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

robertk54 at aol.com robertk54 at aol.com
Mon May 7 07:15:42 PDT 2012

>>>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
>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.

I would love to pre-render the text but I think my use case makes it a bit more complex.  
The video frame is a fixed size ARGB surface which makes sense.  However, the text can 
be any size and often much wider than the video image.  I imagine this prevents me from being 
able to use 'create similar' since this would be using the video frame's surface, no?  I guess 
I could create a new ARGB image surface using the text dimensions?

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