[cairo] Patch improving fallbacks

[Tim Rowley]

On Mon, Jan 31, 2005 at 09:19:59AM +0000, Calum Robinson wrote:
> 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).

As I mentioned in an earlier mail, doing the blit with a
composite function as the quartz backend currently does leads to
incorrect results for partially opaque pixels.

> 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.

In my case, implementing SVG in mozilla, I do care about what was
drawn underneath - SVG fragments are supposed to be composited
with the rest of page, which is drawn with QuickDraw/Quartz.

-tor