The cairo context cairo_t should provide a method to set the current target surface if the new target surface is compatible with the original target surface. This new method would speed up drawing operations in a library I am working on; currently there is no way to either 1.) Change the cairo context target surface while keeping the state stack intact -OR- 2.) Retrieve current or saved painter states and transfer them to a new context I do not want to keep track of the various painter states inside my library due to the additional complexity and subsequent maintenance concerns. As a result, I am essentially forced to draw onto an intermediate target surface, then paint the contents of that surface onto multiple target surfaces via slow compositing operations.
There was a proposal for cairo_/save/restore/_state[1] back in 2006, but it seems it never got implemented. [1] : http://lists.freedesktop.org/archives/cairo/2006-January/006196.html My needs are to be able to replace the target surface without losing internal state (such as the line width settings). For example I could have a widget with a backing store which a user paints on using a cairo_t context. If the widget size changes (e.g. becomes larger), the backing store might have to be reallocated, but then a new cairo_t context has to be created for the new surface. Currently that means losing all internal stack state (e.g. the user's line width, etc). Either the ability to store and load the internal state externally or the ability to replace the internal surface would work for me.
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