Merge lp:~3v1n0/unity/fix-nvidia-glDrawArrays-crash-5.0 into lp:unity/5.0

[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)]

Just tested this fix upstream in Unity 6.0/Nux 3.0. It works. And is identical to this one.

review: Approve

[Unity Merger (unity-merger)]

The prerequisite lp:~thumper/unity/regional-damage-sru has not yet been merged into lp:unity/5.0.

[Łukasz Zemczak (sil2100)]

I see a LOT of conflicts - the diff generated by this branch is also terrible. Is it all just because the prerequisite branch is not yet merged?

review: Needs Information

[Marco Trevisan (Treviño) (3v1n0)]

sil, I forgot to make this request against the correct branch (lp:unity/5.0), this MR is already superseded, follow the top link to get the new request ;)

=== modified file 'plugins/unityshell/src/unityshell.cpp'
--- plugins/unityshell/src/unityshell.cpp	2012-08-01 01:09:21 +0000
+++ plugins/unityshell/src/unityshell.cpp	2012-08-01 01:09:21 +0000
@@ -505,6 +505,15 @@
 
   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();
@@ -534,6 +543,11 @@
   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
   glDepthRangef(0, 1);
   //glViewport(-1, -1, 2, 2);