALineIdx) > 0 then include(Result, cfFoldStart);
end;

function TSynEditFoldProvider.GetLineClassification(ALineIdx: Integer): TFoldNodeClassifications;
begin
  Result := [];
  if (FEdit <> nil) and FEdit.SelAvail and (FEdit.BlockBegin.Y = ALineIdx+1) then
    Result := [fncBlockSelection];
end;

function TSynEditFoldProvider.GetNestedFoldsList: TLazSynEditNestedFoldsList;
begin
  if FNestedFoldsList = nil then
    FNestedFoldsList := TLazSynEditNestedFoldsList.Create(FLines, FHighlighter);
  Result := FNestedFoldsList;
end;

function TSynEditFoldProvider.GetFoldsAvailable: Boolean;
begin
  Result := FEnabled and (
              (FHighlighter <> nil) or
              ((FEdit <> nil) and FEdit.SelAvail)
            );
end;

function TSynEditFoldProvider.GetHighLighterWithLines: TSynCustomFoldHighlighter;
begin
  Result := FHighlighter;
  if (Result = nil) then
    exit;
  Result.CurrentLines := FLines;
end;

procedure TSynEditFoldProvider.SetHighLighter(const AValue: TSynCustomFoldHighlighter);
begin
  if FHighlighter = AValue then exit;
  FHighlighter := AValue;
  if FNestedFoldsList <> nil then
    FNestedFoldsList.HighLighter := FHighlighter;
end;

procedure TSynEditFoldProvider.SetLines(AValue: TSynEditStrings);
begin
  if FLines = AValue then Exit;
  FLines := AValue;
  if FNestedFoldsList <> nil then
    FNestedFoldsList.Lines := FLines;
end;

constructor TSynEditFoldProvider.Create;
begin
  FEnabled := True;
  inherited Create;
end;

destructor TSynEditFoldProvider.Destroy;
begin
  inherited Destroy;
  FreeAndNil(FNestedFoldsList);
end;

function TSynEditFoldProvider.FoldOpenCount(ALineIdx: Integer; AType: Integer = 0): Integer;
begin
  if not FEnabled then
    exit(0);

  if (FHighlighter = nil) or (ALineIdx < 0) then begin
    if (AType=0) and (FEdit <> nil) and FEdit.SelAvail and (FEdit.BlockBegin.Y=ALineIdx+1) then exit(1);
    exit(0);
  end;
  // Need to check alll nodes with FoldNodeInfoCount
  // Hide-able nodes can open and close on the same line "(* comment *)"
  FHighlighter.CurrentLines := FLines;
  Result := FHighlighter.FoldNodeInfo[ALineIdx].CountEx([sfaOpenFold, sfaFold], AType);
  // fallback for HL without GetFoldNodeInfoCountEx
  if Result < 0 then
    Result := FHighlighter.FoldBlockOpeningCount(ALineIdx, AType);
  if (AType=0) and (FEdit <> nil) and FEdit.SelAvail and (FEdit.BlockBegin.Y=ALineIdx+1) then
    inc(Result);
end;

function TSynEditFoldProvider.FoldOpenInfo(ALineIdx, AFoldIdx: Integer;
  AType: Integer = 0): TSynFoldNodeInfo;

  function BlockSelInfo(NIdx: Integer): TSynFoldNodeInfo;
  begin
    Result.LineIndex    := ALineIdx;
    Result.NodeIndex    := NIdx;
    Result.LogXStart    := FEdit.BlockBegin.x;
    Result.LogXEnd      := FEdit.BlockBegin.x;
    Result.FoldLvlStart := 0;
    Result.NestLvlStart := 0;
    Result.NestLvlEnd   := 1;
    Result.FoldLvlEnd   := 1;
    Result.FoldAction   := [sfaOpen, sfaOpenFold, sfaFold, sfaFoldHide];
    Result.FoldType           := nil;
    Result.FoldTypeCompatible := nil;
    Result.FoldGroup := -1;
  end;

begin
  Result.FoldAction := [sfaInvalid];
  if (FHighlighter = nil) or (ALineIdx < 0) then begin
    if (AType=0) and (FEdit <> nil) and FEdit.SelAvail and (FEdit.BlockBegin.Y=ALineIdx+1) then
      exit(BlockSelInfo(0));
    exit;
  end;

  FHighlighter.CurrentLines := FLines;
  if (AType = 0) and (FEdit <> nil) and FEdit.SelAvail and
     (FEdit.BlockBegin.Y=ALineIdx+1) and
     (AFoldIdx = FoldOpenCount(ALineIdx, AType)-1)
  then
    Result := BlockSelInfo(AFoldIdx)
  else
    Result := FHighlighter.FoldNodeInfo[ALineIdx].NodeInfoEx(AFoldIdx, [sfaOpen, sfaFold], AType);
end;

function TSynEditFoldProvider.FoldLineLength(ALine, AFoldIndex: Integer): integer;
begin
  if (FEdit <> nil) and FEdit.SelAvail and (FEdit.BlockBegin.Y=ALine+1) and
    (AFoldIndex = FoldOpenCount(ALine, 0)-1)
  then
    exit(FEdit.BlockEnd.y - FEdit.BlockBegin.y);

  FHighlighter.CurrentLines := FLines;
  Result := FHighlighter.FoldLineLength(ALine, AFoldIndex);
end;

function TSynEditFoldProvider.InfoForFoldAtTextIndex(ALine, AFoldIndex: Integer;
  HideLen: Boolean; NeedLen: Boolean = True): TSynEditFoldProviderNodeInfo;
var
  nd: TSynFoldNodeInfo;
begin
  Result.LineCount := 0;
  Result.Column := 0;
  Result.ColumnLen := 0;
  Result.DefaultCollapsed := False;
  Result.Classification := fncInvalid;
  if not FoldsAvailable then
    exit;

  if NeedLen then begin
    Result.LineCount := FoldLineLength(ALine, AFoldIndex);
    if HideLen then
      inc(Result.LineCount);
  end
  else
    Result.LineCount := -1;
  nd := FoldOpenInfo(ALine, AFoldIndex, 0);
  Result.Column := nd.LogXStart+1;
  Result.ColumnLen := nd.LogXEnd - nd.LogXStart;
  Result.DefaultCollapsed := (sfaDefaultCollapsed in nd.FoldAction);
  Result.FoldTypeCompatible := nd.FoldTypeCompatible;
  Result.FoldGroup := nd.FoldGroup;
  if Result.FoldGroup = -1 then
    Result.Classification := fncBlockSelection
  else
    Result.Classification := fncHighlighter;
end;

function TSynEditFoldProvider.InfoListForFoldsAtTextIndex(ALine: Integer;
  NeedLen: Boolean): TSynEditFoldProviderNodeInfoList;
var
  i: Integer;
begin
  i := FoldOpenCount(ALine);
  SetLength(Result, i);
  while i > 0 do begin
    dec(i);
    Result[i] := InfoForFoldAtTextIndex(ALine, i, False, NeedLen);
  end;
end;

{ TSynEditFoldedView }

constructor TSynEditFoldedView.Create(AOwner: TSynEditBase;
  ACaret: TSynEditCaret);
begin
  FOwner := AOwner;
  inherited Create;
  fTopLine := 0;
  fLinesInWindow := -1;
  fCaret := ACaret;
  fCaret.AddChangeHandler(@DoCaretChanged);
  fFoldTree := TSynTextFoldAVLTree.Create;
  FFoldProvider := TSynEditFoldProvider.Create;
  FFoldProvider.FEdit := FOwner;
  // TODO: if NextLineChanges, update FFoldProvider //     DoSynStringsChanged
  FDisplayView := TLazSynDisplayFold.Create(Self);

  FMarkupInfoFoldedCode := TSynSelectedColor.Create;
  FMarkupInfoFoldedCode.Background := clNone;
  FMarkupInfoFoldedCode.Foreground := clDkGray;
  FMarkupInfoFoldedCode.FrameColor := clDkGray;

  FMarkupInfoFoldedCodeLine := TSynSelectedColor.Create;
  FMarkupInfoFoldedCodeLine.Background := clNone;
  FMarkupInfoFoldedCodeLine.Foreground := clNone;
  FMarkupInfoFoldedCodeLine.FrameColor := clNone;

  FMarkupInfoHiddenCodeLine := TSynSelectedColor.Create;
  FMarkupInfoHiddenCodeLine.Background := clNone;
  FMarkupInfoHiddenCodeLine.Foreground := clNone;
  FMarkupInfoHiddenCodeLine.FrameColor := clNone;

