/***************************************************************************
  qgspallabeling.h
  Smart labeling for vector layers
  -------------------
   begin                : June 2009
   copyright            : (C) Martin Dobias
   email                : wonder dot sk at gmail dot com

 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

//Note: although this file is in the core library, it is not part of the stable API
//and might change at any time!

#ifndef QGSPALLABELING_H
#define QGSPALLABELING_H

#include "qgis_core.h"
#include "qgis_sip.h"
#include <QString>
#include <QFont>
#include <QFontDatabase>
#include <QColor>
#include <QHash>
#include <QList>
#include <QPainter>
#include <QRectF>
#include <QMap>
#include "qgsfeature.h"
#include "qgsgeometry.h"
#include "qgsfields.h"
#include "qgslabelingenginesettings.h"
#include "qgspointxy.h"
#include "qgsmapunitscale.h"
#include "qgsstringutils.h"
#include "qgssymbol.h"
#include "qgstextformat.h"
#include "qgspropertycollection.h"
#include "qgslabelobstaclesettings.h"
#include "qgslabelthinningsettings.h"
#include "qgslabellinesettings.h"
#include "qgslabeling.h"

class QgsTextDocument;

namespace pal SIP_SKIP
{
  class Pal;
  class Layer;
  class LabelPosition;
}

class QgsDiagramLayerSettings;
class QgsRectangle;
class QgsMapToPixel;
class QgsFeature;
class QgsTextLabelFeature;
class QgsVectorLayer;
class QgsExpression;
class QFontMetricsF;
class QPainter;
class QPicture;
class QgsGeometry;
class QgsCoordinateTransform;
class QgsLabelSearchTree;
class QgsMapSettings;
class QgsLabelFeature;
class QgsLabelingEngine;
class QgsPalLayerSettings;
class QgsVectorLayerLabelProvider;
class QgsDxfExport;
class QgsVectorLayerDiagramProvider;
class QgsExpressionContext;
class QgsCallout;

/**
 * \ingroup core
 * \class QgsLabelPosition
 * \brief Represents the calculated placement of a map label.
 */
class CORE_EXPORT QgsLabelPosition
{
  public:

    /**
     * Constructor for QgsLabelPosition.
     * \param id associated feature ID
     * \param r label rotation in degrees clockwise
     * \param corners corner points of label bounding box, in map units
     * \param rect label bounding box, in map units
     * \param w width of label, in map units
     * \param h height of label, in map units
     * \param layer ID of associated map layer
     * \param labeltext text rendered for label
     * \param labelfont font used to render label
     * \param upside_down TRUE if label is upside down
     * \param diagram TRUE if label is a diagram
     * \param pinned TRUE if label has pinned placement
     * \param providerId ID of associated label provider
     * \param labelGeometry polygon geometry of label boundary
     * \param isUnplaced set to TRUE if label was unplaced (e.g. due to collisions with other labels)
     */
    QgsLabelPosition( QgsFeatureId id, double r, const QVector< QgsPointXY > &corners, const QgsRectangle &rect, double w, double h, const QString &layer, const QString &labeltext, const QFont &labelfont, bool upside_down, bool diagram = false, bool pinned = false, const QString &providerId = QString(),
                      const QgsGeometry &labelGeometry = QgsGeometry(), bool isUnplaced = false )
      : featureId( id )
      , rotation( r )
      , cornerPoints( corners )
      , labelRect( rect )
      , labelGeometry( labelGeometry )
      , width( w )
      , height( h )
      , layerID( layer )
      , labelText( labeltext )
      , labelFont( labelfont )
      , upsideDown( upside_down )
      , isDiagram( diagram )
      , isPinned( pinned )
      , providerID( providerId )
      , isUnplaced( isUnplaced )
    {}

    //! Constructor for QgsLabelPosition
    QgsLabelPosition() = default;

    /**
     * ID of feature associated with this label.
     */
    QgsFeatureId featureId = FID_NULL;

    /**
     * Rotation of label, in degrees clockwise.
     */
    double rotation = 0;

    QVector< QgsPointXY > cornerPoints;
    QgsRectangle labelRect;

    /**
     * A polygon geometry representing the label's bounds in map coordinates.
     * \since QGIS 3.4.9
     */
    QgsGeometry labelGeometry;

    /**
     * Width of label bounding box, in map units.
     */
    double width = 0;

    /**
     * Heeght of label bounding box, in map units.
     */
    double height = 0;

    /**
     * ID of associated map layer.
     */
    QString layerID;

    /**
     * String shown in label.
     */
    QString labelText;

    /**
     * Font which the label is rendered using.
     */
    QFont labelFont;

    /**
     * TRUE if label is upside down.
     */
    bool upsideDown = false;

    /**
     * TRUE if label is a diagram.
     */
    bool isDiagram = false;

    /**
     * TRUE if label position has been pinned.
     */
    bool isPinned = false;

    /**
     * ID of the associated label provider.
     * \since QGIS 2.14
     */
    QString providerID;

    /**
     * TRUE if label position corresponds to an unplaced label.
     * \since QGIS 3.10
     */
    bool isUnplaced = false;
};

/**
 * \ingroup core
 * \class QgsPalLayerSettings
 * \brief Contains settings for how a map layer will be labeled.
 */
class CORE_EXPORT QgsPalLayerSettings
{
  public:
    QgsPalLayerSettings();
    QgsPalLayerSettings( const QgsPalLayerSettings &s );
    ~QgsPalLayerSettings();

    //! copy operator - only copies the permanent members
    QgsPalLayerSettings &operator=( const QgsPalLayerSettings &s );

    //TODO QGIS 4.0 - move to QgsLabelingEngine

    /**
     * Placement modes which determine how label candidates are generated for a feature.
     */
    enum Placement
    {
      AroundPoint, //!< Arranges candidates in a circle around a point (or centroid of a polygon). Applies to point or polygon layers only.
      OverPoint, //!< Arranges candidates over a point (or centroid of a polygon), or at a preset offset from the point. Applies to point or polygon layers only.
      Line, //!< Arranges candidates parallel to a generalised line representing the feature or parallel to a polygon's perimeter. Applies to line or polygon layers only.
      Curved, //!< Arranges candidates following the curvature of a line feature. Applies to line layers only.
      Horizontal, //!< Arranges horizontal candidates scattered throughout a polygon feature. Applies to polygon layers only.
      Free, //!< Arranges candidates scattered throughout a polygon feature. Candidates are rotated to respect the polygon's orientation. Applies to polygon layers only.
      OrderedPositionsAroundPoint, //!< Candidates are placed in predefined positions around a point. Preference is given to positions with greatest cartographic appeal, e.g., top right, bottom right, etc. Applies to point layers only.
      PerimeterCurved, //!< Arranges candidates following the curvature of a polygon's boundary. Applies to polygon layers only.
      OutsidePolygons, //!< Candidates are placed outside of polygon boundaries. Applies to polygon layers only. Since QGIS 3.14
    };

