[cairo] Text Grid Performance

[Owen Taylor]

On Wed, 2008-02-06 at 23:28 +0200, Gerdus van Zyl wrote:
> I have written my use case in pyGTK and found out some interesting
> things. First the GTK version is very fast. Secondly GTK seems to
> update the screen in chunks, about 1/3 of the screen at a time. Which
> would explain the perceived speed. I will try to do the same, if
> anyone has any suggestions on this it would be appreciated.

GTK+ double buffers everything to an offscreen surface. This is probably
a DIB, which makes software-fallbacks in cairo fast... the software
fallbacks are much, much slower if they have to fetch data from a DDB or
window than write it back.

(cairo_surface_create_similar() creates a surface backed with a DIB on
windows for this reason.)

However, text is not expected to be hitting a software fallback... I
would expect very fast GDI rendering for text if you are going directly
to a window (along with flashing from clear/redraw cycles.)

- Owen

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