Backends: WebGPU: Use WGSL shaders instead of precompiled SPIR-V + add Gamma uniform. (#6188)

Add gamma correction uniform
Group uniforms in a single binding
The second binding was not satisfying the minimum
BufferBindingType::Uniform alignment (256) and since this alignment is
large it is more idiomatic to group uniforms tegether.

Also ensures that the size of the uniform buffer is aligned to 16 bytes.

backends/imgui_impl_wgpu.cpp

@@ -13,7 +13,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
-//  2023-04-11: Align buffer sizes.
+//  2023-04-11: Align buffer sizes. Use WGSL shaders instead of precompiled SPIR-V.
 //  2023-04-11: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
 //  2023-01-25: Revert automatic pipeline layout generation (see https://github.com/gpuweb/gpuweb/issues/2470)
 //  2022-11-24: Fixed validation error with default depth buffer settings.
@@ -62,6 +62,7 @@ struct FrameResources
 struct Uniforms
 {
     float MVP[4][4];
+    float Gamma;
 };
 
 struct ImGui_ImplWGPU_Data
@@ -89,114 +90,60 @@ static ImGui_ImplWGPU_Data* ImGui_ImplWGPU_GetBackendData()
 // SHADERS
 //-----------------------------------------------------------------------------
 
-// glsl_shader.vert, compiled with:
-// # glslangValidator -V -x -o glsl_shader.vert.u32 glsl_shader.vert
-/*
-#version 450 core
-layout(location = 0) in vec2 aPos;
-layout(location = 1) in vec2 aUV;
-layout(location = 2) in vec4 aColor;
-layout(set=0, binding = 0) uniform transform { mat4 mvp; };
+static const char __shader_vert_wgsl[] = R"(
+struct VertexInput {
+    @location(0) position: vec2<f32>,
+    @location(1) uv: vec2<f32>,
+    @location(2) color: vec4<f32>,
+};
 
-out gl_PerVertex { vec4 gl_Position; };
-layout(location = 0) out struct { vec4 Color; vec2 UV; } Out;
+struct VertexOutput {
+    @builtin(position) position: vec4<f32>,
+    @location(0) color: vec4<f32>,
+    @location(1) uv: vec2<f32>,
+};
 