  FOwner.RegisterStatusChangedHandler(@DoBlockSelChanged, [scSelection]);
  FOwner.RegisterCommandHandler(@ProcessMySynCommand, nil, [hcfPreExec]);
  FOwner.TextViewsManager.AddTextView(Self);
end;

destructor TSynEditFoldedView.Destroy;
begin
  FOwner.UnregisterCommandHandler(@ProcessMySynCommand);
  NextLines := nil;
  fCaret.RemoveChangeHandler(@DoCaretChanged);
  FreeAndNil(FDisplayView);
  fFoldTree.Free;
  fTextIndexList := nil;
  fFoldTypeList := nil;
  FMarkupInfoFoldedCode.Free;
  FMarkupInfoFoldedCodeLine.Free;
  FMarkupInfoHiddenCodeLine.Free;
  FreeAndNil(FFoldProvider);
  inherited Destroy;
end;

function TSynEditFoldedView.TextToViewIndex(aTextIndex: TLineIdx): TLineIdx;
begin
  aTextIndex := InternTextToViewIndex(aTextIndex);
  Result := inherited TextToViewIndex(aTextIndex);
end;

function TSynEditFoldedView.ViewToTextIndex(aViewIndex: TLineIdx): TLineIdx;
begin
  aViewIndex := inherited ViewToTextIndex(aViewIndex);
  Result := InternViewToTextIndex(aViewIndex);
end;

function TSynEditFoldedView.TextXYToViewXY(APhysTextXY: TPhysPoint): TPhysPoint;
begin
  Result := inherited TextXYToViewXY(APhysTextXY);
  Result.y := ToPos(InternTextToViewIndex(ToIdx(Result.y)));
end;

function TSynEditFoldedView.ViewXYToTextXY(APhysViewXY: TPhysPoint): TPhysPoint;
begin
  APhysViewXY.y := ToPos(InternViewToTextIndex(ToIdx(APhysViewXY.y)));
  Result := inherited ViewXYToTextXY(APhysViewXY);
end;

procedure TSynEditFoldedView.LinesInsertedAtTextIndex(AStartIndex, ALineCount, ABytePos: Integer; SkipFixFolding : Boolean);
var top : Integer;
begin
  if ALineCount = 0 then exit;
  top := TopTextIndex;
  fFoldTree.AdjustForLinesInserted(AStartIndex+1, ALineCount, ABytePos);
  if AStartIndex < top then
    TopTextIndex := top + ALineCount;
  if not(SkipFixFolding) then FixFoldingAtTextIndex(AStartIndex, AStartIndex+ALineCount+1)
  else
  if AStartIndex < top + ALineCount then CalculateMaps;
end;

//procedure TSynEditFoldedView.LinesInsertedAtViewPos(AStartPos, ALineCount : Integer; SkipFixFolding : Boolean);
//begin
//  LinesInsertedAtTextIndex(InternViewToTextIndex(ToIdx(AStartPos)), ALineCount, SkipFixFolding);
//end;

procedure TSynEditFoldedView.LinesDeletedAtTextIndex(AStartIndex, ALineCount, ABytePos: Integer; SkipFixFolding : Boolean);
var top : Integer;
begin
  top := TopTextIndex;
  // topline may get out of sync => synedit is always going to change it back
  fFoldTree.AdjustForLinesDeleted(AStartIndex+1, ALineCount, ABytePos);
  if not(SkipFixFolding) then
    FixFoldingAtTextIndex(AStartIndex, AStartIndex+ALineCount+1)
  else
  if AStartIndex < top - ALineCount then CalculateMaps;
end;

//procedure TSynEditFoldedView.LinesDeletedAtViewPos(AStartPos, ALineCount : Integer; SkipFixFolding : Boolean);
//begin
//  LinesDeletedAtTextIndex(InternViewToTextIndex(ToIdx(AStartPos)), ALineCount, SkipFixFolding);
//end;

function TSynEditFoldedView.InternTextToViewIndex(aTextIndex: TLineIdx): TLineIdx;
var
  n: TSynTextFoldAVLNode;
begin
  n := fFoldTree.FindFoldForLine(aTextIndex + 1);
  if n.IsInFold then
    Result := ToIdx(n.StartLine) - 1 - n.FoldedBefore
  else
    Result := aTextIndex - n.FoldedBefore;
end;

function TSynEditFoldedView.TextIndexToScreenLine(aTextIndex : Integer) : Integer;
begin
  Result := InternTextToViewIndex(aTextIndex) - TopLine + 1;
end;

function TSynEditFoldedView.InternViewToTextIndex(aViewIndex: TLineIdx): TLineIdx;
begin
  result := aViewIndex + fFoldTree.FindFoldForFoldedLine(ToPos(aViewIndex)).FoldedBefore;
end;

function TSynEditFoldedView.ScreenLineToTextIndex(aLine : Integer) : Integer;
begin
  Result := InternViewToTextIndex(aLine + TopLine - 1);
end;

function TSynEditFoldedView.TextIndexAddLines(aTextIndex, LineOffset : Integer) : Integer;
var
  node : TSynTextFoldAVLNode;
  boundary : integer;
begin
  node := fFoldTree.FindFoldForLine(aTextIndex+1, True);
  result := aTextIndex;
  if LineOffset < 0 then begin
    boundary := Max(0, InternViewToTextIndex(0));
    if node.IsInFold
    then node := node.Prev
    else node := fFoldTree.FindLastFold;
    while LineOffset < 0 do begin
      dec(Result);
      if Result <= boundary then exit(boundary);
      while node.IsInFold and (Result+1 < node.StartLine + node.MergedLineCount) do begin
        Result := Result - node.MergedLineCount;
        if Result <= boundary then exit(boundary);
        node := node.Prev;
      end;
      inc(LineOffset);
    end;
  end else begin
    boundary := NextLines.Count;
    while LineOffset > 0 do begin
      if Result >= boundary then exit(boundary);
      inc(Result);
      while node.IsInFold and (Result+1 >= node.StartLine) do begin
        Result := Result + node.MergedLineCount;
        if Result >= boundary then exit(boundary);
        if Result >= boundary then exit(boundary-node.MergedLineCount-1);
        node := node.Next;
      end;
      dec(LineOffset);
    end;
  end;
end;

function TSynEditFoldedView.AddVisibleOffsetToTextIndex(aTextIndex: TLineIdx;
  LineOffset: Integer): TLineIdx;
begin
  //TODO: Modify LineOffset then call inherited;
  Result := TextIndexAddLines(aTextIndex, LineOffset);
//  Result := inherited AddVisibleOffsetToTextIndex(aTextIndex, LineOffset);
end;

function TSynEditFoldedView.IsTextIdxVisible(aTextIndex: TLineIdx): Boolean;
begin
  Result := not FoldedAtTextIndex[aTextIndex];
  if Result then
    Result := inherited IsTextIdxVisible(aTextIndex);
end;

procedure TSynEditFoldedView.Lock;
begin
  if fLockCount=0 then begin
    fNeedFixFrom := -1;
    fNeedFixMinEnd := -1;
  end;
  inc(fLockCount);
end;

procedure TSynEditFoldedView.UnLock;
begin
  dec(fLockCount);
  if (fLockCount=0) then begin
    if (fNeedFixFrom >= 0) then
      FixFolding(fNeedFixFrom, fNeedFixMinEnd, fFoldTree);
    if fvfNeedCaretCheck in FFlags then
      DoCaretChanged(fCaret);
    if fvfNeedCalcMaps in FFlags then
      CalculateMaps;
  end;
end;

(* Count *)
function TSynEditFoldedView.GetViewedCount : integer;
begin
  Result := NextLines.ViewedCount - fFoldTree.FindLastFold.FoldedBefore;
end;

function TSynEditFoldedView.GetDisplayView: TLazSynDisplayView;
begin
  Result := FDisplayView;
end;

procedure TSynEditFoldedView.InternalGetInfoForViewedXY(AViewedXY: TPhysPoint;
  AFlags: TViewedXYInfoFlags; out AViewedXYInfo: TViewedXYInfo;
  ALogPhysConvertor: TSynLogicalPhysicalConvertor);
var
  OldY: LongInt;
begin
  OldY := AViewedXY.y;
  AViewedXY.y := ToPos(InternViewToTextIndex(ToIdx(AViewedXY.y)));
  OldY := OldY - AViewedXY.y;
  inherited InternalGetInfoForViewedXY(AViewedXY, AFlags, AViewedXYInfo,
    ALogPhysConvertor);
  AViewedXYInfo.CorrectedViewedXY.y := AViewedXYInfo.CorrectedViewedXY.y + OldY;
end;

function TSynEditFoldedView.GetFoldClasifications(index : Integer): TFoldNodeClassifications;
begin
  if (index < -1) or (index > fLinesInWindow + 1) then exit([]);
  Result := fFoldTypeList[index+1].Classifications;
end;

function TSynEditFoldedView.GetHighLighter: TSynCustomHighlighter;
begin
  Result := FFoldProvider.HighLighter;
  if assigned(Result) then
    Result.CurrentLines := NextLines;
end;

