Title: Create a hole in application running
Use GetWindowRect, CombineRgn WinAPI functions, like this example:
var
Wnd: HWnd;
Region1, Region2: HRgn;
Rect: TRect;
begin
Wnd:=Application.MainForm.Handle;
GetWindowRect(Wnd,Rect);
Region1:=CreateRectRgn(0,0,Rect.Right-Rect.Left,Rect.Bottom-Rect.Top);
Region2:=CreateEllipticRgn(10,30,150,120);
CombineRgn(Region1,Region1,Region2,RGN_DIFF);
SetWindowRgn(Wnd,Region1,True);
end;