Crafter.Graphics/README.md

# Crafter.Graphics

Vulkan + WebGPU graphics library built around C++20 modules and
bindless heaps. Provides window management, ray tracing, and a
compute-shader-driven UI on a single, opinionated stack. Native
builds use Vulkan with `VK_EXT_descriptor_heap` (the compute/UI path
also runs without it, see
[below](#drivers-without-vk_ext_descriptor_heap)); `wasm32-*` builds
target the browser via WebGPU and a DOM window backend.

## Backends

Backends are chosen at build time by the target triple:

| Target              | Window                 | Renderer            | Shaders |
|---------------------|------------------------|---------------------|---------|
| native Linux        | Wayland                | Vulkan (heap-bound) | GLSL → SPIR-V |
| native Windows      | Win32                  | Vulkan (heap-bound) | GLSL → SPIR-V |
| `wasm32-*` (any)    | DOM (canvas + JS env)  | WebGPU              | WGSL (loaded at runtime) |

The two backends share the same C++ surface for the high-level pieces
(`UIRenderer`, `Mesh`, `RenderingElement3D`, `RTPass`, item structs,
`FontAtlas`, `Image2D`, `ComputeShader`). Backend-typed pieces
(`*Vulkan` vs `*WebGPU`) live behind `#ifdef CRAFTER_GRAPHICS_WINDOW_DOM`.
Vulkan ray tracing is hardware (`VK_KHR_ray_tracing_pipeline`); WebGPU
ray tracing is a library-built software path (BVH + traceRay in a
compute pipeline composed from user-supplied WGSL stages). The WebGPU
path supports triangle and AABB (procedural, `VK_GEOMETRY_TYPE_AABBS_KHR`)
geometry, closest-hit / miss / any-hit / intersection shaders — see
[examples/RTVolume](examples/RTVolume/README.md) for procedural spheres
shaded through an intersection shader with an any-hit cut-out.

> **Native RT status:** reading an acceleration structure through
> `VK_EXT_descriptor_heap` aborts with `VK_ERROR_DEVICE_LOST` on NVIDIA
> driver `610.43.02` — a driver-side fault in the brand-new descriptor-heap
> acceleration-structure path, not an engine bug (the setup is correct and
> validation-clean; images/buffers through the same heap work). The engine
> **works around it transparently** (issue #15): on the NVIDIA driver only,
> `VulkanShader` rewrites the compiled SPIR-V so heap AS reads become a
> TLAS-device-address + `OpConvertUToAccelerationStructureKHR` path (which
> reads no descriptor), and `RTPass` supplies the address as push data.
> Shaders and example code are unchanged, and it's a single fenced block
> gated on `Device::workaroundDescriptorHeapAS`, removable once a fixed
> driver ships. **Still present on `615.78.08`**: with the rewrite off,
> `traceRayEXT` still loses the device and an inline ray query renders
> nothing. `tests/HeapASRead` covers the engine path; run
> `HeapASRead --no-workaround` to check a newer driver (it tries both paths
> with the rewrite off). Any app runs with the rewrite off while
> `CRAFTER_GRAPHICS_NO_AS_WORKAROUND` is set, to any value. See
> [examples/VulkanTriangle/README.md](examples/VulkanTriangle/README.md)
> for the full investigation. WebGPU RT is unaffected.

> **Native RT limitation (fixed in NVIDIA `615.78.08`) — dynamic
> `descriptor_heap` indexing in hit shaders:** on NVIDIA `610.43.02`, indexing
> a `descriptor_heap` array with a **runtime (non-constant)** index inside a
> ray-tracing **hit** shader also device-losts (`VK_ERROR_DEVICE_LOST`), for
> plain SSBO **and** sampled-image descriptors. On `615.78.08` it works:
> `tests/HeapDynamicIndexHit` picks a buffer and a texture by a runtime index
> in a closest-hit, including different descriptors in neighbouring lanes of
> a wave. The rest of this note applies to the older drivers. A **constant / spec-constant**
> index is fine (that's why [Sponza](examples/Sponza/README.md)'s
> closest-hit reads `albedo[albedoSlot]` through a spec constant), and
> the identical dynamic pattern works in fragment shaders (the UI
> renderer indexes `uiTextures[]` by per-item runtime slots) — so this
> is **RT-stage-specific**, not a general heap problem. Unlike the
> AS-read fault above this **cannot** be worked around transparently:
> sampled images have no device-address escape hatch the way an
> acceleration structure does (`OpConvertUToAccelerationStructureKHR`).
> The recommended pattern for bindless per-mesh geometry/material is to
> **bind one resource and index *within* it dynamically** rather than
> selecting a descriptor dynamically: pack geometry into a single SSBO
> (or reach it via `buffer_reference`) at a spec-constant slot and index
> by element offset, and put materials in one `texture2DArray` indexed
> by layer. Dynamic addressing *inside* a bound resource is ordinary
> memory/layer addressing and is unaffected; only dynamic selection of a
> *descriptor* faults. This is exactly what the WebGPU path already does
> (bucketed texture arrays + a single buffer). Full investigation and
> GLSL in [examples/Sponza/README.md](examples/Sponza/README.md) (issue
> #23). WebGPU RT is unaffected.

