Shaders
- ui-text and ui-fused turned a sample of the R8_UNORM atlas into a
distance with (128/255 - sdf) * 32. stb_truetype writes kOnEdgeValue +
kPixelDistScale * distance into each byte, so an atlas pixel is
kPixelDistScale / 255 of a sample; 32 made every distance 1024/255
(about 4) times too large, and the coverage ramp, meant to span one
screen pixel, spanned a quarter of one: nearly every edge pixel came out
fully on or fully off, and text looked pixelated at every size. On an
RTX 4090, UIFallbackParity's 22 px label had 98 partly covered pixels
where stb_truetype's own rasterizer has 415. Wrong since the v3 UI
(1f56973), and copied into the fused kernel (574242d).
- The decode now lives once, in ui-shared.glsl: UI_SDF_ON_EDGE and
UI_SDF_PIXEL_DIST_SCALE are FontAtlas's two constants in the encoder's
own units, uiSdfDistance decodes a sample, uiGlyphRamp works out a
glyph's ramp when it is loaded and uiGlyphCoverage the coverage per
pixel. Both kernels call them, and a copy of either should; the UI_
prefix keeps them clear of a copied kernel's own names.
- stb_truetype truncates, so a byte b stands for [b, b + 1) of the encoded
value and the decode takes its middle: decoding b pulled every outline
1/64 atlas pixel inwards.
- The ramp is capped at what a byte holds, about 4 atlas pixels each way
of the outline. With the corrected decode a wider one left every glyph
quad's padding translucent below 4 px.
- The UV span is taken with abs(): a glyph turned by swapping its UVs got
a negative scale, a ramp of 0.0001 and hard edges.
- A glyph scaled differently along x and y ramps along the distance's
gradient, from two one-texel differences. With the corrected decode, one
width for both axes, the more minified one's, would leave a row stretched
three times with stems three pixels soft. Glyphs scaled alike, as
ShapeText's are, keep one multiply-add per pixel, the ramp's reciprocal
worked out with the glyph.
- The atlas size is queried rather than FontAtlas::kAtlasSize hard-coded
as 1024.
WebGPU
- The WGSL text kernel decoded the distance right but ramped over one
atlas pixel whatever the size: half a screen pixel at 16 px, two at
64 px. It now repeats ui-shared.glsl's decode, cap, abs and gradient
path, and renders TextAntialiasing's scene as Vulkan does (run through
Deno's WebGPU: 1.02, 1.07 and 1.09 times the reference's edge pixels,
where the old kernel gave 0.55, 2.19 and 0.89).
FontAtlas
- kOnEdgeValue and kPixelDistScale say the kernels carry copies of them.
Tests
- TextAntialiasing draws one string at 14 px, 64 px and 14 px stretched
three times, a 'g' turned by its UVs and empty atlas texels shrunk to
12.8 atlas pixels per screen pixel, through DispatchText and again
through DispatchFused, and holds them to stb_truetype's antialiased
rasterizer, to the mirror image and to nothing. On master the two plain
rows have 0.31 and 0.21 times the reference's edge pixels; with the
decode fixed alone the stretched row had 1.62 times, the turned 'g' was
127 codes off its mirror and the empty texels drew 48. Now: 1.02, 1.07
and 1.09 times, 0 and 0, on the 4090, on llvmpipe and on descriptor
sets. It skips a swapchain that isn't 8-bit, which the capture can't
read, and captures the first frame.
- FontAtlasDecode reads ui-shared.glsl and dom-webgpu.js and holds their
copies of the two constants to FontAtlas's. No GPU.
Docs
- AGENTS.consumer.md has a custom text shader decode through the helpers
and gives the encoding; README says so in a line; AGENTS.md lists the
tests and where the decode lives.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
LoadImageItem, LoadGlpyhtem, LoadCircleItem and LoadQuadItem in
ui-shared.glsl worked around NVIDIA losing the device when a whole
struct is loaded from a descriptor-heap storage buffer. No kernel here
calls them any more (they read members straight into shared memory), and
NVIDIA 615.78.08 no longer has the fault: every UI kernel rewritten to
whole-struct loads renders the same frame. Shaders that called them read
the item directly instead.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Device::Initialize required twelve device extensions with no capability
check. Mesa Turnip (Adreno) lacks six of them: VK_EXT_descriptor_heap,
VK_KHR_shader_untyped_pointers, VK_EXT_device_fault and the three ray
tracing extensions. vkCreateDevice failed there, so not even a UI-only
program could start, although the UI path is compute-only and needs
nothing else that Turnip is missing.
