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.
This introduces the rect object and adds a rect_distance() and
rect_coverage() function.
_distance() returns the signed distance tp the rectangle.
_coverage() returns the coverage of a pixel centered at that position.
Note that the pixel size is computed using dFdx/dFdy.
When the node bounds were a non-integer size, the texture would get
ceil()ed pixels, but various viewport or scissor computations might
floor() instead, leaving the right/bottom row of pixels untouched.
Make sure those functions ceil(), too.
Vulkan has a different initial coordinate system to GL.
GL:
(-1, 1, -1) +------+.
|`. | `.
| `·--|---·
| : | :
+------+. :
`. : `.:
`·------· (1, -1, 1)
Vulkan:
(-1, -1, 0) +------+.
|`. | `.
| `·--|---·
| : | :
+------+. :
`. : `.:
`·------· (1, 1, 1)
so adjust the near and far plane we pass to
graphene_matrix_init_ortho() to make it end up with the same
projection as the GL renderer.
Most of the time we want to compute them based on the child node we
render to the offscreen, but not always.
For blend and cross-fade nodes, they need to be computed based on the
node's bounds.
Fixes widget-factory page fade animation weirdly resizing the fading
pages.