## What's in here

- **Window** — Wayland, Win32, and DOM backends, swapchain ring / canvas
  framing, input events. Pick a backend at build time via the target
  triple. The DOM backend routes every dynamic symbol through
  [additional/dom-env.js](additional/dom-env.js) and
  [additional/dom-webgpu.js](additional/dom-webgpu.js).
- **Device** *(Vulkan only)* — single-instance bring-up targeting
  `VK_EXT_descriptor_heap`; pipelines are created with
  `VK_PIPELINE_CREATE_2_DESCRIPTOR_HEAP_BIT_EXT` so there are no
  descriptor-set layouts and push constants travel via
  `vkCmdPushDataEXT`. Needs Vulkan 1.3. The heap, ray tracing and
  device-fault extensions are optional groups, detected at start-up
  (`Device::descriptorHeapSupported`, `rayTracingSupported`,
  `deviceFaultSupported`). Device features split by who uses them: the
  ones the binding model and the library's own shaders need are the
  library's to enable; arithmetic, storage and layout features an
  application's shaders use (`shaderInt16` for a `uint16_t` spec
  constant, `scalarBlockLayout`, fp16, 16-bit storage) are the
  application's to ask for, as core feature structs:
  `Device::Initialize({.vulkan10 = {.shaderInt16 = VK_TRUE}})`. A second
  argument takes features to use where the GPU has them, and
  `Device::enabledFeatures` says which it got. A GPU that can't run the
  application is skipped. `VulkanShader` refuses a module that declares,
  directly or implicitly, a capability whose core feature, subgroup
  operation or optional group (ray tracing, the descriptor heap) is off,
  naming the field to pass or saying the GPU lacks it. Capabilities only
  an extension the library never enables could allow are left to the
  driver and the validation layer, as are layout rules
  (`scalarBlockLayout`), which have no capability.
- **DescriptorHeapVulkan / DescriptorHeapWebGPU** — bindless slot
  allocators. Vulkan side allocates image/buffer/sampler slots in a
  `VK_EXT_descriptor_heap`; WebGPU side resolves slots to JS-side
  handle-table cookies that the dispatch bridge binds per pass.
- **VulkanBuffer\<T, Mapped\> / WebGPUBuffer\<T\>** — typed buffer.
  Vulkan variant has optional host mapping and a `FlushDevice` that
  issues the right host-write barrier; WebGPU variant goes through
  `queue.writeBuffer` over the JS bridge.
- **ImageVulkan\<Pixel\> / Image2D\<Pixel\> / Image2DArray\<Pixel\>** —
  image + staging buffer with mip-chain support on Vulkan; on WebGPU,
  `rgba8unorm` 2D / 2D-array textures created and written via the
  bridge. Atlas (`r8unorm`, sub-region writes) is a separate path.
- **PipelineRTVulkan / PipelineRTWebGPU / ShaderBindingTableVulkan /
  ShaderBindingTableWebGPU / RTPass** — ray-tracing pipelines. Vulkan
  uses native RT pipelines + SBTs; WebGPU compiles a **wavefront /
  streaming** software tracer — five `@compute` kernels
  (`GENERATE → PREP → TRACE → SHADE → RESOLVE`) sharing one module,
  connected by GPU ray/hit/payload buffers and a GPU-driven indirect
  bounce loop (`dispatchWorkgroupsIndirect`). TRACE carries zero user
  code (traversal + intersection only); user raygen calls
  `rtEmitPrimaryRay`, and closesthit / miss run in SHADE where they
  `rtEmitRay` continuation/shadow rays and `rtAccumulate` radiance
  (atomic — any number of rays per pixel per bounce, e.g. one shadow
  ray per light). An
  optional Resolve shader tonemaps the linear accumulator. See
  [WAVEFRONT-DESIGN.md](WAVEFRONT-DESIGN.md).
- **ComputeShader / WebGPUComputeShader** — Tier 1 wrapper used by the
  UI system. Vulkan loads a `.spv` and dispatches with
  `vkCmdPushDataEXT` (or the `.sets.spv` build and `vkCmdPushConstants`
  without the heap); WebGPU loads a user-supplied `.wgsl` blob at
  runtime via `wgpuLoadCustomShader`. Use it directly for any custom
  compute.
- **UI** — three-tier UI system; see below. The standard shaders (four
  kernels plus the fused one) ship as `.spv` / `.sets.spv` pairs on
  native and as WGSL strings baked into the WebGPU dispatcher.
- **FontAtlas** — single-channel SDF atlas (1024×1024, 32pt base,
  shelf-packed, lazy `Ensure` per codepoint, dirty-flush via `Update`).
  Backend-agnostic.
- **Mesh / RenderingElement3D / Animation** — BLAS/TLAS construction
  and 3D scene plumbing. Vulkan calls `vkCmdBuildAccelerationStructures`;
  WebGPU registers BLAS data (verts, idx, BVH nodes, primRemap, optional
  per-vertex attribs) into global mesh heaps and builds the TLAS in a
  library compute pass.
- **Clipboard / Input / Gamepad / Router / Dom** — input plumbing.
  Gamepad uses libudev+libevdev on Linux (libevdev is vendored in
  `lib/libevdev`) and WGI on Windows; the DOM
  backend exposes the host page DOM (`Dom::HtmlElement`) and a router
  for hash-routed wasm apps.

