[Cairo] AA-Artifacts during/after gameoflife

Christof Petig christof at petig-baender.de
Tue Nov 18 10:10:49 PST 2003

Carl Worth schrieb:
> On Nov 18, Christof Petig wrote:
>  > I don't know whether the artifacts of 'gameoflife -c 20 -r 20 -p' are 
>  > possible to eliminate by a reasonable amount of work but they confused 
>  > me a bit (unless I realized that they are AA leftovers).
> Looks like just an application bug. I don't see any problem in cairo
> itself.

I thought that drawing a red Circle on white, then a white circle of 
same size and then a black circle should ideally give the same result as 
drawing only a black circle (but with AA it doesn't). And this was the 
problem I suspected - clearing the canvas between game of life cycles is 
cheating IMHO. [Though it will probably good enough for most applications.]

But perhaps repeatedly drawing the same text (or the same line) should 
not darken the corners further.  Possible with cairo?

>  > Keep up the good work, I can hardly wait for a cairo based gtk+.
> Thank you. As for a "cairo based gtk+" you hardly need wait. In CVS,
> the cairo-demo/gtk directory shows you how to draw your own widgets
> using cairo. And the cairo-gtk-engine directory gives you a way to
> make Gtk+ use cairo for drawing all of its core widgets.
> I can't imagine that there is a lot still missing for a cairo based
> gtk+.

What about semi transparent widgets? I was under the impression that 
this needs a client side rendering library for gdk (which is what cairo 
can do). Semi transparent toplevel windows are a different problem 
(solved by keith's X server) but the current gdk implementation uses a 
lot of subwindows (which might also get semitransparent under said 
server without needing cairo?).

All in all I was told (on gtk-devel) that semitransparent widgets need 
cairo. Imagine an semitransparent entry widget on top of an image - 
looks really cool and since I have first seen it in my wife's tax return 
program (Windows 95 and up) I have longed to do such a thing myself (gtk).


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