The descriptor heap, ray tracing and device fault are now optional
groups, detected at start-up from the extension list and the feature
bits (Device::descriptorHeapSupported, rayTracingSupported,
deviceFaultSupported). Ray tracing needs the heap; on a device without
it the ray tracing entry points throw a message naming the cause.
Without the heap the same bindless slots live in one update-after-bind
descriptor set per frame, owned by DescriptorHeapVulkan: binding 0
storage images, 1 sampled images, 2 samplers, 3 storage buffers. Slot
allocation, the slot handles, UIDispatchHeader and the UIRenderer API
are unchanged; buffer slots simply stop being offset. Window::Render
binds that frame's set where it binds the heap, every compute pipeline
shares the heap object's pipeline layout, and push data travels as push
constants.
Each UI kernel is built twice from one source. ui-shared.glsl declares
its resources through UI_HEAP_* macros that expand to descriptor_heap
or, with CRAFTER_GRAPHICS_DESCRIPTOR_SETS defined, to set/binding.
<name>.comp.spv and <name>.comp.sets.spv ship side by side and
ComputeShader::Load picks one. The heap build of every shader is
byte-identical to before.
Breaking:
- ComputeShader::Load takes the heap as a second argument.
- DescriptorHeapVulkan is no longer copyable or movable.
- Custom UI shaders declare heap resources with the UI_HEAP_* macros
and are registered twice in project.cpp (see the README).
- project.cpp uses Shader::defines and Shader::variant, so it needs a
crafter-build that has them (Crafter.Build master, fe38cc1 or later).
Also:
- maintenance5 is enabled as a feature, not only as an extension:
every VulkanBuffer already relied on VkBufferUsageFlags2CreateInfo.
- Barrier stage masks drop RAY_TRACING_SHADER on devices without ray
tracing, and ImageVulkan::Create resolves its default consumer stage
to COMPUTE_SHADER there.
- Window refuses a swapchain whose image count is not numFrames
instead of writing past images[]. The limitation itself is #160.
- CRAFTER_GRAPHICS_NO_DESCRIPTOR_HEAP forces the fallback on a driver
that has the heap, so it can be exercised on a desktop GPU.
Verified on an RTX 4090 in both modes under the validation layer, and
on a Fairphone 6 (Turnip, Adreno 810, postmarketOS), where the fallback
is the only path.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
uiCompactChunk ran the survivor scan entirely on gl_LocalInvocationIndex
== 0: ~64 serial iterations with 63/64 lanes idle, between two barriers,
4x per chunk in the fused kernel. It must emit a stable in-order
(buffer-order) exclusive prefix of the survivors so the per-pixel inner
loop still sees items in draw order.
Replace it with a per-subgroup subgroupExclusiveAdd of the keep bits plus
a carry across subgroups: each subgroup publishes its survivor total to
shared memory, then every lane sums the totals of all lower-id subgroups
for its base. A survivor's slot in s_order[] therefore equals the number
of survivors with a smaller local index — buffer (draw) order preserved
exactly, unlike an atomicAdd which would scramble it.
The carry makes the result correct for any subgroup width (2 subgroups on
the 32-wide descriptor_heap target, up to 8/16 on narrower parts), relying
only on the gl_LocalInvocationIndex <-> (gl_SubgroupID,
gl_SubgroupInvocationID) linear mapping every Vulkan compute
implementation provides. The feature is free at the device baseline
(apiVersion 1.4 + VK_EXT_descriptor_heap implies Vulkan 1.1 subgroup
arithmetic), so no correctness fallback is needed; WebGPU is unaffected
(separate embedded WGSL).
Applied to ui-fused.comp.glsl and the same pattern inlined in
ui-quads/circles/images/text.
Verified: all 23 tests pass (UIFusedShader recompiles + spirv-val +
pins push-constant offsets); a 140k-trial CPU simulation of the algorithm
matches the serial reference for subgroup sizes 1..64; HelloUI renders
correctly on an RTX 4090 (DispatchFused quads+circles+text) with draw
order intact.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The standalone per-category UI shaders (quads/circles/images/text)
unconditionally imageLoad the destination pixel up front and imageStore
it at the end, paying a full read-modify-write even on tiles no item
touches — the common case for a sparse UI. The fused uber-kernel already
amortizes a single load/store across all four categories; the standalone
Dispatch* path has no such umbrella.
Defer the imageLoad to just before the first surviving blend (`loaded`
flag) and skip the imageStore unless something was actually blended.
Output is bit-identical: before the first blend `dst` is unused, and a
skipped store leaves the pixel exactly as a no-op load+store would have
rewritten it.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The cooperative-load section already streams each item into shared memory
once per workgroup, but the per-pixel inner loop then recomputed values
that are constant for the whole item/glyph. The compiler can't hoist them
itself — they read shared memory at a varying index.
