feat: add native material backgrounds

crates/theme/src/source/kde.rs

@@ -93,6 +93,7 @@ impl KdeScheme {
             titlebar_height: Some(px(44.)),
             root_font_size: Some(self.root_font_size.unwrap_or(px(13.33))),
             accessibility,
+            window_background: None,
             source: SourceKind::Kde,
         }
     }

crates/theme/src/source/linux.rs

@@ -38,6 +38,12 @@ fn home_dir() -> Option<PathBuf> {
     std::env::var_os("HOME").map(PathBuf::from)
 }
 
+/// Whether the session runs on Wayland, where compositors state blur protocols.
+fn wayland_session() -> bool {
+    std::env::var_os("WAYLAND_DISPLAY").is_some()
+        || std::env::var("XDG_SESSION_TYPE").is_ok_and(|session| session == "wayland")
+}
+
 fn detect(home: &Path, portal_reachable: bool, gsettings_reachable: bool) -> Backend {
     let omarchy_marker = home
         .join(".local/state/omarchy/current/theme.name")
@@ -164,6 +170,7 @@ impl LinuxSource {
                     .unwrap_or(gpui::px(14.67)),
             ),
             accessibility,
+            window_background: None,
             source: SourceKind::Gnome,
         }
     }
@@ -203,15 +210,24 @@ impl ThemeSource for LinuxSource {
 
         match self.backend {
             Backend::Omarchy => omarchy::io::read_current()
-                .map(|theme| theme.into_system(accessibility))
+                .map(|theme| {
+                    let mut system = theme.into_system(accessibility);
+                    // Hyprland blurs transparent surfaces on its own.
+                    system.window_background = Some(gpui::WindowBackgroundAppearance::Blurred);
+                    system
+                })
                 .unwrap_or_else(|| SystemTheme::fallback(variant)),
             Backend::Kde => kde::io::read_current()
                 .map(|scheme| {
-                    scheme.into_system(
+                    let mut system = scheme.into_system(
                         accessibility,
                         portal_appearance.and_then(|appearance| appearance.accent),
                         portal_appearance.map(|appearance| appearance.variant(variant)),
-                    )
+                    );
+                    // KWin states the blur protocols; X11 compositors do not.
+                    system.window_background =
+                        wayland_session().then_some(gpui::WindowBackgroundAppearance::Blurred);
+                    system
                 })
                 .unwrap_or_else(|| SystemTheme::fallback(variant)),
             Backend::Portal => self.portal_snapshot(variant, portal_appearance, accessibility),

crates/theme/src/source/macos.rs

@@ -121,6 +121,8 @@ impl ThemeSource for MacosSource {
             variant,
             accent: Self::color_to_hsla(&NSColor::controlAccentColor()),
             palette,
+            // macOS blurs what is behind the window natively.
+            window_background: Some(gpui::WindowBackgroundAppearance::Blurred),
             control_radius: Some(gpui::px(CONTROL_RADIUS_PTS)),
             overlay_radius: None,
             sm_radius: None,

crates/theme/src/source/omarchy.rs

@@ -72,6 +72,7 @@ impl OmarchyTheme {
             titlebar_height: None,
             root_font_size: None,
             accessibility,
+            window_background: None,
             source: SourceKind::Omarchy,
         }
     }

crates/theme/src/source/windows.rs

@@ -31,12 +31,12 @@ const TITLEBAR_HEIGHT_PX: f32 = 32.0;
 /// WinUI 11's default body text size, in pixels at 100% scaling.
 const ROOT_FONT_SIZE_PX: f32 = 14.0;
 
-/// The `Personalize` registry values, read once at startup as the fallback
-/// when the WinRT surface is unavailable.
+/// The `Personalize` registry values and the OS build number.
 #[derive(Clone, Copy, Debug, Default)]
 struct RegistrySettings {
     apps_use_light_theme: Option<bool>,
     enable_transparency: Option<bool>,
+    current_build: Option<u32>,
 }
 
 impl RegistrySettings {
@@ -45,6 +45,9 @@ impl RegistrySettings {
             windows_registry::CURRENT_USER
                 .open(r"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize")
         };
+        let current_version = || {
+            windows_registry::LOCAL_MACHINE.open(r"SOFTWARE\Microsoft\Windows NT\CurrentVersion")
+        };
         Self {
             apps_use_light_theme: personalize()
                 .and_then(|key| key.get_u32("AppsUseLightTheme"))
@@ -54,6 +57,10 @@ impl RegistrySettings {
                 .and_then(|key| key.get_u32("EnableTransparency"))
                 .ok()
                 .map(|value| value != 0),
+            current_build: current_version()
+                .and_then(|key| key.get_string("CurrentBuildNumber"))
+                .ok()
+                .and_then(|build| build.parse::<u32>().ok()),
         }
     }
 }
@@ -130,6 +137,17 @@ impl WindowsSource {
                 .unwrap_or(false),
         }
     }
+
+    /// The native backdrop: Mica on Windows 11, acrylic on Windows 10 1809+.
+    fn window_material(&self) -> Option<gpui::WindowBackgroundAppearance> {
+        match self.registry.current_build {
+            // 22621: Windows 11 22H2, where the DWM backdrop types exist.
+            Some(build) if build >= 22621 => Some(gpui::WindowBackgroundAppearance::MicaBackdrop),
+            // 17763: Windows 10 1809, where acrylic blur-behind exists.
+            Some(build) if build >= 17763 => Some(gpui::WindowBackgroundAppearance::Blurred),
+            _ => None,
+        }
+    }
 }
 
 impl ThemeSource for WindowsSource {
@@ -180,6 +198,7 @@ impl ThemeSource for WindowsSource {
             titlebar_height: Some(gpui::px(TITLEBAR_HEIGHT_PX)),
             root_font_size: Some(gpui::px(ROOT_FONT_SIZE_PX * text_scale as f32)),
             accessibility: self.accessibility(),
+            window_background: self.window_material(),
             source: SourceKind::Windows,
         }
     }