C / C++ / MFC

Re: Socket question: When does a client connect to a server?

22-Feb-07 10:18

You're welcome (from led mike) Smile | :)

FreeCastle wrote:
because when I call closesocket() then I also have to create the socket again, before calling the connect function.

That is part of the overhead of using that method.

I recommend:

Also follow led mike's link into Graceful Shutdown, Linger Options, and Socket Closure[^] for more general info.

Then check out DisconnectEx[^] for disconnecting a socket and reusing it (on XP+).

Cheers,
Mark

"Do you know what it's like to fall in the mud and get kicked... in the head... with an iron boot?
Of course you don't, no one does. It never happens. It's a dumb question... skip it."

FreeCastle22-Feb-07 11:12

FreeCastle

22-Feb-07 11:12

Ah thank you a lot, the first link was very informative.
That DisconnectEx function looks cute, but I think I'll avoid it because it only runs on XP or higher. I think I use shutdown, and if I understood that article right, I have also to "create" the socket (by a call to socket(...)) again, when I want to "reuse" it for a new connection.

project on face detection using webcam..

mannur22-Feb-07 7:59

mannur

22-Feb-07 7:59

i have to implement the fft algorithm for comparing the image obtained from webcam with some standard image stored..
can you please help me with this...

Re: project on face detection using webcam..

C^hris L^osinger22-Feb-07 10:31

C^hris L^osinger

22-Feb-07 10:31

try typing 'FFT' in the search box at the top of the page . there are a few articles here about FFT.

image processing toolkits | batch image processing | blogging

Preventing Escape key from closing dialog window

Neil scsn22-Feb-07 7:51

Neil scsn

22-Feb-07 7:51

Hi,
How do I prevent the escape key, when pressed, from closing a dialog window?

Thanks
neil

Re: Preventing Escape key from closing dialog window [modified]

Mark Salsbery22-Feb-07 8:35

Re: Preventing Escape key from closing dialog window

22-Feb-07 8:35

By default the ESC key causes a WM_COMMAND IDCANCEL message to be sent to the dialog proc.

~~You could catch this message and do nothing.~~ *EDIT* dumb answer

Maybe look for WM_KEYDOWN/WM_KEYUP messages for the ESC key and do nothing in response.

Mark

-- modified at 14:42 Thursday 22nd February, 2007

"Do you know what it's like to fall in the mud and get kicked... in the head... with an iron boot?
Of course you don't, no one does. It never happens. It's a dumb question... skip it."

prasad_som22-Feb-07 18:44

Re: Preventing Escape key from closing dialog window

22-Feb-07 18:44

Mark Salsbery wrote:
By default the ESC key causes a WM_COMMAND IDCANCEL

No, it doesn't.

Mark Salsbery wrote:
Maybe look for WM_KEYDOWN/WM_KEYUP messages for the ESC key and do nothing in response.

What about not dispatching the message if its due to escape key pressed ? (Handling PreTranslateMessage).

Prasad
Notifier using ATL | Operator new[],delete[][^]

Mark Salsbery22-Feb-07 20:38

Re: Preventing Escape key from closing dialog window

22-Feb-07 20:38

prasad_som wrote:
No, it doesn't.

I guess I was confused by the documented handling of the ESC key which states "Sends a WM_COMMAND
message to the dialog box procedure. The wParam parameter is set to IDCANCEL."

prasad_som wrote:
What about not dispatching the message if its due to escape key pressed ?

Which is what I meant by do nothing.

Sorry I don't do English as good as y'all.

"Do you know what it's like to fall in the mud and get kicked... in the head... with an iron boot?
Of course you don't, no one does. It never happens. It's a dumb question... skip it."

prasad_som22-Feb-07 21:34

Re: Preventing Escape key from closing dialog window

22-Feb-07 21:34

Mark Salsbery wrote:
Which is what I meant by do nothing.

You talked about handling WM_KEYDOWN message. But Instaead PreTranslateMessage would be better place, I wanted to underscore that.

Mark Salsbery wrote:
I don't do English as good as y'all.

No, You does, Smile | :)

. English is not our native language.

Prasad
Notifier using ATL | Operator new[],delete[][^]

Rajesh R Subramanian22-Feb-07 22:07

Re: Preventing Escape key from closing dialog window

22-Feb-07 22:07

prasad_som wrote:
ou talked about handling WM_KEYDOWN message. But Instaead PreTranslateMessage would be better place,

You may also want to tell him clearly that WM_KEYDOWN won't help at all, with these two keys.

He is no fool who gives what he cannot keep to gain what he cannot lose.
- Jim Elliot

Mark Salsbery23-Feb-07 6:12

Re: Preventing Escape key from closing dialog window [modified]

23-Feb-07 6:12

prasad_som wrote:
But Instaead PreTranslateMessage would be better place, I wanted to underscore that.

I agree. The OP didn't mention MFC. I guess it's a 50-50 shot. I try not to assume Smile | :)

Cheers!
Mark

"Do you know what it's like to fall in the mud and get kicked... in the head... with an iron boot?
Of course you don't, no one does. It never happens. It's a dumb question... skip it."

Rajesh R Subramanian22-Feb-07 22:01

Re: Preventing Escape key from closing dialog window

22-Feb-07 22:01

Mark Salsbery wrote:
Maybe look for WM_KEYDOWN/WM_KEYUP messages for the ESC key and do nothing in response.

