[cairo] pixman: New ARM NEON optimizations

[Bill Spitzak]

Soeren Sandmann wrote:

> (1) The equation would be 
> 
>         (src OP dst) LERP_mask dst
> 
>     and not 
> 
>         (src IN mask) OP dst
> 
> (2) The RGB channels of Alpha-only images would be considered to be
>     the same as the alpha channel, and not 0 as they are now. For
>     example, a 0xb9 pixel in an a8 image would be considered
>     equivalent to 0xb9b9b9b9 and not to 0xb9000000. That is, they
>     would be considered a translucent white rather than a translucent
>     black.

Why not just try making these changes directly to Render? This is pretty 
much what Cairo did and nobody complained. Panicking about 
back-compatibility when it is likely that nobody relies on the current 
behavior is silly.

The only software I know of using Render for anything other than OVER is 
Cairo, and it must be avoiding all the cases where changing this would 
make a difference because it does not match it's rules anyway.

Of course if there are real examples of existing and in-use clients (ie 
something actually distributed on Linux systems) that rely on the 
current behavior then you can't change it.