Improve contrast of built-in themes by leveraging Oklch

core/src/color.rs

@@ -90,12 +90,12 @@ impl Color {
             }
         }
 
-        Self {
+        Self::new(
-            r: gamma_component(r),
+            gamma_component(r),
-            g: gamma_component(g),
+            gamma_component(g),
-            b: gamma_component(b),
+            gamma_component(b),
             a,
-        }
+        )
     }
 
     /// Parses a [`Color`] from a hex string.

core/src/theme/palette.rs

@@ -28,7 +28,7 @@ impl Palette {
         text: Color::BLACK,
         primary: color!(0x5865F2),
         success: color!(0x12664f),
-        warning: color!(0xffc14e),
+        warning: color!(0xb77e33),
         danger: color!(0xc3423f),
     };
 
@@ -453,9 +453,13 @@ pub struct Background {
     /// The weakest version of the base background color.
     pub weakest: Pair,
     /// A weaker version of the base background color.
+    pub weaker: Pair,
+    /// A weak version of the base background color.
     pub weak: Pair,
-    /// A stronger version of the base background color.
+    /// A strong version of the base background color.
     pub strong: Pair,
+    /// A stronger version of the base background color.
+    pub stronger: Pair,
     /// The strongest version of the base background color.
     pub strongest: Pair,
 }
@@ -464,15 +468,19 @@ impl Background {
     /// Generates a set of [`Background`] colors from the base and text colors.
     pub fn new(base: Color, text: Color) -> Self {
         let weakest = deviate(base, 0.03);
-        let weak = muted(deviate(base, 0.1));
+        let weaker = deviate(base, 0.07);
-        let strong = muted(deviate(base, 0.2));
+        let weak = deviate(base, 0.1);
-        let strongest = muted(deviate(base, 0.3));
+        let strong = deviate(base, 0.15);
+        let stronger = deviate(base, 0.175);
+        let strongest = deviate(base, 0.20);
 
         Self {
             base: Pair::new(base, text),
             weakest: Pair::new(weakest, text),
+            weaker: Pair::new(weaker, text),
             weak: Pair::new(weak, text),
             strong: Pair::new(strong, text),
+            stronger: Pair::new(stronger, text),
             strongest: Pair::new(strongest, text),
         }
     }
@@ -517,9 +525,11 @@ pub struct Secondary {
 impl Secondary {
     /// Generates a set of [`Secondary`] colors from the base and text colors.
     pub fn generate(base: Color, text: Color) -> Self {
-        let base = mix(base, text, 0.2);
+        let bump = if is_dark(base) { 0.0 } else { 0.01 };
-        let weak = mix(base, text, 0.1);
+
-        let strong = mix(base, text, 0.3);
+        let weak = mix(deviate(base, 0.1 + bump), text, 0.4);
+        let base = mix(deviate(base, 0.3 + bump), text, 0.4);
+        let strong = mix(deviate(base, 0.5 + bump), text, 0.4);
 
         Self {
             base: Pair::new(base, text),
@@ -604,53 +614,51 @@ impl Danger {
     }
 }
 
-struct Hsl {
+struct Oklch {
-    h: f32,
-    s: f32,
     l: f32,
+    c: f32,
+    h: f32,
     a: f32,
 }
 
 fn darken(color: Color, amount: f32) -> Color {
-    let mut hsl = to_hsl(color);
+    let mut oklch = to_oklch(color);
 
-    hsl.l = if hsl.l - amount < 0.0 {
+    // We try to bump the chroma a bit for more colorful palettes
+    oklch.c *= 1.0 + 2.0 * amount / oklch.l.max(0.05);
+
+    oklch.l = if oklch.l - amount < 0.0 {
         0.0
     } else {
-        hsl.l - amount
+        oklch.l - amount
     };
 
-    from_hsl(hsl)
+    from_oklch(oklch)
 }
 
 fn lighten(color: Color, amount: f32) -> Color {
-    let mut hsl = to_hsl(color);
+    let mut oklch = to_oklch(color);
 
