Update the theme instantly, without the need to restart the app

The theme can be updated correctly if the window is closed and reopened.

GH-102

Author: TolikPylypchuk

src/KeyboardSwitch.Settings/App.axaml

@@ -2,6 +2,7 @@
     xmlns="https://github.com/avaloniaui"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:sys="using:System"
+    xmlns:ui="using:FluentAvalonia.Styling"
     xmlns:l="using:KeyboardSwitch.Settings.Localization"
     xmlns:local="using:KeyboardSwitch.Settings"
     x:Class="KeyboardSwitch.Settings.App"
@@ -11,6 +12,9 @@
     </Application.DataTemplates>
 
     <Application.Styles>
+        <!-- This is a placeholder for the theme that's set in App.axaml.cs -->
+        <ui:FluentAvaloniaTheme PreferSystemTheme="True" PreferUserAccentColor="True" />
+
         <Style Selector="TextBlock.Error">
             <Setter Property="Foreground" Value="{DynamicResource SystemFillColorCriticalBrush}" />
             <Setter Property="Margin" Value="10 2" />

src/KeyboardSwitch.Settings/App.axaml.cs

@@ -1,3 +1,4 @@
+using System.Reactive.Linq;
 using System.Reactive.Subjects;
 using System.Reflection;
 
@@ -49,7 +50,10 @@ public override async void OnFrameworkInitializationCompleted()
 
             var mainViewModel = await this.InitializeApp();
 
-            this.desktop.MainWindow = await this.CreateMainWindow(mainViewModel);
+            var mainWindow = this.CreateMainWindow(mainViewModel);
+            await this.SetWindowSizeFromState(mainWindow);
+
+            this.desktop.MainWindow = mainWindow;
             this.desktop.MainWindow.Show();
 
             this.desktop.Exit += this.OnExit;
@@ -84,10 +88,18 @@ private async Task<MainViewModel> InitializeApp()
             var mainViewModel = new MainViewModel(appSettings);
             openExternally.InvokeCommand(mainViewModel.OpenExternally);
 
+            mainViewModel.PreferencesSaved
+                .Select(p => p.AppTheme)
+                .StartWith(appSettings.AppTheme)
+                .DistinctUntilChanged()
+                .ObserveOn(RxApp.MainThreadScheduler)
+                .Subscribe(this.SetTheme);
+
             mainViewModel.PreferencesSaved
                 .Select(p => p.AppThemeVariant)
                 .StartWith(appSettings.AppThemeVariant)
                 .DistinctUntilChanged()
+                .ObserveOn(RxApp.MainThreadScheduler)
                 .Subscribe(this.SetThemeVariant);
 
             return mainViewModel;
@@ -169,22 +181,13 @@ private JsonConfigurationProvider JsonProvider(string directory, string fileName
             Optional = true
         });
 
-    private async Task<MainWindow> CreateMainWindow(MainViewModel viewModel)
+    private MainWindow CreateMainWindow(MainViewModel viewModel)
     {
-        var state = await RxApp.SuspensionHost.ObserveAppState<AppState>().Take(1);
-
         var window = new MainWindow
         {
             ViewModel = viewModel
         };
 
-        if (state.IsInitialized)
-        {
-            window.Width = state.WindowWidth;
-            window.Height = state.WindowHeight;
-            window.WindowState = state.IsWindowMaximized ? WindowState.Maximized : WindowState.Normal;
-        }
-
         var windowStateChanged = window
             .GetObservable(Window.WindowStateProperty)
             .DistinctUntilChanged()
@@ -207,9 +210,21 @@ private async Task<MainWindow> CreateMainWindow(MainViewModel viewModel)
         return window;
     }
 
+    private async Task SetWindowSizeFromState(MainWindow window)
+    {
+        var state = await RxApp.SuspensionHost.ObserveAppState<AppState>().Take(1);
+
+        if (state.IsInitialized)
+        {
+            window.Width = state.WindowWidth;
+            window.Height = state.WindowHeight;
+            window.WindowState = state.IsWindowMaximized ? WindowState.Maximized : WindowState.Normal;
+        }
+    }
+
     private void SetTheme(AppTheme appTheme)
     {
-        this.Styles.Insert(0, appTheme switch
+        this.Styles[0] = appTheme switch
         {
             AppTheme.MacOS => new MacOSTheme(),
             AppTheme.Simple => new SimpleTheme(),
@@ -218,7 +233,23 @@ private void SetTheme(AppTheme appTheme)
                 PreferUserAccentColor = true,
                 PreferSystemTheme = true
             }
-        });
+        };
+
+        if (this.desktop.MainWindow is MainWindow window)
+        {
+            var newMainWindow = this.CreateMainWindow(window.ViewModel!);
+
+            newMainWindow.Width = window.Width;
+            newMainWindow.Height = window.Height;
+            newMainWindow.WindowState = window.WindowState;
+
+            this.desktop.MainWindow = newMainWindow;
+            this.desktop.MainWindow.Show();
+
+            newMainWindow.Position = window.Position;
+
+            window.Close();
+        }
     }
 
     private void SetThemeVariant(AppThemeVariant appThemeVariant)

src/KeyboardSwitch.Settings/Properties/Messages.Designer.cs

@@ -363,9 +363,6 @@
   <data name="SwitchSettings" xml:space="preserve">
     <value>Switch settings:</value>
   </data>
-  <data name="UpdateThemeHint" xml:space="preserve">
-    <value>Theme will be updated after application restart</value>
-  </data>
   <data name="UseXsel" xml:space="preserve">
     <value>Use xsel for clipboard integration</value>
   </data>

src/KeyboardSwitch.Settings/Properties/Messages.resx

@@ -192,14 +192,6 @@
 
                     <TextBlock Text="{l:Translate AppThemeVariant}" Classes="Label" />
                     <ComboBox x:Name="AppThemeVariantComboBox" Classes="FormControl" />
-
-                    <TextBlock
-                        x:Name="UpdateThemeHintTextBlock"
-                        Text="{l:Translate UpdateThemeHint}"
-                        VerticalAlignment="Center"
-                        Margin="10 0 0 0"
-                        IsVisible="False"
-                    />
                 </StackPanel>
 
                 <TextBlock x:Name="PressCountValidationTextBlock" Classes="Error" IsVisible="False" />

src/KeyboardSwitch.Settings/Views/PreferencesView.axaml

@@ -98,12 +98,6 @@ private void BindControls(CompositeDisposable disposables)
 
         this.Bind(this.ViewModel, vm => vm.AppThemeVariant, v => v.AppThemeVariantComboBox.SelectedItem)
             .DisposeWith(disposables);
-
-        this.ViewModel!.WhenAnyValue(vm => vm.AppTheme)
-            .Merge(this.ViewModel!.Save.Select(p => this.ViewModel!.AppTheme))
-            .Select(theme => theme != this.ViewModel!.PreferencesModel.AppTheme)
-            .BindTo(this, v => v.UpdateThemeHintTextBlock.IsVisible)
-            .DisposeWith(disposables);
     }
 
     private void BindValidations(CompositeDisposable disposables)