    //TODO QGIS 4.0 - move to QgsLabelingEngine
    //! Positions for labels when using the QgsPalLabeling::OrderedPositionsAroundPoint placement mode
    enum PredefinedPointPosition
    {
      TopLeft, //!< Label on top-left of point
      TopSlightlyLeft, //!< Label on top of point, slightly left of center
      TopMiddle, //!< Label directly above point
      TopSlightlyRight, //!< Label on top of point, slightly right of center
      TopRight, //!< Label on top-right of point
      MiddleLeft, //!< Label on left of point
      MiddleRight, //!< Label on right of point
      BottomLeft, //!< Label on bottom-left of point
      BottomSlightlyLeft, //!< Label below point, slightly left of center
      BottomMiddle, //!< Label directly below point
      BottomSlightlyRight, //!< Label below point, slightly right of center
      BottomRight, //!< Label on bottom right of point
    };

    //TODO QGIS 4.0 - move to QgsLabelingEngine

    /**
     * Behavior modifier for label offset and distance, only applies in some
     * label placement modes.
     */
    enum OffsetType
    {
      FromPoint, //!< Offset distance applies from point geometry
      FromSymbolBounds, //!< Offset distance applies from rendered symbol bounds
    };

    //TODO QGIS 4.0 - remove, replaced by QgsLabeling::LinePlacementFlags

    /**
     * Line placement flags, which control how candidates are generated for a linear feature.
     *
     * \deprecated Use QgsLabeling::LinePlacementFlags instead
     */
    enum LinePlacementFlags
    {
      OnLine    = 1,      //!< Labels can be placed directly over a line feature.
      AboveLine = 2,      /**< Labels can be placed above a line feature. Unless MapOrientation is also specified this mode
                               respects the direction of the line feature, so a line from right to left labels will have labels
                               placed placed below the line feature. */
      BelowLine = 4,      /**< Labels can be placed below a line feature. Unless MapOrientation is also specified this mode
                               respects the direction of the line feature, so a line from right to left labels will have labels
                               placed placed above the line feature. */
      MapOrientation = 8, /**< Signifies that the AboveLine and BelowLine flags should respect the map's orientation rather
                               than the feature's orientation. For example, AboveLine will always result in label's being placed
                               above a line, regardless of the line's direction. */
    };

    enum QuadrantPosition
    {
      QuadrantAboveLeft,
      QuadrantAbove,
      QuadrantAboveRight,
      QuadrantLeft,
      QuadrantOver,
      QuadrantRight,
      QuadrantBelowLeft,
      QuadrantBelow,
      QuadrantBelowRight,
    };

    enum UpsideDownLabels
    {
      Upright, //!< Upside-down labels (90 <= angle < 270) are shown upright
      ShowDefined, //!< Show upside down when rotation is layer- or data-defined
      ShowAll //!< Show upside down for all labels, including dynamic ones
    };

    //TODO QGIS 4.0 - Remove -- moved to QgsLabelEngineObstacleSettings

    //! \deprecated use QgsLabelLineSettings::DirectionSymbolPlacement instead
    enum DirectionSymbols
    {
      SymbolLeftRight, //!< Place direction symbols on left/right of label
      SymbolAbove, //!< Place direction symbols on above label
      SymbolBelow //!< Place direction symbols on below label
    };

    enum MultiLineAlign
    {
      MultiLeft = 0,
      MultiCenter,
      MultiRight,
      MultiFollowPlacement, /*!< Alignment follows placement of label, e.g., labels to the left of a feature
                               will be drawn with right alignment*/
      MultiJustify, //!< Justified
    };

    //TODO QGIS 4.0 - Remove -- moved to QgsLabelEngineObstacleSettings

    /**
     * Valid obstacle types, which affect how features within the layer will act as obstacles
     * for labels.
     */
    enum ObstacleType
    {
      PolygonInterior, /*!< avoid placing labels over interior of polygon (prefer placing labels totally
       outside or just slightly inside polygon) */
      PolygonBoundary, /*!< avoid placing labels over boundary of polygon (prefer placing outside or
       completely inside polygon) */
      PolygonWhole /*!< avoid placing labels over ANY part of polygon. Where PolygonInterior will prefer
       to place labels with the smallest area of intersection between the label and the polygon,
       PolygonWhole will penalise any label which intersects with the polygon by an equal amount, so that
       placing labels over any part of the polygon is avoided.*/
    };

    //! Data definable properties.
    enum Property
    {
      // text style
      Size = 0, //!< Label size
      Bold = 1, //!< Use bold style
      Italic = 2, //!< Use italic style
      Underline = 3, //!< Use underline
      Color = 4, //!< Text color
      Strikeout = 5, //!< Use strikeout
      Family = 6, //!< Font family
      FontStyle = 21, //!< Font style name
      FontSizeUnit = 22, //!< Font size units
      FontTransp = 18, //!< Text transparency (deprecated)
      FontOpacity = 92, //!< Text opacity
      FontCase = 27, //!< Label text case
      FontLetterSpacing = 28, //!< Letter spacing
      FontWordSpacing = 29, //!< Word spacing
      FontBlendMode = 30, //!< Text blend mode

      // text formatting
      MultiLineWrapChar = 31,
      AutoWrapLength = 101,
      MultiLineHeight = 32,
      MultiLineAlignment = 33,
      TextOrientation = 110,
      DirSymbDraw = 34,
      DirSymbLeft = 35,
      DirSymbRight = 36,
      DirSymbPlacement = 37,
      DirSymbReverse = 38,
      NumFormat = 39,
      NumDecimals = 40,
      NumPlusSign = 41,

      // text buffer
      BufferDraw = 42,
      BufferSize = 7,
      BufferUnit = 43,
      BufferColor = 8,
      BufferTransp = 19, //!< Buffer transparency (deprecated)
      BufferOpacity = 94, //!< Buffer opacity
      BufferJoinStyle = 44,
      BufferBlendMode = 45,

