locale: fix locale override persisting even when not explicitly set

quickshell/Common/I18n.qml

@@ -8,7 +8,9 @@ import Quickshell.Io
 Singleton {
     id: root
 
-    readonly property string _rawLocale: SettingsData.locale === "" ? Qt.locale().name : SettingsData.locale
+    property string _resolvedLocale: "en"
+
+    readonly property string _rawLocale: SessionData.locale === "" ? Qt.locale().name : SessionData.locale
     readonly property string _lang: _rawLocale.split(/[_-]/)[0]
     readonly property var _candidates: {
         const fullUnderscore = _rawLocale;
@@ -49,22 +51,21 @@ Singleton {
             try {
                 root.translations = JSON.parse(text());
                 root.translationsLoaded = true;
-                console.info(`I18n: Loaded translations for '${SettingsData.locale}' (${Object.keys(root.translations).length} contexts)`);
+                console.info(`I18n: Loaded translations for '${root._resolvedLocale}' (${Object.keys(root.translations).length} contexts)`);
             } catch (e) {
-                console.warn(`I18n: Error parsing '${SettingsData.locale}':`, e, "- falling back to English");
+                console.warn(`I18n: Error parsing '${root._resolvedLocale}':`, e, "- falling back to English");
                 root._fallbackToEnglish();
             }
         }
 
         onLoadFailed: error => {
-            console.warn(`I18n: Failed to load '${SettingsData.locale}' (${error}), ` + "falling back to English");
+            console.warn(`I18n: Failed to load '${root._resolvedLocale}' (${error}), ` + "falling back to English");
             root._fallbackToEnglish();
         }
     }
 
-    // for replacing Qt.locale()
     function locale() {
-        return presentLocales[SettingsData.locale] ?? presentLocales["en"];
+        return presentLocales[_resolvedLocale] ?? presentLocales["en"];
     }
 
     function _loadPresentLocales() {
@@ -83,16 +84,18 @@ Singleton {
     function _pickTranslation() {
         for (let i = 0; i < _candidates.length; i++) {
             const cand = _candidates[i];
-            if (presentLocales[cand] !== undefined) {
-                SettingsData.set("locale", cand);
-                return;
-            }
+            if (presentLocales[cand] === undefined) continue;
+            _resolvedLocale = cand;
+            useLocale(cand, cand.startsWith("en") ? "" : translationsFolder + "/" + cand + ".json");
+            return;
         }
 
+        _resolvedLocale = "en";
         _fallbackToEnglish();
     }
 
     function useLocale(localeTag, fileUrl) {
+        _resolvedLocale = localeTag || "en";
         _selectedPath = fileUrl;
         translationsLoaded = false;
         translations = ({});

quickshell/Common/SessionData.qml

@@ -21,7 +21,9 @@ Singleton {
     property bool _isReadOnly: false
     property bool _hasUnsavedChanges: false
     property var _loadedSessionSnapshot: null
-    readonly property var _hooks: ({})
+    readonly property var _hooks: ({
+        "updateLocale": updateLocale
+    })
     readonly property string _stateUrl: StandardPaths.writableLocation(StandardPaths.GenericStateLocation)
     readonly property string _stateDir: Paths.strip(_stateUrl)
 
@@ -126,6 +128,8 @@ Singleton {
     property var hiddenOutputDeviceNames: []
     property var hiddenInputDeviceNames: []
 
+    property string locale: ""
+
     property string launcherLastMode: "all"
     property string appDrawerLastMode: "apps"
     property string niriOverviewLastMode: "apps"
@@ -1104,6 +1108,14 @@ Singleton {
         saveSettings();
     }
 
+    function updateLocale() {
+        if (!locale) {
+            I18n._pickTranslation();
+            return;
+        }
+        I18n.useLocale(locale, locale.startsWith("en") ? "" : I18n.folder + "/" + locale + ".json");
+    }
+
     function setLauncherLastMode(mode) {
         launcherLastMode = mode;
         saveSettings();

quickshell/Common/SettingsData.qml

@@ -149,7 +149,6 @@ Singleton {
     property int mangoLayoutRadiusOverride: -1
     property int mangoLayoutBorderSize: -1
 
