[PATCH 3/6] d3d9/tests: Add helpers to avoid multiple readbacks of the render target surface.

[Henri Verbeet]

On 8 October 2015 at 01:26, Matteo Bruni <mbruni at codeweavers.com> wrote:
> My feeling is that we could improve the readback performance further in
> wined3d, regardless of this patch.
Possibly, but note that GetRenderTargetData() isn't terribly fast on
Windows either.

I like the concept, but the implementation probably needs some work.
I'd like to have an interface that can work for d3d10/11 as well, so
the device parameter probably needs to go. (See also how
get_texture_color() is used in d3d10core.) Maybe return a structure
that wraps both the readback surface and locked rect to avoid
declaring those as separate parameters. E.g.:

    struct surface_readback rb;

    get_surface_readback(backbuffer, &rb)
    color = get_readback_color(&rb, x, y);
    release_surface_readback(&rb);

(Not sure on the naming.) I also think getPixelColor() should then be
implemented on top of this. I think masking out the alpha/X channel
was the wrong decision, and we should fix that at some point, but for
the time being you can of course still mask the result of
get_readback_color().