delphi - 高级自定义DrawItem时如何绘制TreeView样式选择矩形？

Question

我正在使用 OnAdvancedCustomDrawItem 事件从头开始自定义 TTreeView 绘图，我想知道如何在我的所有者绘制的背景中正确渲染这些选择和热矩形项目？它们是 Vista/7 风格的，所以我不能简单地用纯色填充背景。

我尝试在cdPostPaint阶段绘制我的项目，但如果我在cdPrePaint阶段留下DefaultDraw := True来绘制选择背景，发生完整的默认绘图，包括项目的文本。

procedure TForm1.TreeView1AdvancedCustomDrawItem(Sender: TCustomTreeView;
  Node: TTreeNode; State: TCustomDrawState; Stage: TCustomDrawStage; var PaintImages,
  DefaultDraw: Boolean);
begin
  case Stage of
    cdPreErase:
    begin
      DefaultDraw := True;
    end;

    cdPostErase:
    begin
      DefaultDraw := True;
    end;

    cdPrePaint:
    begin
      // I thought this will paint only the selected/hot backgrounds, 
      // however this will paint whole item, including text.
      DefaultDraw := True;
    end;

    cdPostPaint:
    begin
      DefaultDraw := False;

      // painting my owner-draw text
      // .........
    end;
  end;

  PaintImages := False;
end;

Answer 1

这是我的解决方案(经过测试)。

请注意，TreeView 必须具有 HotTrack := True 才能正常绘制热门项目。

未启用主题时还必须有额外的绘图。

uses
  UxTheme,
  Themes;

const
  TreeExpanderSpacing = 6;

procedure TForm1.DrawExpander(ACanvas: TCanvas; ATextRect: TRect; AExpanded: Boolean;
  AHot: Boolean);
var
  ExpanderRect: TRect;
  Graphics: IGPGraphics;
  Points: array of TGPPoint;
  Brush: IGPBrush;
  Pen: IGPPen;
  ThemeData: HTHEME;
  ElementPart: Integer;
  ElementState: Integer;
  ExpanderSize: TSize;
  UnthemedColor: TColor;
begin
  if ThemeServices.ThemesEnabled then
  begin
    if AHot then
      ElementPart := TVP_HOTGLYPH
    else
      ElementPart := TVP_GLYPH;

    if AExpanded then
      ElementState := GLPS_OPENED
    else
      ElementState := GLPS_CLOSED;

    ThemeData := OpenThemeData(TreeView1.Handle, VSCLASS_TREEVIEW);
    GetThemePartSize(ThemeData, ACanvas.Handle, ElementPart, ElementState, nil,
      TS_TRUE, ExpanderSize);
    ExpanderRect.Left := ATextRect.Left - TreeExpanderSpacing - ExpanderSize.cx;
    ExpanderRect.Right := ExpanderRect.Left + ExpanderSize.cx;
    ExpanderRect.Top := ATextRect.Top + (ATextRect.Bottom - ATextRect.Top - ExpanderSize.cy) div 2;
    ExpanderRect.Bottom := ExpanderRect.Top + ExpanderSize.cy;
    DrawThemeBackground(ThemeData, ACanvas.Handle, ElementPart, ElementState, ExpanderRect, nil);
    CloseThemeData(ThemeData);
  end
  else
  begin

    // Drawing expander without themes enabled

    Graphics := TGPGraphics.Create(ACanvas.Handle);
    Graphics.SmoothingMode := SmoothingModeHighQuality;

    ExpanderRect := ATextRect;
    ExpanderRect.Right := ATextRect.Left - TDPIAware.GetScaledSize(TreeExpanderSpacing96dpi);
    ExpanderRect.Left := ATextRect.Left - TDPIAware.GetScaledSize(TreeExpanderSpacing96dpi) -
      TDPIAware.GetScaledSize(Max(TreeExpanderCollapsedWidth96dpi, TreeExpanderExpandedWidth96dpi));

    if ASelected then
      UnthemedColor := ColorToRGB(clHighlightText)
    else
      if AExpanded then
        UnthemedColor := clBlack
      else
        UnthemedColor := clGray;

