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procedure ResizeWindow(Fullscreen: Boolean; Width, Height, Left, Top: Integer);
begin
  if (Window <> 0) then
  begin
    if (Fullscreen) then
    begin
      WinFullscreen := True;

      WinWidth  := GetScreenWidth;
      WinHeight := GetScreenHeight;
      OuterWidth := WinWidth;
      OuterHeight := WinHeight;
      WinLeft := 0;
      WinTop := 0;

      // Fensterrahmen entfernen
      SetWindowLong(Window, GWL_STYLE,   Integer(WS_POPUP or WS_SYSMENU or WS_MINIMIZEBOX));
      SetWindowLong(Window, GWL_EXSTYLE, Integer(WS_EX_APPWINDOW));
    end
    else
    begin
      WinFullscreen := False;


      WinWidth  := Width;
      WinHeight := Height;

      if (WinWidth <= 0) then
        WinWidth := 400;
      if (WinHeight <= 0) then
        WinHeight := 400;

      OuterWidth  := WinWidth  + GetWindowBorderX;
      OuterHeight := WinHeight + GetWindowBorderY;

      WinLeft := Left;
      WinTop  := Left;

      // Fenster zentrieren
      if (WinLeft < 0) then
        WinLeft := (GetScreenWidth - OuterWidth) div 2;
      if (WinTop < 0) then
        WinTop := (GetScreenHeight - OuterHeight) div 2;

      // Fensterrahmen hinzufügen
      SetWindowLong(Window, GWL_STYLE,   Integer(WS_CAPTION or WS_SYSMENU or WS_MINIMIZEBOX));
      SetWindowLong(Window, GWL_EXSTYLE, Integer(WS_EX_APPWINDOW or WS_EX_WINDOWEDGE));
    end;

    SetWindowPos(Window, 0, 0, 0, 0, 0, SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER or SWP_FRAMECHANGED);
    SetWindowPos(Window, 0, WinLeft, WinTop, OuterWidth, OuterHeight, 0);
    ShowWindow(Window, SW_SHOW);
  end;
end;                    

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PostMessage(HWND_BROADCAST, WM_PAINT, 0, 0);
PostMessage(HWND_BROADCAST, WM_NCPAINT, 0, 0);