Patch settings-only bar config changes in place instead of rebuilding every widget

A shell.json write used to reassign the whole layout, and the module
Repeaters recreate every delegate when their array model changes — so
toggling an inline widget setting (battery percentage, clock format,
tray pinning) tore down and rebuilt every widget on every monitor,
closing any open panel along the way. When the layout structure is
unchanged, hand the new settings to the running widgets instead.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

shell/plugins/bar/Bar.qml

@@ -350,10 +350,35 @@ Item {
     position = normalizePosition(config.position)
     setRequestedTransparency(config.transparent === true)
     centerAnchor = Util.canonicalWidgetId(config.centerAnchor || "")
-    layoutConfig = normalizeLayout(config.layout)
+
+    // layoutEntries feeds plain JS arrays to the module Repeaters, and QML
+    // cannot diff those: reassigning layoutConfig rebuilds every widget on
+    // every monitor. When a shell.json write only changed inline widget
+    // settings, patch the live layout and running widgets in place instead.
+    var next = normalizeLayout(config.layout)
+    var delta = BarModel.inlineSettingsDelta(layoutConfig, next)
+    if (delta) {
+      applySettingsDelta(delta)
+      return
+    }
+    layoutConfig = next
     barConfigSerial++
   }
 
+  function applySettingsDelta(delta) {
+    for (var i = 0; i < delta.length; i++) {
+      var change = delta[i]
+      layoutConfig[change.region][change.index] = change.entry
+      var settings = entrySettings(change.entry)
+      for (var s = 0; s < moduleSlots.length; s++) {
+        var slot = moduleSlots[s]
+        if (!slot || slot.region !== change.region || slot.moduleName !== entryId(change.entry)) continue
+        var item = slot.activeItem
+        if (item && "settings" in item) item.settings = settings
+      }
+    }
+  }
+
   onBarConfigChanged: applyBarConfig()
 
   function layoutEntries(region) {

shell/plugins/bar/BarModel.js

@@ -65,6 +65,42 @@ function entriesAfter(entries, name) {
   return index === -1 ? [] : entries.slice(index + 1)
 }
 
+// A shell.json write that only changes inline widget settings (the battery
+// percentage toggle, a clock format change) must not rebuild the bar.
+// Compare two normalized layouts: when the structure is unchanged — same
+// entry ids in the same order per region — return the settings-only changes
+// as {region, index, entry}. Return null when the change is structural, or
+// touches an entry a live settings push cannot safely reach: custom modules
+// read their entry directly rather than an injected settings property, and
+// a duplicated id makes the push ambiguous.
+function inlineSettingsDelta(current, next) {
+  if (!isPlainObject(current) || !isPlainObject(next)) return null
+  var regions = ["left", "center", "right"]
+  var counts = {}
+  for (var r = 0; r < regions.length; r++) {
+    var entries = Array.isArray(next[regions[r]]) ? next[regions[r]] : []
+    for (var i = 0; i < entries.length; i++) {
+      var id = entryId(entries[i])
+      counts[id] = (counts[id] || 0) + 1
+    }
+  }
+  var changes = []
+  for (var s = 0; s < regions.length; s++) {
+    var region = regions[s]
+    var a = Array.isArray(current[region]) ? current[region] : []
+    var b = Array.isArray(next[region]) ? next[region] : []
+    if (a.length !== b.length) return null
+    for (var j = 0; j < a.length; j++) {
+      if (entryId(a[j]) !== entryId(b[j])) return null
+      if (JSON.stringify(a[j]) === JSON.stringify(b[j])) continue
+      if (customModuleType(a[j]) || customModuleType(b[j])) return null
+      if (counts[entryId(b[j])] > 1) return null
+      changes.push({ region: region, index: j, entry: b[j] })
+    }
+  }
+  return changes
+}
+
 function expandPath(value, home) {
   var path = String(value || "")
   if (path === "") return ""
@@ -162,6 +198,7 @@ if (typeof module !== "undefined") {
     entryIndex: entryIndex,
     entriesBefore: entriesBefore,
     entriesAfter: entriesAfter,
+    inlineSettingsDelta: inlineSettingsDelta,
     expandPath: expandPath,
     customModuleSafeName: customModuleSafeName,
     customModuleType: customModuleType,