Question

I have a project with one FadeIn Timer and One FadeOut Timer. My form is created by FadeIn Timer and is closed by FadeOut Timer. Initially FadeIn Timer is enabled and FadeOut Timer is disabled. FadeIn Timer Code :

if MainForm.AlphaBlendValue >= 235 then
  Timer01.Enabled := false 
else 
  MainForm.AlphaBlendValue := MainForm.AlphaBlendValue + 5;

FadeOut Timer Code :

if MainForm.AlphaBlendValue <= 0 then 
  Timer02.Enabled := false 
else 
  MainForm.AlphaBlendValue := MainForm.AlphaBlendValue - 5; 
close;

My requirement is that the FadeOut Timer will be active if I click on the “X” Button of the Caption Bar. So I defined

if Msg.Result=htClose then 
  FadeOutTimer.Enabled:=true;

But it not working. Please help me.

Answer 1

If the form just closes immediately, then you need a global form variable like FAllowClose that you set to False when the form is created. Then you need to write code for the Form.CloseQuery event. Something simple like this should work:

procedure Form.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  if FAllowClose then
    Exit;

  CanClose := False;
  FadeOut.Enabled := True;
end;

procedure Form.FadeOutOnTimer(Sender: TObject);
begin
  // do fade out
  FAllowClose := True;
  Self.Close
end;

<<< 2012/07/17 Edit >>>

When the user clicks the “X” button on the form, the only one way to stop the form from closing is to cancel it in the OnCloseQuery event. Then when you are done fading out the form, you close the form. You’ll need a global variable like FAllowClose to signal the OnCloseQuery event that you are close the form instead of the user. This code is a little more illustrative, and should handle the situation where a user clicks the “X” again while it is fading out.

interface

  type TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
    procedure FadeOutTimer(Sender: TObject);
  private
    FAllowClose: Boolean;
  public
  end;

implementation

  procedure TForm1.FormCreate(Sender: TObject);
  begin
    FAllowClose := False;
  end;

  procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
  begin
    if FAllowClose then // <- is 'False' when user clicks "X"
      Exit;

    CanClose := False; // <- cancels close when user clicks "X"
    FadeOut.Enabled := True;
  end;

  procedure TForm1.FadeOutTimer(Sender: TObject);
  begin
    if Form1.AlphaBlendValue > 0 then
      Form1.AlphaBlendValue := Form1.AlphaBlendValue - 5
    else
    begin
      FadeOut.Enabled := False;
      FAllowClose := True;
      Self.Close;
    end;
  end;