# (C) Copyright 2004-2022 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!

""" A traits UI editor for editing tabular data (arrays, list of tuples, lists
    of objects, etc).
"""


import wx
import wx.lib.mixins.listctrl as listmix

from traits.api import (
    HasStrictTraits,
    Int,
    List,
    Bool,
    Instance,
    Any,
    Event,
    Property,
    TraitListEvent,
    Dict,
)

from traitsui.ui_traits import Image

from traitsui.tabular_adapter import TabularAdapter

from traitsui.wx.editor import Editor

from pyface.image_resource import ImageResource

from pyface.timer.api import do_later

from .constants import is_mac, scrollbar_dx


try:
    from pyface.wx.drag_and_drop import PythonDropSource, PythonDropTarget
except:
    PythonDropSource = PythonDropTarget = None


# Mapping for trait alignment values to wx alignment values:
alignment_map = {
    "left": wx.LIST_FORMAT_LEFT,
    "center": wx.LIST_FORMAT_CENTRE,
    "right": wx.LIST_FORMAT_RIGHT,
}


class TextEditMixin(listmix.TextEditMixin):
    def __init__(self, edit_labels):
        """edit_labels controls whether the first column is editable"""
        self.edit_labels = edit_labels
        listmix.TextEditMixin.__init__(self)

    def OpenEditor(self, col, row):
        if col == 0 and not self.edit_labels:
            return
        else:
            return listmix.TextEditMixin.OpenEditor(self, col, row)


class wxListCtrl(wx.ListCtrl, TextEditMixin):
    """Subclass of wx.ListCtrl to provide correct virtual list behavior."""

    def __init__(
        self,
        parent,
        ID,
        pos=wx.DefaultPosition,
        size=wx.DefaultSize,
        style=0,
        can_edit=False,
        edit_labels=False,
    ):

        wx.ListCtrl.__init__(self, parent, ID, pos, size, style)

        # if the selected is editable, then we have to init the mixin
        if can_edit:
            TextEditMixin.__init__(self, edit_labels)

    def make_editor(self, col_style=wx.LIST_FORMAT_LEFT):
        # override implementation in base class due to issue with destroying
        # editor

        style = wx.TE_PROCESS_ENTER | wx.TE_PROCESS_TAB | wx.TE_RICH2
        style |= {
            wx.LIST_FORMAT_LEFT: wx.TE_LEFT,
            wx.LIST_FORMAT_RIGHT: wx.TE_RIGHT,
            wx.LIST_FORMAT_CENTRE: wx.TE_CENTRE,
        }[col_style]

        editor = wx.TextCtrl(self, -1, style=style)
        editor.SetBackgroundColour(self.editorBgColour)
        editor.SetForegroundColour(self.editorFgColour)
        font = self.GetFont()
        editor.SetFont(font)

        self.curRow = 0
        self.curCol = 0

        editor.Hide()
        # Base class does explicit Destroy call here.  Should not be needed.
        # Excised code is as follows:
        #   if hasattr(self, 'editor'):
        #       self.editor.Destroy()
        # Dropping the reference to the editor should result in the
        # destruction of the underlying C++ widget just fine.

        self.editor = editor

        self.col_style = col_style
        self.editor.Bind(wx.EVT_CHAR, self.OnChar)
        self.editor.Bind(wx.EVT_KILL_FOCUS, self.CloseEditor)

    def SetVirtualData(self, row, col, text):
        # this method is called but the job is already done by
        # the _end_label_edit method. Commmented code is availabed
        # if needed
        pass
        # edit = self._editor
        # return editor.adapter.set_text( editor.object, editor.name,
        #                                row, col, text )

    def OnGetItemAttr(self, row):
        """Returns the display attributes to use for the specified list item."""
        # fixme: There appears to be a bug in wx in that they do not correctly
        # manage the reference count for the returned object, and it seems to be
        # gc'ed before they finish using it. So we store an object reference to
        # it to prevent it from going away too soon...
        self._attr = attr = wx.ItemAttr()
        editor = self._editor
        object, name = editor.object, editor.name

        color = editor.adapter.get_bg_color(object, name, row)
        if color is not None:
            attr.SetBackgroundColour(color)

        color = editor.adapter.get_text_color(object, name, row)
        if color is not None:
            attr.SetTextColour(color)

        font = editor.adapter.get_font(object, name, row)
        if font is not None:
            attr.SetFont(font)

