This just introduces the variable and sets it to 1 everywhere.
The ultimate goal is to allow one ShaderOp to collect multiple ops into
one, thereby saving memory in the ops array and leading to faster
performance.
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.
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.
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.
Introduce a new GskGpuImageDescriptors object that tracks descriptors
for a set of images that can be managed by the GPU.
Then have each GskGpuShaderOp just reference the descriptors object they are
using, so that the coe can set things up properly.
To reference an image, the ops now just reference their descriptor -
which is the uint32 we've been sending to the shaders since forever.
Pretty much a copy of the Vulkan border shader.
A notable change is that the input arguments are changed, because GL
gets confused if you put a mat4 at the end.
Because GL flips its shit sometimes (ie when it's the framebuffer),
pass the height of the target as the flip variable, so commands
that need to operate on the pixels can flip the y axis around this value.
This heaves over an inital chunk of code from the Vulkan renderer to
execute shaders.
The only shader that exists for now is a shader that draws a single
texture.
We use that to replace the blit op we were doing before.