(* Topline *)
procedure TSynEditFoldedView.SetTopLine(const ALine : integer);
begin
  if fTopLine = ALine then exit;
  FInTopLineChanged := True;
  fTopLine := ALine;
  CalculateMaps;
  FInTopLineChanged := False;
end;

function TSynEditFoldedView.GetTopTextIndex : integer;
begin
  Result := fTopLine + fFoldTree.FindFoldForFoldedLine(fTopLine).FoldedBefore - 1;
end;

procedure TSynEditFoldedView.SetTopTextIndex(const AIndex : integer);
begin
  TopLine := AIndex + 1 - fFoldTree.FindFoldForLine(AIndex+1).FoldedBefore;
end;

(* LinesInWindow*)
procedure TSynEditFoldedView.SetLinesInWindow(const AValue : integer);
begin
  if fLinesInWindow = AValue then exit;
  fLinesInWindow := AValue;
  SetLength(fTextIndexList, AValue + 3);
  SetLength(fFoldTypeList, AValue + 3); // start 1 before topline
  CalculateMaps;
end;

procedure TSynEditFoldedView.DoFoldChanged(AnIndex: Integer);
begin
  SendNotification(senrLineMappingChanged, Self, AnIndex, 0);
end;

procedure TSynEditFoldedView.SetManager(AManager: TSynTextViewsManager);
begin
  if Manager <> nil then begin
    RemoveChangeHandler(senrLineCount, @LineCountChanged);
    RemoveNotifyHandler(senrCleared, @LinesCleared);
    RemoveEditHandler(@LineEdited);
  end;
  inherited SetManager(AManager);
  if Manager <> nil then begin
    AddChangeHandler(senrLineCount, @LineCountChanged);
    AddNotifyHandler(senrCleared, @LinesCleared);
    AddEditHandler(@LineEdited);
  end;
end;

procedure TSynEditFoldedView.SetSynStrings(AValue: TSynEditStrings);
begin
  inherited SetSynStrings(AValue);
  FFoldProvider.FLines := AValue;
end;

procedure TSynEditFoldedView.DoBlockSelChanged(Sender: TObject;
  Changes: TSynStatusChanges);
begin
  CalculateMaps;
end;

procedure TSynEditFoldedView.CalculateMaps;
var
  i, tpos, cnt  : Integer;
  node, tmpnode: TSynTextFoldAVLNode;
  FirstChanged, LastChanged: Integer;
  NewCapability: TSynEditFoldLineCapabilities;
  NewClassifications :TFoldNodeClassifications;
begin
  if fLinesInWindow < 0 then exit;
  if ( (fLockCount > 0) and
       ((not FInTopLineChanged) or (fvfNeedCalcMaps in FFlags)) // TODO: Scan now, to avoid invalidate later
     ) or
     ( (HighLighter <> nil) and HighLighter.NeedScan )
     // TODO: HighLighter.CurrentRanges.NeedsReScanStartIndex < "last line in windows"
  then begin
    assert(fLockCount > 0, 'TSynEditFoldedView.CalculateMaps: fLockCount > 0');
    Include(FFlags, fvfNeedCalcMaps);
    exit;
  end;
  Exclude(FFlags, fvfNeedCalcMaps);

  node := fFoldTree.FindFoldForFoldedLine(fTopLine, true);
  // ftopline is not a folded line
  // so node.FoldedBefore(next node after ftopl) does apply
  tpos  := fTopLine + node.FoldedBefore - 1;
  if node.IsInFold then
    tmpnode := node.Prev
  else
    tmpnode := fFoldTree.FindLastFold;
  if tmpnode.IsInFold and (tmpnode.StartLine + tmpnode.MergedLineCount = tpos + 1) then begin
    node := tmpnode;
    tpos := tpos - node.MergedLineCount;
  end;
  {$IFDEF SynFoldDebug}debugln(['FOLD-- CalculateMaps fTopLine:=', fTopLine, '  tpos=',tpos]);{$ENDIF}
  cnt := NextLines.Count;
  FirstChanged := -1;
  LastChanged := -1;
  for i := 0 to fLinesInWindow + 2 do begin
    if (tpos > cnt) or (tpos < 0) then begin
      // Past end of Text
      fTextIndexList[i] := -1;
      NewCapability := [];
      NewClassifications := [];
    end else begin
      fTextIndexList[i] := tpos - 1; // TextIndex is 0-based
      NewCapability := FFoldProvider.LineCapabilities[tpos - 1];
      NewClassifications := FFoldProvider.LineClassification[tpos - 1];
      if (node.IsInFold) then begin
        if (tpos = node.SourceLine) then begin
          include(NewCapability, cfCollapsedFold);
          include(NewClassifications, node.fData.Classification);
        end
        else if node.IsHide and (tpos + 1 = node.SourceLine) then begin
          include(NewCapability, cfCollapsedHide);
          include(NewClassifications, node.fData.Classification);
        end;
      end;

      inc(tpos);
      while (node.IsInFold) and (tpos >= node.StartLine) do begin
        tpos := tpos + node.MergedLineCount;
        node := node.Next;
      end;
    end;

    if (fFoldTypeList[i].Capability <> NewCapability) or
       (fFoldTypeList[i].Classifications <> NewClassifications)
    then begin
      if FirstChanged < 0 then FirstChanged := tpos - 1;
      LastChanged := tpos;
    end;
    fFoldTypeList[i].Capability := NewCapability;
    fFoldTypeList[i].Classifications := NewClassifications;
  end;
  if (not FInTopLineChanged) and (FirstChanged > 0) then
    FOwner.InvalidateGutterLines(FirstChanged, LastChanged + 1);
end;

(* Lines *)
function TSynEditFoldedView.GetViewedLines(index : Integer) : String;
begin
  if (index < -1) or (index > fLinesInWindow + 1) then
    exit(NextLines.ViewedLines[ScreenLineToTextIndex(Index)]);
  Result := NextLines.ViewedLines[fTextIndexList[index+1]];
end;

function TSynEditFoldedView.GetDisplayNumber(index : Integer) : Integer;
begin
  if (index < -1) or (index > fLinesInWindow + 1)
  or (fTextIndexList[index+1] < 0) then exit(-1);
  Result := fTextIndexList[index+1]+1;
end;

function TSynEditFoldedView.GetTextIndex(index : Integer) : Integer;
begin
  if (index < -1) or (index > fLinesInWindow + 1) then
    exit(ScreenLineToTextIndex(Index));
  Result := fTextIndexList[index+1];
end;

function TSynEditFoldedView.GetFoldType(index : Integer) : TSynEditFoldLineCapabilities;
begin
  if (index < -1) or (index > fLinesInWindow + 1) then exit([]);
  Result := fFoldTypeList[index+1].Capability;
end;

function TSynEditFoldedView.IsFolded(index : integer) : Boolean;
begin
  Result := fFoldTree.FindFoldForLine(index+1).IsInFold;
end;

procedure TSynEditFoldedView.ProcessMySynCommand(Sender: TObject;
  AfterProcessing: boolean; var Handled: boolean;
  var Command: TSynEditorCommand; var AChar: TUTF8Char; Data: pointer;
  HandlerData: pointer);
var
  CY: Integer;
begin
  if Handled then
    exit;

  case Command of
    EcFoldLevel1..EcFoldLevel9:
      begin
        FoldAll(Command - EcFoldLevel1);
        FCaret.Touch;
        Handled := True;
      end;
    EcFoldLevel0:
      begin
        UnfoldAll;
        FCaret.Touch;
        Handled := True;
      end;
    EcFoldCurrent:
      begin
        CY := ExpandedLineForBlockAtLine(FCaret.LinePos);
        if CY > 0 then begin
          FoldAtTextIndex(CY-1);
          FCaret.ChangeOnTouch; // setting the caret always clears selection (even setting to current pos / no change)
          FCaret.LineCharPos:= Point(1, CY);
        end;
        Handled := True;
      end;
    EcUnFoldCurrent:
      begin
        UnFoldAtTextIndex(FCaret.LinePos-1);
        FCaret.Touch;
        Handled := True;
      end;
  end;
end;

procedure TSynEditFoldedView.SetHighLighter(AValue: TSynCustomHighlighter);
begin
  if not(AValue is TSynCustomFoldHighlighter) then
    AValue := nil;
  FFoldProvider.HighLighter := TSynCustomFoldHighlighter(AValue);
  UnfoldAll;
end;

