Application full screen mode

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Introduction

Some applications like some web browsers allow show in full screen mode using key F11. In full screen mode window hasn't border and uses entire screen space.

Standard way

You can switch form to full screen mode simply by assigning wsFullScreen value to TForm.WindowState property. You can do that directly in design time in Object Inspector window or in runtime:

procedure TForm1.FormShow(Sender: TObject);
begin
  WindowState := wsFullScreen;
end;

Universal way to use full-screen

Universal way exists, using LCL, you need to call ShowWindow() with SW_SHOWFULLSCREEN. This ShowWindow call is handled inside widgetset, using low-level API (for example, OS X Carbon API, or GTK2 API). Example:

procedure TfmMain.SetFullScreen_Universal(AValue: boolean);
begin
  if AValue then
    ShowWindow(Handle, SW_SHOWFULLSCREEN)
  else
    ShowWindow(Handle, SW_SHOWNORMAL); 
    //maybe consider here previous maximized state?
end;

Win32 way to use full-screen

Universal way, above, works for Win32, but window border still stays, so better code which works:

procedure TfmMain.SetFullScreen_Win32(AValue: boolean);
begin
  if AValue then
  begin
    FOrigWndState:= WindowState;
    FOrigBounds:= BoundsRect;
 
    BorderStyle:= bsNone;
    BoundsRect:= Monitor.BoundsRect;
  end
  else
  begin
    WindowState:= FOrigWndState;
    BoundsRect:= FOrigBounds;
    BorderStyle:= bsSizeable;
    BoundsRect:= FOrigBounds; //again
  end;
end;

Win32 example program

This is example for Win32 only, since it don't use native full-screen mode on Linux/MacOS, it is here from old times.

To be able to switch to full screen mode you will need:

  • Remember previous form state as position and size and window state
  • Be able to determine screen size
  • Capture some key and perform operation

Best way to capture desired key is using Actions. Simply define new action in action manager and assign key shortcut. Than shortcut will work even if main form would lost focus.

unit Unit1; 
 
{$mode objfpc}{$H+}
 
interface
 
uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls,
  Menus;
 
type
  TForm1 = class(TForm)
    procedure FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
  private
  public
    OriginalBounds: TRect;
    OriginalWindowState: TWindowState;
    ScreenBounds: TRect;
    procedure SwitchFullScreen;
  end; 
 
var
  Form1: TForm1; 
 
implementation
 
{$R *.lfm}
 
{ TForm1 }
 
procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  if Key = VK_F11 then
  begin
    SwitchFullScreen;
    Key := 0;
  end;
end;
 
procedure TForm1.SwitchFullScreen;
begin
  if BorderStyle <> bsNone then begin
    // To full screen
    OriginalWindowState := WindowState;
    OriginalBounds := BoundsRect;
 
    BorderStyle := bsNone;
    BoundsRect := Screen.MonitorFromWindow(Handle).BoundsRect;
  end else begin
    // From full screen
    BorderStyle := bsSizeable;
    if OriginalWindowState = wsMaximized then
      WindowState := wsMaximized
    else
      BoundsRect := OriginalBounds;
  end;
end;
 
end.

Win32: get task bar size

If you want to have task bar visible you have to adjust size according task bar position and size. For Windows:

function GetTaskBarSize: TRect;
begin
  SystemParametersInfo(SPI_GETWORKAREA, 0, @Result, 0);
end;

GTK way to use full-screen

This is low-level code for GTK2, it is used already by LCL in "universal way" above.

To switch form to full screen dimensions:

gdk_window_fullscreen(PGtkWidget(Handle)^.window);

To roll back to normal mode:

gdk_window_unfullscreen(PGtkWidget(Handle)^.window);

This is GTK2 only. You must add to uses section such modules as gtk2, gdk2, glib2. You can do it by the directive

{$IFDEF LCLGTK2}, gtk2, gdk2, glib2{$ENDIF}

Changing screen resolution

There is no OS independent way to switch screen resolution now.

For Windows you can find information in article for Delphi Get and Set Screen Resolution (Display Device Modes)

See also

External links