The X Rendering Extension (Render or XRender) is an extension to the X11 core protocol to implement image compositing in the X server, to allow an efficient display of transparent images.
X Rendering Extension
xclock uses the render extension for rendering translucent and antialiased clock hands
It was written by Keith Packard in 2000 and was first released with XFree86 version 4.0.1. Its design was influenced by rio, the windowing system for Plan 9.[1]
Motivationedit
The core X Window System drawing protocol does not have a way to efficiently draw transparent objects: A computer display is composed of individual pixels, which can only show a single color at a time. Thus transparency can only be achieved by mixing the colors of the transparent object to be drawn with the background color (alpha compositing). However, the standard X protocol only allows drawing with solid color, so the only way to achieve transparency is to fetch the background color from the screen, mix it with the object color, then write it back, which is fairly inefficient.[2]
Since many operations require transparency (for example spatial anti-aliasing, especially during font rasterization, and transparency effects in window managers, such as transparent windows or menus), this limitation caused problems, and Xrender was implemented to address it.
Geometric figures are rendered by client-side tessellation into either triangles or trapezoids. Text is drawn by loading the glyphs into the server and rendering as a group.
It is designed to target the 3D graphics capabilities of newer video cards.
Referencesedit
^"Design and Implementation of the X Rendering Extension". 2000. Retrieved 2013-11-03.
^Xft - the X Font library Drawing anti-aliased text with the core protocol involves fetching pixels from the destination, merging in the glyphs and shipping them back. This can be a performance problem when the latency between client and server is high.
External linksedit
The X Rendering Extension (Keith Packard, Latest Official Specification)
The Xrender Library
A New Rendering Model for X (Keith Packard, USENIX 2000)
High Performance X Servers in the Kdrive Architecture (Emma Anholt, USENIX '04)
rendering, extension, confused, with, xrandr, this, article, multiple, issues, please, help, improve, discuss, these, issues, talk, page, learn, when, remove, these, template, messages, this, article, includes, list, general, references, lacks, sufficient, cor. Not to be confused with Xrandr This article has multiple issues Please help improve it or discuss these issues on the talk page Learn how and when to remove these template messages This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations April 2011 Learn how and when to remove this message This article relies excessively on references to primary sources Please improve this article by adding secondary or tertiary sources Find sources X Rendering Extension news newspapers books scholar JSTOR April 2011 Learn how and when to remove this message Learn how and when to remove this message The X Rendering Extension Render or XRender is an extension to the X11 core protocol to implement image compositing in the X server to allow an efficient display of transparent images X Rendering Extensionxclock uses the render extension for rendering translucent and antialiased clock handsOriginal author s X Org FoundationStable release0 11 July 15 2009 14 years ago 2009 07 15 PlatformUnix Unix like Contents 1 History 2 Motivation 3 Features 4 References 5 External linksHistory editIt was written by Keith Packard in 2000 and was first released with XFree86 version 4 0 1 Its design was influenced by rio the windowing system for Plan 9 1 Motivation editThe core X Window System drawing protocol does not have a way to efficiently draw transparent objects A computer display is composed of individual pixels which can only show a single color at a time Thus transparency can only be achieved by mixing the colors of the transparent object to be drawn with the background color alpha compositing However the standard X protocol only allows drawing with solid color so the only way to achieve transparency is to fetch the background color from the screen mix it with the object color then write it back which is fairly inefficient 2 Since many operations require transparency for example spatial anti aliasing especially during font rasterization and transparency effects in window managers such as transparent windows or menus this limitation caused problems and Xrender was implemented to address it Features editIt provides several rendering operations and also does alpha blending As of 2011 update it serves primarily to implement antialiased fonts but for example KWin KDE s window manager uses it to draw drop shadows and translucency in case OpenGL is not available Geometric figures are rendered by client side tessellation into either triangles or trapezoids Text is drawn by loading the glyphs into the server and rendering as a group It is designed to target the 3D graphics capabilities of newer video cards References edit Design and Implementation of the X Rendering Extension 2000 Retrieved 2013 11 03 Xft the X Font library Drawing anti aliased text with the core protocol involves fetching pixels from the destination merging in the glyphs and shipping them back This can be a performance problem when the latency between client and server is high External links editThe X Rendering Extension Keith Packard Latest Official Specification The Xrender Library A New Rendering Model for X Keith Packard USENIX 2000 High Performance X Servers in the Kdrive Architecture Emma Anholt USENIX 04 X Org Glossary X Org Retrieved from https en wikipedia org w index php title X Rendering Extension amp oldid 1223858076, wikipedia, wiki, book, books, library,
