persist selected theme to AppState

src/SharpIDE.Godot/Features/IdeSettings/AppState.cs

@@ -13,6 +13,7 @@ public class IdeSettings
     public string? DebuggerExecutablePath { get; set; }
     public bool DebuggerUseSharpDbg { get; set; } = true;
     public float UiScale { get; set; } = 1.0f;
+    public string Theme { get; set; } = "Dark";
 }
 
 public record RecentSln

src/SharpIDE.Godot/Features/Settings/SettingsWindow.cs

@@ -28,6 +28,8 @@ public partial class SettingsWindow : Window
         _uiScaleSpinBox.Value = Singletons.AppState.IdeSettings.UiScale;
         _debuggerFilePathLineEdit.Text = Singletons.AppState.IdeSettings.DebuggerExecutablePath;
         _debuggerUseSharpDbgCheckButton.ButtonPressed = Singletons.AppState.IdeSettings.DebuggerUseSharpDbg;
+        var themeOptionIndex = _themeOptionButton.GetOptionIndexOrNullForString(Singletons.AppState.IdeSettings.Theme);
+        if (themeOptionIndex is not null) _themeOptionButton.Selected = themeOptionIndex.Value;
     }
 
     private void OnUiScaleSpinBoxValueChanged(double value)
@@ -52,6 +54,7 @@ public partial class SettingsWindow : Window
     private void OnThemeItemSelected(long index)
     {
         var selectedTheme = _themeOptionButton.GetItemText((int)index);
+        Singletons.AppState.IdeSettings.Theme = selectedTheme;
         this.SetIdeTheme(selectedTheme);
     }
 }

src/SharpIDE.Godot/NodeExtensions.cs

@@ -87,6 +87,21 @@ public static class NodeExtensions
         }
     }
 
+    extension(OptionButton optionButton)
+    {
+        public int? GetOptionIndexOrNullForString(string optionString)
+        {
+            for (var i = 0; i < optionButton.GetItemCount(); i++)
+            {
+                if (optionButton.GetItemText(i) == optionString)
+                {
+                    return i;
+                }
+            }
+            return null;
+        }
+    }
+
     extension(TreeItem treeItem)
     {
         public T? GetTypedMetadata<T>(int column) where T : RefCounted?