-    hsl.l = if hsl.l + amount > 1.0 {
+    // We try to bump the chroma a bit for more colorful palettes
+    oklch.c *= 1.0 + 2.0 * amount / oklch.l.max(0.05);
+
+    oklch.l = if oklch.l + amount > 1.0 {
         1.0
     } else {
-        hsl.l + amount
+        oklch.l + amount
     };
 
-    from_hsl(hsl)
+    from_oklch(oklch)
 }
 
 fn deviate(color: Color, amount: f32) -> Color {
     if is_dark(color) {
         lighten(color, amount)
     } else {
-        darken(color, amount * 0.8)
+        darken(color, amount)
     }
 }
 
-fn muted(color: Color) -> Color {
-    let mut hsl = to_hsl(color);
-
-    hsl.s = hsl.s.min(0.5);
-
-    from_hsl(hsl)
-}
-
 fn mix(a: Color, b: Color, factor: f32) -> Color {
     let b_amount = factor.clamp(0.0, 1.0);
     let a_amount = 1.0 - b_amount;
@@ -680,6 +688,12 @@ fn readable(background: Color, text: Color) -> Color {
         return candidate;
     }
 
+    let candidate = improve(text, 0.2);
+
+    if is_readable(background, candidate) {
+        return candidate;
+    }
+
     let white_contrast = relative_contrast(background, Color::WHITE);
     let black_contrast = relative_contrast(background, Color::BLACK);
 
@@ -691,11 +705,11 @@ fn readable(background: Color, text: Color) -> Color {
 }
 
 fn is_dark(color: Color) -> bool {
-    to_hsl(color).l < 0.6
+    to_oklch(color).l < 0.6
 }
 
 fn is_readable(a: Color, b: Color) -> bool {
-    relative_contrast(a, b) >= 7.0
+    relative_contrast(a, b) >= 6.0
 }
 
 // https://www.w3.org/TR/WCAG21/#dfn-contrast-ratio
@@ -711,65 +725,57 @@ fn relative_luminance(color: Color) -> f32 {
     0.2126 * linear[0] + 0.7152 * linear[1] + 0.0722 * linear[2]
 }
 
-// https://en.wikipedia.org/wiki/HSL_and_HSV#From_RGB
+// https://en.wikipedia.org/wiki/Oklab_color_space#Conversions_between_color_spaces
-fn to_hsl(color: Color) -> Hsl {
+fn to_oklch(color: Color) -> Oklch {
-    let x_max = color.r.max(color.g).max(color.b);
+    let [r, g, b, alpha] = color.into_linear();
-    let x_min = color.r.min(color.g).min(color.b);
-    let c = x_max - x_min;
-    let l = x_max.midpoint(x_min);
 
-    let h = if c == 0.0 {
+    // linear RGB → LMS
-        0.0
+    let l = 0.41222146 * r + 0.53633255 * g + 0.051445995 * b;
-    } else if x_max == color.r {
+    let m = 0.2119035 * r + 0.6806995 * g + 0.10739696 * b;
-        60.0 * ((color.g - color.b) / c).rem_euclid(6.0)
+    let s = 0.08830246 * r + 0.28171885 * g + 0.6299787 * b;
-    } else if x_max == color.g {
-        60.0 * (((color.b - color.r) / c) + 2.0)
-    } else {
-        // x_max == color.b
-        60.0 * (((color.r - color.g) / c) + 4.0)
-    };
 
-    let s = if l == 0.0 || l == 1.0 {
+    // Nonlinear transform (cube root)
-        0.0
+    let l_ = l.cbrt();
-    } else {
+    let m_ = m.cbrt();
-        (x_max - l) / l.min(1.0 - l)
+    let s_ = s.cbrt();
-    };
 
-    Hsl {
+    // LMS → Oklab
-        h,
+    let l = 0.21045426 * l_ + 0.7936178 * m_ - 0.004072047 * s_;
-        s,
+    let a = 1.9779985 * l_ - 2.4285922 * m_ + 0.4505937 * s_;
-        l,
+    let b = 0.025904037 * l_ + 0.78277177 * m_ - 0.80867577 * s_;
-        a: color.a,
+
-    }
+    // Oklab → Oklch
+    let c = (a * a + b * b).sqrt();
+    let h = b.atan2(a); // radians
+
+    Oklch { l, c, h, a: alpha }
 }
 