(* Folding *)

procedure TSynEditFoldedView.FoldAtLine(AStartLine : Integer;
  ColIndex : Integer = -1; ColCount : Integer = 1; Skip: Boolean = False;
  AVisibleLines: Integer = 1);
begin
  FoldAtViewPos(AStartLine + fTopLine, ColIndex, ColCount, Skip, AVisibleLines);
end;

procedure TSynEditFoldedView.FoldAtViewPos(AStartPos : Integer;
  ColIndex : Integer = -1; ColCount : Integer = 1; Skip: Boolean = False;
  AVisibleLines: Integer = 1);
begin
  FoldAtTextIndex(AStartPos - 1 + fFoldTree.FindFoldForFoldedLine(AStartPos).FoldedBefore,
                  ColIndex, ColCount, Skip, AVisibleLines);
end;

function TSynEditFoldedView.FoldNodeAtTextIndex(AStartIndex,
  ColIndex: Integer): TSynTextFoldAVLNode;
var
  tree: TSynTextFoldAVLTree;
begin
  Result := fFoldTree.FindFoldForLine(AStartIndex + 1, True);

  tree := fFoldTree;
  while (not Result.IsInFold) or (Result.SourceLine <> AStartIndex + 1) do begin
    if (not Result.IsInFold) then
      Result := tree.FindLastFold;
    while Result.IsInFold and (Result.SourceLine > AStartIndex + 1) do
      Result := Result.Prev;
    if not Result.IsInFold then break;

    if Result.IsInFold and (Result.SourceLine < AStartIndex + 1) then begin
      if Result.fData.Nested = nil then break;
      tree := fFoldTree.TreeForNestedNode(Result.fData, Result.StartLine);
      Result := tree.FindFirstFold;
      while Result.IsInFold and (Result.SourceLine < AStartIndex + 1) do
        Result := Result.Next;
    end
    else
      break;
  end;

  while Result.IsInFold and (Result.SourceLine = AStartIndex + 1) do begin
    if Result.FoldIndex = ColIndex then
      exit;
    if Result.fData.Nested = nil then break;
    Result := fFoldTree.TreeForNestedNode(Result.fData, Result.StartLine).FindFirstFold;
  end;
  Result.fData := nil;
end;

function TSynEditFoldedView.IsFoldedAtTextIndex(AStartIndex, ColIndex: Integer): Boolean;
begin
  Result := FoldNodeAtTextIndex(AStartIndex, ColIndex).IsInFold;
end;

function TSynEditFoldedView.LogicalPosToNodeIndex(AStartIndex: Integer; LogX: Integer;
  Previous: Boolean): Integer;
var
  hl: TSynCustomFoldHighlighter;
  c, i: Integer;
  nd: TSynFoldNodeInfo;
begin
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then
    exit(0);
  // AStartIndex is 0-based
  // FoldTree is 1-based AND first line remains visble
  c := hl.FoldNodeInfo[AStartIndex].CountEx([sfaOpen, sfaFold]);
  if c = 0 then
    exit(-1);
  i := 0;
  while i < c do begin
    nd := hl.FoldNodeInfo[aStartIndex].NodeInfoEx(i, [sfaOpen, sfaFold]);
    if (nd.LogXStart >= LogX) then begin
      dec(i);
      if not Previous then
        i := -1;
      break;
    end;
    if (nd.LogXEnd >= LogX) then
      break;
    inc(i);
  end;
  Result := i;
end;

procedure TSynEditFoldedView.CollapseDefaultFolds;
var
  i, j, c: Integer;
  hl: TSynCustomFoldHighlighter;
  fldinf: TSynEditFoldProviderNodeInfo;
begin
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then
    exit;

  i := 0;
  while i < NextLines.Count do begin
     // Todo: Highlighter should return a list of types that can return default folded
     // Currently PascalHl Type 2 = Region
    c := hl.FoldBlockOpeningCount(i, 2);
    if c > 0 then begin
      c := hl.FoldNodeInfo[i].CountEx([sfaOpen, sfaFold]);
      j := 0;
      while j < c do begin
        fldinf := FoldProvider.InfoForFoldAtTextIndex(i, j);
        if (fldinf.DefaultCollapsed) and (not IsFoldedAtTextIndex(i, j))
        then begin
          // TODO: detect default hide too
          // currently always VisibleLines=1 => since region only folds
          fFoldTree.InsertNewFold(i+2, j, fldinf.Column, fldinf.ColumnLen, fldinf.LineCount, 1,
                                  fldinf.Classification, fldinf.FoldTypeCompatible);
          DoFoldChanged(i);
        end;
      inc(j);
      end;
    end;
    inc(i);
  end;
  CalculateMaps;
end;

function TSynEditFoldedView.GetFoldDescription(AStartIndex, AStartCol, AEndIndex,
  AEndCol: Integer; AsText: Boolean = False; Extended: Boolean = False): String;
var
  FoldCoders: Array of TSynEditFoldExportCoder;

  function FoldCoderForType(AType: Pointer): TSynEditFoldExportCoder;
  var
    i, j: Integer;
  begin
    i := 0;
    j := length(FoldCoders);
    while (i < j) and (FoldCoders[i].FoldType <> AType) do
      inc(i);
    if (i = j) then begin
      SetLength(FoldCoders, i + 1);
      FoldCoders[i] := TSynEditFoldExportCoder.Create(AType);
    end;
    Result := FoldCoders[i];
  end;

var
  hl: TSynCustomFoldHighlighter;
  FoldHelper: TSynEditFoldExportStream;
  NodeIterator: TSynTextFoldAVLNodeNestedIterator;
  NdiHelper1: TSynFoldNodeInfoHelper;
  Node: TSynTextFoldAVLNode;
  NdInfo, NdInfo2: TSynFoldNodeInfo;
  entry: TFoldExportEntry;
  i: Integer;
  NodeFoldType: TSynEditFoldType;
begin
  Result := '';
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then exit;

  if AEndIndex < 0 then AEndIndex := MaxInt;
  if AEndCol   < 0 then AEndCol   := MaxInt;

  Node := fFoldTree.FindFoldForLine(AStartIndex + 1, True);
  NodeIterator := TSynTextFoldAVLNodeNestedIterator.Create(Node);
  FoldHelper := TSynEditFoldExportStream.Create;
  NdiHelper1 := TSynFoldNodeInfoHelper.Create(hl);
  try
    if (AStartCol > 1) then
      while Node.IsInFold and (Node.StartLine = AStartIndex + 2) do begin
        NdInfo := NdiHelper1.GotoNodeOpenPos(Node);
        if (sfaInvalid in NdInfo.FoldAction) or (ndinfo.LogXStart >= AStartCol) then
          break;
        Node := NodeIterator.Next;
      end;
    dec(AStartCol);
    if not node.IsInFold then
      exit;

    (* Text stores fold length according to AVLNode
       Binary stores line-diff between highlighter open and close line
    *)
    if AsText then
    begin           (* *** Encode as Text for XML *** *)
      {$IFDEF SynFoldSaveDebug}
      DebugLnEnter(['TSynEditFoldedView.GetFoldDescription as Text']);
      {$ENDIF}
      while Node.IsInFold and (Node.fData.Classification <> fncHighlighter) do
        Node := NodeIterator.Next;
      if not node.IsInFold then
        exit;

      NdInfo := NdiHelper1.GotoNodeOpenPos(Node);
      while Node.IsInFold and (Node.StartLine-2 <= AEndIndex) do
      begin
        if (node.StartLine > AStartIndex + 2) then AStartCol := 0;

        NodeFoldType := scftFold;
        if Node.SourceLineOffset = 0 then
          NodeFoldType := scftHide;
        if (NdInfo.FoldAction * [sfaInvalid, sfaDefaultCollapsed] = []) then // Currently skip default nodes
          FoldCoderForType(NdInfo.FoldType).AddNode
                     (NdInfo.LogXStart, NdInfo.LineIndex, Node.FullCount, NodeFoldType);

        Node := NodeIterator.Next;
        while Node.IsInFold and (Node.fData.Classification <> fncHighlighter) do
          Node := NodeIterator.Next;
        if not Node.IsInFold then
          break;

        NdInfo := NdiHelper1.Next;
        while NdiHelper1.IsValid and (not NdiHelper1.IsAtNodeOpenPos(Node)) do begin
          // Add unfolded nodes
          if (NdInfo.FoldAction * [sfaInvalid, sfaDefaultCollapsed] = []) then // Currently skip default nodes
            FoldCoderForType(NdInfo.FoldType).AddNode
                                 (NdInfo.LogXStart, NdInfo.LineIndex, 0, scftOpen);
          NdInfo := NdiHelper1.Next;
        end;
      end;

      for i := 0 to length(FoldCoders) - 1 do begin
        FoldCoders[i].Finish;
        FoldHelper.AppendMem(FoldCoders[i].Stream.Mem, FoldCoders[i].Stream.Len);
      end;
      FoldHelper.AddChecksum;
      FoldHelper.Compress;
      {$IFDEF SynFoldSaveDebug}
      DebugLnExit(['TSynEditFoldedView.GetFoldDescription as Text']);
      {$ENDIF}
    end             (* *** END: Encode as Text for XML *** *)
    else
    begin           (* *** Encode as Binary *** *)
      while Node.IsInFold and (Node.StartLine-2 <= AEndIndex) do
      begin
        if (node.StartLine > AStartIndex + 2) then
          AStartCol := 0;