    SetLength(Points, 3);
    if AExpanded then
    begin
      Points[0] := TGPPoint.Create(ExpanderRect.Right, ExpanderRect.Top +
        (ExpanderRect.Bottom - ExpanderRect.Top - TreeExpanderExpandedHeight96dpi) div 2);
      Points[1] := TGPPoint.Create(ExpanderRect.Right, ExpanderRect.Top +
        (ExpanderRect.Bottom - ExpanderRect.Top + TreeExpanderExpandedHeight96dpi) div 2);
      Points[2] := TGPPoint.Create(ExpanderRect.Right - TreeExpanderExpandedWidth96dpi,
        ExpanderRect.Top + (ExpanderRect.Bottom - ExpanderRect.Top +
        TreeExpanderExpandedHeight96dpi) div 2);
      Brush := TGPSolidBrush.Create(TGPColor.CreateFromColorRef(UnthemedColor));
      Graphics.FillPolygon(Brush, Points);
    end
    else
    begin
      Points[0] := TGPPoint.Create(ExpanderRect.Right - TreeExpanderCollapsedWidth96dpi,
        ExpanderRect.Top + (ExpanderRect.Bottom - ExpanderRect.Top -
        TreeExpanderCollapsedHeight96dpi) div 2);
      Points[1] := TGPPoint.Create(ExpanderRect.Right,
        ExpanderRect.Top + (ExpanderRect.Bottom - ExpanderRect.Top) div 2);
      Points[2] := TGPPoint.Create(ExpanderRect.Right - TreeExpanderCollapsedWidth96dpi,
        ExpanderRect.Top + (ExpanderRect.Bottom - ExpanderRect.Top +
        TreeExpanderCollapsedHeight96dpi) div 2);
      Pen := TGPPen.Create(TGPColor.CreateFromColorRef(UnthemedColor));
      Graphics.DrawPolygon(Pen, Points);
    end;
  end;
end;

procedure TForm1.TreeView1AdvancedCustomDrawItem(Sender: TCustomTreeView;
  Node: TTreeNode; State: TCustomDrawState; Stage: TCustomDrawStage; var PaintImages,
  DefaultDraw: Boolean);
var
  NodeRect: TRect;
  NodeTextRect: TRect;
  Text: string;
  ThemeData: HTHEME;
  TreeItemState: Integer;
begin
  if Stage = cdPrePaint then
  begin
    NodeRect := Node.DisplayRect(False);
    NodeTextRect := Node.DisplayRect(True);

    // Drawing background
    if (cdsSelected in State) and Sender.Focused then
      TreeItemState := TREIS_SELECTED
    else
      if (cdsSelected in State) and (cdsHot in State) then
        TreeItemState := TREIS_HOTSELECTED
      else
        if cdsSelected in State then
          TreeItemState := TREIS_SELECTEDNOTFOCUS
        else
          if cdsHot in State then
            TreeItemState := TREIS_HOT
          else
            TreeItemState := TREEITEMStateFiller0;

    if TreeItemState <> TREEITEMStateFiller0 then
    begin
      ThemeData := OpenThemeData(Sender.Handle, VSCLASS_TREEVIEW);
      DrawThemeBackground(ThemeData, Sender.Canvas.Handle, TVP_TREEITEM, TreeItemState,
        NodeRect, nil);
      CloseThemeData(ThemeData);
    end;

    // Drawing expander
    if Node.HasChildren then
      DrawExpander(Sender.Canvas, NodeTextRect, Node.Expanded, cdsHot in State);

    // Drawing main text
    SetBkMode(Sender.Canvas.Handle, TRANSPARENT);
    SetTextColor(Sender.Canvas.Handle, clBlue);

    Text := Node.Text;
    Sender.Canvas.TextRect(NodeTextRect, Text,
      [tfVerticalCenter, tfSingleLine, tfEndEllipsis, tfLeft]);

    // Some extended drawing...

  end;

  PaintImages := False;
  DefaultDraw := False;
end;