-    property string locale: ""
     property bool use24HourClock: true
     property bool showSeconds: false
     property bool padHours12Hour: false
@@ -1131,10 +1130,6 @@ Singleton {
         Quickshell.execDetached(["sh", "-lc", script]);
     }
 
-    function updateLocale() {
-        I18n.useLocale(locale, locale.startsWith("en") ? "" : I18n.folder + "/" + locale + ".json");
-    }
-
     readonly property var _hooks: ({
             "applyStoredTheme": applyStoredTheme,
             "regenSystemThemes": regenSystemThemes,
@@ -1142,7 +1137,6 @@ Singleton {
             "applyStoredIconTheme": applyStoredIconTheme,
             "updateBarConfigs": updateBarConfigs,
             "updateCompositorCursor": updateCompositorCursor,
-            "updateLocale": updateLocale,
         })
 
     function set(key, value) {
@@ -2646,7 +2640,6 @@ Singleton {
                 _hasLoaded = true;
                 applyStoredTheme();
                 updateCompositorCursor();
-                updateLocale();
             } catch (e) {
                 _parseError = true;
                 const msg = e.message;

quickshell/Common/settings/SessionSpec.js

@@ -79,6 +79,8 @@ var SPEC = {
     hiddenOutputDeviceNames: { def: [] },
     hiddenInputDeviceNames: { def: [] },
 
+    locale: { def: "", onChange: "updateLocale" },
+
     launcherLastMode: { def: "all" },
     appDrawerLastMode: { def: "apps" },
     niriOverviewLastMode: { def: "apps" }

quickshell/Common/settings/SettingsSpec.js

@@ -32,7 +32,6 @@ var SPEC = {
     mangoLayoutRadiusOverride: { def: -1, onChange: "updateCompositorLayout" },
     mangoLayoutBorderSize: { def: -1, onChange: "updateCompositorLayout" },
 
-    locale: { def: "", onChange: "updateLocale" },
     use24HourClock: { def: true },
     showSeconds: { def: false },
     padHours12Hour: { def: false },

quickshell/Modules/Settings/LocaleTab.qml

@@ -5,7 +5,9 @@ import qs.Widgets
 import qs.Modules.Settings.Widgets
 
 Item {
-    id: root
+    id: localeTab
+
+    readonly property string _systemDefaultLabel: I18n.tr("System Default")
 
     function capitalizeNativeLanguageName(localeCode) {
         if (I18n.presentLocales[localeCode] == undefined) {
@@ -15,6 +17,11 @@ Item {
         return nativeName[0].toUpperCase() + nativeName.slice(1);
     }
 
+    function _displayValue() {
+        if (!SessionData.locale) return _systemDefaultLabel;
+        return capitalizeNativeLanguageName(SessionData.locale);
+    }
+
     DankFlickable {
         anchors.fill: parent
         clip: true
@@ -41,17 +48,21 @@ Item {
                     settingKey: "locale"
                     text: I18n.tr("Current Locale")
                     description: I18n.tr("Change the locale used by the DMS interface.")
-                    options: Object.keys(I18n.presentLocales).map(root.capitalizeNativeLanguageName)
+                    options: [localeTab._systemDefaultLabel].concat(Object.keys(I18n.presentLocales).map(localeTab.capitalizeNativeLanguageName))
                     enableFuzzySearch: true
 
                     Component.onCompleted: {
-                        currentValue = root.capitalizeNativeLanguageName(SettingsData.locale);
+                        currentValue = localeTab._displayValue();
                     }
 
                     onValueChanged: value => {
+                        if (value === localeTab._systemDefaultLabel) {
+                            SessionData.set("locale", "");
+                            return;
+                        }
                         for (let code of Object.keys(I18n.presentLocales)) {
-                            if (root.capitalizeNativeLanguageName(code) === value) {
-                                SettingsData.set("locale", code);
+                            if (localeTab.capitalizeNativeLanguageName(code) === value) {
+                                SessionData.set("locale", code);
                                 return;
                             }
                         }