On 03/10/2014 05:19, Chris Carlson wrote:
I discovered there are no visuals available to remote X connections that
support OpenGL double buffering. There used to be, but no longer.
[...]
I thought the two logs that you requested were a bit large for this
e-mail, so I put them on my web site. You can access them as:
Thanks.
So, this is the set visuals that the X server supports.
GL_VERSION: 3.1.0 - Build 8.15.10.2455
GL_VENDOR: Intel
GL_RENDERER: Intel(R) HD Graphics Family
[...]
pxf vis fb render Ste aux
accum MS drawable Group/
idx ID ID VisualType Depth Lvl RGB CI DB Swap reo R G B A Z S buf AR
AG AB AA bufs num W P Pb Float Trans Caveat
-----------------------------------------------------------------------------------------------------------------------------
1 51 42 TrueColor 32 0 y . . . 8 8 8 8 0 0 0 0
0 0 0 0 0 y . y . . 2
2 52 43 TrueColor 32 0 y . y xchg . 8 8 8 8 0 0 0 16
16 16 16 0 0 y . y . . 2
3 53 44 TrueColor 32 0 y . . . 8 8 8 8 24 8 0 0
0 0 0 0 0 y . y . . 2
4 21 45 TrueColor 32 0 y . y xchg . 8 8 8 8 24 8 0 16
16 16 16 0 0 y . y . . 2
5 54 46 TrueColor 32 0 y . . . 8 8 8 8 16 0 0 0
0 0 0 0 0 y . y . . 2
6 55 47 TrueColor 32 0 y . y xchg . 8 8 8 8 16 0 0 16
16 16 16 0 0 y . y . . 2
7 56 48 TrueColor 32 0 y . y copy . 8 8 8 8 0 0 0 16
16 16 16 0 0 y . y . . 2
8 57 49 TrueColor 32 0 y . y copy . 8 8 8 8 16 0 0 16
16 16 16 0 0 y . y . . 2
9 41 4a TrueColor 32 0 y . y copy . 8 8 8 8 24 8 0 16
16 16 16 0 0 y . y . . 2
10 58 4b TrueColor 32 0 y . . . 8 8 8 8 0 0 0 0
0 0 0 1 4 y . y . . 2
11 59 4c TrueColor 32 0 y . y xchg . 8 8 8 8 0 0 0 16
16 16 16 1 4 y . y . . 2
12 5a 4d TrueColor 32 0 y . . . 8 8 8 8 16 0 0 0
0 0 0 1 4 y . y . . 2
13 5b 4e TrueColor 32 0 y . y xchg . 8 8 8 8 16 0 0 16
16 16 16 1 4 y . y . . 2
14 5c 4f TrueColor 32 0 y . . . 8 8 8 8 24 8 0 0
0 0 0 1 4 y . y . . 2
15 5d 50 TrueColor 32 0 y . y xchg . 8 8 8 8 24 8 0 16
16 16 16 1 4 y . y . . 2
The mesa software renderer on the remote host constructs the set of
visuals the client gets offered by picking the visuals from the server's
set of visuals which match one of it's visuals
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 0x300)
OpenGL version string: 2.1 Mesa 8.0.4
[...]
visual x bf lv rg d st colorbuffer sr ax dp st accumbuffer ms cav
id dep cl sp sz l ci b ro r g b a F gb bf th cl r g b a ns b eat
----------------------------------------------------------------------------
0x051 24 tc 0 32 0 r . . 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x053 24 tc 0 32 0 r . . 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
Unfortunately this set is small, and indeed doesn't contain any
double-buffered visuals.
Workarounds are to use either start Cygwin X server with -nowgl (so it
too uses the software renderer and will offer a set of visual which is
probably exactly the same), or to run the client with the
LIBGL_ALWAYS_INDIRECT env var set (so that indirect rendering is used
and the remote client has access to the actual set of visuals the server
supports)
I think the real fix to this is to fix the remote libGL, either so it
matches visuals less precisely, or so it offers more visuals which can
match, but this is not simple.
Believe it or not, I just so happen to have an XWin.0.log from my old,
old, old version of Cygwin. It was:
Package: version 1.15.1-2 built 2014-05-06
Now I can reproduce this, it seems that this can be an unfortunate
side-effect of the "Improve visual matching with a remote libGL by not
reporting pbuffer size limits" change in 1.15.1-3 [1], which was
intended to have the opposite effect, if previously no visuals at all
were matching, so the software renderer was disabled, and we were
falling back to indirect rendering.
[1] https://cygwin.com/ml/cygwin-xfree-announce/2014-06/msg00002.html
--
Jon TURNEY
Volunteer Cygwin/X X Server maintainer
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