Interleaving textures with primitives was solving a problem that does not
exist: within a layer, order is already undefined because freeing an
instance swap-removes it, and layering is what layers are for. So the run
batching is gone.
A layer is now `LayerDraws`: a `Primitives` and a texture `InstanceList`
side by side, with `updated` covering both. `Primitives` holds only
primitives again -- its instance list plus the group-1 data those
instances read -- and `InstanceList` is the shared push/free/apply_free
the two lists have in common rather than a second copy of it.
`PrimitiveHandle` names which list with `InstanceKind`, and
`PrimitiveChange` carries the same, since the two index independently.
The handle no longer carries a group-1 index at all: a primitive
instance already records where its entry is.
The renderer gives each layer a second instance buffer and draws its
textures one at a time after the instanced draw, each binding its own
group 2.
Review fixes alongside: `GlyphAtlas::allocate` returns the `PageUpload`
it reserved instead of a bare tuple; a page or image region uploads
through a new `write_region`, which passes the row stride to
`write_texture` rather than copying the rectangle out first.
Verified by replaying taps into the `tabs` example: three images added
and one deleted leaves two drawn with two live texture slots, and the
masked text-edit tab still clips, with the images freed on tab switch.
Rework of the review on #11. Pages and standalone images were one
`Textures` manager separated by a `TextureKind` tag, and images were a
second instance list beside `Primitives::instances`. The tag forced
`image_index()`/`layer()` to panic on the wrong kind of handle, and the
second list forced an `is_image` branch through `free`, `region_mut`,
`apply_free` and `PrimitiveChange`.
Pages are now their own thing. `GlyphAtlas` owns its page images
outright and hands the renderer dirty rectangles; `GpuPages` owns the
array texture they upload to. `Textures` is standalone images only, so
`TextureHandle` has one kind, `slot()` cannot be wrong, and nothing
needs a free list that skips pages. `GlyphAtlas::insert` no longer takes
a `Textures`, which drops that parameter from `TextData::render` and
`SizeCtx` too.
Images go back through the one instance list. A texture instance is an
ordinary `PrimitiveInstance` whose `idx` names a texture rather than a
group-1 entry, which `PrimitiveHandle::data_idx: Option` records.
`RenderLayer::plan_draws` batches the layer's instances into runs
sharing a bind group, so a ui with no images still plans a single draw,
and an image draws in instance order rather than on top of its layer.
Group 2 is now one `texture_2d_array` and a sampler, bound per run: the
atlas for rects and glyphs, or one image viewed as an array of one. That
removes the second texture binding and the 1x1 null view that had to
fill it. Masks move to group 3, so resizing that buffer no longer stales
every texture bind group, and `GpuTextures` no longer reports whether
the caller must rebuild one.
`GlyphPrimitive` drops its manual pad: the WGSL struct now declares the
uvs as scalars, which matches the Rust layout exactly. `#[repr(C,
align(8))]` would have left real padding bytes, which `bytemuck::Pod`
forbids.
Verified with a headless run of the `tabs` example and of a scratch
example mixing images, rects, glyphs and a mask in one layer; 52 glyphs
at size 300 grew the atlas array from 1 to 4 layers with every earlier
page still sampling correctly.
The renderer bound every texture through one
`binding_array<texture_2d<f32>>` indexed per primitive. That needs
`VK_EXT_descriptor_indexing`, which a real share of Android GPUs do not
have, so the shape did not run there at all.
Split the two things being bound, since they want opposite treatment:
- Glyph atlas pages become layers of one `texture_2d_array`. A glyph
primitive carries a layer rather than a view/sampler index pair, and a
layer index is an ordinary sampling operand -- no extension. Growing the
atlas recreates the array with headroom and copies the old layers across
GPU-side.
- A standalone image gets its own texture and its own bind group, and
draws in its own call. It no longer needs a per-instance entry in
`PrimitiveData` at all: the bind group has already picked the texture.
`Primitives` therefore keeps images in a list of their own, with
`PrimitiveChange::is_image` saying which list a renumbering belongs to --
the two have independent index spaces, so `(layer, inst_idx)` alone would
collide between them.
Verified on this machine's real GPU (Venus onto an RX 7900 XT, confirmed
by the loaded ICD rather than assumed): the `tabs` example renders
byte-identical screenshots before and after, both for a text-and-rect tab
and for one holding a standalone image.
iris