Re: Question RE. CriticalSection - C / C++ / MFC Discussion Boards

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Re: pointer question

mark novak8-Jun-05 14:54

mark novak

8-Jun-05 14:54

Well for starters you are assigning a local variable (t_str) to your array of strings (gz_Nos), as soon as you exit the function, the compiler unwinds the stack and your left with a corrupt string. Try using something like char* t_str = new char[MAX_STRLEN], and make sure to call delete[] t_str when you no longer need it. Strings, memory and pointers are complicated beasts. Check out some good books, like Stroustrup's novel.

IActiveDesktop

neliocc8-Jun-05 10:43

neliocc

8-Jun-05 10:43

Hi everybody, i need your help. Im trying to change the desktop wallpaper, but i must use the IActiveDesktop interface, and i dont know what files i must include in the header, in the msdn help, they tell me, that i must include shlobj.h but with that it doesnt work. If some body can help me i will be gratefull.

Re: IActiveDesktop

mark novak8-Jun-05 15:29

mark novak

8-Jun-05 15:29

Google is your friend.
http://support.microsoft.com/kb/q196342/[^]

Re: IActiveDesktop

neliocc8-Jun-05 16:50

neliocc

8-Jun-05 16:50

Thanks a lot.

Re: IActiveDesktop

ThatsAlok8-Jun-05 18:51

ThatsAlok

8-Jun-05 18:51

you can check this link tooo Smile | :)

http://www.codeproject.com/tools/wallpaperq.asp[^]

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

cheers,
Alok Gupta

Question RE. CriticalSection

Budric B.8-Jun-05 10:26

Budric B.

8-Jun-05 10:26

Hi,
I'm sharing an object between 2 threads and I need to synchronize it. The following is a model of my code:

<br />
class SynchronizedObject<br />
{<br />
<pre>SynchronizedObject()  //constructor<br />
{<br />
InitializeCriticalSection(&m_ThreadSynch);<br />
}<br />
<br />
CRITICAL_SECTION m_ThreadSynch;<br />
void Lock()<br />
{<br />
::EnterCriticalSection(&m_ThreadSynch);<br />
}<br />
void Unlock()<br />
{<br />
::LeaveCriticalSection(&m_ThreadSynch);<br />
}</pre><br />
<br />
//now the functions with problem<br />
void A()<br />
{<br />
Lock();<br />
B();<br />
Unlock();<br />
}<br />
<br />
void B()<br />
{<br />
Lock();<br />
//do some stuff<br />
Unlock();<br />
}<br />
};<br />

For some reason when I call A() my code doesn't lock up. Am I using the Critical Section incorrectly? Or does it check which thread is trying to enter the critical section and allows the same thread to enter it multiple times (which I thought wasn't the case). What about Mutexes? Aside from synchronizing accross processes do they behave differently? What about Semaphores?

Note: I've also tried to just put a member object CCriticalSection synch; and call synch.Lock()/Unlock() where appropriate. Same result.

Re: Question RE. CriticalSection

Blake Miller8-Jun-05 11:21

Blake Miller

8-Jun-05 11:21

Critical sections block separate threads from entering the critical section, not the same thread.
None of the synchronization objects, near as I ever read, will block the same thread from entering them.

Mutexes behave differently because they can be 'abandoned'.
If the process owning a mutex exits before releasing the mutex, another process waiting for it will be rleased with the result WAIT_ABANDONED.

Semaphores are for controlling 'metered access' to an object.

Now, in your instance, if Thread 2 called B(), then Thread1 would not be able to enter A() until Thread2 was done processing B(). Likewise, if Thread1 entered A() first, then thread2 could not enter A() or B() until Thread1 was done with A().

Re: Question RE. CriticalSection

Axter8-Jun-05 18:52

Axter

8-Jun-05 18:52

Both
CriticalSection and Mutex are recursive in Windows.

Recursive mutex will not let the same thread block itself.

You could try using the boost thread library, which does have non-recursive mutex.

If you don't mind sticking with recursive logic, I recommend you use the smart pointers in the following link, which act as synchronized wrapper class for your object.
http://code.axter.com/sync_ptr.h
http://code.axter.com/sync_ctrl.h

Top ten member of C++ Expert Exchange.
http://www.experts-exchange.com/Cplusplus

Re: Question RE. CriticalSection

Bob Stanneveld8-Jun-05 20:53

Bob Stanneveld

8-Jun-05 20:53

If you want your thread to lock up, use a semaphore object and the WairFor... functions. They don't allow a thread to enter the critical section twice when the state of the Semaphore is non-signaled.

Behind every great black man...
... is the police. - Conspiracy brother

Blog[^]

Re: thanks

Budric B.9-Jun-05 3:13

Budric B.

9-Jun-05 3:13

Thanks for your replies. I didn't want the thread to lock up so this is perfect, but I wanted to confirm that that's how it worked and I'm not missing some small part of code.

