[cairo] Text Grid Performance

[Owen Taylor]

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
feasibility.)

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