      // mask buffer
      MaskEnabled = 104, //!< Whether the mask is enabled
      MaskBufferSize = 105, //!< Mask buffer size
      MaskBufferUnit = 106, //!< Mask buffer size unit
      MaskOpacity = 107, //!< Mask opacity
      MaskJoinStyle = 108, //!< Mask join style

      // background
      ShapeDraw = 46,
      ShapeKind = 47,
      ShapeSVGFile = 48,
      ShapeSizeType = 49,
      ShapeSizeX = 50,
      ShapeSizeY = 85,
      ShapeSizeUnits = 51,
      ShapeRotationType = 52,
      ShapeRotation = 53,
      ShapeOffset = 54,
      ShapeOffsetUnits = 55,
      ShapeRadii = 56,
      ShapeRadiiUnits = 57,
      ShapeTransparency = 63, //!< Shape transparency (deprecated)
      ShapeOpacity = 93, //!< Shape opacity
      ShapeBlendMode = 64,
      ShapeFillColor = 58,
      ShapeStrokeColor = 59,
      ShapeStrokeWidth = 60,
      ShapeStrokeWidthUnits = 61,
      ShapeJoinStyle = 62,

      // drop shadow
      ShadowDraw = 65,
      ShadowUnder = 66,
      ShadowOffsetAngle = 67,
      ShadowOffsetDist = 68,
      ShadowOffsetUnits = 69,
      ShadowRadius = 70,
      ShadowRadiusUnits = 71,
      ShadowTransparency = 72, //!< Shadow transparency (deprecated)
      ShadowOpacity = 95, //!< Shadow opacity
      ShadowScale = 73,
      ShadowColor = 74,
      ShadowBlendMode = 75,

      // placement
      CentroidWhole = 76,
      OffsetQuad = 77,
      OffsetXY = 78,
      OffsetUnits = 80,
      LabelDistance = 13,
      DistanceUnits = 81,
      OffsetRotation = 82,
      CurvedCharAngleInOut = 83,
      // (data defined only)
      PositionX = 9, //!< X-coordinate data defined label position
      PositionY = 10, //!< Y-coordinate data defined label position
      Hali = 11, //!< Horizontal alignment for data defined label position (Left, Center, Right)
      Vali = 12, //!< Vertical alignment for data defined label position (Bottom, Base, Half, Cap, Top)
      Rotation = 14, //!< Label rotation (deprecated, for old project compatibility only)
      LabelRotation = 96, //!< Label rotation
      RepeatDistance = 84,
      RepeatDistanceUnit = 86,
      Priority = 87,
      PredefinedPositionOrder = 91,
      LinePlacementOptions = 99, //!< Line placement flags
      OverrunDistance = 102, //!< Distance which labels can extend past either end of linear features
      LabelAllParts = 103, //!< Whether all parts of multi-part features should be labeled
      PolygonLabelOutside = 109, //!< Whether labels outside a polygon feature are permitted, or should be forced (since QGIS 3.14)
      LineAnchorPercent = 111, //!< Portion along line at which labels should be anchored (since QGIS 3.16)

      // rendering
      ScaleVisibility = 23,
      MinScale = 16, //!< Min scale (deprecated, for old project compatibility only)
      MinimumScale = 97, //!< Minimum map scale (ie most "zoomed out")
      MaxScale = 17, //!< Max scale (deprecated, for old project compatibility only)
      MaximumScale = 98, //!< Maximum map scale (ie most "zoomed in")
      FontLimitPixel = 24,
      FontMinPixel = 25,
      FontMaxPixel = 26,
      IsObstacle = 88,
      ObstacleFactor = 89,
      ZIndex = 90,
      CalloutDraw = 100, //!< Show callout

      // (data defined only)
      Show = 15,
      AlwaysShow = 20
    };


    /**
     * Prepare for registration of features.
     * The \a context, \a mapSettings and \a fields parameters give more
     * information about the rendering environment.
     * If target \a crs is not specified, the targetCrs from \a mapSettings
     * will be taken.
     * The parameter \a attributeNames should be updated to contain all the field
     * names which the labeling requires for the rendering.
     *
     * \since QGIS 3.8
     */
    bool prepare( QgsRenderContext &context, QSet<QString> &attributeNames SIP_INOUT, const QgsFields &fields, const QgsMapSettings &mapSettings, const QgsCoordinateReferenceSystem &crs );

    /**
     * Returns all field names referenced by the configuration (e.g. field name or expression, data defined properties).
     * \since QGIS 3.14
     */
    QSet<QString> referencedFields( const QgsRenderContext &context ) const;

    /**
     * Prepares the label settings for rendering.
     *
     * This should be called before rendering any labels, and must be
     * followed by a call to stopRender() in order to gracefully clean up symbols.
     *
     * \since QGIS 3.10
     */
    void startRender( QgsRenderContext &context );

    /**
     * Finalises the label settings after use.
     *
     * This must be called after a call to startRender(), in order to gracefully clean up symbols.
     *
     * \since QGIS 3.10
     */
    void stopRender( QgsRenderContext &context );

    /**
     * Returns the labeling property definitions.
     * \since QGIS 3.0
     */
    static const QgsPropertiesDefinition &propertyDefinitions();

    /**
     * Whether to draw labels for this layer. For some layers it may be desirable
     * to register their features as obstacles for other labels without requiring
     * labels to be drawn for the layer itself. In this case drawLabels can be set
     * to FALSE and obstacle set to TRUE, which will result in the layer acting
     * as an obstacle but having no labels of its own.
     * \since QGIS 2.12
     */
    bool drawLabels = true;

    //-- text style

    /**
     * Name of field (or an expression) to use for label text.
     * If fieldName is an expression, then isExpression should be set to TRUE.
     * \see isExpression
     */
    QString fieldName;

    /**
     * TRUE if this label is made from a expression string, e.g., FieldName || 'mm'
     * \see fieldName
     */
    bool isExpression = false;

    /**
     * Returns the QgsExpression for this label settings. May be NULLPTR if isExpression is FALSE.
     */
    QgsExpression *getLabelExpression();

    /**
     * \deprecated since QGIS 3.10. Use QgsTextFormat::previewBackgroundColor() instead.
     */
    Q_DECL_DEPRECATED QColor previewBkgrdColor = Qt::white;

    //! Substitution collection for automatic text substitution with labels
    QgsStringReplacementCollection substitutions;
    //! True if substitutions should be applied
    bool useSubstitutions = false;

    //-- text formatting

    /**
     * Wrapping character string. If set, any occurrences of this string in the calculated
     * label text will be replaced with new line characters.
     */
    QString wrapChar;