I don't think so. When the user presses the Esc or Enter, CDialog implementations will call EndDialog() immediately rather than passing on this message to WM_KEYDOWN handler. So the handler floats sadly in thin air. There is a lot of confusion on this and I do not find a better way than overriding the PreTranslateMessage</s>

Please read This[^] too!

Last modified: 17mins after originally posted --

The greater the difficulty, the greater the glory.
- Marcus Tullius Cicero

Mark Salsbery23-Feb-07 6:29

Re: Preventing Escape key from closing dialog window

23-Feb-07 6:29

LOL I get it! The OP did not mention MFC - you all assumed that - you got it right...good for
you.
Most times that I assume that, the OP comes back and tells me "I'm not using MFC". I can't win.

I suggested eating the ESC key, exactly what Prasad did in his PreTranslateMsg handler.

You are right it won't work in an MFC OnKeyDown handler - the key has been translated at that
point so an escape key never gets there. That's why in MFC it needs to be caught in
PreTranslateMsg.

In non MFC you'd have to look for the WM_KEYDOWN and not pass it on to be translated.

Either way you're eating the keystroke Smile | :)

Cheers!
Mark

"Do you know what it's like to fall in the mud and get kicked... in the head... with an iron boot?
Of course you don't, no one does. It never happens. It's a dumb question... skip it."

Newbie0022-Feb-07 8:45

Newbie00

22-Feb-07 8:45

You can catch pressed key
if (key==VK_ESC)
flag=true;
and in OnClosing method you can check the flag if it's true, you can forbid closing the dialog. Or after handling VK_ESC key pressed you can change it into some other key so that program would think the ESC wasn't pressed.

Re: Preventing Escape key from closing dialog window

Cedric Moonen22-Feb-07 9:37

Cedric Moonen

22-Feb-07 9:37

I suppose you are using MFC ? If yes, look at the FAQ here[^]

Cédric Moonen
Software developer

Charting control [v1.1]

Re: Preventing Escape key from closing dialog window

ThatsAlok22-Feb-07 17:34

ThatsAlok

22-Feb-07 17:34

NeilDevlin wrote:
How do I prevent the escape key, when pressed, from closing a dialog window?

handle onCancel virtual function of CDialog Class

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief and You

Re: Preventing Escape key from closing dialog window

Rajesh R Subramanian22-Feb-07 18:21

Re: Preventing Escape key from closing dialog window

22-Feb-07 18:21

ThatsAlok wrote:
handle onCancel virtual function of CDialog Class

If you do this, then clicking the cancel button or the close button (the X button) also won't close the dialog. Am I right?

The greater the difficulty, the greater the glory.
- Marcus Tullius Cicero

ThatsAlok22-Feb-07 19:04

ThatsAlok

22-Feb-07 19:04

brahmma wrote:
Am I right?

as usual you are right Smile | :)

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief and You

Re: Preventing Escape key from closing dialog window [modified]

Rajesh R Subramanian22-Feb-07 19:13

Re: Preventing Escape key from closing dialog window

22-Feb-07 19:13

Thanks

I always have wondered why there are no other good ways than handling the PreTranslateMessage to sort this 'It closes if I press the Esc button' issue out. I find handling PreTranslateMessage to be a weird way but that is the only effective way I know to do this.

Last modified: 2hrs 7mins after originally posted --

Glory follows virtue as if it were its shadow.
- Marcus Tullius Cicero

PJ Arends22-Feb-07 21:22

PJ Arends

22-Feb-07 21:22

There is. If you want the close button to still work then handle the WM_CLOSE message and call CDialog::OnCancel from there and override OnCancel() and do nothing.

// Called when user clicks the close button
void CMyDialog::OnClose()
{
    CDialog::OnCancel();
}
 
// called when user presses ESC button or clicks IDCANCEL button
void CMyDialog::OnCancel()
{
    // Do nothing
}

You may be right
I may be crazy
-- Billy Joel --

Within you lies the power for good, use it!!!

Re: Preventing Escape key from closing dialog window

Rajesh R Subramanian22-Feb-07 22:09

Re: Preventing Escape key from closing dialog window

22-Feb-07 22:09

Thank you very much Arends. If I was asked to guess who would teach me this, I would have told your name Big Grin | :-D

Let us not listen to those who think we ought to be angry with our enemies, and who believe this to be great and manly. Nothing is so praiseworthy, nothing so clearly shows a great and noble soul, as clemency and readiness to forgive.
- Marcus Tullius Cicero

prasad_som22-Feb-07 18:13

Re: Preventing Escape key from closing dialog window

22-Feb-07 18:13

Use PreTranslateMessage.

BOOL CMyDlg::PreTranslateMessage(MSG* pMsg)
{
if (pMsg->message == WM_KEYDOWN)
{
int nKey = pMsg->wParam ;
if ( nKey == VK_ESCAPE )
{
  return TRUE; 
}
}
return CDialog::PreTranslateMessage(pMsg);
}

Prasad
Notifier using ATL | Operator new[],delete[][^]

Rajesh R Subramanian22-Feb-07 18:22

Re: Preventing Escape key from closing dialog window

22-Feb-07 18:22

Fast man! I was about to type it, but had to ask Alok a question Big Grin | :-D

He is no fool who gives what he cannot keep to gain what he cannot lose.
- Jim Elliot

prasad_som22-Feb-07 18:39