Can't confirm, works fine for me. Please attach a test file if something is still wrong. Test this with recent builds from buildbot.blender.org. Also include more system info, in particular graphics card.
I can also confirm this bug:
I am using Blender GIT REV 2014-07-07-19-20-33-aac2839 on a Fedora 20 64bit box with Intel 3000 HD gfx
If you open the default scene and activate mapcap from the shading panel and then use ALT+B
The matcap stop working. If you clear alt+b the matcap starts working again.
I have attached my system-info.txt, a blend file and a Video showing the issue I get.
I can confirm on my laptop with
VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA controller])
renderer: 'Mesa DRI Intel(R) Sandybridge Mobile '
vendor: 'Intel Open Source Technology Center'
version: '3.0 Mesa 10.1.5'
not a big deal for me (my workstation with nvidia graphics is just fine), just wanted to drop a note about a config that fails...
I can't confirm either here but I have an NVIDIA.
I seem to remember that you need to set the clipping planes on some GPUs for this to work properly, which I'm not sure we really do for matcaps.
OK, we have explicitly disabled clipvertex on non NVIDIA GPUs see gpu_shader_vertex.glsl and gpu_shader_simple_vert.glsl
That means that clip planes should misbehave on GLSL viewport mode too for affected users?
More digging, this looks like an ATI limitation where driver falls back to software.
We may be able to use projection space clip planes like explained here https://www.opengl.org/discussion_boards/showthread.php/167979-ATI-GLSL-and-custom-cliping-planes/page2
Just pushed a commit that should enable this on Intels. I am not sure if it causes a software fallback but we can test now. For ATIs we might be able to support gl_ClipDistance as suggested on the linked thread above. It should only work on GL 3.0 capable machines though.
Win 7 64 bit - Amd Phenom II 1100T - ATI Radeon 6870
I tried this 32-bit revision 5e3e095 and clipping border works fine with matcaps.
I have tested it on object mode, sculpt mode- dynatopo and sculpt mode-multires.
Excellent, closing then.
Just reassering that we may have to revert the commit if we get any reports on bad performance or GLSL materials not working etc.
Nice to know it works though :)