Instead of having a descriptor set per operation, we just have one
descriptor set and bind all our images into it.
Then the shaders get to use an index into the large texture array
instead.
Getting this to work - because it's a Vulkan extension that needs to be
manually enabled, even though it's officially part of Vulkan 1.2 - is
insane.
If we have a rectangular clip without transforms, we can use
scissoring. This works particularly well because it allows intersecting
rounded rectangles with regular rectangles in all cases:
Use the scissor rect for the rectangle and the normal clipping code for
the rounded rectangle.
The idea is to use it for clip nodes when they are integer-aligned.
To do that, we need to track the scissor rect in the parse state, so we
do that, too.
Also move the viewport offset out of the projection matrix, as it is
part of the transform between clip and scissor, so it needs to live in
the offset.
We align the data to a multiple of vertex stride, that way we use more
memory, but we could compute an offset into the vertex buffer without
changing the offset.
We can set the vertex offset while counting the data, this gets rid of
the need of passing all the counting machinery into the actual data
collection code.
When attempting a complex transform, check if the clip can be ignored
and do that if possible.
That way we don't cause fallbacks when transforming the clip is too
complex.
The idea is that for a rectangle intersection, each corner of the
result is either entirely part of one original rectangle or it is
an intersection point.
By detecting those 2 cases and treating them differently, we can
simplify the code to compare rounded rectangles.
Instead of emitting the render commands once per rectangle of the clip
region, just emit them once with the region's extents.
This is generally faster because it emits fewer commands to the GPU,
even though it may touch significantly more pixels.
For a proper method, we'd need to record the commands per clip rectangle
instead of emitting all of them all the time.
The border and color shaders - the ones that do AA - now multiply their
coordinates by the scale factor, which gives them better rounding
capabilities.
This in particular improves the case where they are used in fractional
scaling situations, where the scale is defined at the root element.
Previously, we just used the defaultscale factor, but now that we're
having it available in push constants, we can read it back for creating
offscreens and rendering fallbacks.
So do that.
It's a 1:1 replacement for GskVulkanPushConstants, just without the
indirection through a different file.
GskVulkanPushConstants as a struct is gone now.
The file still exists to handle the push_constants operation.
1. Use a graphene_vec2_t
2. Ensure it's always positive
3. Don't break with fallback
The scale value is nothing more than an indication of how many pixels to
assume per unit of a node.
We don't want to render the offscreen trnsformed, we want to render it
as-is.
We lose the correct scale factor, but that requires some separate work,
so for now it gets a bit blurry on hidpi.
