TVCustomDraw (Delphi)

Description

The following example is taken from the custom draw demo. It shows how the OnCustomDraw event handler draws the background for the tree view before the items and lines are drawn.

Code

procedure TCustomDrawForm.TVCustomDraw(Sender: TCustomTreeView; const ARect: TRect;
  var DefaultDraw: Boolean);
begin
{
This event should be used to draw any background colors or 
images. ARect represents the entire client area of the TreeView.
Use the TreeView's canvas to do the drawing.
Note that drawing a background bitmap is not really 
supported by CustomDraw, so scrolling can get messy. It is 
best to subclass the TreeView and handle scrolling messages.
  with TV.Canvas do
  begin
    if None1 <> nil then
    begin
      if None1.Checked then //no picture
      begin
        Brush.Color := BkgColorDialog.Color;
        Brush.Style := FBrushStyle;
        FillRect(ARect);
      end else
        if Tile1.Checked then //Tile bitmap
        begin
          Brush.Bitmap := Image1.Picture.Bitmap;
            FillRect(ARect);
          end else //Stretch across the canvas
              StretchDraw(ARect, Image1.Picture.Bitmap);
    end;
  end;
  DefaultDraw := FDefaultDraw;
  // Setting DefaultDraw to False here prevents all calls to
  // OnCustomDrawItem.
end;

Uses

• Vcl.ComCtrls.TCustomTreeView.OnCustomDraw ( fr | de | ja )
• Vcl.ComCtrls.TCustomTreeView.Canvas ( fr | de | ja )
• Vcl.Graphics.TPicture.Bitmap ( fr | de | ja )
• Vcl.Graphics.TCanvas.StretchDraw ( fr | de | ja )