|Source Repository:||Funtoo Overlay|
Summary: A Gentoo/Funtoo utility that allows the active OpenGL implementation on a system to be switched between a variety of installed options.
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Eselect (OpenGL) (also called eselect-opengl) is a module for Eselect that allows the OpenGL implementation on a Funtoo Linux or Gentoo Linux system to be switched between a variety of installed OpenGL implementations. It functions by creating an env.d file at /etc/env.d/03opengl which contains OpenGL settings, as well as managing symbolic links to OpenGL libraries and headers.
Sample env.d File
A sample env.d file for a multilib system with xorg-x11 OpenGL implementation may look like this:
Eselect-opengl is implemented as a single bash-based Eselect module approximately 10K in size, installed at /usr/share/eselect/modules/opengl.eselect. One interfaces with this module via the main eselect command:
# eselect opengl help Manage the OpenGL implementation used by your system Usage: eselect opengl <action> <options> Standard actions: help Display help text usage Display usage information version Display version information Extra actions: list List the available OpenGL implementations. set <target> Select the OpenGL implementation. <target> The profile to activate --use-old If an implementation is already set, use that one instead --prefix=<val> Set the source prefix (default: /usr) --dst-prefix=<val> Set the destination prefix (default: /usr) --ignore-missing Ignore missing files when setting a new implementation show Print the current OpenGL implementation.
What is Switched
Eselect-opengl handles switching of the active:
- Libraries (32-bit and 64-bit):
- C Headers:
Ebuilds that provide an active OpenGL implementation install their libraries, headers, etc. in:
On multilib systems, ebuilds that provide an OpenGL implementation install 32-bit libraries in /usr/lib32/opengl/(implementation name)/lib and 64-bit libraries in /usr/lib64/opengl/(implementation name)/lib.
Eselect-opengl looks in these directories for active OpenGL implementations.
Violation of Build Consistency
As documented in FL-1309, sometimes packages fail to merge when the "wrong" eselect opengl implementation is selected. This violates Portage's ability to consistently build a package from source, assuming all its dependencies are satisfied. This could be classified as a design bug -- eselect-opengl is functioning as intended, but its underlying theory of operation is not correct.
A possible solution to this problem, discussed in FL-1309, is to redesign eselect-opengl to only select the runtime OpenGL implementation, but to have all ebuilds build against the official xorg-x11 OpenGL implementation.
The rationale for this design change is that:
- There should be a consistent and repeatable build/linking process for all OpenGL applications.
- AMD and NVIDIA implementations of OpenGL are designed to be more of a "drop-in" runtime replacement for xorg-x11, rather than a standalone replacement for xorg-x11, and thus appear to exhibit more build-time bugs.