-void main()
-{
-    Out.Color = aColor;
-    Out.UV = aUV;
-    gl_Position = mvp * vec4(aPos, 0, 1);
-}
-*/
-static uint32_t __glsl_shader_vert_spv[] =
-{
-    0x07230203,0x00010000,0x00080007,0x0000002c,0x00000000,0x00020011,0x00000001,0x0006000b,
-    0x00000001,0x4c534c47,0x6474732e,0x3035342e,0x00000000,0x0003000e,0x00000000,0x00000001,
-    0x000a000f,0x00000000,0x00000004,0x6e69616d,0x00000000,0x0000000b,0x0000000f,0x00000015,
-    0x0000001b,0x00000023,0x00030003,0x00000002,0x000001c2,0x00040005,0x00000004,0x6e69616d,
-    0x00000000,0x00030005,0x00000009,0x00000000,0x00050006,0x00000009,0x00000000,0x6f6c6f43,
-    0x00000072,0x00040006,0x00000009,0x00000001,0x00005655,0x00030005,0x0000000b,0x0074754f,
-    0x00040005,0x0000000f,0x6c6f4361,0x0000726f,0x00030005,0x00000015,0x00565561,0x00060005,
-    0x00000019,0x505f6c67,0x65567265,0x78657472,0x00000000,0x00060006,0x00000019,0x00000000,
-    0x505f6c67,0x7469736f,0x006e6f69,0x00030005,0x0000001b,0x00000000,0x00050005,0x0000001d,
-    0x6e617274,0x726f6673,0x0000006d,0x00040006,0x0000001d,0x00000000,0x0070766d,0x00030005,
-    0x0000001f,0x00000000,0x00040005,0x00000023,0x736f5061,0x00000000,0x00040047,0x0000000b,
-    0x0000001e,0x00000000,0x00040047,0x0000000f,0x0000001e,0x00000002,0x00040047,0x00000015,
-    0x0000001e,0x00000001,0x00050048,0x00000019,0x00000000,0x0000000b,0x00000000,0x00030047,
-    0x00000019,0x00000002,0x00040048,0x0000001d,0x00000000,0x00000005,0x00050048,0x0000001d,
-    0x00000000,0x00000023,0x00000000,0x00050048,0x0000001d,0x00000000,0x00000007,0x00000010,
-    0x00030047,0x0000001d,0x00000002,0x00040047,0x0000001f,0x00000022,0x00000000,0x00040047,
-    0x0000001f,0x00000021,0x00000000,0x00040047,0x00000023,0x0000001e,0x00000000,0x00020013,
-    0x00000002,0x00030021,0x00000003,0x00000002,0x00030016,0x00000006,0x00000020,0x00040017,
-    0x00000007,0x00000006,0x00000004,0x00040017,0x00000008,0x00000006,0x00000002,0x0004001e,
-    0x00000009,0x00000007,0x00000008,0x00040020,0x0000000a,0x00000003,0x00000009,0x0004003b,
-    0x0000000a,0x0000000b,0x00000003,0x00040015,0x0000000c,0x00000020,0x00000001,0x0004002b,
-    0x0000000c,0x0000000d,0x00000000,0x00040020,0x0000000e,0x00000001,0x00000007,0x0004003b,
-    0x0000000e,0x0000000f,0x00000001,0x00040020,0x00000011,0x00000003,0x00000007,0x0004002b,
-    0x0000000c,0x00000013,0x00000001,0x00040020,0x00000014,0x00000001,0x00000008,0x0004003b,
-    0x00000014,0x00000015,0x00000001,0x00040020,0x00000017,0x00000003,0x00000008,0x0003001e,
-    0x00000019,0x00000007,0x00040020,0x0000001a,0x00000003,0x00000019,0x0004003b,0x0000001a,
-    0x0000001b,0x00000003,0x00040018,0x0000001c,0x00000007,0x00000004,0x0003001e,0x0000001d,
-    0x0000001c,0x00040020,0x0000001e,0x00000002,0x0000001d,0x0004003b,0x0000001e,0x0000001f,
-    0x00000002,0x00040020,0x00000020,0x00000002,0x0000001c,0x0004003b,0x00000014,0x00000023,
-    0x00000001,0x0004002b,0x00000006,0x00000025,0x00000000,0x0004002b,0x00000006,0x00000026,
-    0x3f800000,0x00050036,0x00000002,0x00000004,0x00000000,0x00000003,0x000200f8,0x00000005,
-    0x0004003d,0x00000007,0x00000010,0x0000000f,0x00050041,0x00000011,0x00000012,0x0000000b,
-    0x0000000d,0x0003003e,0x00000012,0x00000010,0x0004003d,0x00000008,0x00000016,0x00000015,
-    0x00050041,0x00000017,0x00000018,0x0000000b,0x00000013,0x0003003e,0x00000018,0x00000016,
-    0x00050041,0x00000020,0x00000021,0x0000001f,0x0000000d,0x0004003d,0x0000001c,0x00000022,
-    0x00000021,0x0004003d,0x00000008,0x00000024,0x00000023,0x00050051,0x00000006,0x00000027,
-    0x00000024,0x00000000,0x00050051,0x00000006,0x00000028,0x00000024,0x00000001,0x00070050,
-    0x00000007,0x00000029,0x00000027,0x00000028,0x00000025,0x00000026,0x00050091,0x00000007,
-    0x0000002a,0x00000022,0x00000029,0x00050041,0x00000011,0x0000002b,0x0000001b,0x0000000d,
-    0x0003003e,0x0000002b,0x0000002a,0x000100fd,0x00010038
+struct Uniforms {
+    mvp: mat4x4<f32>,
+    gamma: f32,
 };
 