Precompute them once per item at load time into new shared slots:
- ui-images / ui-text / ui-fused (images+text phases): invRectSize =
1.0/rect.zw, turning the per-pixel `(sp-rect.xy)/rect.zw` vec2 divide
into a multiply.
- ui-text / ui-fused (text phase): the SDF AA `band` (a vec2 divide +
two maxes depending only on the glyph's uv span and rect size).
In ui-fused the new slots (s_inv, s_band) are reused across phases like
the existing s_v* scratch, so the LDS bump is per-category, not summed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Add a fifth UI compute path — DispatchFused — alongside the four
per-element Dispatch* calls. It composites quads → circles → images →
text (canonical back-to-front order) in ONE dispatch that loads the
destination image once and stores once, eliminating the per-pass
load+store and the inter-pass VkMemoryBarriers a run of consecutive
Dispatch* calls would pay. The win materialises at >= 2 non-empty
categories; an absent category is a zero-trip, push-constant-uniform
loop (~free).
The new uber-kernel (shaders/ui-fused.comp.glsl) reuses each category's
exact cooperative shared-memory tile-cull + per-pixel accumulate, so a
fused category is pixel-identical to its standalone pass. Categories run
sequentially per thread and share one set of shared-memory scratch, so
the VGPR/shared high-water mark stays at the per-category level, not the
sum.
Additive and non-breaking: the per-element Dispatch* calls and the
frozen 48-byte UIDispatchHeader are untouched. DispatchFused gets its own
128-byte push-constant layout (UIFusedHeader: four uvec4 headers + four
per-category clip vec4s). To interleave a custom ui.Dispatch() between
standard passes, bracket it with two DispatchFused calls — the dispatch
boundary is the explicit, app-declared flush point.
WebGPU (Vulkan-second): DispatchFused falls back to the per-element
Dispatch* calls in canonical order — one texture/sampler per dispatch
there can't feed the bindless image phase — so the result matches; only
the load/store fusion is Vulkan-only.
HelloUI now composites its background quads, mouse circle, and label
text in a single DispatchFused. Verified rendering identical on a live
Vulkan/Wayland session.
Resolves#47
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
uiResolveScreenPixel ran four float compares against hdr.clipRectPx for
every pixel of every UI dispatch, even though the clip rect is the
full-surface default {0,0,1e9,1e9} in the overwhelmingly common case.
Reserve the high bit of the header flags word (UI_FLAG_CLIP) and have
FillHeader set it only when the clip rect is narrower than the surface
(extracted into the unit-testable UIRenderer::ClipFlags). The shader
gates the compares on the bit; the branch is push-constant-uniform so it
never diverges. When the rect covers the surface the skipped compares
could never reject an in-surface pixel, so output is pixel-identical.
Mirrored on the WebGPU/WGSL path (dom-webgpu.js) for parity. Adds the
UIClipFlag CPU test covering the gate decision.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Each 8×8-tile workgroup previously had all 64 threads walk the entire
item list, re-reading every item from the SSBO 64× and running the
per-pixel reject for items that never touch the tile — O(tiles × N)
item loads dominated by SSBO traffic.
The workgroup now streams the item list in chunks of 64: each thread
loads one item, tests its AABB against the whole tile, and the survivors
are compacted — in original buffer order — into shared memory. Every
thread then runs the unchanged per-pixel accumulate over only those
survivors. This drops SSBO traffic ~64× (each item read once per
workgroup instead of once per pixel) and shrinks the inner loop to the
items that actually overlap the tile.
Draw order is preserved exactly: chunks run in array order and the
in-chunk compaction is a stable in-order scan, so later items still
overdraw earlier ones (no atomic-append nondeterminism). The inner loop
body is byte-for-byte the original per-pixel logic, so output is
pixel-identical — the cull only decides which items reach it. Threads
no longer early-return so every thread reaches the workgroup barriers.
Applied to ui-quads, ui-circles, ui-images and ui-text; shared helpers
(uiTileBounds / uiAabbOverlapsTile) live in ui-shared.glsl.
Resolves#46
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
fontTextureSlot/fontSamplerSlot are push constants, hence provably
dynamically uniform. Wrapping them in nonuniformEXT forced the
per-invocation divergent-descriptor path and blocked hoisting the
uniform descriptor load out of the per-pixel glyph loop.
Removing the decoration is zero correctness risk — it is purely a
read-index hint. Not applied to ui-images.comp.glsl, whose slots come
from an SSBO load the compiler cannot prove uniform.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
