Add way of using map-to-image

[stuaxo]

I might be wrong, but it looks like there is no cairocffi way of using cairo-map-to-image, (unless this is the same as passing data to ImageSurface constructor?) - map-to-image and set-dirty and flush seem to be a way to get cairo to act on some existing data.

[SimonSapin]

Hi. I don’t know what cairo-map-to-image is, and Google Search is not very helpful. Can you explain?

[stuaxo]

The first mention I can find is here:
http://cairographics.org/news/cairo-1.11.4/

Think I found some other info the other day, will need to keep looking .. think it's for making a cairo surface that just uses existing memory as opposed to just copying existing data in.

Here is a RUBY info here, though not quite sure whats going on..
http://ruby-doc.org//gems/docs/c/cairo-1.12.9/Cairo/Surface.html#method-i-map_to_image

A patch to add it to some LUA bindings...
awesomeWM/oocairo@8ea8648

Can't actually find any examples that use it so far + haven't been able to test it..

[SimonSapin]

Ok, I see. This is the cairo_surface_map_to_image function. It does not have bindings in cairocffi yet. I’d review a pull request to add it. It would not be a lot of code, but it looks a bit tricky to get right as the returned surface needs to clean itself up with cairo_surface_unmap_image instead of cairo_surface_destroy.

I’m not sure when it is useful, but it does not look like it creates a surface from an existing memory buffer (that’s ImageSurface.create_for_data or passing data to the ImageSurface constructor) since it works with an existing surface.