-// glsl_shader.frag, compiled with:
-// # glslangValidator -V -x -o glsl_shader.frag.u32 glsl_shader.frag
-/*
-#version 450 core
-layout(location = 0) out vec4 fColor;
-layout(set=0, binding=1) uniform sampler s;
-layout(set=1, binding=0) uniform texture2D t;
-layout(location = 0) in struct { vec4 Color; vec2 UV; } In;
-void main()
-{
-    fColor = In.Color * texture(sampler2D(t, s), In.UV.st);
+@group(0) @binding(0) var<uniform> uniforms: Uniforms;
+
+@vertex
+fn main(in: VertexInput) -> VertexOutput {
+    var out: VertexOutput;
+    out.position = uniforms.mvp * vec4<f32>(in.position, 0.0, 1.0);
+    out.color = in.color;
+    out.uv = in.uv;
+    return out;
 }
-*/
-static uint32_t __glsl_shader_frag_spv[] =
-{
-    0x07230203,0x00010000,0x00080007,0x00000023,0x00000000,0x00020011,0x00000001,0x0006000b,
-    0x00000001,0x4c534c47,0x6474732e,0x3035342e,0x00000000,0x0003000e,0x00000000,0x00000001,
-    0x0007000f,0x00000004,0x00000004,0x6e69616d,0x00000000,0x00000009,0x0000000d,0x00030010,
-    0x00000004,0x00000007,0x00030003,0x00000002,0x000001c2,0x00040005,0x00000004,0x6e69616d,
-    0x00000000,0x00040005,0x00000009,0x6c6f4366,0x0000726f,0x00030005,0x0000000b,0x00000000,
-    0x00050006,0x0000000b,0x00000000,0x6f6c6f43,0x00000072,0x00040006,0x0000000b,0x00000001,
-    0x00005655,0x00030005,0x0000000d,0x00006e49,0x00030005,0x00000015,0x00000074,0x00030005,
-    0x00000019,0x00000073,0x00040047,0x00000009,0x0000001e,0x00000000,0x00040047,0x0000000d,
-    0x0000001e,0x00000000,0x00040047,0x00000015,0x00000022,0x00000001,0x00040047,0x00000015,
-    0x00000021,0x00000000,0x00040047,0x00000019,0x00000022,0x00000000,0x00040047,0x00000019,
-    0x00000021,0x00000001,0x00020013,0x00000002,0x00030021,0x00000003,0x00000002,0x00030016,
-    0x00000006,0x00000020,0x00040017,0x00000007,0x00000006,0x00000004,0x00040020,0x00000008,
-    0x00000003,0x00000007,0x0004003b,0x00000008,0x00000009,0x00000003,0x00040017,0x0000000a,
-    0x00000006,0x00000002,0x0004001e,0x0000000b,0x00000007,0x0000000a,0x00040020,0x0000000c,
-    0x00000001,0x0000000b,0x0004003b,0x0000000c,0x0000000d,0x00000001,0x00040015,0x0000000e,
-    0x00000020,0x00000001,0x0004002b,0x0000000e,0x0000000f,0x00000000,0x00040020,0x00000010,
-    0x00000001,0x00000007,0x00090019,0x00000013,0x00000006,0x00000001,0x00000000,0x00000000,
-    0x00000000,0x00000001,0x00000000,0x00040020,0x00000014,0x00000000,0x00000013,0x0004003b,
-    0x00000014,0x00000015,0x00000000,0x0002001a,0x00000017,0x00040020,0x00000018,0x00000000,
-    0x00000017,0x0004003b,0x00000018,0x00000019,0x00000000,0x0003001b,0x0000001b,0x00000013,
-    0x0004002b,0x0000000e,0x0000001d,0x00000001,0x00040020,0x0000001e,0x00000001,0x0000000a,
-    0x00050036,0x00000002,0x00000004,0x00000000,0x00000003,0x000200f8,0x00000005,0x00050041,
-    0x00000010,0x00000011,0x0000000d,0x0000000f,0x0004003d,0x00000007,0x00000012,0x00000011,
-    0x0004003d,0x00000013,0x00000016,0x00000015,0x0004003d,0x00000017,0x0000001a,0x00000019,
-    0x00050056,0x0000001b,0x0000001c,0x00000016,0x0000001a,0x00050041,0x0000001e,0x0000001f,
-    0x0000000d,0x0000001d,0x0004003d,0x0000000a,0x00000020,0x0000001f,0x00050057,0x00000007,
-    0x00000021,0x0000001c,0x00000020,0x00050085,0x00000007,0x00000022,0x00000012,0x00000021,
-    0x0003003e,0x00000009,0x00000022,0x000100fd,0x00010038
+)";
+
+static const char __shader_frag_wgsl[] = R"(
+struct VertexOutput {
+    @builtin(position) position: vec4<f32>,
+    @location(0) color: vec4<f32>,
+    @location(1) uv: vec2<f32>,
+};
+
+struct Uniforms {
+    mvp: mat4x4<f32>,
+    gamma: f32,
 };
 
