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Frequently Asked Questions

Trapping the Windows system key 'PrintScreen'

Question:

How can I globally trap the Windows system key "PrintScreen"?

Answer:

The following example demonstrates registering a hot key with the
system to globally trap the windows printscreen key.

Example:

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    procedure WMHotKey(var Msg : TWMHotKey); message WM_HOTKEY;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

const id_SnapShot = 101;

procedure TForm1.WMHotKey (var Msg : TWMHotKey);
begin
  if Msg.HotKey = id_SnapShot then
    ShowMessage('GotIt');
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  RegisterHotKey(Form1.Handle,
                 id_SnapShot,
                 0,
                 VK_SNAPSHOT);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  UnRegisterHotKey (Form1.Handle, id_SnapShot);
end;

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