TCustomTreeView.OnCustomDraw Event

Occurs immediately prior to painting the tree view control.

Pascal

property OnCustomDraw: TTVCustomDrawEvent;

C++

__property TTVCustomDrawEvent OnCustomDraw;

Description

Write an OnCustomDraw event handler to paint an owner-drawn tree view. Use the Canvas property as a drawing surface when painting the image of the tree view.

To paint individual items, use the OnCustomDrawItem event instead.

Note: OnCustomDraw only occurs prior to painting the tree view control. To customize the painting at other stages of the paint process (such as after the default drawing), use OnAdvancedCustomDraw instead.

C++ Examples:

Copy Code

/*
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.
*/
void __fastcall TCustomDrawForm::TVCustomDraw(TCustomTreeView *Sender,
      const TRect &ARect, bool &DefaultDraw)
{
/*
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. Best to
subclass the TreeView and handle scrolling messages.
*/
  if (None1 != NULL)
  {
    if (None1->Checked) //no picture
    {
      TV->Canvas->Brush->Color = BkgColorDialog->Color;
      TV->Canvas->Brush->Style = FBrushStyle;
      TV->Canvas->FillRect(ARect);
    }
    else if (Tile1->Checked) //tile bitmap
    {
      TV->Canvas->Brush->Bitmap = Image1->Picture->Bitmap;
      TV->Canvas->FillRect(ARect);
    }
    else //Stretch across the canvas.
      TV->Canvas->StretchDraw(ARect, Image1->Picture->Bitmap);
  };
  DefaultDraw = FDefaultDraw;
  // Setting DefaultDraw to false here prevents all calls to
  // OnCustomDrawItem.
}

Delphi Examples:

Copy Code

{
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.
}
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. 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;