+@group(0) @binding(0) var<uniform> uniforms: Uniforms;
+@group(0) @binding(1) var s: sampler;
+@group(1) @binding(0) var t: texture_2d<f32>;
+
+@fragment
+fn main(in: VertexOutput) -> @location(0) vec4<f32> {
+    let color = in.color * textureSample(t, s, in.uv);
+    let corrected_color = pow(color.rgb, vec3<f32>(uniforms.gamma));
+    return vec4<f32>(corrected_color, color.a);
+}
+)";
+
 static void SafeRelease(ImDrawIdx*& res)
 {
     if (res)
@@ -277,17 +224,16 @@ static void SafeRelease(FrameResources& res)
     SafeRelease(res.VertexBufferHost);
 }
 
-static WGPUProgrammableStageDescriptor ImGui_ImplWGPU_CreateShaderModule(uint32_t* binary_data, uint32_t binary_data_size)
+static WGPUProgrammableStageDescriptor ImGui_ImplWGPU_CreateShaderModule(const char* wgsl_source)
 {
     ImGui_ImplWGPU_Data* bd = ImGui_ImplWGPU_GetBackendData();
 
-    WGPUShaderModuleSPIRVDescriptor spirv_desc = {};
-    spirv_desc.chain.sType = WGPUSType_ShaderModuleSPIRVDescriptor;
-    spirv_desc.codeSize = binary_data_size;
-    spirv_desc.code = binary_data;
+    WGPUShaderModuleWGSLDescriptor wgsl_desc = {};
+    wgsl_desc.chain.sType = WGPUSType_ShaderModuleWGSLDescriptor;
+    wgsl_desc.source = wgsl_source;
 
     WGPUShaderModuleDescriptor desc = {};
-    desc.nextInChain = reinterpret_cast<WGPUChainedStruct*>(&spirv_desc);
+    desc.nextInChain = reinterpret_cast<WGPUChainedStruct*>(&wgsl_desc);
 
     WGPUProgrammableStageDescriptor stage_desc = {};
     stage_desc.module = wgpuDeviceCreateShaderModule(bd->wgpuDevice, &desc);
@@ -325,7 +271,38 @@ static void ImGui_ImplWGPU_SetupRenderState(ImDrawData* draw_data, WGPURenderPas
             { 0.0f,         0.0f,           0.5f,       0.0f },
             { (R+L)/(L-R),  (T+B)/(B-T),    0.5f,       1.0f },
         };
-        wgpuQueueWriteBuffer(bd->defaultQueue, bd->renderResources.Uniforms, 0, mvp, sizeof(mvp));
+        wgpuQueueWriteBuffer(bd->defaultQueue, bd->renderResources.Uniforms, offsetof(Uniforms, MVP), mvp, sizeof(Uniforms::MVP));
+        float gamma;
+        switch (bd->renderTargetFormat)
+        {
+        case WGPUTextureFormat_ASTC10x10UnormSrgb:
+        case WGPUTextureFormat_ASTC10x5UnormSrgb:
+        case WGPUTextureFormat_ASTC10x6UnormSrgb:
+        case WGPUTextureFormat_ASTC10x8UnormSrgb:
+        case WGPUTextureFormat_ASTC12x10UnormSrgb:
+        case WGPUTextureFormat_ASTC12x12UnormSrgb:
+        case WGPUTextureFormat_ASTC4x4UnormSrgb:
+        case WGPUTextureFormat_ASTC5x5UnormSrgb:
+        case WGPUTextureFormat_ASTC6x5UnormSrgb:
+        case WGPUTextureFormat_ASTC6x6UnormSrgb:
+        case WGPUTextureFormat_ASTC8x5UnormSrgb:
+        case WGPUTextureFormat_ASTC8x6UnormSrgb:
+        case WGPUTextureFormat_ASTC8x8UnormSrgb:
+        case WGPUTextureFormat_BC1RGBAUnormSrgb:
+        case WGPUTextureFormat_BC2RGBAUnormSrgb:
+        case WGPUTextureFormat_BC3RGBAUnormSrgb:
+        case WGPUTextureFormat_BC7RGBAUnormSrgb:
+        case WGPUTextureFormat_BGRA8UnormSrgb:
+        case WGPUTextureFormat_ETC2RGB8A1UnormSrgb:
+        case WGPUTextureFormat_ETC2RGB8UnormSrgb:
+        case WGPUTextureFormat_ETC2RGBA8UnormSrgb:
+        case WGPUTextureFormat_RGBA8UnormSrgb:
+            gamma = 2.2f;
+            break;
+        default:
+            gamma = 1.0f;
+        }
+        wgpuQueueWriteBuffer(bd->defaultQueue, bd->renderResources.Uniforms, offsetof(Uniforms, Gamma), &gamma, sizeof(Uniforms::Gamma));
     }
 
