6502735f01
This function gets hit even today on relatively modern Intel systems (I have a Haswell Desktop with Mesa 18.2.4) if the pixel format is right. Presumably it makes things slower for no longer a reason. According to cb146dc515bf484192a8edfab716550a996b05df, this functionality was refactored into a workaround path in 2012. The commit message mentions the problem existing before Mesa 8.0.2. The number refers to https://bugs.freedesktop.org/show_bug.cgi?id=46631 . The use case where I hit this is when improving support for DisplayLink video outputs. These are used through a "secondary GPU", and since DisplayLink does not have a GPU, Mutter uses the CPU copy path with Cogl read-pixels[1]. If the DisplayLink framebuffer was allocated as DRM_FORMAT_XRGB8888 (the only format it currently handles correctly), mesa_46631_slow_read_pixels_workaround would get hit. The render buffer is the same format as the framebuffer, yet doing the copy XRGB -> XRGB ends up being slower than XRGB -> XBGR which makes no sense. This patch is not sufficient to fix the XRGB -> XRGB copy performance, but it is required. This patch reverts CoglGpuInfoDriverBug into what it was before cb146dc515bf484192a8edfab716550a996b05df. [1] This is not actually true until https://gitlab.gnome.org/GNOME/mutter/merge_requests/278 is merged. https://gitlab.gnome.org/GNOME/mutter/merge_requests/313
Mutter
Mutter is a Wayland display server and X11 window manager and compositor library.
When used as a Wayland display server, it runs on top of KMS and libinput. It implements the compositor side of the Wayland core protocol as well as various protocol extensions. It also has functionality related to running X11 applications using Xwayland.
When used on top of Xorg it acts as a X11 window manager and compositing manager.
It contains functionality related to, among other things, window management, window compositing, focus tracking, workspace management, keybindings and monitor configuration.
Internally it uses a fork of Cogl, a hardware acceleration abstraction library used to simplify usage of OpenGL pipelines, as well as a fork af Clutter, a scene graph and user interface toolkit.
Mutter is used by, for example, GNOME Shell, the GNOME core user interface, and by Gala, elementary OS's window manager. It can also be run standalone, using the command "mutter", but just running plain mutter is only intended for debugging purposes.
License
Mutter is distributed under the terms of the GNU General Public License, version 2 or later. See the COPYING file for detalis.