        NdInfo2 := NdiHelper1.GotoNodeClosePos(Node);
        if (sfaInvalid in NdInfo2.FoldAction) or
           (NdInfo2.LineIndex > AEndIndex) or
           ((NdInfo2.LineIndex = AEndIndex) and (ndinfo2.LogXEnd > AEndCol))
        then begin
          node := NodeIterator.Next;
          continue;
        end;

        NdInfo := NdiHelper1.GotoNodeOpenPos(Node);

        with entry do begin
          LogX   := NdInfo.LogXStart - AStartCol;
          LogX2  := NdInfo.LogXEnd - ndinfo.LogXStart + (ndinfo.LogXStart - AStartCol);
          Line   := NdInfo.LineIndex - AStartIndex;
          ELogX  := NdInfo2.LogXStart;
          ELogX2 := NdInfo2.LogXEnd;
          ELine  := NdInfo2.LineIndex - AStartIndex;
          //if sfaLastLineClose in NdInfo2.FoldAction then
          //  ELine := -1; // unfinished fold
          FType  := PtrUInt(NdInfo.FoldType);
          LinesFolded := node.FullCount;
        end;
        FoldHelper.AppendMem(@entry, SizeOf(TFoldExportEntry));

        Node := NodeIterator.Next;
      end;
    end;            (* *** END: Encode as Binary *** *)

    Result := FoldHelper.Text;
  finally
    FoldHelper.Free;
    for i := 0 to length(FoldCoders) - 1 do
      FoldCoders[i].Free;
    NodeIterator.Free;
    NdiHelper1.Free;
  end;
end;

procedure TSynEditFoldedView.ApplyFoldDescription(AStartIndex, AStartCol, AEndIndex,
  AEndCol: Integer; FoldDesc: PChar; FoldDescLen: Integer; IsText: Boolean = False);
var
  FoldCoders: Array of TSynEditFoldExportCoder;

  function FoldCoderForType(AType: Pointer): TSynEditFoldExportCoder;
  var
    j: Integer;
  begin
    j := length(FoldCoders) - 1;
    while (j >= 0) and (FoldCoders[j] <> nil) and (FoldCoders[j].FoldType <> AType) do
      dec(j);
    if (j < 0) then
      Result := nil
    else
      Result := FoldCoders[j];
  end;

  procedure RemoveCoderForType(AType: Pointer);
  var
    j: Integer;
  begin
    j := length(FoldCoders) - 1;
    while (j >= 0) and (FoldCoders[j] <> nil) and (FoldCoders[j].FoldType <> AType) do
      dec(j);
    if (j >= 0) then begin
      debugln(['FoldState loading removed data for foldtype: ', PtrUInt(AType)]);
      FreeAndNil(FoldCoders[j]);
    end;
  end;


var
  hl: TSynCustomFoldHighlighter;
  FoldHelper: TSynEditFoldExportStream;
  NdiHelper1: TSynFoldNodeInfoHelper;
  NdInfo, ndinfo2: TSynFoldNodeInfo;
  i: Integer;
  Line, FL: Integer;
  entry: TFoldExportEntry;
  Coder: TSynEditFoldExportCoder;
  IsFold, IsHide: Boolean;
begin
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then
    exit;
  if (FoldDesc = nil) or (FoldDescLen = 0) then exit;

  NdiHelper1 := TSynFoldNodeInfoHelper.Create(hl);
  FoldHelper := TSynEditFoldExportStream.Create;
  try
    FoldHelper.Mem := FoldDesc;
    FoldHelper.Len := FoldDescLen;

    if IsText then
    begin           (* *** Decode from Text for XML *** *)
      try
        FoldHelper.Decompress;
      except
        exit;
      end;
      if not FoldHelper.VerifyChecksum then
        exit; //raise ESynEditError.Create('fold checksum error');

      i := 0;
      while not FoldHelper.EOF do begin
        SetLength(FoldCoders, i + 1);
        FoldCoders[i] := TSynEditFoldExportCoder.Create(FoldHelper);
        if not FoldCoders[i].ReadIsValid then
          break;
        inc(i);
      end;

      NdInfo := NdiHelper1.FirstOpen;

      while NdiHelper1.IsValid do begin
        if (sfaDefaultCollapsed in NdInfo.FoldAction) then begin // Currently skip default nodes
          NdInfo := NdiHelper1.Next;
          continue;
        end;
        Coder := FoldCoderForType(NdInfo.FoldType);
        if coder <> nil then begin
          i := FoldProvider.InfoForFoldAtTextIndex(NdInfo.LineIndex, NdInfo.NodeIndex).LineCount;
          case coder.ReadNode(NdInfo.LogXStart, NdInfo.LineIndex, i) of
            scftFold:  FoldAtTextIndex(NdInfo.LineIndex, NdInfo.NodeIndex);
            scftHide:  FoldAtTextIndex(NdInfo.LineIndex, NdInfo.NodeIndex, 1, False, 0);
            scftInvalid: RemoveCoderForType(NdInfo.FoldType);
          end;
        end;
        NdInfo := NdiHelper1.Next;
      end;
    end             (* *** END: Encode as Text for XML *** *)
    else
    begin           (* *** Decode from Binary *** *)
      entry.Line := 0;
      if AStartCol > 0 then
        dec(AStartCol);
      while not FoldHelper.EOF do begin
        if not FoldHelper.ReadMem(@entry, sizeof(TFoldExportEntry)) then
          break;
        if entry.Line > 0 then AStartCol := 0;

        Line := AStartIndex + entry.Line;
        if Line >= NextLines.Count then
          continue;

        ndinfo :=NdiHelper1.GotoOpenAtChar(Line, entry.LogX);
        Fl := FoldProvider.InfoForFoldAtTextIndex(Line, ndinfo.NodeIndex).LineCount;
        IsFold := (sfaFoldFold in NdInfo.FoldAction) and (entry.LinesFolded = FL);
        IsHide := (sfaFoldHide in NdInfo.FoldAction) and (entry.LinesFolded = FL + 1);
        if (sfaInvalid in ndinfo.FoldAction) or
           (ndinfo.LogXStart <> entry.LogX + AStartCol) or
           (ndinfo.LogXEnd <> entry.LogX2 + AStartCol)  or
           //(ndinfo.FoldType <> entry.FType) or
           (not (IsHide or IsFold))
        then
          continue;

        ndinfo2 := NdiHelper1.FindClose;
        if (sfaInvalid in ndinfo2.FoldAction) or
           (ndinfo2.LogXStart <> entry.ELogX) or
           (ndinfo2.LogXEnd <> entry.ELogX2)
        then
          continue;

        i := 1;
        if IsHide then i := 0;;
        FoldAtTextIndex(Line, NdInfo.NodeIndex, 1, False, i);
      end;
    end;            (* *** END: Encode as Binary *** *)
  finally
    for i := 0 to length(FoldCoders) - 1 do
      FoldCoders[i].Free;
    FreeAndNil(FoldHelper);
    FreeAndNil(NdiHelper1);
  end;
end;

procedure TSynEditFoldedView.FoldAtTextIndex(AStartIndex : Integer;
  ColIndex : Integer = -1; ColCount : Integer = 1; Skip: Boolean = False;
  AVisibleLines: Integer = 1);
var
  NodeCount, top: Integer;
  down: Boolean;
  NFolded: TSynTextFoldAVLNode;
  IsHide: Boolean;
  fldinf: TSynEditFoldProviderNodeInfo;
begin
  if not FoldProvider.FoldsAvailable then exit;
  top := TopTextIndex;

  // AStartIndex is 0-based
  // FoldTree is 1-based AND first line remains visble
  NodeCount := FoldProvider.FoldOpenCount(AStartIndex);
  if ColCount = 0 then
    ColCount := NodeCount;

  down := ColIndex < 0;
  if down then
    ColIndex := NodeCount + ColIndex;

  IsHide := AVisibleLines = 0;

  while ColCount > 0 do begin
    if (ColIndex < 0) or (ColIndex >= NodeCount) then break;
    NFolded := FoldNodeAtTextIndex(AStartIndex, ColIndex);
    // TODO: Check if position can Hide or fold
    if skip and (   ( (AVisibleLines=0) and NFolded.IsHide  ) or
                    ( (AVisibleLines>0) and NFolded.IsInFold  )   )
    then begin
      if down
      then dec(ColIndex)
      else inc(ColIndex);
      continue;
    end;

