refactor(core): share dropdown helpers and refresh Panel on focus

Extract WithNoneOption / ResolveDropdownValue / NormalizeDropdownSelection
plus the NoneDropdownOption constant into EditorUtils so the three
package-dropdown call sites (SettingsUIBuilder, BootstrapEditorUI,
PanelUI) no longer each reimplement the same sentinel / fallback /
clear-on-None logic.

Additionally override Panel.OnFocus to rebuild its content when the
window regains focus, so the Package dropdown reflects renames made
in the AssetBundle Collector window without having to close and
reopen the Panel. Skipped while a build is in progress to avoid
losing BuildManager state and the log view contents.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: JasonXuDeveloper - 傑 <jason@xgamedev.net>

Author: JasonXuDeveloper

UnityProject/Packages/com.jasonxudeveloper.jengine.core/Editor/CustomEditor/Panel.cs

@@ -73,6 +73,20 @@ private void CreateGUI()
             CreateDefaultGUI();
         }
 
+        /// <summary>
+        /// Rebuilds the panel when it regains focus so dropdown choices (e.g. YooAsset
+        /// packages, hot scenes) reflect changes made in other editor windows. Skipped mid-build
+        /// to avoid losing <see cref="BuildManager"/> state or the log view contents.
+        /// </summary>
+        private void OnFocus()
+        {
+            if (_root == null) return;
+            if (_buildManager != null && _buildManager.IsBuilding) return;
+
+            _root.Clear();
+            CreateGUI();
+        }
+
         private void CreateDefaultGUI()
         {
             // Load stylesheets - Panel first, then Common to override

UnityProject/Packages/com.jasonxudeveloper.jengine.core/Editor/CustomEditor/SettingsUIBuilder.cs

@@ -46,26 +46,19 @@ public static VisualElement CreatePackageSettingsGroup(Settings settings)
             // Package Name field (dropdown or text field based on useDropdown)
             var packageNameRow = EditorUIUtils.CreateFormRow("Package");
 
-            // Use PopupField for Panel (with available packages). Prepend a "None" sentinel so
-            // the dropdown always has >=2 entries and renamed/missing packages surface as "None"
-            // instead of silently desyncing with the serialized value.
-            const string noneOption = "None";
-            var packageOptions = new List<string> { noneOption };
-            packageOptions.AddRange(EditorUtils.GetAvailableYooAssetPackages());
-            var currentPackage = string.IsNullOrEmpty(settings.packageName) ||
-                                 !packageOptions.Contains(settings.packageName)
-                ? noneOption
-                : settings.packageName;
+            // Prepend a "None" sentinel so renamed/missing packages surface as "None" instead of
+            // silently desyncing with the serialized value.
+            var packageOptions = EditorUtils.WithNoneOption(EditorUtils.GetAvailableYooAssetPackages());
             var packageNameField = new PopupField<string>()
             {
                 choices = packageOptions,
-                value = currentPackage
+                value = EditorUtils.ResolveDropdownValue(settings.packageName, packageOptions)
             };
             packageNameField.AddToClassList("form-control");
             EditorUIUtils.MakeTextResponsive(packageNameField);
             packageNameField.RegisterValueChangedCallback(evt =>
             {
-                settings.packageName = evt.newValue == noneOption ? string.Empty : evt.newValue;
+                settings.packageName = EditorUtils.NormalizeDropdownSelection(evt.newValue);
                 settings.Save();
             });
             packageNameRow.Add(packageNameField);

UnityProject/Packages/com.jasonxudeveloper.jengine.core/Editor/EditorUtils.cs

@@ -36,6 +36,45 @@ namespace JEngine.Core.Editor
 {
     public static class EditorUtils
     {
+        /// <summary>
+        /// Sentinel shown in dropdowns when the stored value is missing or no longer in the
+        /// available choices (e.g. a YooAsset package was renamed). Guarantees >=2 entries and
+        /// gives the user an explicit "clear" option.
+        /// </summary>
+        public const string NoneDropdownOption = "None";
+
+        /// <summary>
+        /// Returns a new list with <see cref="NoneDropdownOption"/> prepended to the given
+        /// choices. Safe to call with a null choices list.
+        /// </summary>
+        public static List<string> WithNoneOption(IList<string> choices)
+        {
+            var options = new List<string> { NoneDropdownOption };
+            if (choices != null) options.AddRange(choices);
+            return options;
+        }
+
+        /// <summary>
+        /// Returns the value that should be displayed in a dropdown. Falls back to
+        /// <see cref="NoneDropdownOption"/> when the stored value is empty or no longer present
+        /// in the current options.
+        /// </summary>
+        public static string ResolveDropdownValue(string storedValue, List<string> options)
+        {
+            return string.IsNullOrEmpty(storedValue) || options == null || !options.Contains(storedValue)
+                ? NoneDropdownOption
+                : storedValue;
+        }
+
+        /// <summary>
+        /// Converts a dropdown selection into the value to persist. The sentinel
+        /// <see cref="NoneDropdownOption"/> is mapped to an empty string.
+        /// </summary>
+        public static string NormalizeDropdownSelection(string value)
+        {
+            return value == NoneDropdownOption ? string.Empty : value;
+        }
+
         public static List<string> GetAvailableYooAssetPackages()
         {
             var packages = new List<string>();