[cairo] Using Cairo and Pango to scroll text on video

Maarten Bosmans mkbosmans at gmail.com
Sat May 5 11:51:09 PDT 2012


Please make sure that you also include the mailing list in the CC.

>>Another workaround is to prerender the text to a similar surface
>>(cairo_surface_create_similar) and paint that intermediate surface to
>>the destination surface with the correct offset.
>
> Would using the latter method prevent me from using semi-transparent text
> and / or backgrounds?

It would not if you pass CAIRO_CONTENT_COLOR_ALPHA to the function, see
http://cairographics.org/manual/cairo-cairo-surface-t.html#cairo-surface-create-similar

Prerendering the text is much faster that having to render the text
again in every frame. It's only really a reasonable shortcut when the
text is only translated and perhaps rotated, but not zoomed though.

Maarten


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