Merge lp:~3v1n0/unity/fix-nvidia-glDrawArrays-crash into lp:unity

[Marco Trevisan (Treviño)]

unityshell: fix the nvidia crash on glDrawArrays disabling/enabling the client state on nuxPrologue/Epilogue (LP: #982626) (LP: #1031554)

Fix some crashes with the NVIDIA driver, happening on glDrawArray call.
Thanks to Sam for the hint.

[Sam Spilsbury (smspillaz)]

Test coverage would be nice so that people don't accidentally nuke this code, though it would kinda involve wrapping those gl calls. Dunno if we want to do that.

review: Approve

[Daniel van Vugt (vanvugt)]

Works for me. Crash fixed.

review: Approve

[Unity Merger (unity-merger)]

The Jenkins job https://jenkins.qa.ubuntu.com/job/automerge-unity/984/console reported an error when processing this lp:~3v1n0/unity/fix-nvidia-glDrawArrays-crash branch.
Not merging it.

[Unity Merger (unity-merger)]

The Jenkins job https://jenkins.qa.ubuntu.com/job/automerge-unity/987/console reported an error when processing this lp:~3v1n0/unity/fix-nvidia-glDrawArrays-crash branch.
Not merging it.

[jenkins (martin-mrazik+qa)]

FAILED: Continuous integration, rev:2530
http://jenkins.qa.ubuntu.com/job/unity-ci/129/
Executed test runs:
    FAILURE: http://jenkins.qa.ubuntu.com/job/unity-ci/./distribution=quantal,flavor=amd64/129/console
    FAILURE: http://jenkins.qa.ubuntu.com/job/unity-ci/./distribution=quantal,flavor=i386/129/console

review: Needs Fixing (continuous-integration)

=== modified file 'plugins/unityshell/src/unityshell.cpp'
--- plugins/unityshell/src/unityshell.cpp	2012-07-30 17:12:48 +0000
+++ plugins/unityshell/src/unityshell.cpp	2012-08-01 01:27:18 +0000
@@ -501,6 +501,15 @@
 
   glMatrixMode(GL_MODELVIEW);
   glPushMatrix();
+
+  /* This is needed to Fix a crash in glDrawArrays with the NVIDIA driver
+   * see bugs #1031554 and #982626.
+   * The NVIDIA driver looks to see if the legacy GL_VERTEX_ARRAY,
+   * GL_TEXTURE_COORDINATES_ARRAY and other such client states are enabled
+   * first before checking if a vertex buffer is bound and will prefer the
+   * client buffers over the the vertex buffer object. */
+  glDisableClientState(GL_VERTEX_ARRAY);
+  glDisableClientState(GL_TEXTURE_COORD_ARRAY);
 #endif
 
   glGetError();
@@ -530,6 +539,11 @@
   glReadBuffer(GL_BACK);
 
   glPopAttrib();
+
+  /* Re-enable the client states that have been disabled in nuxPrologue, for
+   * NVIDIA compatibility reasons */
+  glEnableClientState(GL_VERTEX_ARRAY);
+  glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 #else
 #ifdef USE_GLES
   glDepthRangef(0, 1);