## UI system (three tiers)

The UI is *deliberately* layered to balance no-boilerplate against
no-lock-in:

- **Tier 1 — `ComputeShader`.** Load any `.spv`, dispatch with push
  constants, library inserts inter-dispatch barriers. The escape hatch:
  if the standard shaders don't fit, write your own compute and
  dispatch it next to them.
- **Tier 2 — `UIRenderer` + standard shaders.** Four shipped compute
  shaders (`drawQuads`, `drawCircles`, `drawImages`, `drawText`), POD
  item structs (`QuadItem`, `CircleItem`, `ImageItem`, `GlyphItem`), a
  shared GLSL contract in [shaders/ui-shared.glsl](shaders/ui-shared.glsl),
  and helpers (`RegisterBuffer`, `RegisterImage`, `RegisterSampler`,
  `FillHeader`, `Dispatch*`, `ShapeText`). You build your own per-shader
  SSBOs (manual batching) and call one `Dispatch*` per shader type per
  frame. Item array order = draw order.
- **Tier 3 — stateless presentation functions.** `DrawButton`,
  `DrawCheckbox`, `DrawSlider`, `DrawProgressBar`. Each is a small
  function that *appends* items to your buffers — they don't dispatch.
  Colors come in as small inline `*Colors` aggregates, no library
  `Theme` type. **The source is the customization API**: if a
  component doesn't fit, copy its body and edit it. No virtual hooks,
  no extension points.

What's *not* in the UI: widget tree, layout engine (just a `Rect::SubRect`
carving helper), theming, hit-testing, focus management. State for
interactive components (hover, drag, focus) lives in user-owned POD
structs, not the library.

### UI dispatch model

Standard shaders dispatch one workgroup per 8×8 *screen tile* — each
thread iterates every item in the SSBO in array order, accumulating
into a local `dst`, and stores once. Total cost is `O(W·H·N)`; works
well up to a few hundred items at 1080p. Splitting one buffer into
multiple dispatches doesn't help — the same total work plus barrier
overhead. If you need to render thousands of UI items, you want a
different shader (tile binning, per-item-list resolve), not more
dispatches.

### Drivers without `VK_EXT_descriptor_heap`

The compute/UI path also runs on Vulkan drivers that lack
`VK_EXT_descriptor_heap` (Mesa Turnip on Qualcomm Adreno, for one).
`Device::Initialize` detects this and sets
`Device::descriptorHeapSupported = false`. The same slots then live in
one bindless descriptor set per frame instead of the heap, and push
constants go through `vkCmdPushConstants`. Slot handles, item structs,
`UIDispatchHeader` and the `UIRenderer` API are unchanged, so
application code does not branch on it. Ray tracing is heap-only: on
such a driver `Device::rayTracingSupported` is false and the RT entry
points throw.