SHBrowseForFolder question

Lynsen8-Jun-05 10:18

Lynsen

8-Jun-05 10:18

Hi,
How can I show hidden folders when calling SHBrowseForFolder function?
Thanks.

Lynsen

Re: SHBrowseForFolder question

mark novak8-Jun-05 15:20

mark novak

8-Jun-05 15:20

From what they say: http://groups-beta.google.com/group/microsoft.public.vc.mfc/browse_thread/thread/6beca664725eb48a/af56d62d17b9d4e8?q=show+hidden+folders+SHBrowseForFolder&rnum=2#af56d62d17b9d4e8[^] SHBrowseForFolder will not show hidden folders.

Creating ODBC source

Richard Jones8-Jun-05 9:50

Richard Jones

8-Jun-05 9:50

I need to create a source to the <targetdir>data.mdb in Installshield.
I'm thinking either a function call, or directly adding Registry entries(yuck) Dead | X|

Can anyone help?

Re: Creating ODBC source

Tom Archer8-Jun-05 10:10

Tom Archer

8-Jun-05 10:10

You need to call the SQLConfigDataSource function:

BOOL bStat = SQLConfigDataSource(NULL,
                                 ODBC_ADD_DSN,
                                 "Microsoft Access Driver (*.mdb)",
                                 szDSNName);

Re: Creating ODBC source

Richard Jones9-Jun-05 2:24

Richard Jones

9-Jun-05 2:24

Thanks for the function, but I was hoping to do this in Installshield (I'm using version 6 for C++).

The users won't have Admin access, so it has to be setup when I install it.

The registry screen in IS only allows 1 key below HKLM. There's a bunch of Reg functions in the help I can try.

Font Style in CListCtrl

RickyC8-Jun-05 9:32

RickyC

8-Jun-05 9:32

Hi All,
there's anybody who knows if there is a way to set the font style (size, stuff like that) in a CListCtrl item? Confused | :confused:

Thanks a lot!
cheers! Smile | :)

Re: Font Style in CListCtrl

mark novak8-Jun-05 15:00

mark novak

8-Jun-05 15:00

Use .SetFont() on the control. It is going to want a CFont, you can call CFont's CreatePointFont(), or if your feeling picky call CreateFont() with 14 arguments of font flexibility.

Re: Font Style in CListCtrl

RickyC9-Jun-05 2:02

RickyC

9-Jun-05 2:02

Thanks Mark!
works good! Smile | :)

cheers!

Trying to load bitmap from a path in GDI+

Anonymous8-Jun-05 8:05

Anonymous

8-Jun-05 8:05

I'm trying to load up a GDI+ bitmap using a pathname, and it does not work.

Here is what I try to do:
Bitmap bitmap(L"Images\\picture.bmp");

What DOES work is:
Bitmap bitmap(L"picture.bmp");
i.e., if the bitmap is in the same directory as the program

Bitmap bitmap(L"C:\\Images\\picture.bmp");
i.e., providing the full path name from the C drive

However, I cannot load it up from the base directory of the program for some reason. The picture is, of course, in the folder, and it works if I specify the entire path name starting from C drive, but not if I attempt to start from the program's directory.

Help ??

Thanks

Re: Trying to load bitmap from a path in GDI+

PJ Arends8-Jun-05 9:27

PJ Arends

8-Jun-05 9:27

Just a guess, but try L".\\Images\\picture.bmp".

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Re: Trying to load bitmap from a path in GDI+

Tom Archer8-Jun-05 10:15

Tom Archer

8-Jun-05 10:15

Since you know that the image is in the Images folder that is in the folder of the app, you could use the GetModuleFileName to get the app's folder and then append the Images\\[imagename] to it.

Re: Trying to load bitmap from a path in GDI+

Anonymous8-Jun-05 11:50

Anonymous

8-Jun-05 11:50

Indeed, this is what I ended up doing. I guess it ends up being the same thing in the end.

Get resources strings

Kaworu28-Jun-05 6:34

Kaworu2

8-Jun-05 6:34

Hi,

I use EnumResourceTypes & EnumResourceNames to get all the Resources of my multilanguage DLLs system, trying to translate the DLLs strings.

But I can’t get the strings of the dialogs (statics, group boxs, ...), menus, ..., and I don’t know how can I do it. May you help me?

Thanks in advance.

Re: Get resources strings

David Crow8-Jun-05 9:14

David Crow

8-Jun-05 9:14

Kaworu2 wrote:
But I can’t get the strings of the dialogs...

That's going to be tricky. See this article for more.

"Ideas are a dime a dozen. People who put them into action are priceless." - Unknown

Re: Get resources strings

Kaworu28-Jun-05 20:13

Kaworu2

8-Jun-05 20:13

Hi,

Link doesn't works, I'll try it later, what's the article that I must see?

Thanks for reply.

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