Add configurable native glass window backgrounds

apps/desktop/src-tauri/src/settings.rs

@@ -7,6 +7,19 @@ use std::{
     path::{Path, PathBuf},
 };
 
+#[derive(Clone, Copy, Debug, Default, Deserialize, Serialize, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum BackgroundMaterial {
+    Solid,
+    Glass,
+    #[default]
+    Frosted,
+}
+
+fn default_background_opacity() -> u8 {
+    90
+}
+
 const SETTINGS_VERSION: u32 = 2;
 const MAX_SETTINGS_BYTES: u64 = 128 * 1024;
 
@@ -14,6 +27,10 @@ const MAX_SETTINGS_BYTES: u64 = 128 * 1024;
 #[serde(deny_unknown_fields)]
 pub struct Settings {
     pub version: u32,
+    #[serde(default)]
+    pub background_material: BackgroundMaterial,
+    #[serde(default = "default_background_opacity")]
+    pub background_opacity: u8,
     pub roots: Vec<PathBuf>,
     pub cpu_threads: usize,
     /// Managed local Google EmbeddingGemma2 artifacts. Older settings default
@@ -26,6 +43,8 @@ impl Default for Settings {
     fn default() -> Self {
         Self {
             version: SETTINGS_VERSION,
+            background_material: BackgroundMaterial::default(),
+            background_opacity: default_background_opacity(),
             roots: Vec::new(),
             cpu_threads: 2,
             model_directory: None,
@@ -38,6 +57,9 @@ impl Settings {
         if self.version != SETTINGS_VERSION {
             return Err(format!("Unsupported settings version {}", self.version));
         }
+        if !(70..=100).contains(&self.background_opacity) {
+            return Err("Background opacity must be between 70 and 100 percent.".into());
+        }
         if !(1..=8).contains(&self.cpu_threads) {
             return Err("CPU threads must be between 1 and 8.".into());
         }
@@ -229,3 +251,31 @@ mod budget_migration_tests {
         assert_eq!(SettingsStore::load(path).unwrap().value.cpu_threads, 8);
     }
 }
+
+#[cfg(test)]
+mod appearance_tests {
+    use super::*;
+    #[test]
+    fn legacy_defaults_and_saved_appearance_round_trip() {
+        let directory = tempfile::tempdir().unwrap();
+        let path = directory.path().join("settings.json");
+        fs::write(&path, r#"{"version":2,"roots":[],"cpu_threads":2}"#).unwrap();
+        let mut store = SettingsStore::load(path.clone()).unwrap();
+        assert_eq!(store.value.background_material, BackgroundMaterial::Frosted);
+        assert_eq!(store.value.background_opacity, 90);
+        let mut next = store.value.clone();
+        next.background_material = BackgroundMaterial::Glass;
+        next.background_opacity = 70;
+        store.save(next.clone()).unwrap();
+        assert_eq!(SettingsStore::load(path.clone()).unwrap().value, next);
+        let bytes = fs::read(&path).unwrap();
+        for opacity in [0, 69, 101, 255] {
+            let mut invalid = next.clone();
+            invalid.background_opacity = opacity;
+            assert!(store.save(invalid).is_err());
+            assert_eq!(store.value, next);
+            assert_eq!(fs::read(&path).unwrap(), bytes);
+        }
+        assert!(serde_json::from_str::<BackgroundMaterial>("\"other\"").is_err());
+    }
+}