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Re: [Gnash-dev] OpenGL buffering question

From: Dima Codreanu
Subject: Re: [Gnash-dev] OpenGL buffering question
Date: Tue, 14 Mar 2006 07:44:58 -0800 (PST)

Is it possible that two consequitive SwapBuffers() are called (with only irelevant calls between them),
or maybe gl_ClearBuffers(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | ...<other used buffers>) isnt called between the SwapBuffers() so a previous image is in the buffer, and the new triangles don't get rendered since the z-test whould prevent them from being drawn (or any other tests of a buffer that has not been cleaned).
The second case whould show the effect you are describing, while the first whould result in some flickering (I doubt it could be done so fast that the human eye wouldn't notice the flickering).
If this is a multithreading problem, then it is more serious.

Rob Savoye <address@hidden> wrote:
On the assumption there are people on this list that have more OpenGL
experience than I do (I don't have much), I have a question. My current
working version of the plugin appears to play movies, but instead of the
rendered frames, I get the hardcoded triangle/square graphics instead.
The odd thing is the code to draw the hard-coded graphic is never
executed. It's like it's stuck in the double buffer, and when I swap
buffer, I get an older stored image ? Maybe I should check in my current
version after a little more cleanup.

I figured out the problem with the player was a mutex locking up. For
some odd reason, the mutex as accessed by the player thread was
non-functional, although it worked just fine in the plugin thread. I
replaced the use of SDL_Mutex with Mozilla's PRLock, and now it works
fine. I've been reading through the NSPR API docs, and I think I'm going
to completely modify the plugin to use Mozilla's NSPR API for mutexes
and threads instead of SDL on the assumption they're better supported
within Mozilla.

- rob -

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