-// https://en.wikipedia.org/wiki/HSL_and_HSV#HSL_to_RGB
+// https://en.wikipedia.org/wiki/Oklab_color_space#Conversions_between_color_spaces
-fn from_hsl(hsl: Hsl) -> Color {
+fn from_oklch(oklch: Oklch) -> Color {
-    let c = (1.0 - (2.0 * hsl.l - 1.0).abs()) * hsl.s;
+    let Oklch { l, c, h, a: alpha } = oklch;
-    let h = hsl.h / 60.0;
-    let x = c * (1.0 - (h.rem_euclid(2.0) - 1.0).abs());
 
-    let (r1, g1, b1) = if h < 1.0 {
+    let a = c * h.cos();
-        (c, x, 0.0)
+    let b = c * h.sin();
-    } else if h < 2.0 {
-        (x, c, 0.0)
-    } else if h < 3.0 {
-        (0.0, c, x)
-    } else if h < 4.0 {
-        (0.0, x, c)
-    } else if h < 5.0 {
-        (x, 0.0, c)
-    } else {
-        // h < 6.0
-        (c, 0.0, x)
-    };
 
-    let m = hsl.l - (c / 2.0);
+    // Oklab → LMS (nonlinear)
+    let l_ = l + 0.39633778 * a + 0.21580376 * b;
+    let m_ = l - 0.105561346 * a - 0.06385417 * b;
+    let s_ = l - 0.08948418 * a - 1.2914855 * b;
 
-    Color {
+    // Cubing back
-        r: r1 + m,
+    let l = l_ * l_ * l_;
-        g: g1 + m,
+    let m = m_ * m_ * m_;
-        b: b1 + m,
+    let s = s_ * s_ * s_;
-        a: hsl.a,
+
-    }
+    let r = 4.0767417 * l - 3.3077116 * m + 0.23096994 * s;
+    let g = -1.268438 * l + 2.6097574 * m - 0.34131938 * s;
+    let b = -0.0041960863 * l - 0.7034186 * m + 1.7076147 * s;
+
+    Color::from_linear_rgba(
+        r.clamp(0.0, 1.0),
+        g.clamp(0.0, 1.0),
+        b.clamp(0.0, 1.0),
+        alpha,
+    )
 }

core/src/widget/text.rs

@@ -441,7 +441,7 @@ pub fn primary(theme: &Theme) -> Style {
 /// Text conveying some secondary information, like a footnote.
 pub fn secondary(theme: &Theme) -> Style {
     Style {
-        color: Some(theme.extended_palette().secondary.strong.color),
+        color: Some(theme.extended_palette().secondary.base.color),
     }
 }
 

examples/styling/snapshots/catppuccin_frappé-tiny-skia.sha256

@@ -1 +1 @@
-e440e5e00db4fff0a79251aaf493c4af86241196a746d9147a895d14f01b1283
+a496cc09220283466d5eb3635f6b63d011ec1dc765726b81213a823825836e4a

examples/styling/snapshots/catppuccin_latte-tiny-skia.sha256

@@ -1 +1 @@
-d81cf7c3974fc5b49251e8287c536fd3477c18e7afd3e9e42619364db7787fcc
+661e3f5313b98c65fd0ce9615d9a42201f2b1bafe0285b4a9c5c5af403782452

examples/styling/snapshots/catppuccin_macchiato-tiny-skia.sha256

@@ -1 +1 @@
-ad4fbda3cc3d60209320dd713b7be6b0a5e6b55650689d70ac563a0a81f2eefc
+a530ad9b59628d95e9aaa187af2681b26e7219786b5a114848f41690ed25ef21