        return attr

    def OnGetItemImage(self, row):
        """Returns the image index to use for the specified list item."""
        editor = self._editor
        image = editor._get_image(
            editor.adapter.get_image(editor.object, editor.name, row, 0)
        )
        if image is not None:
            return image

        return -1

    def OnGetItemColumnImage(self, row, column):
        """Returns the image index to use for the specified list item."""
        editor = self._editor
        image = editor._get_image(
            editor.adapter.get_image(editor.object, editor.name, row, column)
        )
        if image is not None:
            return image

        return -1

    def OnGetItemText(self, row, column):
        """Returns the text to use for the specified list item."""
        editor = self._editor
        return editor.adapter.get_text(editor.object, editor.name, row, column)


class TabularEditor(Editor):
    """A traits UI editor for editing tabular data (arrays, list of tuples,
    lists of objects, etc).
    """

    # -- Trait Definitions ----------------------------------------------------

    #: The event fired when a table update is needed:
    update = Event()

    #: The event fired when a simple repaint is needed:
    refresh = Event()

    #: The current set of selected items (which one is used depends upon the
    #: initial state of the editor factory 'multi_select' trait):
    selected = Any()
    multi_selected = List()

    #: The current set of selected item indices (which one is used depends upon
    #: the initial state of the editor factory 'multi_select' trait):
    selected_row = Int(-1)
    multi_selected_rows = List(Int)

    #: The most recently actived item and its index:
    activated = Any()
    activated_row = Int()

    #: The most recent left click data:
    clicked = Instance("TabularEditorEvent")

    #: The most recent left double click data:
    dclicked = Instance("TabularEditorEvent")

    #: The most recent right click data:
    right_clicked = Instance("TabularEditorEvent")

    #: The most recent right double click data:
    right_dclicked = Instance("TabularEditorEvent")

    #: The most recent column click data:
    column_clicked = Instance("TabularEditorEvent")

    #: Is the tabular editor scrollable? This value overrides the default.
    scrollable = True

    #: Row index of item to select after rebuilding editor list:
    row = Any()

    #: Should the selected item be edited after rebuilding the editor list:
    edit = Bool(False)

    #: The adapter from trait values to editor values:
    adapter = Instance(TabularAdapter)

    #: Dictionary mapping image names to wx.ImageList indices:
    images = Dict()

    #: Dictionary mapping ImageResource objects to wx.ImageList indices:
    image_resources = Dict()

    #: An image being converted:
    image = Image

    #: Flag for marking whether the update was within the visible area
    _update_visible = Bool(False)

    def init(self, parent):
        """Finishes initializing the editor by creating the underlying toolkit
        widget.
        """
        factory = self.factory

        # Set up the adapter to use:
        self.adapter = factory.adapter

        # Determine the style to use for the list control:
        style = wx.LC_REPORT | wx.LC_VIRTUAL | wx.BORDER_NONE

        if factory.editable_labels:
            style |= wx.LC_EDIT_LABELS

        if factory.horizontal_lines:
            style |= wx.LC_HRULES

        if factory.vertical_lines:
            style |= wx.LC_VRULES

        if not factory.multi_select:
            style |= wx.LC_SINGLE_SEL

        if not factory.show_titles:
            style |= wx.LC_NO_HEADER

        # Create the list control and link it back to us:
        self.control = control = wxListCtrl(
            parent,
            -1,
            style=style,
            can_edit=factory.editable,
            edit_labels=factory.editable_labels,
        )
        control._editor = self

        # Create the list control column:
        # fixme: what do we do here?
        # control.InsertColumn( 0, '' )

        # Set up the list control's event handlers:
        id = control.GetId()
        parent.Bind(wx.EVT_LIST_BEGIN_DRAG, self._begin_drag, id=id)
        parent.Bind(
            wx.EVT_LIST_BEGIN_LABEL_EDIT, self._begin_label_edit, id=id
        )
        parent.Bind(wx.EVT_LIST_END_LABEL_EDIT, self._end_label_edit, id=id)
        parent.Bind(wx.EVT_LIST_ITEM_SELECTED, self._item_selected, id=id)
        parent.Bind(wx.EVT_LIST_ITEM_DESELECTED, self._item_selected, id=id)
        parent.Bind(wx.EVT_LIST_KEY_DOWN, self._key_down, id=id)
        parent.Bind(wx.EVT_LIST_ITEM_ACTIVATED, self._item_activated, id=id)
        parent.Bind(wx.EVT_LIST_COL_END_DRAG, self._size_modified, id=id)
        parent.Bind(
            wx.EVT_LIST_COL_RIGHT_CLICK, self._column_right_clicked, id=id
        )
        parent.Bind(wx.EVT_LIST_COL_CLICK, self._column_clicked, id=id)
        control.Bind(wx.EVT_LEFT_DOWN, self._left_down)
        control.Bind(wx.EVT_LEFT_DCLICK, self._left_dclick)
        control.Bind(wx.EVT_RIGHT_DOWN, self._right_down)
        control.Bind(wx.EVT_RIGHT_DCLICK, self._right_dclick)
        control.Bind(wx.EVT_MOTION, self._motion)
        control.Bind(wx.EVT_SIZE, self._size_modified)

