Set-the-background-color-of-a-mdi-form


            {*******************************************************************************
 *
 * Hintergrundfarbe eines MDI-Formulars setzen ohne die Farbe der darauf
 * liegenden Objekte wie TGroupBox oder TPageControl zu verändern.
 *
 * Setting the Background color of a MDI Form without changing the color
 * of overlayed objects like TGroupBox or TPageControl.
 *
 ******************************************************************************}
unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 Dialogs;
type
 TForm1 = class(TForm)
 private
 FClientInstance: TFarProc;
 FPrevClientProc: TFarProc;
 BkBrush: HBRUSH;
 procedure ClientWndProc(var Message: TMessage);
 public
 constructor Create(AOwner: TComponent); override;
 destructor Destroy; override;
 end;
implementation
{$R *.dfm}
constructor TForm1.Create(AOwner: TComponent);
begin
 inherited;
 BkBrush := CreateSolidBrush(clGray);
 FClientInstance := Classes.MakeObjectInstance(ClientWndProc);
 FPrevClientProc := Pointer(GetWindowLong(ClientHandle, GWL_WNDPROC));
 SetWindowLong(ClientHandle, GWL_WNDPROC, Longint(FClientInstance));
end;
destructor TForm1.Destroy;
begin
 DeleteObject(BkBrush);
 inherited;
end;
procedure TForm1.ClientWndProc(var Message: TMessage);
var
 DC: HDC;
 BrushOld: HBRUSH;
begin
 with Message do 
 begin
 case Msg of
 WM_ERASEBKGND:
 begin
 DC := TWMEraseBkGnd(Message).DC;
 BrushOld := SelectObject(DC, BkBrush);
 FillRect(DC, ClientRect, BkBrush);
 SelectObject(DC, BrushOld);
 Result := 1;
 end;
 else
 Result := CallWindowProc(FPrevClientProc, ClientHandle, Msg, wParam, lParam);
 end;
 end;
end;
end.
Forms Delphi
