C / C++ / MFC Discussion Boards

Nish Nishant18-Jan-02 5:46

18-Jan-02 5:46

If his program exits, he need not call ReleaseMutex as the mutex object itself gets destroyed [or am I highly erroneous here?]

Nish

Sonork ID 100.9786 voidmain
www.busterboy.org
If you don't find me on CP, I'll be at Bob's HungOut

Re: avoiding multiple instances

Jon Hulatt18-Jan-02 5:48

Jon Hulatt

18-Jan-02 5:48

"highly erroneous"? that sounds painful!

Sorry to dissapoint you all with my lack of a witty or poignant signature.

Re: avoiding multiple instances

Nish Nishant18-Jan-02 6:57

Nish Nishant

18-Jan-02 6:57

LOL

Nish

Sonork ID 100.9786 voidmain
www.busterboy.org
If you don't find me on CP, I'll be at Bob's HungOut

Re: avoiding multiple instances

Joaquín M López Muñoz18-Jan-02 6:04

Joaquín M López Muñoz

18-Jan-02 6:04

Hi Nish,

Well, the thing is a little tricky, because the documentation is not conclusive on this. I haven't found nowehere that closing a mutex handle implies also releasing it, so to the best of my knowledge not calling ReleaseMutex is undefined behavior (though it is perfectly possible that everything works nevertheless).
All in all, as the guy didn't need ownership at all, I think it is better to remain on the safe side and simply setting bInitialOwner to FALSE

Regards,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: avoiding multiple instances

Nish Nishant18-Jan-02 7:04

Nish Nishant

18-Jan-02 7:04

Thanks for your thoughts and time Joaquín!
I guess you were correct in your advice to him Smile | :)

Regards
Nish

Sonork ID 100.9786 voidmain
www.busterboy.org
If you don't find me on CP, I'll be at Bob's HungOut

Re: avoiding multiple instances

Tim Smith18-Jan-02 7:20

Tim Smith

18-Jan-02 7:20

Mutexes are automatically released.

Here is a quote from Helen Custler's Inside Windows NT book which talks about this history of mutants and mutexes in NT.

"The name /mutant/ has a colorful [sic] history. Early in Windows NT's development, Dave Cutler created a kernel mutex object that implemented low-level mutual exclusion. Later he discovered that OS/2 required a version of the mutual-exclusion semaphore with additional semantics, which Dave considered "brain-damaged" and which was incompatible with the original object. (Specifically, a thread could abandon the object and leave it inaccessible.) So he created an OS/2 version of the mutex and gave it the name /mutant/. Later Dave modified the mutant object to remove the OS/2 semantics, allowing the Win32 subsystem to use the object. The Win32 API calls the modified object /mutex/, but the native services retain the name /mutant/."

Tim Smith
Descartes Systems Sciences, Inc.

Re: avoiding multiple instances

Joaquín M López Muñoz18-Jan-02 7:34

Joaquín M López Muñoz

18-Jan-02 7:34

Beautiful piece of wisdom Smile | :)

Anyway, I wouldn't rely on only this paragraph to merrily abandon mutexes unreleased, withouth stronger confirmation from the documentation.

Regards,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: avoiding multiple instances

Mark Donkers18-Jan-02 5:55

Mark Donkers

18-Jan-02 5:55

Joaquín... You have shed some light in this dark world of mine. Dead | X|

It made as much sense as it could for a beginner C++ programmer.

where can I find the docs on how to use other tags (or are there any other)

thanks again.

Marcus

Make no little plans; they have no magic to stir your blood to action. Make big plans, aim high in work and hope
-- Daniel Burnham

Re: avoiding multiple instances

Joaquín M López Muñoz18-Jan-02 6:09

Joaquín M López Muñoz

18-Jan-02 6:09

Apart from <pre> you can use <code> to get an effect like this.
If you're including code of yours that may have the character '<', replace those with the escape sequence <
Also, you can use regular HTML tags as well.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: avoiding multiple instances

Michael Dunn18-Jan-02 7:46

Michael Dunn

18-Jan-02 7:46

Marcus2001 wrote:
where can I find the docs on how to use other tags

In the VC forum FAQ Smile | :)

--Mike--
My really out-of-date homepage
"Hey, you wanna go to the Espresso Pump and get sugared up on mochas?"
-- Willow Rosenberg
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan.

Re: avoiding multiple instances

Nish Nishant18-Jan-02 5:44

Nish Nishant

18-Jan-02 5:44

Use the <pre> tags!

this is between two 'pre' tags

Nish

Sonork ID 100.9786 voidmain
www.busterboy.org
If you don't find me on CP, I'll be at Bob's HungOut

Check if "Enter" hit

Stan the man18-Jan-02 4:43

Stan the man

18-Jan-02 4:43

I am trying to see if the "enter" key is hit when some object has the focus. I have tried many things and all other keys are gotten except for the "enter."

Thanks.

