Title: Change MDI parent background
The decision consists in interception of the WM_ERASEBKGND, WM_VSCROLL and WM_HSCROLL messages and carry out draw of area by using DrawImage procedure or InvalidateRect procedure.
CreateWnd procedure uses SetWindowLong procedure for installation of new procedure of a window.
Don't forget to remove line
Application.CreateForm(TForm2, Form2) from project file and line
var Form2: TForm2 from unit2.pas file.
type
TForm1 = class(TForm)
...
private
{ Private declarations }
public
procedure ClientWndProc(var Message: TMessage);
procedure DrawImage;
{ Public declarations }
protected
procedure CreateWnd; override;
end;
var
Form1: TForm1;
NewClient, OldClient: TFarProc;
MyDC: hDC;
implementation
uses unit2;
{$R *.DFM}
procedure TForm1.CreateWnd;
begin
inherited CreateWnd;
NewClient:=MakeObjectInstance(ClientWndProc);
OldClient:=Pointer(GetWindowLong(ClientHandle, GWL_WNDPROC));
SetWindowLong(ClientHandle, GWL_WNDPROC, LongInt(NewClient));
end;
procedure TForm1.DrawImage;
{ This procedure tiles the image on the form's client area }
var
i, j: Integer;
WndRect, ImageRect: TRect;
Rows, Cols: Integer;
begin
GetWindowRect(ClientHandle, WndRect);
ImageRect:=Image1.ClientRect;
Rows:=WndRect.Bottom div ImageRect.Bottom;
Cols:=WndRect.Right div ImageRect.Right;
with Image1 do
for i:=0 to Rows+1 do
for j:=0 to Cols+1 do
BitBlt(MyDC, j*Picture.Width, i*Picture.Height, Picture.Width,
Picture.Height, Picture.Bitmap.Canvas.Handle, 0, 0, SRCCOPY);
end;
procedure TForm1.ClientWndProc(var Message: TMessage);
begin
case Message.Msg of
WM_ERASEBKGND:
begin
CallWindowProc(OldClient,
ClientHandle,
Message.Msg,
Message.wParam,
Message.lParam);
MyDC:=TWMEraseBkGnd(Message).DC;
DrawImage;
Message.Result:=1;
end;
WM_VSCROLL, WM_HSCROLL:
begin
Message.Result := CallWindowProc(OldClient,
ClientHandle,
Message.Msg,
Message.wParam,
Message.lParam);
InvalidateRect(ClientHandle, nil, True);
end;
else
Message.Result := CallWindowProc(OldClient,
ClientHandle,
Message.Msg,
Message.wParam,
Message.lParam);
end;
end;