Add GSK_GPU_IMAGE_RENDERABLE and GSK_GPU_IMAGE_FILTERABLE and make sure
to check formats for this feature.
This requires reorganizing code to actually do this work instead of just
pretending formats are supported.
This fixes GLES upload tests with NGL.
Carry an n_external_textures variable around when selecting programs and
compile different programs for different amounts of external textures.
For now, this code is unused, but dmabufs will need it.
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.
Add a GSK_GPU_IMAGE_STRAIGHT_ALPHA and use it for images that have
straight alpha.
Make sure those images get passed through a premultiplying pass with
the new straight alpha shader.
Also remove the old Postprocess flags from the Vulkan image that were a
leftover from copying that code from the old Vulkan renderer.
For now, the flags are just there because, and nobody uses them yet.
The only flag is EXTERNAL, which for now I'm using for YUV buffers,
though it's a bit undefined what that means.
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.
... and use it to initialize the "proper" projection matrix to use in
shaders.
The resulting viewport will go from top left (0,0) to bottom right
(width, height) and the z clipping plane will go from -10000 to 10000.
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