Re: Check if "Enter" hit

Nish Nishant18-Jan-02 4:55

Nish Nishant

18-Jan-02 4:55

over-ride PreTranslateMessage

Nish

Sonork ID 100.9786 voidmain
www.busterboy.org
If you don't find me on CP, I'll be at Bob's HungOut

Re: Check if "Enter" hit

Roger Allen18-Jan-02 6:23

Roger Allen

18-Jan-02 6:23

As nish says, PreTranslate message is the way to go,

if (pMsg->message == WM_KEYDOWN)
    {
    if (GetFocus() != GetDlgItem(IDC_ASSAY) && pMsg->wParam == VK_ENTER)
        {

Roger Allen
Sonork 100.10016

If I'm not breathing, I'm either dead or holding my breath.

Editing CListCtrl item

Ken Goguen18-Jan-02 4:40

Ken Goguen

18-Jan-02 4:40

I have a simple CListCtrl that allows the user to edit the item (0). To do this the user needs to click on the item once or twice to get into "Edit" mode.

Is there a way to allow the user other ways to get into edit mode? Like pressing the right arrow key (VK_RIGHT) or something?

-kg

Ken Goguen

Re: Editing CListCtrl item

Joaquín M López Muñoz18-Jan-02 4:54

Joaquín M López Muñoz

18-Jan-02 4:54

Sure, you can use something like this in the appropriate handler:

int nItem=m_list.GetNextItem(-1,LVNI_SELECTED);
if(nItem>=0){
  GotoDlgCtrl(&m_list); // security measure, may not be necessary
  m_list.EditLabel(nItem);
}

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: Editing CListCtrl item

Ken Goguen18-Jan-02 4:54

Ken Goguen

18-Jan-02 4:54

Sometimes we over look the simple things. Thanks.

-kg

Ken Goguen

Accessing a COM Object in a DLL

Steve Thresher18-Jan-02 2:34

Steve Thresher

18-Jan-02 2:34

I have a DLL that contains a COM object. Can anybody give me some pointers on how to create an instance of that object and call one of its methods from a Win32 C++ program. The object was originally written using Visual Basic but HAS to be used in a program written in C++ using just Win32 API not MFC. I have full access to the Visual Basic source and a small understanding of COM.

Thanks in advance for any help you can give.

Steve.

Re: Accessing a COM Object in a DLL

Michael P Butler18-Jan-02 2:49

Michael P Butler

18-Jan-02 2:49

If you know the CLSID and the IID, you can use CoCreateInstance. Do a search on MSDN for it. I can't remember if the #import works on DLL's but it does make life easier.

Michael Smile | :)

Re: Accessing a COM Object in a DLL

18-Jan-02 3:06

You can use my XYDispDriver class to access the com object. Or if you are comfortable with ATL, use the #import directive.

Good luck. Smile | :)

HOWTO: Create Fonts

18-Jan-02 1:43

Hi Folks,

What the proper way of creating fonts so that their size don't change during a zoom in/out printing preview?

Cheers,
- xico -

Terminology & Books

Jon Hulatt18-Jan-02 0:37

Jon Hulatt

18-Jan-02 0:37

Hi all,

I'm looking at creating one of those explorer bars in ie. Not done anything like this before, more of an MFC person up to now.

First question is, what am I trying to do? COM? COM+? ActiveX ? there are too many different terms and i'm not sure which one is relevant!

secondly, what books are a good starting point for the above?

Thanks

Jon

PS.. I've read the related articles on CP already, but still want a book.

Sorry to dissapoint you all with my lack of a witty or poignant signature.

Re: Terminology & Books

Michael Dunn18-Jan-02 13:13

Michael Dunn

18-Jan-02 13:13

Explorer bars are COM objects. As for where to start, my Intro to COM article, then tutorials on Explorer bars by me and Erik Thompson.

--Mike--
My really out-of-date homepage
"Hey, you wanna go to the Espresso Pump and get sugared up on mochas?"
-- Willow Rosenberg
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan.

SendMessage(WM_MDIACTIVATE)

18-Jan-02 0:16

Hi,

I am trying to activate a CView derived MDI window from a CControlBar containing an image list of view thumbnails. When I double click on the thumb I want to activate the view, i.e. bring it to the top. I cannot seem to get the SendCommand message right. Can someone help me with this.

::SendMessage(???,WM_MDIACTIVATE,(WPARAM)pTheViewToActivate,0);

Where do I need to send the message to for it to process the MDI activate message? MSDN also seems to be confused about the lparam, is it needed or not?

Many thanks

Matthew

Re: SendMessage(WM_MDIACTIVATE)

Jon Hulatt18-Jan-02 0:32

Jon Hulatt

18-Jan-02 0:32

(WPARAM)pTheViewToActivate looks like you're trying to send a CView pointer as the wParam. You should be sending an hWnd (window handle) instead.

But that's besides the point, because i think that CMDIChildWnd::MDIActivate() does exactly what you want.

jon

Sorry to dissapoint you all with my lack of a witty or poignant signature.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.