Editing EXA (section)

==History==
Historically, a distinction has been made between 2D and 3D acceleration. 2D acceleration was provided by the venerable [[XFree86 Acceleration Architecture]], XAA, which made the video card's 2D hardware acceleration available to the X server.

The 3D acceleration set was provided via the [[Direct Rendering Manager]], which worked by mapping 3D rendered pictures on top of the 2D picture. This had some buggy corner cases, but more or less worked, until [[compositing window manager|compositing]] entered into the desktop. This distinction has become the source of a lot of bugs, and performance problems.

EXA was introduced as a stopgap measure, to provide better integration with [[X Rendering Extension|XRender]] than XAA did, improving the X.Org Server 2D performance. In practice, while this proved quite advantageous in some respects, it also exhibited a number of corner cases and regressions.

The solution was to move to hardware acceleration with [[OpenGL]] for both 2D and 3D graphics with 2D graphics becoming just a subset of 3D rendering. Switching entirely over is unfortunately not so simple and not without some major obstacles.

EXA was adapted from KAA, the [[KDrive]] Acceleration Architecture, from the experimental [[Freedesktop.org]] [[KDrive|Xserver]]. Per the initial mailing list announcement,<ref>[http://lists.freedesktop.org/archives/xorg/2005-June/008321.html New acceleration architecture] (announcement on Xorg mailing list, Zack Rusin, 25 June 2005)</ref> the goals are:

# Properly accelerate XRender
# Be as simple as possible.

Many XAA drivers had EXA support added for X11R6.9/7.0 and support continues to be added to more drivers. Making this transition as easy as possible was an important design consideration.<ref name="exa-driver.txt">{{cite web|url=https://gitlab.freedesktop.org/xorg/xserver/blob/master/hw/xfree86/doc/exa-driver.txt|title=Adding EXA support to your X.Org video driver|author=Jesse Barnes|accessdate=2010-05-18|date=2006-03-09}}</ref>

[[UXA]] is a reimplementation of the EXA API developed by Intel, using the [[Graphics Execution Manager]].<ref>[http://keithp.com/blogs/UMA_Acceleration_Architecture/ UMA Acceleration Architecture]</ref>

The [[Free and open-source graphics device driver#ATI/AMD|Radeon free and open-source device driver]] supports 2D acceleration through EXA and [[Glamor (software)|Glamor]].<ref>{{cite web |url=http://xorg.freedesktop.org/wiki/RadeonFeature/ |title=Radeon Feature Matrix |work=[[freedesktop.org]]}}</ref>

[[Glamor (software)|Glamor]] is supposed to obsolete all previous attempts.<ref>{{cite web |url=http://www.freedesktop.org/wiki/Software/Glamor/ |title=What is Glamor? |work=[[freedesktop.org]]}}</ref>