theme: derive elevations from the platform's native shadows

crates/theme/src/lib.rs

@@ -84,10 +84,10 @@ impl Default for Radius {
     }
 }
 
-/// One drop shadow of a floating layer,
-/// transcribed from the platform's native overlay shadows.
+/// One layer of a floating panel's drop shadow.
 #[derive(Clone, Copy, Debug, PartialEq)]
-pub struct Elevation {
+pub struct Shadow {
+    pub offset_x: Pixels,
     pub offset_y: Pixels,
     pub blur_radius: Pixels,
     pub spread_radius: Pixels,
@@ -95,43 +95,109 @@ pub struct Elevation {
     pub color: Hsla,
 }
 
+impl Shadow {
+    fn none() -> Self {
+        Self {
+            offset_x: px(0.),
+            offset_y: px(0.),
+            blur_radius: px(0.),
+            spread_radius: px(0.),
+            color: colors::scrim(0.),
+        }
+    }
+
+    fn black(offset_x: f32, offset_y: f32, blur_radius: f32, alpha: f32) -> Self {
+        Self {
+            offset_x: px(offset_x),
+            offset_y: px(offset_y),
+            blur_radius: px(blur_radius),
+            spread_radius: px(0.),
+            color: colors::scrim(alpha),
+        }
+    }
+}
+
+/// The drop shadow stack of a floating layer.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Elevation {
+    /// Key shadow first, ambient grounding second.
+    pub layers: [Shadow; 2],
+}
+
 impl Elevation {
+    fn single(key: Shadow) -> Self {
+        Self {
+            layers: [key, Shadow::none()],
+        }
+    }
+
+    fn layered(key: Shadow, ambient: Shadow) -> Self {
+        Self {
+            layers: [key, ambient],
+        }
+    }
+
     /// The gpui shadow list an overlay panel paints with.
     pub fn shadows(self) -> Vec<gpui::BoxShadow> {
-        vec![gpui::BoxShadow {
-            color: self.color,
-            offset: gpui::point(px(0.), self.offset_y),
-            blur_radius: self.blur_radius,
-            spread_radius: self.spread_radius,
-            inset: false,
-        }]
+        self.layers
+            .iter()
+            .filter(|layer| layer.color.a > 0.)
+            .map(|layer| gpui::BoxShadow {
+                color: layer.color,
+                offset: gpui::point(layer.offset_x, layer.offset_y),
+                blur_radius: layer.blur_radius,
+                spread_radius: layer.spread_radius,
+                inset: false,
+            })
+            .collect()
     }
 }
 
 /// The drop shadows of each floating layer class.
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct Elevations {
-    /// Popovers and menus ride above content on a tight shadow.
+    /// Popovers, menus, and pushed alerts ride above content.
     pub popover: Elevation,
     /// Modal dialogs sit higher with a wider one.
     pub dialog: Elevation,
 }
 
-impl Default for Elevations {
-    fn default() -> Self {
-        Self {
-            popover: Elevation {
-                offset_y: px(4.),
-                blur_radius: px(24.),
-                spread_radius: px(0.),
-                color: colors::scrim(0.3),
+impl Elevations {
+    pub(crate) fn for_platform(source: SourceKind, variant: ThemeVariant) -> Self {
+        if variant == ThemeVariant::Dark {
+            return Self {
+                popover: Elevation::single(Shadow::black(0., 4., 24., 0.3)),
+                dialog: Elevation::single(Shadow::black(0., 8., 40., 0.35)),
+            };
+        }
+
+        match source {
+            SourceKind::Macos => Self {
+                popover: Elevation::layered(
+                    Shadow::black(0., 4., 24., 0.12),
+                    Shadow::black(0., 1., 1., 0.05),
+                ),
+                dialog: Elevation::layered(
+                    Shadow::black(0., 8., 40., 0.14),
+                    Shadow::black(0., 1., 2., 0.06),
+                ),
             },
-            dialog: Elevation {
-                offset_y: px(8.),
-                blur_radius: px(40.),
-                spread_radius: px(0.),
-                color: colors::scrim(0.35),
+            SourceKind::Windows => Self {
+                popover: Elevation::layered(
+                    Shadow::black(0., 8., 16., 0.14),
+                    Shadow::black(0., 2., 4., 0.1),
+                ),
+                dialog: Elevation::layered(
+                    Shadow::black(0., 16., 32., 0.16),
+                    Shadow::black(0., 4., 8., 0.1),
+                ),
             },
+            SourceKind::Omarchy | SourceKind::Kde | SourceKind::Gnome | SourceKind::Fallback => {
+                Self {
+                    popover: Elevation::single(Shadow::black(0., 3., 6., 0.2)),
+                    dialog: Elevation::single(Shadow::black(0., 9., 18., 0.24)),
+                }
+            }
         }
     }
 }