delphi – 如何从TListBox中删除虚线焦点矩形？

procedure TCustomListBox.CNDrawItem(var Message: TWMDrawItem); 

...

  ..
    if Integer(itemID) >= 0 then
      DrawItem(itemID,rcItem,State)      //-> calls message handler
    else
      FCanvas.FillRect(rcItem);
    if (odFocused in State) and not TStyleManager.IsCustomStyleActive then
      DrawFocusRect(hDC,rcItem);          //-> draws focus rectangle
  ..
..

无论你在事件处理程序中绘制什么,以后都会被VCL集中.

但请注意VCL使用DrawFocusRect绘制焦点矩形：

Because DrawFocusRect is an XOR function,calling it a second time
with the same rectangle removes the rectangle from the screen.

所以只需自己调用DrawFocusRect并让VCL调用擦除它：

procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer;
  ARect: TRect; State: TOwnerDrawState);
begin
  with ListBox1.Canvas do begin
    Brush.Color := clWhite;
    Pen.Color := clWhite;
    FillRect(ARect);
    if odFocused in State then  // also check for styles if there's a possibility of using ..
      DrawFocusRect(ARect);
  end;
end;

(*)通常,默认窗口过程为所有者绘制的列表框项目绘制焦点矩形以响应WM_DRAWITEM消息.但是,在VCL处理消息时,不会为列表框调用默认窗口过程.