Change the way app settings Apply button works

We were passing a reference to MainController in, and calling a
method on it, which is a little convoluted.  Now the main controller
subscribes to a "settings applied" event, and handles the update with
an event handler.

No change in behavior.

SourceGen/MainController.cs

@@ -453,20 +453,6 @@ namespace SourceGen {
             }
         }
 
-        /// <summary>
-        /// Replaces the contents of the global settings object with the new settings,
-        /// then applies them to the project.
-        /// </summary>
-        /// <param name="settings">New settings.</param>
-        public void SetAppSettings(AppSettings settings) {
-            AppSettings.Global.ReplaceSettings(settings);
-            ApplyAppSettings();
-
-            // We get called whenever Apply or OK is hit in the settings editor, so it's
-            // a pretty good time to save the settings out.
-            SaveAppSettings();
-        }
-
         /// <summary>
         /// Sets the app window's location and size.  This should be called before the window has
         /// finished initialization.
@@ -1519,22 +1505,30 @@ namespace SourceGen {
         }
 
         /// <summary>
-        /// Opens the application settings dialog.  All changes to settings are made directly
-        /// to the AppSettings.Global object.
+        /// Handles Edit &gt; App Settings.
         /// </summary>
         public void EditAppSettings() {
             ShowAppSettings(mMainWin, WpfGui.EditAppSettings.Tab.Unknown,
                 AsmGen.AssemblerInfo.Id.Unknown);
         }
 
+        /// <summary>
+        /// Opens the application settings dialog.  All changes to settings are made directly
+        /// to the AppSettings.Global object.
+        /// </summary>
         public void ShowAppSettings(Window owner, EditAppSettings.Tab initialTab,
                     AsmGen.AssemblerInfo.Id initialAsmId) {
-            // TODO: this can be done in a less-awkward way by subscribing to an event
-            EditAppSettings dlg = new EditAppSettings(owner, mMainWin, this,
-                initialTab, initialAsmId);
+            EditAppSettings dlg = new EditAppSettings(owner, mMainWin, initialTab, initialAsmId);
+            dlg.SettingsApplied += SetAppSettings;      // called when "Apply" is clicked
             dlg.ShowDialog();
+        }
 
-            // The settings code calls SetAppSettings() directly whenever "Apply" is hit.
+        /// <summary>
+        /// Applies settings to the project, and saves them to the settings files.
+        /// </summary>
+        private void SetAppSettings() {
+            ApplyAppSettings();
+            SaveAppSettings();
         }
 
         public void HandleCodeListDoubleClick(int row, int col) {

SourceGen/WpfGui/EditAppSettings.xaml.cs

@@ -37,18 +37,19 @@ namespace SourceGen.WpfGui {
     /// Application settings dialog.
     /// </summary>
     public partial class EditAppSettings : Window, INotifyPropertyChanged {
+        /// <summary>
+        /// Event that the controller can subscribe to if it wants to be notified when the
+        /// "Apply" or "OK" button is hit.
+        /// </summary>
+        public event SettingsAppliedHandler SettingsApplied;
+        public delegate void SettingsAppliedHandler();
+
         /// <summary>
         /// Reference to main window.  Needed for examination of the code list font and
         /// column widths.
         /// </summary>
         private MainWindow mMainWin;
 
-        /// <summary>
-        /// Reference to main controller.  Needed to push settings out when Apply/OK is clicked.
-        /// TODO: use an Event instead?
-        /// </summary>
-        private MainController mMainCtrl;
-
         /// <summary>
         /// Copy of settings that we make changes to.  On "Apply" or "OK", this is pushed
         /// into the global settings object, and applied to the ProjectView.
@@ -103,14 +104,13 @@ namespace SourceGen.WpfGui {
         }
 
 
-        public EditAppSettings(Window owner, MainWindow mainWin, MainController mainCtrl,
-                Tab initialTab, AssemblerInfo.Id initialAsmId) {
+        public EditAppSettings(Window owner, MainWindow mainWin, Tab initialTab,
+                AssemblerInfo.Id initialAsmId) {
             InitializeComponent();
             Owner = owner;
             DataContext = this;
 
             mMainWin = mainWin;
-            mMainCtrl = mainCtrl;
             mInitialTab = initialTab;
             mInitialAsmId = initialAsmId;
 
@@ -204,7 +204,8 @@ namespace SourceGen.WpfGui {
                 // QueryVersions() can sometimes be slow under Win10 (mid 2019), possibly
                 // because of the built-in malware detection, so pop up a wait cursor.
                 Mouse.OverrideCursor = Cursors.Wait;
-                mMainCtrl.SetAppSettings(mSettings);
+                AppSettings.Global.ReplaceSettings(mSettings);
+                OnSettingsApplied();
                 AsmGen.AssemblerVersionCache.QueryVersions();
             } finally {
                 Mouse.OverrideCursor = null;
@@ -213,6 +214,16 @@ namespace SourceGen.WpfGui {
             IsDirty = false;
         }
 
+        /// <summary>
+        /// Raises the "settings applied" event.
+        /// </summary>
+        private void OnSettingsApplied() {
+            SettingsAppliedHandler handler = SettingsApplied;
+            if (handler != null) {
+                handler();
+            }
+        }
+
 
         #region Code View