custom shader webgpu

interfaces/Crafter.Graphics-WebGPUComputeShader.cppm

@@ -4,22 +4,74 @@ Copyright (C) 2026 Catcrafts®
 catcrafts.net
 */
 
-// Placeholder ComputeShader for DOM mode. The four standard UI pipelines
-// are compiled JS-side at startup (see additional/dom-webgpu.js); the C++
-// side never sees a WGSL handle. This type exists so UIRenderer can
-// declare `WebGPUComputeShader drawQuads;` members for symmetry with the
-// Vulkan side, but `Load()` and `Dispatch()` are intentionally absent —
-// the DispatchQuads / DispatchCircles / etc convenience methods on
-// UIRenderer route directly to the JS bridge.
+// User-authored compute shader for DOM mode.
+//
+// Contract:
+//   - WGSL source authored by the user.
+//   - Group 0 binding 0 is reserved for the UIDispatchHeader uniform
+//     (with dynamic offset). The library writes it from the first 48
+//     bytes of the push data each dispatch.
+//   - Group 1 is reserved for the ping-pong textures: binding 0 is the
+//     storage `out` (texture_storage_2d<rgba8unorm, write>), binding 1
+//     is the sampled `prev` (texture_2d<f32>). The library auto-binds
+//     the right textures depending on the current ping-pong state.
+//   - Groups 2+ are user-defined. The user declares each binding via a
+//     UICustomBinding descriptor at Load time, naming:
+//        - the @group(N) and @binding(N) numbers,
+//        - the resource KIND (buffer / sampled texture / sampler),
+//        - the BYTE OFFSET in the per-dispatch push data where a
+//          uint32 heap slot index lives.
+//     At Dispatch time the renderer reads each declared slot out of
+//     push data, looks the GPU handle up in the heap (bufferTable /
+//     imageTable / samplerTable), and assembles the bind group.
 
 export module Crafter.Graphics:WebGPUComputeShader;
 #ifdef CRAFTER_GRAPHICS_WINDOW_DOM
 import std;
+import :WebGPU;
 
 export namespace Crafter {
-    struct WebGPUComputeShader {
-        // Marker only; pipelines live JS-side per dispatchStandard in
-        // dom-webgpu.js. No state required.
+    enum class UICustomBindingKind : std::uint8_t {
+        Buffer         = 0,   // read-only-storage SSBO, handle is a slot into heap.bufferTable
+        SampledTexture = 1,   // sampled texture_2d<f32>, handle is a slot into heap.imageTable
+        Sampler        = 2,   // filtering sampler, handle is a slot into heap.samplerTable
+    };
+
+    struct UICustomBinding {
+        std::uint8_t  group;        // @group(N), must be >= 2 (0 and 1 are reserved)
+        std::uint8_t  binding;      // @binding(N)
+        UICustomBindingKind kind;
+        std::uint8_t  _pad;
+        std::uint32_t pushOffset;   // offset in push data where the slot uint32 lives
+    };
+    static_assert(sizeof(UICustomBinding) == 8);
+
+    class WebGPUComputeShader {
+    public:
+        std::uint32_t pipelineHandle = 0;
+        std::vector<UICustomBinding> customBindings;
+
+        WebGPUComputeShader() = default;
+        WebGPUComputeShader(const WebGPUComputeShader&) = delete;
+        WebGPUComputeShader& operator=(const WebGPUComputeShader&) = delete;
+        WebGPUComputeShader(WebGPUComputeShader&& o) noexcept
+            : pipelineHandle(o.pipelineHandle),
+              customBindings(std::move(o.customBindings)) {
+            o.pipelineHandle = 0;
+        }
+
+        // Compile + link a custom compute shader. `wgsl` is the source
+        // string; the library does NOT add anything to it — the user's
+        // shader must declare @group(0)/@group(1) bindings matching the
+        // contract above. `bindings` lists every additional resource
+        // (groups 2+) that the renderer should bind at dispatch time.
+        void Load(std::string_view wgsl,
+                  std::span<const UICustomBinding> bindings = {});
+
+        // Path-based overload for symmetry with the Vulkan ComputeShader.
+        // Reads the file from disk (browser VFS) and forwards to Load(wgsl).
+        void Load(const std::filesystem::path& wgslPath,
+                  std::span<const UICustomBinding> bindings = {});
     };
 }
 #endif // CRAFTER_GRAPHICS_WINDOW_DOM