Don't convert web text colors to linear

Author: grovesNL

src/lib.rs

@@ -51,7 +51,7 @@ pub(crate) struct GlyphToRender {
     dim: [u16; 2],
     uv: [u16; 2],
     color: u32,
-    content_type: u32,
+    content_type_with_srgb: [u16; 2],
     depth: f32,
 }
 

src/shader.wgsl

@@ -4,7 +4,7 @@ struct VertexInput {
     @location(1) dim: u32,
     @location(2) uv: u32,
     @location(3) color: u32,
-    @location(4) content_type: u32,
+    @location(4) content_type_with_srgb: u32,
     @location(5) depth: f32,
 }
 
@@ -32,8 +32,7 @@ var mask_atlas_texture: texture_2d<f32>;
 @group(0) @binding(3)
 var atlas_sampler: sampler;
 
-fn srgb_to_linear(srgb: u32) -> f32 {
-    let c = f32(srgb) / 255.0;
+fn srgb_to_linear(c: f32) -> f32 {
     if c <= 0.04045 {
         return c / 12.92;
     } else {
@@ -78,15 +77,31 @@ fn vs_main(in_vert: VertexInput) -> VertexOutput {
 
     vert_output.position.y *= -1.0;
 
-    vert_output.color = vec4<f32>(
-        srgb_to_linear((color & 0x00ff0000u) >> 16u),
-        srgb_to_linear((color & 0x0000ff00u) >> 8u),
-        srgb_to_linear(color & 0x000000ffu),
-        f32((color & 0xff000000u) >> 24u) / 255.0,
-    );
+    let content_type = in_vert.content_type_with_srgb & 0xffffu;
+    let srgb = (in_vert.content_type_with_srgb & 0xffff0000u) >> 16u;
+
+    switch srgb {
+        case 0u: {
+            vert_output.color = vec4<f32>(
+                f32((color & 0x00ff0000u) >> 16u) / 255.0,
+                f32((color & 0x0000ff00u) >> 8u) / 255.0,
+                f32(color & 0x000000ffu) / 255.0,
+                f32((color & 0xff000000u) >> 24u) / 255.0,
+            );
+        }
+        case 1u: {
+            vert_output.color = vec4<f32>(
+                srgb_to_linear(f32((color & 0x00ff0000u) >> 16u) / 255.0),
+                srgb_to_linear(f32((color & 0x0000ff00u) >> 8u) / 255.0),
+                srgb_to_linear(f32(color & 0x000000ffu) / 255.0),
+                f32((color & 0xff000000u) >> 24u) / 255.0,
+            );
+        }
+        default: {}
+    }
 
     var dim: vec2<u32> = vec2(0u);
-    switch in_vert.content_type {
+    switch content_type {
         case 0u: {
             dim = textureDimensions(color_atlas_texture);
             break;
@@ -98,7 +113,7 @@ fn vs_main(in_vert: VertexInput) -> VertexOutput {
         default: {}
     }
 
-    vert_output.content_type = in_vert.content_type;
+    vert_output.content_type = content_type;
 
     vert_output.uv = vec2<f32>(uv) / vec2<f32>(dim);
 

src/text_atlas.rs

@@ -271,6 +271,7 @@ pub struct TextAtlas {
     pub(crate) shader: ShaderModule,
     pub(crate) vertex_buffers: [wgpu::VertexBufferLayout<'static>; 1],
     pub(crate) format: TextureFormat,
+    pub(crate) color_mode: ColorMode,
 }
 
 impl TextAtlas {
@@ -450,6 +451,7 @@ impl TextAtlas {
             shader,
             vertex_buffers,
             format,
+            color_mode,
         }
     }
 

src/text_render.rs

@@ -1,6 +1,6 @@
 use crate::{
-    FontSystem, GlyphDetails, GlyphToRender, GpuCacheStatus, Params, PrepareError, RenderError,
-    Resolution, SwashCache, SwashContent, TextArea, TextAtlas,
+    ColorMode, FontSystem, GlyphDetails, GlyphToRender, GpuCacheStatus, Params, PrepareError,
+    RenderError, Resolution, SwashCache, SwashContent, TextArea, TextAtlas,
 };
 use std::{iter, mem::size_of, slice, sync::Arc};
 use wgpu::{
@@ -276,7 +276,13 @@ impl TextRenderer {
                             dim: [width as u16, height as u16],
                             uv: [atlas_x, atlas_y],
                             color: color.0,
-                            content_type: content_type as u32,
+                            content_type_with_srgb: [
+                                content_type as u16,
+                                match atlas.color_mode {
+                                    ColorMode::Accurate => TextColorConversion::ConvertToLinear,
+                                    ColorMode::Web => TextColorConversion::None,
+                                } as u16,
+                            ],
                             depth,
                         })
                         .take(4),
@@ -405,13 +411,20 @@ impl TextRenderer {
     }
 }
 
-#[repr(u32)]
+#[repr(u16)]
 #[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub enum ContentType {
     Color = 0,
     Mask = 1,
 }
 
+#[repr(u16)]
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+enum TextColorConversion {
+    None = 0,
+    ConvertToLinear = 1,
+}
+
 fn next_copy_buffer_size(size: u64) -> u64 {
     let align_mask = COPY_BUFFER_ALIGNMENT - 1;
     ((size.next_power_of_two() + align_mask) & !align_mask).max(COPY_BUFFER_ALIGNMENT)