    /**
     * If non-zero, indicates that label text should be automatically wrapped to (ideally) the specified
     * number of characters. If zero, auto wrapping is disabled.
     *
     * \see useMaxLineLengthForAutoWrap
     * \since QGIS 3.4
     */
    int autoWrapLength = 0;

    /**
     * If TRUE, indicates that when auto wrapping label text the autoWrapLength length indicates the maximum
     * ideal length of text lines. If FALSE, then autoWrapLength indicates the ideal minimum length of text
     * lines.
     *
     * If autoWrapLength is 0 then this value has no effect.
     *
     * \see autoWrapLength
     * \since QGIS 3.4
     */
    bool useMaxLineLengthForAutoWrap = true;

    //! Horizontal alignment of multi-line labels.
    MultiLineAlign multilineAlign = MultiFollowPlacement;

    /**
     * Set to TRUE to format numeric label text as numbers (e.g. inserting thousand separators
     * and fixed number of decimal places).
     * \see decimals
     * \see plusSign
     */
    bool formatNumbers = false;

    /**
     * Number of decimal places to show for numeric labels. formatNumbers must be TRUE for this
     * setting to have an effect.
     * \see formatNumbers
     */
    int decimals = 3;

    /**
     * Whether '+' signs should be prepended to positive numeric labels. formatNumbers must be TRUE for this
     * setting to have an effect.
     * \see formatNumbers
     */
    bool plusSign = false;

    //-- placement

    Placement placement = AroundPoint;

    /**
     * Returns the polygon placement flags, which dictate how polygon labels can be placed.
     *
     * \see setPolygonPlacementFlags()
     * \since QGIS 3.14
     */
    QgsLabeling::PolygonPlacementFlags polygonPlacementFlags() const { return mPolygonPlacementFlags; }

    /**
     * Sets the polygon placement \a flags, which dictate how polygon labels can be placed.
     *
     * \see polygonPlacementFlags()
     * \since QGIS 3.14
     */
    void setPolygonPlacementFlags( QgsLabeling::PolygonPlacementFlags flags ) { mPolygonPlacementFlags = flags; }

    /**
     * TRUE if feature centroid should be calculated from the whole feature, or
     * FALSE if only the visible part of the feature should be considered.
     */
    bool centroidWhole = false;

    /**
     * TRUE if centroid positioned labels must be placed inside their corresponding
     * feature polygon, or FALSE if centroids which fall outside the polygon
     * are permitted.
     */
    bool centroidInside = false;

    /**
     * Ordered list of predefined label positions for points. Positions earlier
     * in the list will be prioritized over later positions. Only used when the placement
     * is set to QgsPalLayerSettings::OrderedPositionsAroundPoint.
     * \note not available in Python bindings
     */
    QVector< PredefinedPointPosition > predefinedPositionOrder SIP_SKIP;

    /**
     * TRUE if only labels which completely fit within a polygon are allowed.
     */
    bool fitInPolygonOnly = false;

    /**
     * Distance from feature to the label. Units are specified via distUnits.
     * \see distUnits
     * \see distMapUnitScale
     */
    double dist = 0;

    /**
     * Units the distance from feature to the label.
     * \see dist
     * \see distMapUnitScale
     */
    QgsUnitTypes::RenderUnit distUnits = QgsUnitTypes::RenderMillimeters;

    /**
     * Map unit scale for label feature distance.
     * \see dist
     * \see distUnits
     */
    QgsMapUnitScale distMapUnitScale;

    //! Offset type for layer (only applies in certain placement modes)
    OffsetType offsetType = FromPoint;

    /**
     * Distance for repeating labels for a single feature.
     * \see repeatDistanceUnit
     * \see repeatDistanceMapUnitScale
     */
    double repeatDistance = 0;

    /**
     * Units for repeating labels for a single feature.
     * \see repeatDistance
     * \see repeatDistanceMapUnitScale
     */
    QgsUnitTypes::RenderUnit repeatDistanceUnit = QgsUnitTypes::RenderMillimeters;

    /**
     * Map unit scale for repeating labels for a single feature.
     * \see repeatDistance
     * \see repeatDistanceUnit
     */
    QgsMapUnitScale repeatDistanceMapUnitScale;

    /**
     * Sets the quadrant in which to offset labels from feature.
     */
    QuadrantPosition quadOffset = QuadrantOver;

    /**
     * Horizontal offset of label. Units are specified via offsetUnits.
     * \see yOffset
     * \see offsetUnits
     * \see labelOffsetMapUnitScale
     */
    double xOffset = 0;

    /**
     * Vertical offset of label. Units are specified via offsetUnits.
     * \see xOffset
     * \see offsetUnits
     * \see labelOffsetMapUnitScale
     */
    double yOffset = 0;

    /**
     * Units for offsets of label.
     * \see xOffset
     * \see yOffset
     * \see labelOffsetMapUnitScale
     */
    QgsUnitTypes::RenderUnit offsetUnits = QgsUnitTypes::RenderMillimeters;

    /**
     * Map unit scale for label offset.
     * \see xOffset
     * \see yOffset
     * \see offsetUnits
     */
    QgsMapUnitScale labelOffsetMapUnitScale;

    //! Label rotation, in degrees clockwise
    double angleOffset = 0;

    //! True if label rotation should be preserved during label pin/unpin operations.
    bool preserveRotation = true;

    /**
     * Maximum angle between inside curved label characters (valid range 20.0 to 60.0).
     * \see maxCurvedCharAngleOut
     */
    double maxCurvedCharAngleIn = 25.0;

    /**
     * Maximum angle between outside curved label characters (valid range -20.0 to -95.0)
     * \see maxCurvedCharAngleIn
     */
    double maxCurvedCharAngleOut = -25.0;

    /**
     * Label priority. Valid ranges are from 0 to 10, where 0 = lowest priority
     * and 10 = highest priority.
     */
    int priority = 5;

    //-- rendering

    /**
     * Set to TRUE to limit label visibility to a range of scales.
     * \see maximumScale
     * \see minimumScale
     */
    bool scaleVisibility = false;

    /**
     * The maximum map scale (i.e. most "zoomed in" scale) at which the labels will be visible.
     * The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map.
     * A scale of 0 indicates no maximum scale visibility.
     *
     * This setting is only considered if scaleVisibility is TRUE.
     *
     * \see minimumScale
     * \see scaleVisibility
    */
    double maximumScale = 0;

