procedure TForm1.DoInvisible;
var
AControl : TControl;
A, Margin, X, Y, CtlX, CtlY : Integer;
begin
Margin := ( Width - ClientWidth ) div 2;
//First, get form region
FullRgn := CreateRectRgn(0, 0, Width, Height);
//Find client area region
X := Margin;
Y := Height - ClientHeight - Margin;
ClientRgn := CreateRectRgn( X, Y, X + ClientWidth, Y + ClientHeight );
//'Mask' out all but non-client areas
CombineRgn( FullRgn, FullRgn, ClientRgn, RGN_DIFF );
//Now, walk through all the controls on the form and 'OR' them
// into the existing Full region.
for A := 0 to ControlCount - 1 do begin
AControl := Controls[A];
if ( AControl is TWinControl ) or ( AControl is TGraphicControl )
then with AControl do begin
if Visible then begin
CtlX := X + Left;
CtlY := Y + Top;
CtlRgn := CreateRectRgn( CtlX, CtlY, CtlX + Width, CtlY + Height );
CombineRgn( FullRgn, FullRgn, CtlRgn, RGN_OR );
end;
end;
end;
//When the region is all ready, put it into effect:
SetWindowRgn(Handle, FullRgn, TRUE);
end;