[cairo] cairo design

Jon Smirl jonsmirl at yahoo.com
Sat Apr 24 09:36:51 PDT 2004

--- Owen Taylor <otaylor at redhat.com> wrote:
> Or maybe instead we should do some apps and see if they are actually
> necessary? Presumably a display list looks a whole lot like a 
> "stored group" - I don't imagine that introducing them later compatibly
> would be a problem.

There should be a big difference on the net. Displays can cut out thousands of
unnecessary round trips. Display lists are not a full retained mode model. You
can only delete a display list, it can't be edited.

Locally display list have another advantage in that they can be compiled. So
lots of moveto/lineto calls can be collapsed into vertex arrarys. Images in the
wrong pixel format are converted to the native format and cached in the list.
There are lots of other optimizations that vary with the OpenGL implementation. 
Another advantage is that they can be shared letting the toolkit build the lists
once and share them with all of the apps. Once the app builds the list it can
discard everything used to build it, display lists don't disappear.

They may not make that much difference on an xlib implementation since xlib
doesn't have display lists but OpenGL already supports and compiles them.

I tend to think if they get introduced later no one will use them.

Jon Smirl
jonsmirl at yahoo.com

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