        # Set up the drag and drop target:
        if PythonDropTarget is not None:
            control.SetDropTarget(PythonDropTarget(self))

        # Set up the selection listener (if necessary):
        if factory.multi_select:
            self.sync_value(
                factory.selected, "multi_selected", "both", is_list=True
            )
            self.sync_value(
                factory.selected_row,
                "multi_selected_rows",
                "both",
                is_list=True,
            )
        else:
            self.sync_value(factory.selected, "selected", "both")
            self.sync_value(factory.selected_row, "selected_row", "both")

        # Synchronize other interesting traits as necessary:
        self.sync_value(factory.update, "update", "from", is_event=True)
        self.sync_value(factory.refresh, "refresh", "from", is_event=True)

        self.sync_value(factory.activated, "activated", "to")
        self.sync_value(factory.activated_row, "activated_row", "to")

        self.sync_value(factory.clicked, "clicked", "to")
        self.sync_value(factory.dclicked, "dclicked", "to")

        self.sync_value(factory.right_clicked, "right_clicked", "to")
        self.sync_value(factory.right_dclicked, "right_dclicked", "to")

        self.sync_value(factory.column_clicked, "column_clicked", "to")

        # Make sure we listen for 'items' changes as well as complete list
        # replacements:
        try:
            self.context_object.on_trait_change(
                self.update_editor,
                self.extended_name + "_items",
                dispatch="ui",
            )
        except:
            pass

        # If the user has requested automatic update, attempt to set up the
        # appropriate listeners:
        if factory.auto_update:
            self.context_object.on_trait_change(
                self.refresh_editor, self.extended_name + ".-", dispatch="ui"
            )

        # Create the mapping from user supplied images to wx.ImageList indices:
        for image_resource in factory.images:
            self._add_image(image_resource)

        # Refresh the editor whenever the adapter changes:
        self.on_trait_change(self._refresh, "adapter.+update", dispatch="ui")

        # Rebuild the editor columns and headers whenever the adapter's
        # 'columns' changes:
        self.on_trait_change(
            self._rebuild_all, "adapter.columns", dispatch="ui"
        )

        # Make sure the tabular view gets initialized:
        self._rebuild()

        # Set the list control's tooltip:
        self.set_tooltip()

    def dispose(self):
        """Disposes of the contents of an editor."""
        # Remove all of the wx event handlers:
        control = self.control
        parent = control.GetParent()
        id = control.GetId()
        parent.Bind(wx.EVT_LIST_BEGIN_DRAG, None, id=id)
        parent.Bind(wx.EVT_LIST_BEGIN_LABEL_EDIT, None, id=id)
        parent.Bind(wx.EVT_LIST_END_LABEL_EDIT, None, id=id)
        parent.Bind(wx.EVT_LIST_ITEM_SELECTED, None, id=id)
        parent.Bind(wx.EVT_LIST_ITEM_DESELECTED, None, id=id)
        parent.Bind(wx.EVT_LIST_KEY_DOWN, None, id=id)
        parent.Bind(wx.EVT_LIST_ITEM_ACTIVATED, None, id=id)
        parent.Bind(wx.EVT_LIST_COL_END_DRAG, None, id=id)
        parent.Bind(wx.EVT_LIST_COL_RIGHT_CLICK, None, id=id)
        parent.Bind(wx.EVT_LIST_COL_CLICK, None, id=id)
        control.Unbind(wx.EVT_LEFT_DOWN)
        control.Unbind(wx.EVT_LEFT_DCLICK)
        control.Unbind(wx.EVT_RIGHT_DOWN)
        control.Unbind(wx.EVT_RIGHT_DCLICK)
        control.Unbind(wx.EVT_MOTION)
        control.Unbind(wx.EVT_SIZE)

        self.context_object.on_trait_change(
            self.update_editor, self.extended_name + "_items", remove=True
        )

