This by itself is just more work refcounting all those images, but
there's actually a goal here, that will become visible in future
commits.
But this is split out for correctness and benchmarking purposes (the
overhead from refcounting seems to be negligible on my computer).
The alternative color state is used as the interpolation color state.
Colors are transformed into that space on the CPU.
For now we set the interpolation color state to SRGB, because ultimately
we want to let callers specify it, so having something that's easy to
map to that behavior is desirable.
Otherwise we might have chosen to interpolate in the compositing
colorstate.
It also means that we need to premultiply colors on the CPU now because
of the limitations of the shader colorstates APIs.
This adds a GdkColorStates that encodes 2 of the default GdkColorStates
and wether their values are premultiplied or not.
Neither do the shaders do anything with this information yet, nor do the
shaders do anything with it yet, this is just the plumbing.
Make the generator generate calls for the correct glBindAttribLocation()
calls.
Usually this was done correctly, but we can't rely on it. So do it
explicitly.
Unless GSK_GPU_SKIP=gradients is given, we sample every point 4x instead
of 1x. That makes the shader run slower (by roughly a factor of 2.5x)
but it improves quality quite a bit.
A variation is a #define/specialization constant that every shader can
use to specialize itself as it sees fit.
This commit adds the infrastrcture, future commits will add
implementations.
If there are more than 7 color stops, we can split the gradient into
multiple gradients with color stops like so:
0, 1, 2, 3, 4, 5, transparent
transparent, 6, 7, 8, 9, 10, transparent
...
transparent, n-2, n-1, n
and use the new BLEND_ADD to draw them on top of each other.
Adapt the testcae that tests this to use colors that work with the fancy
algorithm we use now, so that BLEND_ADD and transitions to transparent
do not cause issues.
The shader can only deal with up to 7 color stops - but that's good
enough for the real world.
Plus, we have the uber shader.
And if that fails, we can still fall back to Cairo.
The code also doesn't handle repeating linear gradients yet.
