This makes the (currently single) storage buffer handled by
GskGpuDescriptors.
A side effect is that we now have support for multiple buffers in place.
We just have to use it.
Mixed into this commit is a complete rework of the pattern writer.
Instead of writing straight into the buffer (complete with repeatedly
backtracking when we have to do offscreens), write into a temporary
buffer and copy into the storage buffer on committing.
This adds GSK_GPU_IMAGE_CAN_MIPMAP and GSK_GPU_IMAGE_MIPMAP flags and
support to ensure_image() and image creation functions for creating a
mipmapped image.
Mipmaps are created using the new mipmap op that uses
glGenerateMipmap() on GL and equivalent blit ops on Vulkan.
This is then used to ensure the image is mipmapped when rendering it
with a texture-scale node.
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.
The env var allows skipping various optimizations in the GPU shader.
This is useful for testing during development when trying to figure
out how to make a renderer as fast as possible.
We could also use it to enable/disable optimizations depending on GL
version or so, but I didn't think about that too much yet.
Frames now carry a timestamp for when they are used.
This is mainly intended to attach timestamps to cached items (textures
or glyphs), but it could in theory also be used when profiling.
We use wallclock time here, not server time, because it's cheaper and
because we're more intereseted in the local machine we're rendering on.
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.
For now, it just renders using cairo, uploads the result to the GPU,
blits it onto the framebuffer and then is happy.
But it can do that using Vulkan and using GL (no idea which version).
The most important thing still missing is shaders.
It also has a bunch of copy/paste from the Vulkan renderer that isn't
used yet.
But I didn't want to rip it out and then try to copy it back later