     // Setup viewport
@@ -555,7 +532,7 @@ static void ImGui_ImplWGPU_CreateUniformBuffer()
         nullptr,
         "Dear ImGui Uniform buffer",
         WGPUBufferUsage_CopyDst | WGPUBufferUsage_Uniform,
-        MEMALIGN(sizeof(Uniforms), 4),
+        MEMALIGN(sizeof(Uniforms), 16),
         false
     };
     bd->renderResources.Uniforms = wgpuDeviceCreateBuffer(bd->wgpuDevice, &ub_desc);
@@ -582,7 +559,7 @@ bool ImGui_ImplWGPU_CreateDeviceObjects()
     // Bind group layouts
     WGPUBindGroupLayoutEntry common_bg_layout_entries[2] = {};
     common_bg_layout_entries[0].binding = 0;
-    common_bg_layout_entries[0].visibility = WGPUShaderStage_Vertex;
+    common_bg_layout_entries[0].visibility = WGPUShaderStage_Vertex | WGPUShaderStage_Fragment;
     common_bg_layout_entries[0].buffer.type = WGPUBufferBindingType_Uniform;
     common_bg_layout_entries[1].binding = 1;
     common_bg_layout_entries[1].visibility = WGPUShaderStage_Fragment;
@@ -612,7 +589,7 @@ bool ImGui_ImplWGPU_CreateDeviceObjects()
     graphics_pipeline_desc.layout = wgpuDeviceCreatePipelineLayout(bd->wgpuDevice, &layout_desc);
 
     // Create the vertex shader
-    WGPUProgrammableStageDescriptor vertex_shader_desc = ImGui_ImplWGPU_CreateShaderModule(__glsl_shader_vert_spv, sizeof(__glsl_shader_vert_spv) / sizeof(uint32_t));
+    WGPUProgrammableStageDescriptor vertex_shader_desc = ImGui_ImplWGPU_CreateShaderModule(__shader_vert_wgsl);
     graphics_pipeline_desc.vertex.module = vertex_shader_desc.module;
     graphics_pipeline_desc.vertex.entryPoint = vertex_shader_desc.entryPoint;
 
@@ -634,7 +611,7 @@ bool ImGui_ImplWGPU_CreateDeviceObjects()
     graphics_pipeline_desc.vertex.buffers = buffer_layouts;
 
     // Create the pixel shader
-    WGPUProgrammableStageDescriptor pixel_shader_desc = ImGui_ImplWGPU_CreateShaderModule(__glsl_shader_frag_spv, sizeof(__glsl_shader_frag_spv) / sizeof(uint32_t));
+    WGPUProgrammableStageDescriptor pixel_shader_desc = ImGui_ImplWGPU_CreateShaderModule(__shader_frag_wgsl);
 
     // Create the blending setup
     WGPUBlendState blend_state = {};
@@ -677,7 +654,7 @@ bool ImGui_ImplWGPU_CreateDeviceObjects()
     // Create resource bind group
     WGPUBindGroupEntry common_bg_entries[] =
     {
-        { nullptr, 0, bd->renderResources.Uniforms, 0, sizeof(Uniforms), 0, 0 },
+        { nullptr, 0, bd->renderResources.Uniforms, 0, MEMALIGN(sizeof(Uniforms), 16), 0, 0 },
         { nullptr, 1, 0, 0, 0, bd->renderResources.Sampler, 0 },
     };
 

docs/CHANGELOG.txt

@@ -90,7 +90,7 @@ Other changes:
   (#6315) [@PathogenDavid]
 - Backends: OSX: Added support for io.AddMouseSourceEvent() to discriminate Mouse/Pen.
   (#6314) [@PathogenDavid]
-- Backends: WebGPU: Align buffers. (#6188) [@eliemichel]
+- Backends: WebGPU: Align buffers. Use WGSL shaders instead of SPIR-V. Add gamma uniform. (#6188) [@eliemichel]
 - Backends: WebGPU: Reorganized to store data in io.BackendRendererUserData like other backends.
 - Examples: Windows: Added 'misc/debuggers/imgui.natstepfilter' file to all Visual Studio projects,
   now that VS 2022 17.6 Preview 2 support adding Debug Step Filter spec files into projects.