    /**
     * The minimum map scale (i.e. most "zoomed out" scale) at which the labels will be visible.
     * The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map.
     * A scale of 0 indicates no minimum scale visibility.
     *
     * This setting is only considered if scaleVisibility is TRUE.
     *
     * \see maximumScale
     * \see scaleVisibility
    */
    double minimumScale = 0;

    /**
     * TRUE if label sizes should be limited by pixel size.
     * \see fontMinPixelSize
     * \see fontMaxPixelSize
     */
    bool fontLimitPixelSize = false;

    /**
     * Minimum pixel size for showing rendered map unit labels (1 - 1000).
     * \see fontLimitPixelSize
     * \see fontMaxPixelSize
     */
    int fontMinPixelSize = 0;

    /**
     * Maximum pixel size for showing rendered map unit labels (1 - 10000).
     * \see fontLimitPixelSize
     * \see fontMinPixelSize
     */
    int fontMaxPixelSize = 10000;

    //! If TRUE, all features will be labelled even when overlaps occur.
    bool displayAll = false;

    //! Controls whether upside down labels are displayed and how they are handled.
    UpsideDownLabels upsidedownLabels = Upright;

    /**
     * TRUE if every part of a multi-part feature should be labeled. If FALSE,
     * only the largest part will be labeled.
     */
    bool labelPerPart = false;

    // TODO QGIS 4.0 - remove this junk

#ifdef SIP_RUN
    SIP_PROPERTY( name = limitNumLabels, get = _limitNumLabels, set = _setLimitNumLabels )
    SIP_PROPERTY( name = maxNumLabels, get = _maxNumLabels, set = _setMaxNumLabels )
    SIP_PROPERTY( name = minFeatureSize, get = _minFeatureSize, set = _setMinFeatureSize )
    SIP_PROPERTY( name = obstacle, get = _getIsObstacle, set = _setIsObstacle )
    SIP_PROPERTY( name = obstacleFactor, get = _getObstacleFactor, set = _setObstacleFactor )
    SIP_PROPERTY( name = obstacleType, get = _getObstacleType, set = _setObstacleType )
    SIP_PROPERTY( name = placementFlags, get = _getLinePlacementFlags, set = _setLinePlacementFlags )
    SIP_PROPERTY( name = mergeLines, get = _getMergeLines, set = _setMergeLines )
    SIP_PROPERTY( name = addDirectionSymbol, get = _getAddDirectionSymbol, set = _setAddDirectionSymbol )
    SIP_PROPERTY( name = leftDirectionSymbol, get = _getLeftDirectionSymbol, set = _setLeftDirectionSymbol )
    SIP_PROPERTY( name = rightDirectionSymbol, get = _getRightDirectionSymbol, set = _setRightDirectionSymbol )
    SIP_PROPERTY( name = reverseDirectionSymbol, get = _getReverseDirectionSymbol, set = _setReverseDirectionSymbol )
    SIP_PROPERTY( name = placeDirectionSymbol, get = _getPlaceDirectionSymbol, set = _setPlaceDirectionSymbol )

    SIP_PROPERTY( name = overrunDistance, get = _getOverrunDistance, set = _setOverrunDistance )
    SIP_PROPERTY( name = overrunDistanceUnit, get = _getOverrunDistanceUnit, set = _setOverrunDistanceUnit )
    SIP_PROPERTY( name = overrunDistanceMapUnitScale, get = _getOverrunDistanceMapUnitScale, set = _setOverrunDistanceMapUnitScale )
#endif

    ///@cond PRIVATE
    bool _limitNumLabels() const { return mThinningSettings.limitNumberOfLabelsEnabled(); }
    void _setLimitNumLabels( bool limit ) { mThinningSettings.setLimitNumberLabelsEnabled( limit ); }
    int _maxNumLabels() const { return mThinningSettings.maximumNumberLabels(); }
    void _setMaxNumLabels( int max ) { mThinningSettings.setMaximumNumberLabels( max ); }
    double _minFeatureSize() const { return mThinningSettings.minimumFeatureSize(); }
    void _setMinFeatureSize( double size ) { mThinningSettings.setMinimumFeatureSize( size ); }
    bool _getIsObstacle() const { return mObstacleSettings.isObstacle(); }
    void _setIsObstacle( bool obstacle ) { mObstacleSettings.setIsObstacle( obstacle ); }
    double _getObstacleFactor() const { return mObstacleSettings.factor(); }
    void _setObstacleFactor( double factor ) { mObstacleSettings.setFactor( factor ); }
    ObstacleType _getObstacleType() const { return static_cast< ObstacleType>( mObstacleSettings.type() ); }
    void _setObstacleType( ObstacleType type ) { mObstacleSettings.setType( static_cast< QgsLabelObstacleSettings::ObstacleType>( type ) ); }
    unsigned int _getLinePlacementFlags() const { return static_cast< unsigned int >( mLineSettings.placementFlags() ); }
    void _setLinePlacementFlags( unsigned int flags ) { mLineSettings.setPlacementFlags( static_cast< QgsLabeling::LinePlacementFlags >( flags ) ); }
    bool _getMergeLines() const { return mLineSettings.mergeLines(); }
    void _setMergeLines( bool merge ) { mLineSettings.setMergeLines( merge ); }
    bool _getAddDirectionSymbol() const { return mLineSettings.addDirectionSymbol(); }
    void _setAddDirectionSymbol( bool add ) { mLineSettings.setAddDirectionSymbol( add ); }
    QString _getLeftDirectionSymbol() const { return mLineSettings.leftDirectionSymbol(); }
    void _setLeftDirectionSymbol( const QString &symbol ) { mLineSettings.setLeftDirectionSymbol( symbol ); }
    QString _getRightDirectionSymbol() const { return mLineSettings.rightDirectionSymbol(); }
    void _setRightDirectionSymbol( const QString &symbol ) { mLineSettings.setRightDirectionSymbol( symbol ); }
    bool _getReverseDirectionSymbol() const { return mLineSettings.reverseDirectionSymbol(); }
    void _setReverseDirectionSymbol( bool reverse ) { mLineSettings.setReverseDirectionSymbol( reverse ); }
    Q_NOWARN_DEPRECATED_PUSH
    DirectionSymbols _getPlaceDirectionSymbol() const { return static_cast< DirectionSymbols>( mLineSettings.directionSymbolPlacement() ); }
    void _setPlaceDirectionSymbol( DirectionSymbols placement ) { mLineSettings.setDirectionSymbolPlacement( static_cast< QgsLabelLineSettings::DirectionSymbolPlacement>( placement ) ); }
    Q_NOWARN_DEPRECATED_POP
    double _getOverrunDistance() const { return mLineSettings.overrunDistance(); }
    void _setOverrunDistance( double distance ) { mLineSettings.setOverrunDistance( distance ); }
    QgsUnitTypes::RenderUnit _getOverrunDistanceUnit() const { return mLineSettings.overrunDistanceUnit(); }
    void _setOverrunDistanceUnit( QgsUnitTypes::RenderUnit unit ) { mLineSettings.setOverrunDistanceUnit( unit ); }
    QgsMapUnitScale _getOverrunDistanceMapUnitScale() const { return mLineSettings.overrunDistanceMapUnitScale(); }
    void _setOverrunDistanceMapUnitScale( const QgsMapUnitScale &scale ) { mLineSettings.setOverrunDistanceMapUnitScale( scale ); }
    ///@endcond

