wglMakeCurrent fails

[slotdev]

Sometimes, on various hardware platform we use, wglMakeCurrent fails and GetLastError returns 170 ("The requested resource is in use."). A quick hack to retry 100 times also fails.

I have 2, sometimes 3 windows, but our program is single threaded. Does anyone have any ideas why this might happen, and how I can check for what has control of this context?

Our program has 9 OpenGL contexts (that is, I can see 9 calls to createContext) which might be too many for this crappy hardware

Thanks

[Laurent]

I have no idea, sorry. This is the first time I ever hear about this error

Maybe OpenGL debuggers/tracers could help?

Do you use custom OpenGL calls? Multiple threads dealing with contexts?

Our program has 9 OpenGL contexts (that is, I can see 9 calls to createContext) which might be too many for this crappy hardware

SFML creates hidden contexts, but most of them are not active and are there only for resource sharing.

[slotdev]

Using a tracing program, I found the following when the problem occurs:

glViewport(0,0,1920,1081)
glMatrixMode(GL_MODELVIEW)
glPopMatrix()
glMatrixMode(GL_PROJECTION)
glPopMatrix()
glMatrixMode(GL_TEXTURE)
glPopMatrix()
glMatrixMode(GL_MODELVIEW)
wglSwapBuffers(42010BE0)=true
glEnable(GL_TEXTURE_2D)
wglMakeCurrent(A5010C00,00010003)=false                            <------------------ This is the problem
wglMakeCurrent(A5010C00,00010003)=false
(repeated another ~10 times)

So basically it's failing here - which is the 2nd window I have open. Very strange.

[slotdev]

I'm trying certain things to try and fix this. Is there a way to force use of a specific version of OpenGL?

[Laurent]

Is there a way to force use of a specific version of OpenGL?

See the sf::ContextSettings that you pass at window creation.

[slotdev]

Been doing some work on this problem. I can see there is more than 1 thread which is calling wglMakeCurrent, from a log file:

wglMakeCurrent call, thread ID 3812
wglMakeCurrent call, thread ID 2880
wglMakeCurrent call, thread ID 3812

So, in a single threaded application, what can be creating another thread? I know for sure that our code doesn't create any. Strange.

[Laurent]

SFML doesn't create extra graphics threads.

Where do you put your log call? Did you install some kind of global hook on the wglMakeCurrent function?

[slotdev]

I just added:

DWORD dwThread = GetCurrentThreadId();
err() << "wglMakeCurrent call, thread ID " << dwThread << std::endl;
 

to WglContext::makeCurrent. The only hook is to SetWindowPos function.

Also, it seems that our application has 11 threads running. I assume audio could be responsible for some of these threads....

[slotdev]

Just looking at what threads are running, and of my 11 threads, 8 are audio (OK), 1 is window (OK), 1 is main thread (duh!) and 1 is caused by this line of code

gfxEngine = new GfxEngine();

..which calls the constructor of this class, and I guess since SFML gets initialised here, this is why it makes another thread?

[Laurent]

There's no global SFML initialization, and there's no thread launched by SFML other than in the audio module.

[slotdev]

There is something strange going on where another thread is created by something Windows does when this class is instatitated.

But, I found the problem - I was doing a display(); call from a callback function which is triggered by an external process 

Hope I didn't waste anyone's time..

[Laurent]

No problem, I'm glad you solved it