Threads inside DLL: MFC, C++, DLL, threads

by: nonubikPosted on 2009-01-22 at 01:53:54ID: 23437858

It may be a problem of synchronization between the thread you create and the main thread. Or maybe some faulty pointer references. Can you please post some of the code that runs ok "directly' and crashes if run in another thread?

by: doront99Posted on 2009-01-22 at 07:09:05ID: 23439927

here is an example

CString temp;
		
temp = "search.query(\"";
temp+="Test";
temp+="\", \"ActiveDoc\");";
 
AFExecuteThisScript(pdDoc,(LPCTSTR)temp,NULL);

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by: doront99Posted on 2009-01-22 at 07:21:01ID: 23440031

BTW, I don't believe there is a synchronization problem since the thread has no option to handle any request before it finished.

by: DanRollinsPosted on 2009-01-22 at 16:04:00ID: 23445133

The most common problem with DLLs in MFC is failure to put

AFX_MANAGE_STATE(AfxGetStaticModuleState());

at each and every entry point into the DLL -- including each method of an exposed C++ object.

The most common problem with using threads in MFC is to attempt to access CWnd-derived objects from a non-primary thread. Worker threads should do work that is other than window-related. For instance, rather than updating the screen during a long calculation, you should do calculations and update a status variable and have the main thread examine that status periodically to do screen updates.

by: doront99Posted on 2009-01-23 at 00:54:26ID: 23447351

I have already the AFX_MANAGE_STATE MACRO on each function.

As for the second paragraph: how can I make the main thread to do something?
Let's say I did the calculation, now how can I tell the main thread to draw it on the screen?

by: nonubikPosted on 2009-01-23 at 03:18:47ID: 23447964

>Let's say I did the calculation, now how can I tell the main thread to draw it on the screen?

You can define a custom window message that you can handle yourself in the main app window. And after you have done the calculation you may PostMessage(..) to your main window (i.e. handled in the main thread) and there handle the drawing.

by: doront99Posted on 2009-01-23 at 04:49:27ID: 23448424

I have tried that as well - hooking into the App class of the DLL with BEGIN_MESSAGE_MAP, but with no success.
It seems that the DLL doesn't actually listen to messages / there is no message loop running.

Does a DLL have some kind of a message loop that I can hook into?

by: DanRollinsPosted on 2009-01-23 at 13:21:52ID: 23453124

My preferred method is to put a timer in the main window (or any window running on the main thread). Lets say that you have it execute 4 times per second. In most cases, that's plenty fast enough so that the user thinks he's seeing real-time updates.

by: doront99Posted on 2009-02-05 at 09:42:59ID: 23561911

well, I'm sorry but it was not really helpful :(
but thank you for trying :)

many thanks,
Doron Tal

by: khunPosted on 2009-02-05 at 23:22:18ID: 23567447

If you're still stuck here, let's see if we still can't help you! I think you need to describe your problem a little more in detail for us. After rereading everything, I still can't quite figure out exactly what your setup is here :-)

So, you are making a plugin for Adobe Acrobat. I'm assuming this is done through some well-defined interface Adobe provides for the purpose? Which I'm sure is documented somewhere, if you'll let us know exactly how you're interfacing with Acrobat. Is Acrobat calling your function through some menu command, your plugin starts, calculates something and then updates something on the screen? Or is it hooked into one or more messages in Acrobat, doing something every time a document view is updated e.g.? Or are you trying to get your dll start some calculation while the user is continuing working in Acrobat, wanting the results to be shown as soon as they are ready?

You make a dll. Does this have any user interface of it's own, or is it sending messages to Acrobat when it needs something drawn?

Why do you want a thread in your dll? It seems like you're having some lengthy calculation? Are you trying to achieve progress reporting during calculation? Or do you just want to have your dll wait for the calculation and then show the results?

If it's progress reporting you're looking for, you could have your main dll thread make a signal that you pass on to the worker thread doing the calculation. Then the main dll thread can do a WAIT for any signal from the worker thread (and for the worker thread to finish). The worker thread sets the signal every now and then, letting the main thread update the progress bar or whatever.

What does AFExecuteThisScript do? You haven't shown anything about how this starts the thread or how it calls into Acrobat? It seems like it somehow runs a script to search the current document for the phrase "Test", but I can't see why you want a thread for this? Isn't this just a message to Acrobat to perform a search task?

I hope this list of questions helps you understand what it is I don't understand :-)

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Threads inside DLL

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