    //! Z-Index of label, where labels with a higher z-index are rendered on top of labels with a lower z-index
    double zIndex = 0;

    //! The geometry generator expression. Null if disabled.
    QString geometryGenerator;

    //! The type of the result geometry of the geometry generator.
    QgsWkbTypes::GeometryType geometryGeneratorType = QgsWkbTypes::GeometryType::PointGeometry;

    //! Defines if the geometry generator is enabled or not. If disabled, the standard geometry will be taken.
    bool geometryGeneratorEnabled = false;

    /**
     * Geometry type of layers associated with these settings.
     * \since QGIS 3.10
     */
    QgsWkbTypes::GeometryType layerType = QgsWkbTypes::UnknownGeometry;

    /**
     * Calculates the space required to render the provided \a text in map units.
     * Results will be written to \a labelX and \a labelY.
     * If the text orientation is set to rotation-based, the spaced taken to render
     * vertically oriented text will be written to \a rotatedLabelX and \a rotatedLabelY .
     */
#ifndef SIP_RUN
    void calculateLabelSize( const QFontMetricsF *fm, const QString &text, double &labelX, double &labelY, const QgsFeature *f = nullptr, QgsRenderContext *context = nullptr, double *rotatedLabelX SIP_OUT = nullptr, double *rotatedLabelY SIP_OUT = nullptr,
                             QgsTextDocument *document = nullptr );
#else
    void calculateLabelSize( const QFontMetricsF *fm, const QString &text, double &labelX, double &labelY, const QgsFeature *f = nullptr, QgsRenderContext *context = nullptr, double *rotatedLabelX SIP_OUT = nullptr, double *rotatedLabelY SIP_OUT = nullptr );
#endif

    /**
     * Register a feature for labeling.
     * \param f feature to label
     * \param context render context. The QgsExpressionContext contained within the render context
     * must have already had the feature and fields sets prior to calling this method.
     * \param labelFeature if using QgsLabelingEngine, this will receive the label feature. Not available
     * in Python bindings.
     * \param obstacleGeometry optional obstacle geometry, if a different geometry to the feature's geometry
     * should be used as an obstacle for labels (e.g., if the feature has been rendered with an offset point
     * symbol, the obstacle geometry should represent the bounds of the offset symbol). If not set,
     * the feature's original geometry will be used as an obstacle for labels. Not available
     * in Python bindings.
     * \param symbol feature symbol to label (ownership is not transferred, and \a symbol must exist until the labeling is complete)
     */
    void registerFeature( const QgsFeature &f, QgsRenderContext &context,
                          QgsLabelFeature **labelFeature SIP_PYARGREMOVE = nullptr,
                          QgsGeometry obstacleGeometry SIP_PYARGREMOVE = QgsGeometry(), const QgsSymbol *symbol SIP_PYARGREMOVE = nullptr );

    /**
     * Read settings from a DOM element
     * \since QGIS 2.12
     */
    void readXml( const QDomElement &elem, const QgsReadWriteContext &context );

    /**
     * Write settings into a DOM element
     * \since QGIS 2.12
     */
    QDomElement writeXml( QDomDocument &doc, const QgsReadWriteContext &context ) const;

    /**
     * Returns a reference to the label's property collection, used for data defined overrides.
     * \see setDataDefinedProperties()
     * \since QGIS 3.0
     */
    QgsPropertyCollection &dataDefinedProperties() { return mDataDefinedProperties; }

    /**
     * Returns a reference to the label's property collection, used for data defined overrides.
     * \see setDataDefinedProperties()
     * \see Property
     * \note not available in Python bindings
     * \since QGIS 3.0
     */
    const QgsPropertyCollection &dataDefinedProperties() const SIP_SKIP { return mDataDefinedProperties; }

    /**
     * Sets the label's property collection, used for data defined overrides.
     * \param collection property collection. Existing properties will be replaced.
     * \see dataDefinedProperties()
     * \see Property
     * \since QGIS 3.0
     */
    void setDataDefinedProperties( const QgsPropertyCollection &collection ) { mDataDefinedProperties = collection; }

    /**
     * Returns the label text formatting settings, e.g., font settings, buffer settings, etc.
     * \see setFormat()
     * \since QGIS 3.0
     */
    const QgsTextFormat &format() const { return mFormat; }

    /**
     * Sets the label text formatting settings, e.g., font settings, buffer settings, etc.
     * \param format label text format
     * \see format()
     * \since QGIS 3.0
     */
    void setFormat( const QgsTextFormat &format ) { mFormat = format; }

    /**
     * Returns the label callout renderer, responsible for drawing label callouts.
     *
     * Ownership is not transferred.
     *
     * \see setCallout()
     * \since QGIS 3.10
     */
    QgsCallout *callout() const { return mCallout.get(); }

    /**
     * Sets the label \a callout renderer, responsible for drawing label callouts.
     *
     * Ownership of \a callout is transferred to the settings.