        if self.factory.auto_update:
            self.context_object.on_trait_change(
                self.refresh_editor, self.extended_name + ".-", remove=True
            )

        self.on_trait_change(self._refresh, "adapter.+update", remove=True)
        self.on_trait_change(self._rebuild_all, "adapter.columns", remove=True)

        super().dispose()

    def _update_changed(self, event):
        """Handles the 'update' event being fired."""
        if event is True:
            self.update_editor()
        elif isinstance(event, int):
            self._refresh_row(event)
        else:
            self._refresh_editor(event)

    def refresh_editor(self, item, name, old, new):
        """Handles a table item attribute being changed."""
        self._refresh_editor(item)

    def _refresh_editor(self, item):
        """Handles a table item being changed."""
        adapter = self.adapter
        object, name = self.object, self.name
        agi = adapter.get_item
        for row in range(adapter.len(object, name)):
            if item is agi(object, name, row):
                self._refresh_row(row)
                return

        self.update_editor()

    def _refresh_row(self, row):
        """Updates the editor control when a specified table row changes."""
        self.control.RefreshRect(
            self.control.GetItemRect(row, wx.LIST_RECT_BOUNDS)
        )

    def _update_editor(self, object, name, old_value, new_value):
        """Performs updates when the object trait changes.
        Overloads traitsui.editor.UIEditor
        """
        self._update_visible = True

        super()._update_editor(object, name, old_value, new_value)

    def update_editor(self):
        """Updates the editor when the object trait changes externally to the
        editor.
        """
        control = self.control
        n = self.adapter.len(self.object, self.name)
        top = control.GetTopItem()
        pn = control.GetCountPerPage()
        bottom = min(top + pn - 1, n)

        control.SetItemCount(n)

        if self._update_visible:
            control.RefreshItems(0, n - 1)
            self._update_visible = False

        if len(self.multi_selected_rows) > 0:
            self._multi_selected_rows_changed(self.multi_selected_rows)
        if len(self.multi_selected) > 0:
            self._multi_selected_changed(self.multi_selected)

        edit, self.edit = self.edit, False
        row, self.row = self.row, None

        if row is not None:
            if row >= n:
                row -= 1
                if row < 0:
                    row = None

        if row is None:
            visible = bottom
            if visible >= 0 and visible < control.GetItemCount():
                control.EnsureVisible(visible)
            return

        if 0 <= (row - top) < pn:
            control.EnsureVisible(
                min(top + pn - 2, control.GetItemCount() - 1)
            )
        elif row < top:
            control.EnsureVisible(
                min(row + pn - 1, control.GetItemCount() - 1)
            )
        else:
            control.EnsureVisible(row)

        control.SetItemState(
            row,
            wx.LIST_STATE_SELECTED | wx.LIST_STATE_FOCUSED,
            wx.LIST_STATE_SELECTED | wx.LIST_STATE_FOCUSED,
        )

        if edit:
            control.EditLabel(row)

    # -- Trait Event Handlers -------------------------------------------------

    def _selected_changed(self, selected):
        """Handles the editor's 'selected' trait being changed."""
        if not self._no_update:
            if selected is None:
                for row in self._get_selected():
                    self.control.SetItemState(row, 0, wx.LIST_STATE_SELECTED)
            else:
                try:
                    self.control.SetItemState(
                        self.value.index(selected),
                        wx.LIST_STATE_SELECTED,
                        wx.LIST_STATE_SELECTED,
                    )
                except:
                    pass

    def _selected_row_changed(self, old, new):
        """Handles the editor's 'selected_index' trait being changed."""
        if not self._no_update:
            if new < 0:
                if old >= 0:
                    self.control.SetItemState(old, 0, wx.LIST_STATE_SELECTED)
            else:
                self.control.SetItemState(
                    new, wx.LIST_STATE_SELECTED, wx.LIST_STATE_SELECTED
                )

    def _multi_selected_changed(self, selected):
        """Handles the editor's 'multi_selected' trait being changed."""
        if not self._no_update:
            values = self.value
            try:
                self._multi_selected_rows_changed(
                    [values.index(item) for item in selected]
                )
            except:
                pass

    def _multi_selected_items_changed(self, event):
        """Handles the editor's 'multi_selected' trait being modified."""
        values = self.value
        try:
            self._multi_selected_rows_items_changed(
                TraitListEvent(
                    index=0,
                    removed=[values.index(item) for item in event.removed],
                    added=[values.index(item) for item in event.added],
                )
            )
        except:
            pass

    def _multi_selected_rows_changed(self, selected_rows):
        """Handles the editor's 'multi_selected_rows' trait being changed."""
        if not self._no_update:
            control = self.control
            selected = self._get_selected()

