[Bug 34263] New: Framebuffer read-before-write causes graphical glitches

[wine-bugs at winehq.org]

http://bugs.winehq.org/show_bug.cgi?id=34263

             Bug #: 34263
           Summary: Framebuffer read-before-write causes graphical
                    glitches
           Product: Wine
           Version: 1.7.0
          Platform: x86
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: directx-d3d
        AssignedTo: wine-bugs at winehq.org
        ReportedBy: achurch+wine at achurch.org
    Classification: Unclassified


Created attachment 45608
  --> http://bugs.winehq.org/attachment.cgi?id=45608
Suboptimal but functional patch

In at least the Final Fantasy XIV: A Realm Reborn character creation benchmark
(http://na.finalfantasyxiv.com/benchmark/index.html), framebuffer
read-before-write results in graphical glitches such as the entire display or
UI overlays flickering or incorrect textures being drawn.  This program uses
multithreaded rendering (though I don't know whether that's relevant), and in
some cases, Direct3D calls which get translated to glBlitFramebuffer() attempt
to read from a framebuffer before the GPU has finished rendering to it.

The cause was found by dumping OpenGL calls using apitrace
(https://github.com/apitrace/apitrace) and observing that replaying the same
frame sporadically caused the same sort of glitches as observed in Wine, but
the glitches went away when a glFinish() call was inserted at each thread
switch.

The attached patch fixes these glitches by inserting a glFinish() call before
each glBlitFramebuffer() call.  This is almost certainly suboptimal, and in my
case it causes the benchmark result to drop from ~3500 to ~3000, but it fixes
all graphical glitches aside from black squares seen in some cases when the HDR
option is enabled in rendering settings.

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