os: linux
distribution: Crux 3.2
kernel: 4.4.3
gpu: nvidia quadro k600

Broken: 2.77 22a2853
Worked: 2.76b (both official binary and self built)

When in pose mode, bones become unselectable if bones have custom shapes. RMB clicks
anywhere in the 3d viewport will only cycle through each bone in the armature, rather
than select the bone beneath the cursor.

I have included attached a .blend file with what I think is as simple as possible example of issue.
With 'Armature.001' selected and blender in Pose mode, try to select either of the bones (set to
sphere custom shape), or even click anywhere else in viewport. This issue only seems to occur when
using opensource driver and libraries, not the proprietary ones.

I have approached this from a few different angles to try to narrow down the issue.

First, I have compared results using opensource drivers/libraries to the proprietary ones;
as mentioned above, issue does not seem to be present when using proprietary drivers/libraries.

Next, I ran git bisect on the blender-v2.77-release branch to try to find where/when the issue
first occurs. I found that commit rBc402a37 is the point when the issue first appears.

Someone on freenode #blender suggested to change the selection mode in userprefs; this made
the issue go away. I was not satisfied that the issue was truly addressed, only bandaged. The attached
patch that is working well here.

John Vogel <jvogel4 at stny dot rr dot com>