[Bug 92363] [BSW/BDW] ogles1conform Gets test fails

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=92363

Ian Romanick <idr at freedesktop.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |krh at bitplanet.net
          Component|Drivers/DRI/i915            |Drivers/DRI/i965
         QA Contact|                            |intel-3d-bugs at lists.freedes
                   |                            |ktop.org

--- Comment #3 from Ian Romanick <idr at freedesktop.org> ---
This is actually a pretty significant bug that appears to have existed since
commit 2f28a0dc... which landed in master in August 2014.  Here's the
problem...

In OpenGL ES (all versions!) and OpenGL compatibility profile, applications
don't have to call Gen functions.  This comes from the old days of textures and
display lists where applications wanted to do clever things like make a display
list that drew the letter "A" named (GLint)'A'.  The GL spec is very clear
about how you can mix-and-match generated names and non-generated names: you
can use any name you want for a particular object type until you call the Gen
function for that object type.

Enter brw_meta_fast_clear which calls brw_fast_clear_init which calls
_mesa_GenVertexArrays and _mesa_GenBuffers.  A perfectly valid application
could do something like:

    glClear(GL_COLOR_BUFFER_BIT);

    // bind my cool buffer
    glBindBuffer(GL_ARRAY_BUFFER, 1);
    glBufferData(GL_ARRAY_BUFFER, ...);

    glClear(GL_COLOR_BUFFER_BIT);

    // draw using the data in my cool buffer
    glDrawArrays(...);

Too bad the second call to glClear smashed the data the application put in its
buffer.

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