            # Select any new items that aren't already selected:
            for row in selected_rows:
                if row in selected:
                    selected.remove(row)
                else:
                    control.SetItemState(
                        row, wx.LIST_STATE_SELECTED, wx.LIST_STATE_SELECTED
                    )

            # Unselect all remaining selected items that aren't selected now:
            for row in selected:
                control.SetItemState(row, 0, wx.LIST_STATE_SELECTED)

    def _multi_selected_rows_items_changed(self, event):
        """Handles the editor's 'multi_selected_rows' trait being modified."""
        control = self.control

        # Remove all items that are no longer selected:
        for row in event.removed:
            control.SetItemState(row, 0, wx.LIST_STATE_SELECTED)

        # Select all newly added items:
        for row in event.added:
            control.SetItemState(
                row, wx.LIST_STATE_SELECTED, wx.LIST_STATE_SELECTED
            )

    def _refresh_changed(self):
        self.update_editor()

    # -- List Control Event Handlers ------------------------------------------

    def _left_down(self, event):
        """Handles the left mouse button being pressed."""
        self._mouse_click(event, "clicked")

    def _left_dclick(self, event):
        """Handles the left mouse button being double clicked."""
        self._mouse_click(event, "dclicked")

    def _right_down(self, event):
        """Handles the right mouse button being pressed."""
        self._mouse_click(event, "right_clicked")

    def _right_dclick(self, event):
        """Handles the right mouse button being double clicked."""
        self._mouse_click(event, "right_dclicked")

    def _begin_drag(self, event):
        """Handles the user beginning a drag operation with the left mouse
        button.
        """
        if PythonDropSource is not None:
            adapter = self.adapter
            object, name = self.object, self.name
            selected = self._get_selected()
            drag_items = []

            # Collect all of the selected items to drag:
            for row in selected:
                drag = adapter.get_drag(object, name, row)
                if drag is None:
                    return

                drag_items.append(drag)

            # Save the drag item indices, so that we can later handle a
            # completed 'move' operation:
            self._drag_rows = selected

            try:
                # If only one item is being dragged, drag it as an item, not a
                # list:
                if len(drag_items) == 1:
                    drag_items = drag_items[0]

                # Perform the drag and drop operation:
                ds = PythonDropSource(self.control, drag_items)

                # If moves are allowed and the result was a drag move:
                if (ds.result == wx.DragMove) and (
                    self._drag_local or self.factory.drag_move
                ):
                    # Then delete all of the original items (in reverse order
                    # from highest to lowest, so the indices don't need to be
                    # adjusted):
                    rows = self._drag_rows
                    rows.reverse()
                    for row in rows:
                        adapter.delete(object, name, row)
            finally:
                self._drag_rows = None
                self._drag_local = False

    def _begin_label_edit(self, event):
        """Handles the user starting to edit an item label."""
        if not self.adapter.get_can_edit(
            self.object, self.name, event.GetIndex()
        ):
            event.Veto()

    def _end_label_edit(self, event):
        """Handles the user finishing editing an item label."""
        self.adapter.set_text(
            self.object,
            self.name,
            event.GetIndex(),
            event.GetColumn(),
            event.GetText(),
        )
        self.row = event.GetIndex() + 1

    def _item_selected(self, event):
        """Handles an item being selected."""
        self._no_update = True
        try:
            get_item = self.adapter.get_item
            object, name = self.object, self.name
            selected_rows = self._get_selected()
            if self.factory.multi_select:
                self.multi_selected_rows = selected_rows
                self.multi_selected = [
                    get_item(object, name, row) for row in selected_rows
                ]
            elif len(selected_rows) == 0:
                self.selected_row = -1
                self.selected = None
            else:
                self.selected_row = selected_rows[0]
                self.selected = get_item(object, name, selected_rows[0])
        finally:
            self._no_update = False

    def _item_activated(self, event):
        """Handles an item being activated (double-clicked or enter pressed)."""
        self.activated_row = event.GetIndex()
        self.activated = self.adapter.get_item(
            self.object, self.name, self.activated_row
        )

