[cairo] cairo_clip and dirty_area

Carl Worth cworth at cworth.org
Wed Sep 24 12:51:51 PDT 2008

On Sat, 2008-09-20 at 11:30 +0800, duan tao wrote:
>      I use cairo to render my flash_player, and i konw the Dirty_Area
> between the current frame and
> the next frame, so should I use cairo_clip to render the Dirty_Area
> only? It does beeter or worse to
> the performance?

Hi there.

Using cairo_clip is better *if* you are using integer rectangles for the
path, (and with an identity transformation matrix).

It can make performance worse if you are doing some non-pixel aligned
clipping path, (whether by using curves, or with a non-integer scale, or
rotation, etc.).

See here for more details:


And have fun with cairo!


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