Each compute shader is shipped in two builds of the same source:
`<name>.spv` for the heap and `<name>.sets.spv` for descriptor sets.
`ComputeShader::Load(path, heap)` takes the `.spv` path and picks the
right file itself. For a custom shader that means three things:

- Declare bindless resources with the `UI_HEAP_*` macros from
  [shaders/ui-shared.glsl](shaders/ui-shared.glsl), not with a literal
  `descriptor_heap`:

  ```glsl
  layout(UI_HEAP_BUFFERS, std430) readonly buffer MyBuf { MyItem items[]; } myHeap[];
  ```

- Register the shader twice in `project.cpp`, the second time with the
  define and the variant name:

  ```cpp
  cfg.shaders.emplace_back(fs::path("my.comp.glsl"), std::string("main"), ShaderType::Compute);
  Shader& sets = cfg.shaders.emplace_back(fs::path("my.comp.glsl"), std::string("main"), ShaderType::Compute);
  sets.defines = {"CRAFTER_GRAPHICS_DESCRIPTOR_SETS"};
  sets.variant = "sets";
  ```

- Keep the push-constant block within the device's
  `maxPushConstantsSize` (256 bytes on common drivers). Without the
  heap a larger payload throws in `ComputeShader::Dispatch`.

Set the environment variable `CRAFTER_GRAPHICS_NO_DESCRIPTOR_HEAP` to
force the descriptor-set path on a driver that does have the heap; the
`UIFallbackParity` test uses it to compare the two paths frame for
frame.

## Build

The repository is built with `crafter-build` (a project-config based
build system; the project description lives in `project.cpp`):

```bash
crafter-build                        # native: Wayland on Linux, Win32 on Windows
crafter-build --target=wasm32-wasip1 # browser: DOM window + WebGPU renderer
crafter-build -r                     # build and run (in an example directory)
```

The build picks the window + renderer pair automatically from the
target triple: any `wasm32-*` triple flips to DOM + WebGPU (no Vulkan
loader linked), everything else stays on the native Vulkan path. Each
example with both backends ships GLSL *and* WGSL copies of its shaders
side-by-side (e.g. [raygen.glsl](examples/Sponza/raygen.glsl) +
[raygen.wgsl](examples/Sponza/raygen.wgsl)); `project.cpp` selects the
right set per target.

## Examples

See [examples/](examples/). Quick map:

- [HelloWindow](examples/HelloWindow/) — minimal native window, no rendering.
- [HelloDom](examples/HelloDom/) — wasm-only smoke test of the DOM
  partition: page-level events, `HtmlElement::CreateInBody`, and
  `Router::PushState`-driven SPA navigation. No GPU work.
- [VulkanTriangle](examples/VulkanTriangle/) — ray-traced triangle on
  both Vulkan and WebGPU. The smallest test of the bindless + RT path
  on each backend.
- [RTStress](examples/RTStress/) — wavefront RT benchmark: an N×N×N grid
  of a cube mesh (instance-count knob `kGrid`, 512 → 8000) shaded with
  primary + shadow rays. Prints a GPU timestamp-query per-pass breakdown
  each second. WebGPU/DOM only.
- [Sponza](examples/Sponza/) — ray-traced Sponza atrium on both
  backends. Exercises `.cmesh` / `.ctex` decompression (GPU
  `VK_EXT_memory_decompression` on Vulkan, CPU on WebGPU) and a
  textured closest-hit. See [its README](examples/Sponza/README.md)
  for asset provenance.
- [HelloUI](examples/HelloUI/) — UI smoke test using all three tiers
  (background quad, slider, progress bar, button with text label,
  cursor-tracking circle).
- [CustomShader](examples/CustomShader/) — Tier 1 demo: a user-authored
  compute shader inverting RGB under a list of item-circles, dispatched
  alongside the standard `drawQuads`. Shipped as both
  [`.comp.glsl`](examples/CustomShader/inverse-circle.comp.glsl) and
  [`.comp.wgsl`](examples/CustomShader/inverse-circle.comp.wgsl).
- [Decompression](examples/Decompression/) — `Crafter::Compression`
  CPU round-trip smoke test (used by the WebGPU asset path).
- [InputSystem](examples/InputSystem/) — keyboard / mouse / gamepad
  event surface check.

## License

This library is licensed under the GNU Lesser General Public License, version 3 only (LGPL-3.0-only). See [LICENSE](LICENSE) for the license text. The LGPL supplements the GNU General Public License version 3, a copy of which is included as [LICENSE.GPL](LICENSE.GPL).

The example code under [examples/](examples/) is licensed under the MIT license (see [examples/LICENSE](examples/LICENSE)), so it can be freely copied into your own projects.

The [lib/](lib/) directory contains vendored third-party code (stb, Wayland protocol bindings) that remains under its own permissive licenses; see the headers of those files.

## Copyright

Copyright (C) 2026 Catcrafts®
catcrafts.net