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

@@ -76,6 +76,7 @@ struct FrameResources
 struct Uniforms
 {
     float MVP[4][4];
+    float Gamma;
 };
 
 struct ImGui_ImplWGPU_Data
@@ -116,12 +117,17 @@ struct VertexOutput {
     @location(1) uv: vec2<f32>,
 };
 
-@group(0) @binding(0) var<uniform> mvp: mat4x4<f32>;
+struct Uniforms {
+    mvp: mat4x4<f32>,
+    gamma: f32,
+};
+
+@group(0) @binding(0) var<uniform> uniforms: Uniforms;
 
 @vertex
 fn main(in: VertexInput) -> VertexOutput {
     var out: VertexOutput;
-    out.position = mvp * vec4<f32>(in.position, 0.0, 1.0);
+    out.position = uniforms.mvp * vec4<f32>(in.position, 0.0, 1.0);
     out.color = in.color;
     out.uv = in.uv;
     return out;
@@ -135,14 +141,19 @@ struct VertexOutput {
     @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(0) @binding(2) var<uniform> gamma: f32;
 @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>(gamma));
+    let corrected_color = pow(color.rgb, vec3<f32>(uniforms.gamma));
     return vec4<f32>(corrected_color, color.a);
 }
 )";
@@ -278,7 +289,38 @@ 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
@@ -508,7 +550,7 @@ 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);
@@ -535,7 +577,7 @@ 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;
@@ -630,7 +672,7 @@ 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 },
     };