[Pixman] [PATCH 2/4] general: Fetch the source directly into the destination

[Søren Sandmann]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> This is principally used by external renderers to convert a procedural
> pixman_image_t (SourcePict) into an image that they can handle, using a
> simple pixman_image_composite(SRC, source, NULL, dst). For these cases
> we typicall hit the general_composite_rect and so retrieve the source
> into a temporary buffer before copying back to the destination. This
> allows us to eliminate that extra copy.

If something like this is really necessary, it should be done as a fast
path in pixman-fast.c.

But I don't really like it. It is legal for an iterator to assume that
its buffer doesn't change from one call to _get_scanline() to the next,
and while it may be true currently that iterators only rely on that if
they also use _pixman_get_scanline_noop so that your special casing of
that function makes it work, this is a rather fragile assumption.

> Only benefit for cairo-image is lost in the noise.

And it sounds like it isn't really necessary.


Søren