examples/styling/snapshots/catppuccin_mocha-tiny-skia.sha256

@@ -1 +1 @@
-3863252d1f15750d7f5375bd23e8363c6a70d77ac9aac853e3515f7ff5170bce
+f959b1b8ca2d7f87110e0decf63bf04bb685a8958de6879e008edb40415a84e8

examples/styling/snapshots/dark-tiny-skia.sha256

@@ -1 +1 @@
-c0bc58fcbde8e7ac4447ba4a454c5c2cb2c6d570e873897887c626b2dc07329b
+043d53e59e66ed06105abac613ed49c6beaf57f5009e605107cb77307807790b

examples/styling/snapshots/dracula-tiny-skia.sha256

@@ -1 +1 @@
-1f17779b3291c133399f1eba9f7e517889108d60dbaa8d5b6cd024ad67ef1c8c
+f7894c6738710e8054b41c2d958eb50182d9655d8651d1fd2371a9ed05f28ddc

examples/styling/snapshots/ferra-tiny-skia.sha256

@@ -1 +1 @@
-51d7bfc1af8ba7503b9800ae7eaaa660047d9b16b0bdc1e8a3850df1d9901652
+e0ec3911121e303bdfe3956c72af423ec21a17a958768116ee452adcace02e15

examples/styling/snapshots/gruvbox_dark-tiny-skia.sha256

@@ -1 +1 @@
-5423fa06a1dc73f9cce42447f3134768114e8321c8f2367da1e04db4d4673f52
+81e4f065fc985a2c5fc9d15fea941667e914dbc6fe7a5262dac5390955e34f67

examples/styling/snapshots/gruvbox_light-tiny-skia.sha256

@@ -1 +1 @@
-b7ea69b9ce1f73694cccb8b0bc9acab35fc4dcedd01795e3897215c416550fc2
+9d91bfb3504ebf59881ca1554fa63f7293c2750f7ff15a91ff8e86ccf65a0f6f

examples/styling/snapshots/kanagawa_dragon-tiny-skia.sha256

@@ -1 +1 @@
-fa43206adec5dce05c4181ec5d9c71d15067dd3b1d7f5b3267c452cf1de2ca95
+491041848f77c6e9b70b7e677d0809bff5ceae783326f6dbdd10bdcd45eb56e2

examples/styling/snapshots/kanagawa_lotus-tiny-skia.sha256

@@ -1 +1 @@
-5d7445700ff415428ae43d32ef30b279c38ddc6ffd0e3619ea28044b1d8c709b
+8209ef9862c56280f711a477843f6d9ab2d1b201ba257f553c9ad2caf0c78731

examples/styling/snapshots/kanagawa_wave-tiny-skia.sha256

@@ -1 +1 @@
-52d424e4dfa3ae9b1195e95f17eb655675e4507ec8fb4e36372612fd57a5d86d
+304163accbfcd947b5231beaeb4d8194aab02409df9e334862fe5eb79a835116

examples/styling/snapshots/light-tiny-skia.sha256

@@ -1 +1 @@
-a0c84b36979f6a6f780af80689425b92a1b68743c39f8e519efcb11b46b9de42
+dd82fb5d72db1a33c52bbd27836dbed0c51af5a8bc726c4d73865af779701aba

examples/styling/snapshots/moonfly-tiny-skia.sha256

@@ -1 +1 @@
-21820cf793f0a3af6fd339132b32cc77cbca52f1ca32f7ae334f74849a046ba8
+bc88452bb81a702a8c29c9dde933bf0bdb1723af1c910cb44e56180dc64270b5

examples/styling/snapshots/nightfly-tiny-skia.sha256

@@ -1 +1 @@
-1ba92e64ddcc5f5fc6f841d5fde961382099e7698a253ac93670b900287ee55c
+140ca7cf98bec0d955678b5160e0ccb43d85a829eed62c54f09d5e0b1a401e6f

examples/styling/snapshots/nord-tiny-skia.sha256

@@ -1 +1 @@
-f6559f58f9acae81d929ee1aa5f8db33fca9d4ff49d21acf1e627d891ed77565
+e8b2b050896d2b2cfd1c31b2c8773f74b2c23b94b3d94e8f16b8fb6604e8b2f2

