Re: cairo & pixmap

["control H" <control h gmail com>]

> The signal handler for the expose event is passed some parameters
> specifying which part of the screen has become invalidated. If you use
> these in a Cairo drawing mask, then redraw your canvas, it should be
> quite fast, as Cairo will ignore all operations to areas outside the
> mask.

But this means -if I understand correctly- that I still have to redraw
"from scratch", be it not the complete drawing area but only the
invalidated part. Therefore, it will still be slower than in my old
"GDK based" situation, especially when the to be drawn picture becomes
more complex (which in my situation is the case).

Do you/does anybody know what the technical reason is why cairo
contexts fail outside the expose signal? I'm just curious.