What is Direct Rendering?
In the purest form of direct rendering, an application will create data to be displayed in exactly the same format required by the hardware, and send that data to the graphics hardware to be displayed as it is created. It is probably safe to say that this case never appears in anything but dedicated sytems which have been designed to run a single applicaiton requiring very high bandwidth graphics. In most systems, data is massaged, manipulated, stored, retrieved, transmitted, etc., many times before it finally ends up displayed on the computer screen. In an X11 environment, most rendering operations are indirect because application drawing commands are converted by a library into X11 protocol requests, transmitted to the X Server and then interpreted by the X Server. The X Server then executes the drawing commands on behalf of the Application. We use the term Direct Rendering to mean the client applications are allowed to directly access the graphics hardware, with an absolute minimum