    def _key_down(self, event):
        """Handles the user pressing a key in the list control."""
        key = event.GetKeyCode()
        if key == wx.WXK_PAGEDOWN:
            self._append_new()
        elif key in (wx.WXK_BACK, wx.WXK_DELETE):
            self._delete_current()
        elif key == wx.WXK_INSERT:
            self._insert_current()
        elif key == wx.WXK_LEFT:
            self._move_up_current()
        elif key == wx.WXK_RIGHT:
            self._move_down_current()
        elif key in (wx.WXK_RETURN, wx.WXK_ESCAPE):
            self._edit_current()
        else:
            event.Skip()

    def _column_right_clicked(self, event):
        """Handles the user right-clicking a column header."""
        column = event.GetColumn()
        if (self._cached_widths is not None) and (
            0 <= column < len(self._cached_widths)
        ):
            self._cached_widths[column] = None
            self._size_modified(event)

    def _column_clicked(self, event):
        """Handles the right mouse button being double clicked."""
        editor_event = TabularEditorEvent(
            editor=self, row=0, column=event.GetColumn()
        )

        setattr(self, "column_clicked", editor_event)
        event.Skip()

    def _size_modified(self, event):
        """Handles the size of the list control being changed."""
        control = self.control
        n = control.GetColumnCount()
        if n == 1:
            dx, dy = control.GetClientSize()
            control.SetColumnWidth(0, dx - 1)
        elif n > 1:
            do_later(self._set_column_widths)

        event.Skip()

    def _motion(self, event):
        """Handles the user moving the mouse."""
        x = event.GetX()
        column = self._get_column(x)
        row, flags = self.control.HitTest(wx.Point(x, event.GetY()))
        if (row != self._last_row) or (column != self._last_column):
            self._last_row, self._last_column = row, column
            if (row == -1) or (column is None):
                tooltip = ""
            else:
                tooltip = self.adapter.get_tooltip(
                    self.object, self.name, row, column
                )
            if tooltip != self._last_tooltip:
                self._last_tooltip = tooltip
                wx.ToolTip.Enable(False)
                wx.ToolTip.Enable(True)
                self.control.SetToolTip(wx.ToolTip(tooltip))

    # -- Drag and Drop Event Handlers -----------------------------------------

    def wx_dropped_on(self, x, y, data, drag_result):
        """Handles a Python object being dropped on the list control."""
        row, flags = self.control.HitTest(wx.Point(x, y))

        # If the user dropped it on an empty list, set the target as past the
        # end of the list:
        if (
            (row == -1)
            and ((flags & wx.LIST_HITTEST_NOWHERE) != 0)
            and (self.control.GetItemCount() == 0)
        ):
            row = 0

        # If we have a valid drop target row, proceed:
        if row != -1:
            if not isinstance(data, list):
                # Handle the case of just a single item being dropped:
                self._wx_dropped_on(row, data)
            else:
                # Handles the case of a list of items being dropped, being
                # careful to preserve the original order of the source items if
                # possible:
                data.reverse()
                for item in data:
                    self._wx_dropped_on(row, item)

            # If this was an inter-list drag, mark it as 'local':
            if self._drag_indices is not None:
                self._drag_local = True

            # Return a successful drop result:
            return drag_result

        # Indicate we could not process the drop:
        return wx.DragNone

    def _wx_dropped_on(self, row, item):
        """Helper method for handling a single item dropped on the list
        control.
        """
        adapter = self.adapter
        object, name = self.object, self.name

        # Obtain the destination of the dropped item relative to the target:
        destination = adapter.get_dropped(object, name, row, item)

        # Adjust the target index accordingly:
        if destination == "after":
            row += 1

        # Insert the dropped item at the requested position:
        adapter.insert(object, name, row, item)

        # If the source for the drag was also this list control, we need to
        # adjust the original source indices to account for their new position
        # after the drag operation:
        rows = self._drag_rows
        if rows is not None:
            for i in range(len(rows) - 1, -1, -1):
                if rows[i] < row:
                    break

                rows[i] += 1

    def wx_drag_over(self, x, y, data, drag_result):
        """Handles a Python object being dragged over the tree."""
        if isinstance(data, list):
            rc = wx.DragNone
            for item in data:
                rc = self.wx_drag_over(x, y, item, drag_result)
                if rc == wx.DragNone:
                    break

            return rc

        row, flags = self.control.HitTest(wx.Point(x, y))

        # If the user is dragging over an empty list, set the target to the end
        # of the list:
        if (
            (row == -1)
            and ((flags & wx.LIST_HITTEST_NOWHERE) != 0)
            and (self.control.GetItemCount() == 0)
        ):
            row = 0