    // TODO: missing check, that hl-node is hideable
    fldinf := FoldProvider.InfoForFoldAtTextIndex(AStartIndex, ColIndex, IsHide);
    if not NFolded.IsInFold then begin
      if fldinf.LineCount > 0 then
        fFoldTree.InsertNewFold(AStartIndex+1+AVisibleLines, ColIndex,
                                fldinf.Column, fldinf.ColumnLen, fldinf.LineCount,
                                AVisibleLines,
                                fldinf.Classification, fldinf.FoldTypeCompatible)
    end
    else begin
      if (AVisibleLines=0) and (not NFolded.IsHide) and (fldinf.LineCount > 0) then begin
        // upgrade to hide
        fFoldTree.RemoveFoldForNodeAtLine(NFolded, -1);
        fFoldTree.InsertNewFold(AStartIndex+1, ColIndex,
                                fldinf.Column, fldinf.ColumnLen, fldinf.LineCount,
                                AVisibleLines,
                                fldinf.Classification, fldinf.FoldTypeCompatible);
      end;
    end;
    if down
    then dec(ColIndex)
    else inc(ColIndex);
    dec(ColCount);
  end;

  fTopLine := -1;  // make sure seting TopLineTextIndex, will do CalculateMaps;
  TopTextIndex := top;
  DoFoldChanged(AStartIndex);
end;

procedure TSynEditFoldedView.UnFoldAtLine(AStartLine : Integer;
  ColIndex : Integer = -1; ColCount : Integer = 0; Skip: Boolean = False;
  AVisibleLines: Integer = 1);
begin
  UnFoldAtViewPos(AStartLine + fTopLine, ColIndex, ColCount, Skip, AVisibleLines);
end;

procedure TSynEditFoldedView.UnFoldAtViewPos(AStartPos : Integer;
  ColIndex : Integer = -1; ColCount : Integer = 0; Skip: Boolean = False;
  AVisibleLines: Integer = 1);
begin
  UnFoldAtTextIndex(AStartPos - 1 + fFoldTree.FindFoldForFoldedLine(AStartPos).FoldedBefore,
                    ColIndex, ColCount, Skip, AVisibleLines);
end;

procedure TSynEditFoldedView.UnFoldAtTextIndex(AStartIndex : Integer;
  ColIndex : Integer = -1; ColCount : Integer = 0; Skip: Boolean = False;
  AVisibleLines: Integer = 1);
var
  top, c, r, r2 : Integer;
  down: Boolean;
  NFolded: TSynTextFoldAVLNode;
begin
  top := TopTextIndex;
  c := FoldProvider.FoldOpenCount(AStartIndex);

  //TODO move to FoldProvider
  NFolded := fFoldTree.FindFoldForLine(AStartIndex+1, True);
  while NFolded.IsInFold and (NFolded.StartLine = AStartIndex+1) do begin
    if NFolded.FoldIndex + 1 > c then c := NFolded.FoldIndex + 1;
    NFolded := fFoldTree.TreeForNestedNode(NFolded.fData, NFolded.StartLine).FindFoldForLine(AStartIndex, True);
  end;

  if c < 1 then begin
    // TODO: foldprovider to return all folded nodes, for hte line
    ColCount := 0;
  end;

  r := -1;
  if ColCount = 0 then begin
    r := fFoldTree.RemoveFoldForLine(AStartIndex+AVisibleLines+1); // r is 1-based num of first (ex-)hidden line
  end
  else begin
    down := ColIndex < 0;
    if down then
      ColIndex := c + ColIndex ;
    while ColCount > 0 do begin
      if (ColIndex < 0) or (ColIndex >= c) then break;
      NFolded := FoldNodeAtTextIndex(AStartIndex, ColIndex);
      if skip and (   ( (AVisibleLines=0) and not NFolded.IsHide  ) or
                      ( (AVisibleLines>0) and not NFolded.IsInFold  )   )
      then begin
        if down
        then dec(ColIndex)
        else inc(ColIndex);
        continue;
      end;
      r2 := fFoldTree.RemoveFoldForLine(AStartIndex+1+AVisibleLines, ColIndex);
      if r2 > 0 then dec(r2);
      if (r < 0) or (r2 < r) then r := r2;
      if down
      then dec(ColIndex)
      else inc(ColIndex);
      dec(ColCount);
    end;
  end;

  fTopLine := -1;  // make sure seting TopLineTextIndex, will do CalculateMaps;
  TopTextIndex := top;
  if (r >= 0) then
    DoFoldChanged(Max(0, r - 2));
end;

procedure TSynEditFoldedView.UnFoldAtTextIndexCollapsed(AStartIndex: Integer);
var
  top, r: Integer;
begin
  top := TopTextIndex;
  r := fFoldTree.RemoveFoldForLine(AStartIndex+1) - 1;
  fTopLine := -1;  // make sure seting TopLineTextIndex, will do CalculateMaps;
  TopTextIndex := top;
  DoFoldChanged(r);
end;

procedure TSynEditFoldedView.UnfoldAll;
var
  top : Integer;
begin
  top := TopTextIndex;
  fFoldTree.Clear;
  fTopLine := -1;  // make sure seting TopLineTextIndex, will do CalculateMaps;
  TopTextIndex := top;
  DoFoldChanged(0);
end;

procedure TSynEditFoldedView.FoldAll(StartLevel : Integer = 0; IgnoreNested : Boolean = False);
var
  c, i, top, t: Integer;
  hl: TSynCustomFoldHighlighter;
  fldinf: TSynEditFoldProviderNodeInfo;
begin
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then
    exit;

  t := 1; // TODO: Highlighter default type; or iterate through all types
  top := TopTextIndex;
  fFoldTree.Clear;
  i := 0;
  while i < NextLines.Count do begin
    if (hl.FoldBlockOpeningCount(i, t) > 0)
    and (hl.FoldBlockEndLevel(i, t) > StartLevel) then begin
      c := hl.FoldBlockOpeningCount(i) -1;
      fldinf := FoldProvider.InfoForFoldAtTextIndex(i, c);
      // i is 0-based
      // FoldTree is 1-based AND first line remains visble
      fFoldTree.InsertNewFold(i+2, c, fldinf.Column, fldinf.ColumnLen, fldinf.LineCount, 1,
                              fldinf.Classification, fldinf.FoldTypeCompatible); // TODO: hide too? currently VisibleLines=1
      if IgnoreNested then
        i := i + fldinf.LineCount;
    end;
    inc(i);
  end;
  fTopLine := -1;
  TopTextIndex := top;
  DoFoldChanged(0);
end;

function TSynEditFoldedView.FixFolding(AStart: Integer; AMinEnd: Integer;
  aFoldTree: TSynTextFoldAVLTree): Boolean;
var
  FirstchangedLine, MaxCol: Integer;
  SrcLineForFldInfos: Integer;
  FldInfos: TSynEditFoldProviderNodeInfoList;

  function DoFixFolding(doStart: Integer; doMinEnd, AtColumn: Integer;
    doFoldTree: TSynTextFoldAVLTree; node: TSynTextFoldAVLNode) : Boolean;

    Procedure DoRemoveNode(var theNode: TSynTextFoldAVLNode);
    var
      tmpnode: TSynTextFoldAVLNode;
      l: Integer;
    begin
      Result := True;
      tmpnode := theNode.Prev;
      l := theNode.SourceLine;
      doFoldTree.RemoveFoldForNodeAtLine(theNode, -1); // Don't touch any nested node
      if tmpnode.IsInFold then theNode := tmpnode.Next
      else theNode := doFoldTree.FindFirstFold;
      if (FirstchangedLine < 0) or (l < FirstchangedLine) then
        FirstchangedLine := l;
    end;

  var
    FldSrcLine, FldSrcIndex, FLdNodeLine, FldLen, FndLen: Integer;
    i, j, CurLen: Integer;
    SubTree: TSynTextFoldAVLTree;
  begin
    {$IFDEF SynFoldDebug}try DebugLnEnter(['>>FOLD-- DoFixFolding: doStart=', doStart, '  AMinEnd=',AMinEnd]);{$ENDIF}
    {$IFDEF SynFoldDebug}aFoldTree.Debug;{$ENDIF}
    Result := False;
    FldSrcLine := doStart;
    while node.IsInFold do begin
      {$IFDEF SynFoldDebug}debugln(['>>FOLD-- Node StartLine=', node.StartLine, ' FoldColumn=', node.FoldColumn, ' FoldIndex=', node.FoldIndex, ' FullCount=', node.FullCount, ' Classification=', dbgs(node.Classification)]);{$ENDIF}
      FldSrcLine := node.SourceLine; // the 1-based cfCollapsed (last visible) Line (or 1st hidden)
      FLdNodeLine := node.StartLine; // the 1 based, first hidden line
      FldSrcIndex := FldSrcLine - 1;
      FldLen := node.FullCount;
      if (FldLen <= 0) then begin
        {$IFDEF SynFoldDebug}debugln(['>>FOLD-- FixFolding: Remove node with len<0 FldSrcLine=', FldSrcLine]);{$ENDIF}
        DoRemoveNode(node);
        continue;
      end;