     * \see callout()
     * \since QGIS 3.10
     */
    void setCallout( QgsCallout *callout SIP_TRANSFER );

    /**
     * Returns the label line settings, which contain settings related to how the label
     * engine places and formats labels for line features (or polygon features which are labeled in
     * a "perimeter" style mode).
     * \see setLineSettings()
     * \note Not available in Python bindings
     * \since QGIS 3.16
     */
    const QgsLabelLineSettings &lineSettings() const { return mLineSettings; } SIP_SKIP

    /**
     * Returns the label line settings, which contain settings related to how the label
     * engine places and formats labels for line features (or polygon features which are labeled in
     * a "perimeter" style mode).
     * \see setLineSettings()
     * \since QGIS 3.16
     */
    QgsLabelLineSettings &lineSettings() { return mLineSettings; }

    /**
     * Sets the label line \a settings, which contain settings related to how the label
     * engine places and formats labels for line features (or polygon features which are labeled in
     * a "perimeter" style mode).
     * \see lineSettings()
     * \since QGIS 3.16
     */
    void setLineSettings( const QgsLabelLineSettings &settings ) { mLineSettings = settings; }

    /**
     * Returns the label obstacle settings.
     * \see setObstacleSettings()
     * \note Not available in Python bindings
     * \since QGIS 3.10.2
     */
    const QgsLabelObstacleSettings &obstacleSettings() const { return mObstacleSettings; } SIP_SKIP

    /**
     * Returns the label obstacle settings.
     * \see setObstacleSettings()
     * \since QGIS 3.10.2
     */
    QgsLabelObstacleSettings &obstacleSettings() { return mObstacleSettings; }

    /**
     * Sets the label obstacle \a settings.
     * \see obstacleSettings()
     * \since QGIS 3.10.2
     */
    void setObstacleSettings( const QgsLabelObstacleSettings &settings ) { mObstacleSettings = settings; }

    /**
     * Returns the label thinning settings.
     * \see setThinningSettings()
     * \note Not available in Python bindings
     * \since QGIS 3.12
     */
    const QgsLabelThinningSettings &thinningSettings() const { return mThinningSettings; } SIP_SKIP

    /**
     * Returns the label thinning settings.
     * \see setThinningSettings()
     * \since QGIS 3.12
     */
    QgsLabelThinningSettings &thinningSettings() { return mThinningSettings; }

    /**
     * Sets the label thinning \a settings.
     * \see thinningSettings()
     * \since QGIS 3.12
     */
    void setThinningSettings( const QgsLabelThinningSettings &settings ) { mThinningSettings = settings; }

    /**
    * Returns a pixmap preview for label \a settings.
    * \param settings label settings
    * \param size target pixmap size
    * \param previewText text to render in preview, or empty for default text
    * \param padding space between icon edge and color ramp
    * \since QGIS 3.10
    */
    static QPixmap labelSettingsPreviewPixmap( const QgsPalLayerSettings &settings, QSize size, const QString &previewText = QString(), int padding = 0 );

    // temporary stuff: set when layer gets prepared or labeled
    const QgsFeature *mCurFeat = nullptr;
    QgsFields mCurFields;
    int fieldIndex = 0;
    const QgsMapToPixel *xform = nullptr;
    QgsCoordinateTransform ct;

    QgsPointXY ptZero;
    QgsPointXY ptOne;
    QgsGeometry extentGeom;
    int mFeaturesToLabel = 0; // total features that will probably be labeled, may be less (figured before PAL)
    int mFeatsSendingToPal = 0; // total features tested for sending into PAL (relative to maxNumLabels)
    int mFeatsRegPal = 0; // number of features registered in PAL, when using limitNumLabels
  private:

    friend class QgsVectorLayer;  // to allow calling readFromLayerCustomProperties()

    /**
     * Reads labeling configuration from layer's custom properties to support loading of simple labeling from QGIS 2.x projects.
     * \since QGIS 3.0
     */
    void readFromLayerCustomProperties( QgsVectorLayer *layer );

    /**
     * Reads data defined properties from a QGIS 2.x project.
     */
    void readOldDataDefinedPropertyMap( QgsVectorLayer *layer, QDomElement *parentElem );

    /**
     * Reads a data defined property from a QGIS 2.x project.
     */
    void readOldDataDefinedProperty( QgsVectorLayer *layer, QgsPalLayerSettings::Property p );

    enum DataDefinedValueType
    {
      DDBool,
      DDInt,
      DDIntPos,
      DDDouble,
      DDDoublePos,
      DDRotation180,
      DDOpacity, //!< Data defined opacity (double between 0 and 100)
      DDString,
      DDUnits,
      DDColor,
      DDJoinStyle,
      DDBlendMode,
      DDPointF,
      DDSizeF, //!< Data defined size
    };

    // convenience data defined evaluation function
    bool dataDefinedValEval( DataDefinedValueType valType,
                             QgsPalLayerSettings::Property p,
                             QVariant &exprVal, QgsExpressionContext &context, const QVariant &originalValue = QVariant() );

    void parseTextStyle( QFont &labelFont,
                         QgsUnitTypes::RenderUnit fontunits,
                         QgsRenderContext &context );

    void parseTextBuffer( QgsRenderContext &context );

    void parseTextMask( QgsRenderContext &context );

    void parseTextFormatting( QgsRenderContext &context );

    void parseShapeBackground( QgsRenderContext &context );

    void parseDropShadow( QgsRenderContext &context );

    /**
     * Checks if a feature is larger than a minimum size (in mm)
     * \returns TRUE if above size, FALSE if below
    */
    bool checkMinimumSizeMM( const QgsRenderContext &ct, const QgsGeometry &geom, double minSize ) const;

    /**
     * Registers a feature as an obstacle only (no label rendered)
     */
    void registerObstacleFeature( const QgsFeature &f, QgsRenderContext &context, QgsLabelFeature **obstacleFeature, const QgsGeometry &obstacleGeometry = QgsGeometry() );

    QMap<Property, QVariant> dataDefinedValues;

    //! Property collection for data defined label settings
    QgsPropertyCollection mDataDefinedProperties;

    QgsExpression *expression = nullptr;

    QFontDatabase mFontDB;

    QgsTextFormat mFormat;

    std::unique_ptr< QgsCallout > mCallout;

    QgsLabelLineSettings mLineSettings;
    QgsLabelObstacleSettings mObstacleSettings;
    QgsLabelThinningSettings mThinningSettings;

    QgsLabeling::PolygonPlacementFlags mPolygonPlacementFlags = QgsLabeling::PolygonPlacementFlag::AllowPlacementInsideOfPolygon;

    QgsExpression mGeometryGeneratorExpression;

    bool mRenderStarted = false;

    static void initPropertyDefinitions();
};

/**
 * \ingroup core
 * \brief Represents a label candidate.
 */
class CORE_EXPORT QgsLabelCandidate
{
  public:
    QgsLabelCandidate( const QRectF &r, double c ): rect( r ), cost( c ) {}

    QRectF rect;
    double cost;
};




/**
 * \ingroup core
 * \brief Class that stores computed placement from labeling engine.
 * \since QGIS 2.4
 */
class CORE_EXPORT QgsLabelingResults
{
  public:
    QgsLabelingResults();
    ~QgsLabelingResults();