examples/styling/snapshots/oxocarbon-tiny-skia.sha256

@@ -1 +1 @@
-d3d34b3b02b11156cb9a545d60cba078e78e4124c8f3ae61be66908a42799166
+d40514ab3f75e4aa08d8d21e197e5fa486dd0689a4e81027ae335e9abd2ea311

examples/styling/snapshots/solarized_dark-tiny-skia.sha256

@@ -1 +1 @@
-3c983866c4feaa10ed34206c1a4c98933e87ba6239849bd7e1b7876f6c9596e7
+3ea703ef5d769c6184777bee6caa71e49adc381e1a47f3241f03250ab27b6988

examples/styling/snapshots/solarized_light-tiny-skia.sha256

@@ -1 +1 @@
-dc6fc66e651d938a42f0a9c642a99e33865b87aefc3fdeafa1848f6a3fab20c3
+73f01efd56087daa9372aed4b5e5d72d8f5713d75812978bf09a726684ea2b40

examples/styling/snapshots/tokyo_night-tiny-skia.sha256

@@ -1 +1 @@
-7104099471f9c712f00cd2ac80e150e10f7d21604d7edc6b13181e74d42eb877
+82a173e0c1b9c665fbf06de60acbb0523b7f9ab5af429d5ec29ce908f640d5ec

examples/styling/snapshots/tokyo_night_light-tiny-skia.sha256

@@ -1 +1 @@
-263b5eb190d7db2ab0a67dc8b73778d9130755b07a8295345c758e158fb52881
+91d09c382a9d615a1ba68f74463c9a92baba705e35bb84173945d2fa5fd240d0

examples/styling/snapshots/tokyo_night_storm-tiny-skia.sha256

@@ -1 +1 @@
-6fd5700c7a63ba004957601e0d91b02e8d08b710cff81710d3b8cd1cb668faa6
+dfc3317f39c204b8509c1b8f7e8e1d9b0911bfc1a7bd5fbde822a7a5c6c54e12

widget/src/button.rs

@@ -718,13 +718,13 @@ pub fn subtle(theme: &Theme, status: Status) -> Style {
         Status::Active => base,
         Status::Pressed => Style {
             background: Some(Background::Color(
-                palette.background.strongest.color,
+                palette.background.strong.color,
             )),
             ..base
         },
         Status::Hovered => Style {
             background: Some(Background::Color(
-                palette.background.strong.color,
+                palette.background.weaker.color,
             )),
             ..base
         },

widget/src/text_editor.rs

@@ -1423,7 +1423,7 @@ pub fn default(theme: &Theme, status: Status) -> Style {
             color: palette.background.strong.color,
         },
         icon: palette.background.weak.text,
-        placeholder: palette.background.strong.color,
+        placeholder: palette.secondary.base.color,
         value: palette.background.base.text,
         selection: palette.primary.weak.color,
     };
@@ -1447,6 +1447,7 @@ pub fn default(theme: &Theme, status: Status) -> Style {
         Status::Disabled => Style {
             background: Background::Color(palette.background.weak.color),
             value: active.placeholder,
+            placeholder: palette.background.strongest.color,
             ..active
         },
     }

widget/src/text_input.rs

@@ -1817,10 +1817,10 @@ pub fn default(theme: &Theme, status: Status) -> Style {
         border: Border {
             radius: 2.0.into(),
             width: 1.0,
-            color: palette.background.strongest.color,
+            color: palette.background.strong.color,
         },
         icon: palette.background.weak.text,
-        placeholder: palette.background.strongest.color,
+        placeholder: palette.secondary.base.color,
         value: palette.background.base.text,
         selection: palette.primary.weak.color,
     };
@@ -1844,6 +1844,7 @@ pub fn default(theme: &Theme, status: Status) -> Style {
         Status::Disabled => Style {
             background: Background::Color(palette.background.weak.color),
             value: active.placeholder,
+            placeholder: palette.background.strongest.color,
             ..active
         },
     }