      //{$IFDEF SynAssertFold}
      //With mixed fold/hide => line goes up/down
      //SynAssert(FldSrcLine >= SrcLineForFldInfos, 'TSynEditFoldedView.FixFolding: FoldLine went backwards now %d was %d', [FldSrcLine, SrcLineForFldInfos]);
      //{$ENDIF}
      if (FldSrcLine <> SrcLineForFldInfos) then begin
        // Next Line
        SrcLineForFldInfos := FldSrcLine;
        AtColumn := 0;
                  // AtColumn is used for nodes, behing the HLs index-range (fncHighlighterEx, fncBlockSelection)
                  // TODO: At Colum may be wrong for mixed fold/hide
        FldInfos := FoldProvider.InfoListForFoldsAtTextIndex(FldSrcIndex, False);
        MaxCol := length(FldInfos)-1;
        {$IFDEF SynFoldDebug}debugln(['>>FOLD-- Got FldInfos for FldSrcIndex=', FldSrcIndex, ' MaxCol=', MaxCol]);{$ENDIF}
      end;

      if node.fData.Classification in [fncHighlighter, fncHighlighterEx] then begin
        // find node in list
        i := -1;
        while (i < MaxCol) do begin
          inc(i);
          if (FldInfos[i].Classification <> fncHighlighter) or
             (FldInfos[i].FoldTypeCompatible <> node.fData.FoldTypeCompatible)
          then
            continue;
          FndLen := -1;
          j := abs(FldInfos[i].Column - node.FoldColumn);
          if (j > 0) and (j < node.FoldColumnLen) then begin
            //maybe
            FndLen := FoldProvider.FoldLineLength(FldSrcIndex, i);
            if node.IsHide then inc(FndLen);
            if FndLen <> node.FullCount then Continue;
            {$IFDEF SynFoldDebug}debugln('******** FixFolding: Adjusting x pos');{$ENDIF}
            //FldInfos[i].Column := node.FoldColumn;
          end;
          if (FndLen > 0) or (FldInfos[i].Column = node.FoldColumn) then begin
            if FndLen < 0 then begin
              FndLen := FoldProvider.FoldLineLength(FldSrcIndex, i);
              if node.IsHide then inc(FndLen);
            end;
            if abs(FndLen - node.FullCount) > 1 then continue;
            if (node.fData.Classification <> fncHighlighter) or
               (node.FoldColumn <> FldInfos[i].Column) or
               (node.FoldIndex <> i)
            then
              Result := true;
            {$IFDEF SynFoldDebug}if (node.fData.Classification <> fncHighlighter) then debugln(['>>FOLD-- FixFolding: set Node to fncHighlighter (FOUND) FldSrcLine=', FldSrcLine]);{$ENDIF}
            node.fData.Classification :=  fncHighlighter;
            node.FoldColumn := FldInfos[i].Column;
            node.fData.FoldIndex := i;
            i := -1;
            break;
          end;
        end;
        if i = MaxCol then begin
          {$IFDEF SynFoldDebug}debugln(['>>FOLD-- FixFolding: set Node to fncHighlighterEx (NOT FOUND) FldSrcLine=', FldSrcLine]);{$ENDIF}
          node.fData.Classification :=  fncHighlighterEx;
          node.fData.FoldIndex := MaxCol + AtColumn;
          inc(AtColumn);
          Result := True;
        end;
      end
      else begin
        if node.fData.FoldIndex <> MaxCol + AtColumn then
          Result := True;
        node.fData.FoldIndex := MaxCol + AtColumn;
        inc(AtColumn);
      end;

      if (node.fData.Nested <> nil) then begin
        SubTree := doFoldTree.TreeForNestedNode(node.fData, FLdNodeLine);
        CurLen := node.MergedLineCount;
        if DoFixFolding(FldSrcLine, FLdNodeLine + CurLen, AtColumn, SubTree, SubTree.FindFirstFold)
        then begin
          if CurLen > FldLen then begin
            node.fData.MergedLineCount:= max(node.FullCount,
              doFoldTree.TreeForNestedNode(node.fData, 0).LastFoldedLine + 1);
            if CurLen <> node.MergedLineCount then
              node.fData.AdjustParentLeftCount(node.MergedLineCount - CurLen);
          end;
        end;
      end;

      // the node was ok
      if node.StartLine >= doMinEnd then break;
      node := node.Next;
    end;
    {$IFDEF SynFoldDebug}finally DebugLnExit(['<<FOLD-- DoFixFolding: DONE=', Result]); end{$ENDIF}
  end;

var
  node, tmpnode: TSynTextFoldAVLNode;
begin
  {$IFDEF SynFoldDebug}try DebugLnEnter(['>>FOLD-- FixFolding: Start=', AStart, '  AMinEnd=',AMinEnd]);{$ENDIF}
  Result := false;
  if fLockCount > 0 then begin
    Include(FFlags, fvfNeedCaretCheck);
    if fNeedFixFrom < 0 then fNeedFixFrom := AStart
    else fNeedFixFrom := Min(fNeedFixFrom, AStart);
    fNeedFixMinEnd := Max(fNeedFixMinEnd, AMinEnd);
    exit;
  end;

  node := aFoldTree.FindFoldForLine(aStart, true);
  if not node.IsInFold then node:= aFoldTree.FindLastFold;
  if not node.IsInFold then begin
    CalculateMaps;
    exit;
  end;
  If aMinEnd < node.StartLine then aMinEnd := node.StartLine; // XXX SourceLine

  // FullCount is allowed to be -1
  while node.IsInFold and (node.StartLine + node.FullCount + 1 >= aStart) do begin
    tmpnode := node.Prev;
    if tmpnode.IsInFold
    then node := tmpnode
    else break; // first node
  end;

  FirstchangedLine := -1;
  FldInfos := nil;
  MaxCol := -1;
  SrcLineForFldInfos := -1;
  Result := DoFixFolding(-1, AMinEnd, 0, aFoldTree, node);
  CalculateMaps;
  if (FirstchangedLine >= 0) then
    DoFoldChanged(FirstchangedLine);
  {$IFDEF SynFoldDebug}finally DebugLnExit(['<<FOLD-- FixFolding: DONE=', Result]); end{$ENDIF}
end;

procedure TSynEditFoldedView.DoCaretChanged(Sender : TObject);
var
  i: Integer;
begin
  if fLockCount > 0 then begin
    Include(FFlags, fvfNeedCaretCheck);
    exit;
  end;
  Exclude(FFlags, fvfNeedCaretCheck);
  i := TSynEditCaret(Sender).LinePos-1;
  {$IFDEF SynFoldDebug}if FoldedAtTextIndex[i] then debugln(['FOLD-- DoCaretChanged  about to unfold at Index=', i]);{$ENDIF}
  if FoldedAtTextIndex[i] then
    UnFoldAtTextIndexCollapsed(i);
end;

procedure TSynEditFoldedView.LineCountChanged(Sender: TSynEditStrings; AIndex, ACount : Integer);
begin
  {$IFDEF SynFoldDebug}try DebugLnEnter(['>> FOLD-- LineCountChanged AIndex=', AIndex, '  Acount=',ACount]);{$ENDIF}
  // no need for fix folding => synedit will be called, and scanlines will call fixfolding
  {TODO: a "need fix folding" flag => to ensure it will be called if synedit doesnt
         SynEdit.ScanRanges, calls Fixfolding as workaroound => review
  }
  if (fLockCount > 0) and (AIndex < max(fNeedFixFrom, fNeedFixMinEnd)) then begin
    // adapt the fixfold range. Could be done smarter, but it doesn't matter if the range gets bigger than needed.
    if (ACount < 0) and (AIndex < fNeedFixFrom) then inc(fNeedFixFrom, ACount);
    if (ACount > 0) and (AIndex < fNeedFixMinEnd) then inc(fNeedFixMinEnd, ACount);
  end;
  if NextLines.IsInEditAction then exit;
  if ACount<0
  then LinesDeletedAtTextIndex(AIndex+1, -ACount, 1, true)
  else LinesInsertedAtTextIndex(AIndex+1, ACount, 1, true);
  {$IFDEF SynFoldDebug}finally DebugLnExit(['<< FOLD-- LineCountChanged']); end;{$ENDIF}
end;

procedure TSynEditFoldedView.LinesCleared(Sender: TObject);
begin
  UnfoldAll;
end;

