[mythtv] Captions/subtitles partially broken by mythrender_opengl.cpp commit

[Lawrence Rust]

On Mon, 2016-01-04 at 09:33 -0800, Jim Stichnoth wrote:
> [This is mostly directed to lvr since I don't really know how this part of
> the code base works.]
> 
> Regarding commit a437b178, "UI: Avoid texture memory exhaustion by
> shrinking the painter image cache".
> 
> The change to mythrender_opengl.cpp, where ClearTexture() now fails if
> glCheck() reports an error, is having a weird effect on closed caption
> display on my systems.
> 
> When it tries to draw the first line of text, glCheck() fails for some
> reason and nothing is drawn.  Subsequent caption lines display fine.  The
> black background rectangles display fine.  Repeated messages like this
> appear in the logs:
> 
> 2016-01-03 18:09:29.515569 E  OpenGL: : 1281 @ mythrender_opengl.cpp, 1481
> 2016-01-03 18:09:29.515582 E  OpenGL: glTexImage size 180096 failed
> 2016-01-03 18:09:29.518569 E  Failed to create OpenGL texture.
> 
> The log lines repeat once per video frame.
> 
> Reverting that glCheck() call makes everything work fine.
> 
> I see this with both cc708 and srt captions.  For some recordings, the
> first few captions will display fine, but then it drops into the mode where
> the first text line fails.
> 
> Wondering if anyone else is seeing this problem and has any ideas.

Hi Jim,

Thanks for finding this.  Apologies for causing you the problem.  As you
have a system which demonstrates this problem perhaps you would help
debug the problem?

1. Can you add this '-O UIPainterMaxCacheHW=96' to the FE command line
and see if the problem continues.

2. If no change then would you add this patch:

--- a/mythtv/libs/libmythui/mythrender_opengl.cpp
+++ b/mythtv/libs/libmythui/mythrender_opengl.cpp
@@ -1461,6 +1461,7 @@ bool MythRenderOpenGL::ClearTexture(uint tex)
 
     memset(scratch, 0, tmp_size);
 
+    glCheck();
     if ((m_textures[tex].m_type == GL_TEXTURE_1D) && m_glTexImage1D)
     {
         m_glTexImage1D(m_textures[tex].m_type, 0,


If the problem is resolved by this patch then the GL error is occurring
in some previous code but being detected in ClearTexture.  In which case
would you move the glCheck() to various lines in
MythRenderOpenGL::CreateTexture to track which GL call is failing.  My
guess is it's in EnableTextures.

Sorry to impose but you're in the ideal position to find the cause.

-- Lawrence Rust