Cancelling Esc key being pressed

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3 total messages Started by Russell Allen Mon, 25 Sep 2006 14:31

#3072

Author: Russell Allen
Date: Mon, 25 Sep 2006 14:31

25 lines
1717 bytes

Hi all,

I have a form with a FormKeyUp event handler intended to intercept the Esc key, and do something, as below (semi-pseudo-code).

TForm1::FormKeyUp(Sender, Key) {
  if (Key == 27)
    ShowMessage("Esc key pressed");
}

TForm1::Button1Click(Sender) {
  MessageDlg("Proceed?", mtConfirmation, TMsgDlgButtons() <<
     mbYes << mbCancel, 0);

  // Can I put some code here to stop FormKeyUp firing when
  // the user presses Esc?
}

The problem I'm having - when a piece of code elsewhere pops up a dialog box with a Cancel option, if the user presses "Esc" to cancel the dialog box, not only is the dialog box cancelled, the onkeyup event is being fired off as well!

Can I include a line to stop the Esc key press firing other events, or can I maybe unhook the OnKeyUp event handler before the dialog and rehook it after the dialog box?

Thanks in advance,

Russ

Re: Cancelling Esc key being pressed

#3073

Author: Remy Lebeau (TeamB)
Date: Mon, 25 Sep 2006 17:32

33 lines
1870 bytes

"Russell Allen" <russell.allen@bt.com> wrote in message
news:4517e850$1@newsgroups.borland.com...

> The problem I'm having - when a piece of code elsewhere pops up
> a dialog box with a Cancel option, if the user presses "Esc" to cancel
> the dialog box, not only is the dialog box cancelled, the onkeyup event
> is being fired off as well!

    void __fastcall TForm1::FormKeyUp(TObject *Sender, char &Key)
    {
        if( Key == VK_ESCAPE )
            Key = 0;
    }


> Can I include a line to stop the Esc key press firing other events

No.

> can I maybe unhook the OnKeyUp event handler before the dialog
> and rehook it after the dialog box?

    void __fastcall TForm1::Button1Click(TObject *Sender)
    {
        this->OnKeyUp = NULL;
        MessageDlg("Proceed?", mtConfirmation, TMsgDlgButtons() << mbYes <<
mbCancel, 0);
        this->OnKeyUp = FormKeyUp;
    }


Gambit

Re: Cancelling Esc key being pressed

#3076

Author: 4N
Date: Tue, 26 Sep 2006 17:14

49 lines
2545 bytes

The problem is that OnActivate of a form isn't called when a form changes is 
Focused status.
I tryed catching WM_ACTIVATE but the form is activated before it receives 
the Escape message so you can't block esc when the form is not focused.
I was thinking to add a timer (which autodisables itself) of 300 ms  that is 
enabled when WM_ACTIVATE is catched and drop the Escape key in OnKeyUp() 
function till the timer is active...
but I dunno if there's a better solution.

If you have a better idea let me know it :)


"Remy Lebeau (TeamB)" <no.spam@no.spam.com> ha scritto nel messaggio 
news:45181312$1@newsgroups.borland.com...
>
> "Russell Allen" <russell.allen@bt.com> wrote in message
> news:4517e850$1@newsgroups.borland.com...
>
>> The problem I'm having - when a piece of code elsewhere pops up
>> a dialog box with a Cancel option, if the user presses "Esc" to cancel
>> the dialog box, not only is the dialog box cancelled, the onkeyup event
>> is being fired off as well!
>
>    void __fastcall TForm1::FormKeyUp(TObject *Sender, char &Key)
>    {
>        if( Key == VK_ESCAPE )
>            Key = 0;
>    }
>
>
>> Can I include a line to stop the Esc key press firing other events
>
> No.
>
>> can I maybe unhook the OnKeyUp event handler before the dialog
>> and rehook it after the dialog box?
>
>    void __fastcall TForm1::Button1Click(TObject *Sender)
>    {
>        this->OnKeyUp = NULL;
>        MessageDlg("Proceed?", mtConfirmation, TMsgDlgButtons() << mbYes <<
> mbCancel, 0);
>        this->OnKeyUp = FormKeyUp;
>    }
>
>
> Gambit
>
>

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