procedure TSynEditFoldedView.LineEdited(Sender: TSynEditStrings; aLinePos, aBytePos, aCount,
  aLineBrkCnt: Integer; aText: String);
begin
  {$IFDEF SynFoldDebug}try DebugLnEnter(['>> FOLD-- LineEditied aLinePos=', aLinePos, ' aBytePos=', aBytePos, '  Acount=',ACount, ' aLineBrkCnt=',aLineBrkCnt]);{$ENDIF}
  if aLineBrkCnt<0
  then LinesDeletedAtTextIndex(aLinePos, -aLineBrkCnt, ABytePos, true)
  else if aLineBrkCnt > 0
  then LinesInsertedAtTextIndex(aLinePos, aLineBrkCnt, ABytePos, true)
  else begin
    fFoldTree.AdjustColumn(aLinePos, aBytePos, aCount);
    //if not(SkipFixFolding) then FixFoldingAtTextIndex(AStartIndex, AStartIndex+ALineCount+1)
    //else
    //if aLinePos < top + ALineCount then CalculateMaps;
  end;
  {$IFDEF SynFoldDebug}finally DebugLnExit(['<< FOLD-- LineEditied']); end;{$ENDIF}
end;

procedure TSynEditFoldedView.FixFoldingAtTextIndex(AStartIndex: Integer; AMinEndLine : Integer);
begin
  FixFolding(AStartIndex + 1, AMinEndLine, fFoldTree);
end;

function TSynEditFoldedView.OpenFoldCount(aStartIndex: Integer; AType: Integer = 0): Integer;
// Todo: move entirely to FoldProvider
var
  hl: TSynCustomFoldHighlighter;
begin
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then
    exit(-1);
  Result := hl.FoldBlockEndLevel(AStartIndex-1, AType) + FoldProvider.FoldOpenCount(AStartIndex);
end;

function TSynEditFoldedView.OpenFoldInfo(aStartIndex, ColIndex: Integer; AType: Integer = 0): TFoldViewNodeInfo;
var
  hl: TSynCustomFoldHighlighter;
  TypeCnt, Lvl: Integer;
  EndLvl, CurLvl: Array of integer;
  i, c, t, n, o: Integer;
  nd: TSynFoldNodeInfo;
  FN: TSynTextFoldAVLNode;

  procedure GetEndLvl(l: Integer);
  var i: integer;
  begin
    if AType = 0 then begin;
      for i := 1 to TypeCnt do begin
        EndLvl[i] := hl.FoldBlockEndLevel(l-1, i);
        EndLvl[i] := EndLvl[i] + FoldProvider.FoldOpenCount(l, i);
        CurLvl[i] := EndLvl[i];
      end;
    end
    else begin
      EndLvl[0] := hl.FoldBlockEndLevel(l-1, AType);
      EndLvl[0] := EndLvl[0] + FoldProvider.FoldOpenCount(l, AType);
      CurLvl[0] := EndLvl[0];
    end;
  end;

begin
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then
    exit;  // ToDo: Initialize Result

  nd.LogXStart := 0;
  nd.LogXEnd := 0;
  nd.FoldAction := [];
  nd.FoldType := Nil;
  nd.FoldGroup := 0;
  n := 0;
  if AType <> 0 then
    TypeCnt := 1
  else
    TypeCnt := hl.FoldTypeCount;
  Lvl := hl.FoldBlockEndLevel(AStartIndex-1, AType);
  if ColIndex >= Lvl then begin
    n := ColIndex - Lvl;
    if AType = 0 then begin
      o :=  hl.FoldNodeInfo[aStartIndex].CountEx([sfaOpen, sfaFold]);
      nd := hl.FoldNodeInfo[aStartIndex].NodeInfoEx(n, [sfaOpen, sfaFold]);
    end else begin
      // no sfaFold
      o :=  hl.FoldNodeInfo[aStartIndex].CountEx([sfaOpenFold],AType);
      nd := hl.FoldNodeInfo[aStartIndex].NodeInfoEx(n, [sfaOpenFold], AType);
    end;
  end
  else begin
    SetLength(EndLvl, TypeCnt+1);
    SetLength(CurLvl, TypeCnt+1);
    GetEndLvl(aStartIndex);
    aStartIndex := aStartIndex;
    while (ColIndex < Lvl) and (aStartIndex > 0) do begin
      dec(aStartIndex);
      o := hl.FoldBlockOpeningCount(AStartIndex, AType);
      if (o > 0) or (hl.FoldBlockClosingCount(aStartIndex, AType) > 0) then begin
        n := o;
        c := hl.FoldNodeInfo[aStartIndex].CountEx([], AType) - 1;
        for i := c downto 0 do begin
          nd := hl.FoldNodeInfo[aStartIndex].NodeInfoEx(i, [], AType);
          if (AType = 0) and not(sfaFold in nd.FoldAction) then
            continue;
          if AType = 0 then
            t := nd.FoldGroup
          else
            t := 0;
          if sfaOpenFold in nd.FoldAction then begin
            dec(n);
            dec(CurLvl[t]);
            if CurLvl[t] < EndLvl[t] then begin
              dec(EndLvl[t]);
              dec(Lvl);
              if ColIndex = Lvl then begin
                break;
              end;
            end;
          end else
          if sfaCloseFold in nd.FoldAction then begin
            inc(CurLvl[t]);
          end;
        end;
      end
      else
      if hl.FoldBlockEndLevel(AStartIndex-1, AType) = 0 then break;
    end;
  end;
  Result.HNode := nd;
  Result.OpenCount := o;
  Result.Text := NextLines[aStartIndex];
  if not(sfaInvalid in nd.FoldAction) then
    Result.Keyword := copy(Result.Text, 1 + nd.LogXStart, nd.LogXEnd-nd.LogXStart);
  Result.LineNum := aStartIndex + 1;
  Result.ColIndex := n;
  FN := FoldNodeAtTextIndex(aStartIndex, n);
  Result.IsFold := FN.IsInFold;
  Result.IsHide := fn.IsHide;
end;

function TSynEditFoldedView.ExpandedLineForBlockAtLine(ALine : Integer;
  HalfExpanded: Boolean = True) : Integer;
var
  i, l : Integer;
  node: TSynTextFoldAVLNode;
  hl: TSynCustomFoldHighlighter;
begin
  Result := -1;
  hl := TSynCustomFoldHighlighter(HighLighter);
  if not assigned(hl) then
    exit;

  i := ALine;
  l := hl.FoldBlockOpeningCount(i - 1);
  if l > 0 then begin
    node := fFoldTree.FindFoldForLine(ALine, true);
    if node.IsInFold and (node.StartLine = ALine +1) then begin
      dec(l);
      if HalfExpanded then while (l >= 0) do begin
        if not IsFoldedAtTextIndex(ALine-1, l) then exit(ALine);
        dec(l);
      end;
      dec(i);
    end
    else
      exit(ALine);
  end
  else if hl.FoldBlockClosingCount(i - 1) > 0 then
    dec(i);
  if (i < 0) or (hl.FoldBlockEndLevel(i-1) = 0) then
    exit;

  l := 0;
  while (i > 0) and (l >= 0) do begin // (FoldMinLevel[i] >= l) do
    dec(i);
    l := l - hl.FoldBlockOpeningCount(i);
    if l >= 0 then
      l := l + hl.FoldBlockClosingCount(i);
  end;
  if (hl.FoldBlockEndLevel(i) > 0) then // TODO, check for collapsed at index = 0
    Result := i + 1;
end;

function TSynEditFoldedView.GetPhysicalCharWidths(Index: Integer): TPhysicalCharWidths;
begin
  Result := NextLines.GetPhysicalCharWidths(InternViewToTextIndex(Index));
end;

function TSynEditFoldedView.CollapsedLineForFoldAtLine(ALine : Integer) : Integer;
// for hides => line before the hide
var
  node, tmpnode: TSynTextFoldAVLNode;
begin
  Result := -1;
  node := fFoldTree.FindFoldForLine(ALine, false);
  if node.IsInFold then begin
    tmpnode := node.Prev;
    while tmpnode.IsInFold and
          (tmpnode.StartLine + tmpnode.MergedLineCount = node.StartLine)
    do begin
      node := tmpnode;
      tmpnode := node.Prev;
    end;
    Result := node.StartLine-1;
    // Can be 0, if lines are hiden at begin of file
  end;
end;

function dbgs(AClassification: TFoldNodeClassification): String;
begin
  WriteStr(Result{%H-}, AClassification);
end;

function dbgs(AFoldLineCapability: TSynEditFoldLineCapability): String;
begin
  WriteStr(Result{%H-}, AFoldLineCapability);
end;

{$IFDEF SynDebug}
procedure TSynEditFoldedView.debug;
begin
  fFoldTree.debug;
end;
{$ENDIF}

initialization
  InitNumEncodeValues;
  //SYN_FOLD_DEBUG := DebugLogger.RegisterLogGroup('SynFoldDebug' {$IFDEF SynFoldDebug} , True {$ENDIF} );

end.