        # If the drag target index is valid and the adapter says it is OK to
        # drop the data here, then indicate the data can be dropped:
        if (row != -1) and self.adapter.get_can_drop(
            self.object, self.name, row, data
        ):
            return drag_result

        # Else indicate that we will not accept the data:
        return wx.DragNone

    # -- UI preference save/restore interface ---------------------------------

    def restore_prefs(self, prefs):
        """Restores any saved user preference information associated with the
        editor.
        """
        self._cached_widths = cws = prefs.get("cached_widths")
        if cws is not None:
            set_column_width = self.control.SetColumnWidth
            for i, width in enumerate(cws):
                if width is not None:
                    set_column_width(i, width)

    def save_prefs(self):
        """Returns any user preference information associated with the editor."""
        cws = self._cached_widths
        if cws is not None:
            cws = [cw if cw is not None and cw >= 0 else None for cw in cws]

        return {"cached_widths": cws}

    # -- Private Methods ------------------------------------------------------

    def _refresh(self):
        """Refreshes the contents of the editor's list control."""
        n = self.adapter.len(self.object, self.name)
        if n > 0:
            self.control.RefreshItems(0, n - 1)

    def _rebuild(self):
        """Rebuilds the contents of the editor's list control."""
        control = self.control
        control.ClearAll()
        adapter, object, name = self.adapter, self.object, self.name
        adapter.object, adapter.name = object, name
        get_alignment = adapter.get_alignment
        get_width = adapter.get_width
        for i, label in enumerate(adapter.label_map):
            control.InsertColumn(
                i,
                label,
                alignment_map.get(
                    get_alignment(object, name, i), wx.LIST_FORMAT_LEFT
                ),
            )
        self._set_column_widths()

    def _rebuild_all(self):
        """Rebuilds the structure of the list control, then refreshes its
        contents.
        """
        self._rebuild()
        self.update_editor()

    def _set_column_widths(self):
        """Set the column widths for the current set of columns."""
        control = self.control
        if control is None:
            return

        object, name = self.object, self.name
        dx, dy = control.GetClientSize()
        if is_mac:
            dx -= scrollbar_dx
        n = control.GetColumnCount()
        get_width = self.adapter.get_width
        pdx = 0
        wdx = 0.0
        widths = []
        cached = self._cached_widths
        current = [control.GetColumnWidth(i) for i in range(n)]
        if (cached is None) or (len(cached) != n):
            self._cached_widths = cached = [None] * n

        for i in range(n):
            cw = cached[i]
            if (cw is None) or (-cw == current[i]):
                width = float(get_width(object, name, i))
                if width <= 0.0:
                    width = 0.1
                if width <= 1.0:
                    wdx += width
                    cached[i] = -1
                else:
                    width = int(width)
                    pdx += width
                    if cw is None:
                        cached[i] = width
            else:
                cached[i] = width = current[i]
                pdx += width

            widths.append(width)

        adx = max(0, dx - pdx)

        control.Freeze()
        for i in range(n):
            width = cached[i]
            if width < 0:
                width = widths[i]
                if width <= 1.0:
                    widths[i] = w = max(30, int(round((adx * width) / wdx)))
                    wdx -= width
                    width = w
                    adx -= width
                    cached[i] = -w

            control.SetColumnWidth(i, width)

        control.Thaw()

    def _add_image(self, image_resource):
        """Adds a new image to the wx.ImageList and its associated mapping."""
        bitmap = image_resource.create_image().ConvertToBitmap()

        image_list = self._image_list
        if image_list is None:
            self._image_list = image_list = wx.ImageList(
                bitmap.GetWidth(), bitmap.GetHeight()
            )
            self.control.AssignImageList(image_list, wx.IMAGE_LIST_SMALL)

        self.image_resources[image_resource] = self.images[
            image_resource.name
        ] = row = image_list.Add(bitmap)

        return row

    def _get_image(self, image):
        """Converts a user specified image to a wx.ListCtrl image index."""
        if isinstance(image, str):
            self.image = image
            image = self.image

        if isinstance(image, ImageResource):
            result = self.image_resources.get(image)
            if result is not None:
                return result

            return self._add_image(image)

        return self.images.get(image)

    def _get_selected(self):
        """Returns a list of the rows of all currently selected list items."""
        selected = []
        item = -1
        control = self.control

