Printing Delphi

Title: Detect Print Screen key pressing
You should set your own procedure to OnIdle event of application. Use GetAsyncKeyState function in it.
type
TForm1 = class(TForm)
Label1: TLabel;
procedure FormCreate(Sender: TObject);
private
procedure PrintScreenDetect(Sender: TObject; var Result: Boolean);
public
end;
...
procedure TForm1.FormCreate(Sender: TObject);
begin
Application.OnIdle:=PrintScreenDetect;
end;
procedure TForm1.PrintScreenDetect(Sender: TObject; var Result: Boolean);
begin
if GetAsyncKeyState(VK_SNAPSHOT)0 then
Label1.Caption:='PrintScreen Key was pressed';
Result:=True;
end;