What we might know about the Linux, X-server, is that it offers pure X-protocol to render such features efficiently to the display, as Text with Fonts, Simple GUI-elements, and small Bitmaps such as Icons… But then, when it’s needed to send moving pictures to the display, we need extensions, which serious Linux-users take for granted. One such extension is the Shared-Memory extension.
Its premise is that the X-server shares a region of RAM with the client application, into which the client-application can draw pixels, which the X-server then transfers to Graphics Memory.
For moving pictures, this offers one way in which they can also be ~accelerated~, because that memory-region stays mapped, even when the client-application redraws it many times.
But this extension does not make significant use of the GPU, only of the CPU.
And so there exists something called SDL, which stands for Simple Direct Media Layer. And one valid question we may ask ourselves about this protocol, is how it achieves a speed improvement, if it’s only installed on Linux systems as a set of user-space libraries, not drivers.
(Updated 10/06/2017 : )