I'm having a problem with the nsIEventQueueService's ResolveEventQueue
method that really has me baffled. I believe it's the cause of a related
problem that I've recently posted in the embedding newsgroup, but I haven't
received an answer there and am hoping someone here might know. In any
case, it seems to be more appropriate to this newsgroup.
The problem is that 3 out of 4 times I run my app, everything works great
and this method returns the correct event queue. However, on certain rare
(and seemingly random occassions), this method returns NS_ERROR_FAILURE and
does so consistently. I've traced the error back to this block of code in
GetThreadEventQueue, which is called by ResolveEventQueue:
else if (keyThread == NS_UI_THREAD)
{
nsCOMPtr<nsIThread> mainIThread;
// Get the primordial thread
nsresult rv = nsIThread::GetMainThread(getter_AddRefs(mainIThread));
if (NS_FAILED(rv)) return rv;
rv = mainIThread->GetPRThread(&keyThread);
if (NS_FAILED(rv)) return rv; //<---Returns NS_ERROR_FAILURE
}
When I looked at the code for GetPRThread, the only reason it would return
NS_ERROR_FAILURE is if the thread's mDead member is true, meaning that my
primordial thread is dead. As far as I can tell, mDead only gets set by
nsThread::Exit. I have absolutely no idea why my primordial thread would be
considered dead, as it is still happily running the Windows message pump,
and since ResolveEventQueue works just fine most times I run my app.
This problem came up while trying to create an nsISupports proxy on the UI
thread. Since of course GetPRThread returns NS_ERROR_FAILURE, neither
proxies nor PLEvents work.
In case it helps, the following is a detailed description of what I'm
attempting to do. I'm embedding Mozilla into a Java app. Here are the
basic steps:
1. Java loads my DLL that has some JNI methods as well as my Mozilla
embedding code
2. Java calls an initialization method inside my DLL to initialize Mozilla
embedding
3. My initialization method creates a native Win32 thread that is to act as
the primordial thread and Windows message pump, and then calls
NS_InitEmbedding, etc.
4. Sometime later, from another Java thread, I call into my DLL to create
an instance of nsWebBrowser, via nsIProxyObjectManager::GetProxy so that I
can safely use it on a non-primordial thread.
5. Use the proxy to navigate, etc.
I originally thought my problem was that nsWebBrowser does not have a
thread-safe nsISupports implementation, but it turns out in fact that it
works great as long as ResolveEventQueue (which is called by the proxy code)
works, and when it doesn't work, I have verified that ResolveEventQueue is
failing. When I tried to use PLEvents to accomplish the same thing (for
fear that the non-thread-safe nsISupports was causing the problem), I
discovered the root of the problem.
It appears that for some reason my native thread isn't being attached
properly to a PRThread, or else something is calling Exit on it too soon.
If anyone could give me some hints as to possible causes I would greatly
appreciate it. With all the event queues, proxies, nsIThreads, PRThreads,
etc., I just don't know what the possible cause could be. Thanks in
advance.
--
Brad Fish
[EMAIL PROTECTED]
TALL Group Programmer
