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WM_NCCREATE
WM_NCCALCSIZE
WM_NCHITTEST
WM_NCLBUTTONDBLCLK
WM_NCLBUTTONDOWN
WM_NCPAINT
WM_NCACTIVATE					

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  procedure TFrmMain.DrawTitleBar;
  var
    Canvas: TCanvas;
    TitleBarHeight: Integer;
  begin
    TitleBarHeight := GetSystemMetrics( SM_CYCAPTION ) + 8 + FAdditionalTop; { Ursprüngliche Titlebar-Höhe + 8-Pixel Fensterrand (köntne man auch noch abfragen...) + Die zusätzliche Höhe } 
    Canvas := TCanvas.Create;
    try
      Canvas.Handle := GetWindowDC( Handle );
      with Canvas do
        begin
          // Rote Titlebar
          Brush.Color := clRed;
          Rectangle( 0, 0, Width, TitleBarHeight );
          // Blauer Rand
          Brush.Color := clBlue;
          // Links
          Rectangle( 0, TitleBarHeight, 8, Height );
          // Unten
          Rectangle( 0, Height - 8, Width, Height );
          // Rechts
          Rectangle( Width - 8, TitleBarHeight, Width, Height );
          // Clear
          Brush.Style := bsClear;
        end;
    finally
      Canvas.Free;
    end;
  end;

  procedure TFrmMain.WMNCPaint( var AMsg: TWMNCPaint );
  begin
    DrawTitleBar;
  end;

  procedure TFrmMain.WMNCCalcSize( var message: TWMNCCalcSize );
  begin
    inherited;
    FAdditionalTop := 17;
    Inc( message.CalcSize_Params^.rgrc[ 0 ].Top, FAdditionalTop );
  end;