    //! QgsLabelingResults cannot be copied.
    QgsLabelingResults( const QgsLabelingResults & ) = delete;
    //! QgsLabelingResults cannot be copied.
    QgsLabelingResults &operator=( const QgsLabelingResults &rh ) = delete;

    //! Returns infos about labels at a given (map) position
    QList<QgsLabelPosition> labelsAtPosition( const QgsPointXY &p ) const;
    //! Returns infos about labels within a given (map) rectangle
    QList<QgsLabelPosition> labelsWithinRect( const QgsRectangle &r ) const;

    /**
     * Sets the map \a settings associated with the labeling run.
     * \since QGIS 3.4.8
     */
    void setMapSettings( const QgsMapSettings &settings );

  private:
#ifdef SIP_RUN
    QgsLabelingResults( const QgsLabelingResults & );
#endif

    std::unique_ptr< QgsLabelSearchTree > mLabelSearchTree;

    friend class QgsPalLabeling;
    friend class QgsVectorLayerLabelProvider;
    friend class QgsVectorLayerDiagramProvider;
};

/**
 * \ingroup core
 * \class QgsPalLabeling
 * \brief PAL labeling utilities.
 */
class CORE_EXPORT QgsPalLabeling
{
  public:

    /**
     * Called to find out whether a specified \a layer is used for labeling.
     * \since QGIS 2.4
     */
    static bool staticWillUseLayer( const QgsMapLayer *layer );

    //! \note not available in Python bindings
    static void drawLabelCandidateRect( pal::LabelPosition *lp, QPainter *painter, const QgsMapToPixel *xform, QList<QgsLabelCandidate> *candidates = nullptr ) SIP_SKIP;

    /**
     * Prepares a geometry for registration with PAL. Handles reprojection, rotation, clipping, etc.
     * \param geometry geometry to prepare
     * \param context render context
     * \param ct coordinate transform, or invalid transform if no transformation required
     * \param clipGeometry geometry to clip features to, if applicable
     * \param mergeLines TRUE if touching lines from this layer will be merged and treated as single features during labeling
     * \returns prepared geometry
     * \since QGIS 2.9
     */
    static QgsGeometry prepareGeometry( const QgsGeometry &geometry, QgsRenderContext &context, const QgsCoordinateTransform &ct, const QgsGeometry &clipGeometry = QgsGeometry(), bool mergeLines = false ) SIP_FACTORY;

    /**
     * Checks whether a geometry requires preparation before registration with PAL
     * \param geometry geometry to prepare
     * \param context render context
     * \param ct coordinate transform, or invalid transform if no transformation required
     * \param clipGeometry geometry to clip features to, if applicable
     * \param mergeLines TRUE if touching lines from this layer will be merged and treated as single features during labeling
     * \returns TRUE if geometry requires preparation
     * \since QGIS 2.9
     */
    static bool geometryRequiresPreparation( const QgsGeometry &geometry, QgsRenderContext &context, const QgsCoordinateTransform &ct, const QgsGeometry &clipGeometry = QgsGeometry(), bool mergeLines = false );

    /**
     * Splits a \a text string to a list of separate lines, using a specified wrap character (\a wrapCharacter).
     * The text string will be split on either newline characters or the wrap character.
     *
     * Since QGIS 3.4 the \a autoWrapLength argument can be used to specify an ideal length of line to automatically
     * wrap text to (automatic wrapping is disabled if \a autoWrapLength is 0). This automatic wrapping is performed
     * after processing wrapping using \a wrapCharacter. When auto wrapping is enabled, the \a useMaxLineLengthWhenAutoWrapping
     * argument controls whether the lines should be wrapped to an ideal maximum of \a autoWrapLength characters, or
     * if FALSE then the lines are wrapped to an ideal minimum length of \a autoWrapLength characters.
     *
     * \since QGIS 2.9
     */
    static QStringList splitToLines( const QString &text, const QString &wrapCharacter, int autoWrapLength = 0, bool useMaxLineLengthWhenAutoWrapping = true );

    /**
     * Splits a text string to a list of graphemes, which are the smallest allowable character
     * divisions in the string. This accounts for scripts were individual characters are not
     * allowed to be split apart (e.g., Arabic and Indic based scripts)
     * \param text string to split
     * \returns list of graphemes
     * \since QGIS 2.10
     */
    static QStringList splitToGraphemes( const QString &text );

  private:
    //! Update temporary QgsPalLayerSettings with any data defined text style values
    static void dataDefinedTextStyle( QgsPalLayerSettings &tmpLyr,
                                      const QMap< QgsPalLayerSettings::Property, QVariant > &ddValues );

    //! Update temporary QgsPalLayerSettings with any data defined text formatting values
    static void dataDefinedTextFormatting( QgsPalLayerSettings &tmpLyr,
                                           const QMap< QgsPalLayerSettings::Property, QVariant > &ddValues );

    //! Update temporary QgsPalLayerSettings with any data defined text buffer values
    static void dataDefinedTextBuffer( QgsPalLayerSettings &tmpLyr,
                                       const QMap< QgsPalLayerSettings::Property, QVariant > &ddValues );

    //! Update temporary QgsPalLayerSettings with any data defined mask values
    static void dataDefinedTextMask( QgsPalLayerSettings &tmpLyr,
                                     const QMap< QgsPalLayerSettings::Property, QVariant > &ddValues );

    //! Update temporary QgsPalLayerSettings with any data defined shape background values
    static void dataDefinedShapeBackground( QgsPalLayerSettings &tmpLyr,
                                            const QMap< QgsPalLayerSettings::Property, QVariant > &ddValues );

    //! Update temporary QgsPalLayerSettings with any data defined drop shadow values
    static void dataDefinedDropShadow( QgsPalLayerSettings &tmpLyr,
                                       const QMap< QgsPalLayerSettings::Property, QVariant > &ddValues );

    friend class QgsVectorLayerLabelProvider; // to allow calling the static methods above
    friend class QgsDxfExport;                // to allow calling the static methods above

    /**
     * Checks whether a geometry exceeds the minimum required size for a geometry to be labeled.
     * \param context render context
     * \param geom geometry
     * \param minSize minimum size for geometry
     * \returns TRUE if geometry exceeds minimum size
     * \since QGIS 2.9
     */
    static bool checkMinimumSizeMM( const QgsRenderContext &context, const QgsGeometry &geom, double minSize );

    friend class QgsPalLayerSettings;
};


#endif // QGSPALLABELING_H
