[mythtv-commits] Ticket #12902: Cannot make QOpenGLContext current in a different thread (occurred while watching live tv)

[MythTV]

#12902: Cannot make QOpenGLContext current in a different thread (occurred while
watching live tv)
-------------------------------------------------+-------------------------
 Reporter:  William L. DeRieux IV                |          Owner:
  <WilliamDeRieux@…>                             |
     Type:  Bug Report - Crash                   |         Status:  new
 Priority:  critical                             |      Milestone:  0.28.1
Component:  Qt5 issues                           |        Version:  0.28.0
 Severity:  high                                 |     Resolution:
 Keywords:                                       |  Ticket locked:  0
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Comment (by WilliamDeRieux@…):

 Replying to [comment:10 WilliamDeRieux@…]:
 > It's already testing if the version of QT is greater than or equal to
 5.4, but because USE_OPENGL_QT5 is not defined unless OpenGLES is being
 used -- the QT5 version of makeCurrent(m_window) is never called -- it
 defaults to calling QGLContext::makeCurrent(); with no surface.
 > Also, there is no point in comparing the context to
 MythRenderOpenGL::currentContext() -- since it will just end up calling
 QGLContext::makeCurrent() anyways
 >
 > And since I am using QT 5.7 -- it would make since to call the QT5
 version.
 > I think the method would better written like this (but I have not tried
 this variant):
 > {{{
 > void MythRenderOpenGL::makeCurrent()
 > {
 >     m_lock.lock();
 >     // Testing MythRenderOpenGL::currentContext is not reliable
 >     if (!m_lock_level++)
 >     {
 > #if QT_VERSION >= QT_VERSION_CHECK(5, 4, 0)
 >         QOpenGLContext::makeCurrent(m_window);
 > #else
 >             QGLContext::makeCurrent();
 > #endif
 >     }
 >     m_lock_level++;
 > }
 > }}}
 >
 >

 I can see that the modification to this method (that I just mentioned)
 would not take into account version(s) of QT less than 5.4 and as a result
 would no longer call this part:

 {{{
     if (this != MythRenderOpenGL::currentContext())
         QGLContext::makeCurrent();
     m_lock_level++;
 }}}

 However, I suspect that versions of QT less than 5.4 should be deprecated,
 especially since the use 5.4 and later should be widespread by now.

 I don't know if that would be an issue.

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Ticket URL: <https://code.mythtv.org/trac/ticket/12902#comment:11>
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