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Bug 778006 - glitchy rendering on llvmpipe
glitchy rendering on llvmpipe
Status: RESOLVED OBSOLETE
Product: gtk+
Classification: Platform
Component: Widget: GtkGLArea
3.22.x
Other Linux
: Normal normal
: ---
Assigned To: gtk-bugs
gtk-bugs
Depends on:
Blocks:
 
 
Reported: 2017-01-31 22:56 UTC by Lukas
Modified: 2018-05-02 18:01 UTC
See Also:
GNOME target: ---
GNOME version: ---

Attachments
broken rendering (10.92 KB, image/png)
2017-01-31 22:56 UTC, Lukas 		Details

Description Lukas 2017-01-31 22:56:44 UTC 
Created attachment 344671 [details]
broken rendering

How to reproduce: Run the OpenGL demo from gtk3-demo on X11 with llvmpipe and observe glitchy rendering. See attached screenshot on how it looks like. By moving the mouse and resizing the window, you can make various portions of the window appear and disappear.

partial output from glxinfo:
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: VMware, Inc. (0xffffffff)
    Device: llvmpipe (LLVM 3.9, 256 bits) (0xffffffff)
    Version: 13.0.3
    Accelerated: no
    Video memory: 493MB
    Unified memory: no
    Preferred profile: core (0x1)
    Max core profile version: 3.3
    Max compat profile version: 3.0
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.0
OpenGL vendor string: VMware, Inc.
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 3.9, 256 bits)
OpenGL core profile version string: 3.3 (Core Profile) Mesa 13.0.3
Comment 1 Emmanuele Bassi (:ebassi) 2017-01-31 23:41:22 UTC 
Generally speaking, this looks like a driver issue.

Aside from the GL renderer being llvmpipe, which GPU are you using?
Comment 2 Lukas 2017-01-31 23:58:16 UTC 
Uh, I forgot to mention that this is on a Digitalocean droplet over VNC. Their virtualisation solution provides a "Cirrus Logic GD 5446".

The same issue happens on Ubuntu 16.04 (Gtk 3.18 on Virtualbox as well) That setup seems to use the modesetting driver.

Probably the same issue also appears with a more complex application https://github.com/carrotIndustries/horizon of mine. This time on an intel gpu.
I'll try to provide a stripped-down version that makes it easier to pinpoint the issue.
Comment 3 Matthias Clasen 2017-02-15 23:53:39 UTC 
as ebassi said: driver issue
Comment 4 Lukas 2017-02-19 21:03:31 UTC 
I'm still not sure whether this really is a driver issue, I've narrowed down this bug to https://git.gnome.org/browse/gtk+/tree/gdk/x11/gdkglcontext-x11.c?h=3.22.8&id=dad4aecfc017dbe97074a188c972c0af013c5a08#n273

When doing the "blit swap", the glitches appear. Doing glXSwapBuffers is jus fine.
Comment 5 GNOME Infrastructure Team 2018-05-02 18:01:57 UTC 
-- GitLab Migration Automatic Message --

This bug has been migrated to GNOME's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.gnome.org/GNOME/gtk/issues/747.