libXrender - documentation?

[Clemens Eisserer]

Most likely I will write some XRender documentation as part of my
bachelor thesis.

> In a subsequent thread "2D antialiasing?" on this list, I was bemoaning
> the fact that antialiasing by that method would waste huge amounts of
> bandwidth if the client were separated from the Xserver by some slow
> network, and someone claimed to me, offlist, that Xrender provided
> server-side antialiasing.
>
> So I wanted to verify that claim. Now that this list has pointed me to
> Keith Packard's "The X Rendering Extension", I have done a quick scan of
> that, but can still find no mention of antialiasing. Moreover, that
> describes the protocol, rather than the libXrender interface that is more
> conveniently used to access it,
Yes, that was me ;)

Antialiasing is usually done by transferring the geometry you intend
to render into a mask-pixmap, this can be done with:
- XPutImage (client-side geometry rasterization)
- XRenderAddTraps

and doing a composite operation with that mask.

or by using an implicit mask with:
- XRenderCompositeTrapezoids

However as far as I know xft already has a XRender aware backend
(using the XRender*Glyphs functions), as well as legacy support for
pre-xrender servers.

- Clemens