Ya he encontrado solución con este código de ejemplo funciona perfecto en win10 x64:
Código PHP:
TForm1 = class(TForm)
....
protected
FPreviousBoundsRect: TRect;
procedure FlipFullScreen;
....
public
....
end;
implementation
procedure TForm1.FormCreate(Sender: TObject);
begin
FPreviousBoundsRect := BoundsRect;
end;
procedure TForm1.FlipFullScreen;
var
WindowStyle: NativeInt;
begin
WindowStyle := GetWindowLong(Handle, GWL_STYLE);
if ((WindowStyle and WS_OVERLAPPEDWINDOW) > 0) then
begin
FPreviousBoundsRect := BoundsRect;
BoundsRect := Screen.MonitorFromWindow(Handle).BoundsRect;
SetWindowLong(Handle, GWL_STYLE, WindowStyle and (not WS_OVERLAPPEDWINDOW));
end else
begin
SetWindowLong(Handle, GWL_STYLE, WindowStyle or WS_OVERLAPPEDWINDOW);
BoundsRect := FPreviousBoundsRect;
end;
end;