[cairo] Patch improving fallbacks

[Calum Robinson]

On 30 Jan 2005, at 23:52, Owen Taylor wrote:

> The semantics of these functions wasn't fully specified, but basically
> they allow getting the entire surface as an image or setting an image
> over the entire surface. When working on the Win32 backend, I ran
> into various problems with these. Getting the entire image was hugely
> expensive.

For the Quartz backend I just avoided getting the contents of the 
CGContext completely. There is just a CGImage that I use to blit into 
the CGContext every time _cairo_surface_set_image is called (which is 
returned via a cairo_image_surface_t from _cairo_surface_get_image).

I decided that it's unlikelt anyone using Cairo was going to care what 
was in the window before they drew into it - they only care about the 
stuff they've drawn.


Calum