[cairo] Text Grid Performance

Owen Taylor otaylor at redhat.com
Tue Feb 5 08:48:31 PST 2008

On Tue, 2008-02-05 at 17:10 +0200, Gerdus van Zyl wrote:
> Hi,
> Does anybody have any idea on how to speed up text rendering
> performance? Below is a table of my current performance values, the #
> is the number of individual text elements of string length 2 that is
> being rendered. My goal is to have 250 text elements, since that is
> what a typical Excel spreadsheet displays at one time. Currently is
> runs at 8 FPS where to have smooth scrolling a minimum of say 15-24
> FPS is required. The use case is a spreadsheet like table/grid.
> Caching is not an option since the dataset is so large that scrolling
> fills the view with all new values. Any thoughts are appreciated.

If there is no overlap/coherency between frames .... then I doubt frame
rate has much effect on smoothness... you are just flashing numbers
across the screen faster. Normally people copy unchanged areas to get
smooth scrolling.

- Owen

(But certainly I'd expect 250*2*20 = 10,000 character per second is
doable unless something is going wrong either with your
test code or with the cairo/X rendering paths. I get considerably
more than that with the attached test case, though considerably less
than I *should* get all things considered.

Note that there are a lot of subtle things about measuring cairo
performance that are handled well by the cairo performance tests
and not at all by the attached code. Just meant to demonstrate ballpark

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