        # Handle case where the list is cleared
        if len(self.value) == 0:
            return selected

        while True:
            item = control.GetNextItem(
                item, wx.LIST_NEXT_ALL, wx.LIST_STATE_SELECTED
            )
            if item == -1:
                break

            selected.append(item)

        return selected

    def _append_new(self):
        """Append a new item to the end of the list control."""
        if "append" in self.factory.operations:
            adapter = self.adapter
            self.row = self.control.GetItemCount()
            self.edit = True
            adapter.insert(
                self.object,
                self.name,
                self.row,
                adapter.get_default_value(self.object, self.name),
            )

    def _insert_current(self):
        """Inserts a new item after the currently selected list control item."""
        if "insert" in self.factory.operations:
            selected = self._get_selected()
            if len(selected) == 1:
                adapter = self.adapter
                adapter.insert(
                    self.object,
                    self.name,
                    selected[0],
                    adapter.get_default_value(self.object, self.name),
                )
                self.row = selected[0]
                self.edit = True

    def _delete_current(self):
        """Deletes the currently selected items from the list control."""
        if "delete" in self.factory.operations:
            selected = self._get_selected()
            if len(selected) == 0:
                return

            delete = self.adapter.delete
            selected.reverse()
            for row in selected:
                delete(self.object, self.name, row)

            n = self.adapter.len(self.object, self.name)
            if not self.factory.multi_select:
                self.selected_row = self.row = n - 1 if row >= n else row
            else:
                # FIXME: What should the selection be?
                self.multi_selected = []
                self.multi_selected_rows = []

    def _move_up_current(self):
        """Moves the currently selected item up one line in the list control."""
        if "move" in self.factory.operations:
            selected = self._get_selected()
            if len(selected) == 1:
                row = selected[0]
                if row > 0:
                    adapter = self.adapter
                    object, name = self.object, self.name
                    item = adapter.get_item(object, name, row)
                    adapter.delete(object, name, row)
                    adapter.insert(object, name, row - 1, item)
                    self.row = row - 1

    def _move_down_current(self):
        """Moves the currently selected item down one line in the list control."""
        if "move" in self.factory.operations:
            selected = self._get_selected()
            if len(selected) == 1:
                row = selected[0]
                if row < (self.control.GetItemCount() - 1):
                    adapter = self.adapter
                    object, name = self.object, self.name
                    item = adapter.get_item(object, name, row)
                    adapter.delete(object, name, row)
                    adapter.insert(object, name, row + 1, item)
                    self.row = row + 1

    def _edit_current(self):
        """Allows the user to edit the current item in the list control."""
        if "edit" in self.factory.operations and self.factory.editable_labels:
            selected = self._get_selected()
            if len(selected) == 1:
                self.control.EditLabel(selected[0])

    def _get_column(self, x, translate=False):
        """Returns the column index corresponding to a specified x position."""
        if x >= 0:
            control = self.control
            for i in range(control.GetColumnCount()):
                x -= control.GetColumnWidth(i)
                if x < 0:
                    if translate:
                        return self.adapter.get_column(
                            self.object, self.name, i
                        )

                    return i

        return None

    def _mouse_click(self, event, trait):
        """Generate a TabularEditorEvent event for a specified mouse event and
        editor trait name.
        """
        x = event.GetX()
        row, flags = self.control.HitTest(wx.Point(x, event.GetY()))
        if row == wx.NOT_FOUND:
            if self.factory.multi_select:
                self.multi_selected = []
                self.multi_selected_rows = []
            else:
                self.selected = None
                self.selected_row = -1
        else:
            if self.factory.multi_select and event.ShiftDown():
                # Handle shift-click multi-selections because the wx.ListCtrl
                # does not (by design, apparently).
                # We must append this to the event queue because the
                # multi-selection will not be recorded until this event handler
                # finishes and lets the widget actually handle the event.
                do_later(self._item_selected, None)

            setattr(
                self,
                trait,
                TabularEditorEvent(
                    editor=self,
                    row=row,
                    column=self._get_column(x, translate=True),
                ),
            )

        # wx should continue with additional event handlers. Skip(False)
        # actually means to skip looking, skip(True) means to keep looking.
        # This seems backwards to me...
        event.Skip(True)


class TabularEditorEvent(HasStrictTraits):

    #: The index of the row:
    row = Int()

    #: The id of the column (either a string or an integer):
    column = Any()

    #: The row item:
    item = Property()

    # -- Private Traits -------------------------------------------------------

    #: The editor the event is associated with:
    editor = Instance(TabularEditor)

    # -- Property Implementations ---------------------------------------------

    def _get_item(self):
        editor = self.editor
        return editor.adapter.get_item(editor.object, editor.name, self.row)
