Introduce `web-colors` feature flag to enable sRGB linear blending

This is how browsers perform color management. They treat
gamma-corrected sRGB colors as if they were linear RGB.

Correctness aside, this mode is introduced for legacy reasons. Most
UI/UX tooling uses this color management as well, and many have created
an intuition about how color should behave from interacting with a
browser.

This feature flag should facilitate application development with `iced`
in those cases.

More details: https://webcolorisstillbroken.com/

7 files changed, 29 insertions, 18 deletions

diff --git a/wgpu/src/backend.rs b/wgpu/src/backend.rs
index 844987f2..b524c615 100644
--- a/wgpu/src/backend.rs
+++ b/wgpu/src/backend.rs
@@ -1,6 +1,7 @@
 use crate::core;
 use crate::core::{Color, Font, Point, Size};
 use crate::graphics::backend;
+use crate::graphics::color;
 use crate::graphics::{Primitive, Transformation, Viewport};
 use crate::quad;
 use crate::text;
@@ -239,7 +240,7 @@ impl Backend {
                         load: match clear_color {
                             Some(background_color) => wgpu::LoadOp::Clear({
                                 let [r, g, b, a] =
-                                    background_color.into_linear();
+                                    color::pack(background_color).components();
 
                                 wgpu::Color {
                                     r: f64::from(r),
diff --git a/wgpu/src/geometry.rs b/wgpu/src/geometry.rs
index 740ec20c..f81b5b2f 100644
--- a/wgpu/src/geometry.rs
+++ b/wgpu/src/geometry.rs
@@ -1,5 +1,6 @@
 //! Build and draw geometry.
 use crate::core::{Point, Rectangle, Size, Vector};
+use crate::graphics::color;
 use crate::graphics::geometry::fill::{self, Fill};
 use crate::graphics::geometry::{
     LineCap, LineDash, LineJoin, Path, Stroke, Style, Text,
@@ -68,7 +69,7 @@ impl BufferStack {
             (Style::Solid(color), Buffer::Solid(buffer)) => {
                 Box::new(tessellation::BuffersBuilder::new(
                     buffer,
-                    TriangleVertex2DBuilder(color.into_linear()),
+                    TriangleVertex2DBuilder(color::pack(*color)),
                 ))
             }
             (Style::Gradient(gradient), Buffer::Gradient(buffer)) => {
@@ -91,7 +92,7 @@ impl BufferStack {
             (Style::Solid(color), Buffer::Solid(buffer)) => {
                 Box::new(tessellation::BuffersBuilder::new(
                     buffer,
-                    TriangleVertex2DBuilder(color.into_linear()),
+                    TriangleVertex2DBuilder(color::pack(*color)),
                 ))
             }
             (Style::Gradient(gradient), Buffer::Gradient(buffer)) => {
@@ -526,7 +527,7 @@ impl tessellation::StrokeVertexConstructor<primitive::GradientVertex2D>
     }
 }
 
-struct TriangleVertex2DBuilder([f32; 4]);
+struct TriangleVertex2DBuilder(color::Packed);
 
 impl tessellation::FillVertexConstructor<primitive::ColoredVertex2D>
     for TriangleVertex2DBuilder
diff --git a/wgpu/src/layer.rs b/wgpu/src/layer.rs
index 1a870c15..71570e3d 100644
--- a/wgpu/src/layer.rs
+++ b/wgpu/src/layer.rs
@@ -11,6 +11,7 @@ pub use text::Text;
 use crate::core;
 use crate::core::alignment;
 use crate::core::{Color, Font, Point, Rectangle, Size, Vector};
+use crate::graphics::color;
 use crate::graphics::{Primitive, Viewport};
 use crate::quad::{self, Quad};
 
