When Longhorn release, Linux got end. 3509

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1

Only a small subset of the drawing operations are accelerated. In addition, what current toolkits want to do with the graphics card means that some of the acceleration functions are no longer useful.

There's a good explanation here:

are doing 2D drawing with Xlib or Gdk, you are drawing to a Drawable, which is conceptually a simple bitmap or pixmap, and you send commands to draw lines, circles, filled polygons, etc.. With X11 this might exist in the X server, and the drawing commands go over the wire. To display it, it will have to be put on the framebuffer, which usually means copying it to the graphics card memory. The GPU can accelerate stuff like stippled fills, but for images, each bit will need sending.

With current toolkits, font rendering is client side. Each glyph is rendered as a graymap (with FreeType), and composited onto the drawable. This is tedious and boring, and can't be accelerated. The final composed pixmap is sent to the X server. With 3D hardware, each glyph could potentially be composited on the fly with the GPU. If your glyph is 24x24, and you want it coloured pale blue, that's 576 4-byte pixels to transform to the correct colour (from the graymap) and paint onto the drawable. Compositing an entire page of text for each expose event is expensive, yet the GPU could do it without breaking a sweat (from a stored cache of glyph surfaces).

Cairo should be accelerated in precisely this way (with the OpenGL backend).

It's not the only way, but modern toolkits want to do alpha-compositing and other funky stuff, which are expensive operations. 3D hardware can do the operations quickly and cheaply. So it's not like the toolkits are using fancy 3D effects; they are just making use of the 3D rendering facilities to do advanced 2D rendering, which would otherwise be done by the host CPU.

BTW, I'm not an X expert. The nearest I've come to X11 is using GdkDrawables and GdkPixmaps, so my facts might not be 100% accurate.

Regards, Roger

- -- Roger Leigh GPG Public Key: 0x25BFB848. Please sign and encrypt your mail. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (GNU-Linux)

iD8DBQFCc9sYVcFcaSW-uEgRAtkbAJ9pS7dX3KI44s3IWGLr7PNGnvn4BACgmqUU AnsPfFT5qVvqwUGK3Y90gU8= =tG7z -----END PGP SIGNATURE-----