@@ -150,7 +151,7 @@ impl<'a> Layer<'a> {
                         bounds.y + translation.y,
                     ],
                     size: [bounds.width, bounds.height],
-                    border_color: border_color.into_linear(),
+                    border_color: color::pack(*border_color),
                     border_radius: *border_radius,
                     border_width: *border_width,
                 };
diff --git a/wgpu/src/quad.rs b/wgpu/src/quad.rs
index 9c5ed05f..37d0c623 100644
--- a/wgpu/src/quad.rs
+++ b/wgpu/src/quad.rs
@@ -5,6 +5,7 @@ use gradient::Gradient;
 use solid::Solid;
 
 use crate::core::{Background, Rectangle};
+use crate::graphics::color;
 use crate::graphics::{self, Transformation};
 
 use bytemuck::{Pod, Zeroable};
@@ -217,7 +218,7 @@ pub struct Quad {
     pub size: [f32; 2],
 
     /// The border color of the [`Quad`], in __linear RGB__.
-    pub border_color: [f32; 4],
+    pub border_color: color::Packed,
 
     /// The border radii of the [`Quad`].
     pub border_radius: [f32; 4],
@@ -250,7 +251,7 @@ impl Batch {
         let kind = match background {
             Background::Color(color) => {
                 self.solids.push(Solid {
-                    color: color.into_linear(),
+                    color: color::pack(*color),
                     quad,
                 });
 
diff --git a/wgpu/src/quad/solid.rs b/wgpu/src/quad/solid.rs
index f667c42c..f8f1e3a5 100644
--- a/wgpu/src/quad/solid.rs
+++ b/wgpu/src/quad/solid.rs
@@ -1,3 +1,4 @@
+use crate::graphics::color;
 use crate::quad::{self, Quad};
 use crate::Buffer;
 
@@ -9,7 +10,7 @@ use std::ops::Range;
 #[repr(C)]
 pub struct Solid {
     /// The background color data of the quad.
-    pub color: [f32; 4],
+    pub color: color::Packed,
 
     /// The [`Quad`] data of the [`Solid`].
     pub quad: Quad,
diff --git a/wgpu/src/text.rs b/wgpu/src/text.rs
index 714e0400..a12bc9f7 100644
--- a/wgpu/src/text.rs
+++ b/wgpu/src/text.rs
@@ -2,6 +2,7 @@ use crate::core::alignment;
 use crate::core::font::{self, Font};
 use crate::core::text::{Hit, LineHeight, Shaping};
 use crate::core::{Pixels, Point, Rectangle, Size};
+use crate::graphics::color;
 use crate::layer::Text;
 
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -155,7 +156,8 @@ impl Pipeline {
                             bottom: (clip_bounds.y + clip_bounds.height) as i32,
                         },
                         default_color: {
-                            let [r, g, b, a] = section.color.into_linear();
+                            let [r, g, b, a] =
+                                color::pack(section.color).components();
 
                             glyphon::Color::rgba(
                                 (r * 255.0) as u8,
diff --git a/wgpu/src/window/compositor.rs b/wgpu/src/window/compositor.rs
index 500458e8..2eaafde0 100644
--- a/wgpu/src/window/compositor.rs
+++ b/wgpu/src/window/compositor.rs
@@ -1,6 +1,7 @@
 //! Connect a window with a renderer.
 use crate::core::Color;
 use crate::graphics;
+use crate::graphics::color;
 use crate::graphics::compositor;
 use crate::graphics::{Error, Primitive, Viewport};
 use crate::{Backend, Renderer, Settings};
@@ -69,16 +70,19 @@ impl<Theme> Compositor<Theme> {
         let format = compatible_surface.as_ref().and_then(|surface| {
             let capabilities = surface.get_capabilities(&adapter);
 
-            capabilities
-                .formats
-                .iter()
-                .copied()
-                .find(wgpu::TextureFormat::is_srgb)
-                .or_else(|| {
-                    log::warn!("No sRGB format found!");
+            let mut formats = capabilities.formats.iter().copied();
 
-                    capabilities.formats.first().copied()
-                })
+            let format = if color::GAMMA_CORRECTION {
+                formats.find(wgpu::TextureFormat::is_srgb)
+            } else {
+                formats.find(|format| !wgpu::TextureFormat::is_srgb(format))
+            };
+
+            format.or_else(|| {
+                log::warn!("No format found!");
+
+                capabilities.formats.first().copied()
+            })
         })?;
 
         log::info!("Selected format: {:?}", format);