Optimize applying the theme

- Don't re-apply the theme when opening the configuration or wizard. It's already applied at that time.
- Apply the theme before first Showing the MainWindow. This fixes an issue with the default material theme being shown until the connectors are loaded.

src/Soloplan.WhatsON.GUI/App.xaml.cs

@@ -70,8 +70,6 @@ public void ApplyTheme(bool? isDark = null)
 
     protected override void OnStartup(StartupEventArgs e)
     {
-      base.OnStartup(e);
-
       var configDirArg = e.Args.FirstOrDefault(a => a.ToLower().StartsWith(ConfigDirArgName.ToLower()));
       if (configDirArg != null)
       {
@@ -112,10 +110,17 @@ protected override void OnStartup(StartupEventArgs e)
       this.themeHelper.Initialize(this.handler.VisualSettings?.ColorSettings);
       this.ApplyTheme();
 
+      if (!this.config.OpenMinimized)
+      {
+        this.handler.ShowOrHideWindow();
+      }
+
       Timeline.DesiredFrameRateProperty.OverrideMetadata(typeof(Timeline), new FrameworkPropertyMetadata { DefaultValue = 15 });
 
       this.scheduler.Start();
       ComponentDispatcher.ThreadPreprocessMessage += this.ComponentDispatcherThreadPreprocessMessage;
+
+      base.OnStartup(e);
     }
 
     /// <summary>

src/Soloplan.WhatsON.GUI/Configuration/AboutPage.xaml

@@ -40,8 +40,8 @@
       <TextBlock TextWrapping="Wrap" Text="Configuration:" Margin="20,0,20,10" FontWeight="Bold"/>
 
       <DockPanel Margin="20,0,20,20">
-        <Button Style="{StaticResource MaterialDesignFlatMidBgButton}" Content="{x:Static properties:Resources.Export}" DockPanel.Dock="Right" Click="ExportButtonClick"/>
-        <Button Style="{StaticResource MaterialDesignFlatMidBgButton}" Content="{x:Static properties:Resources.Import}" Margin="10,0,10,0"  DockPanel.Dock="Right" Click="ImportButtonClick"/>
+        <Button Style="{StaticResource MaterialDesignFlatMidBgButton}" Content="{x:Static properties:Resources.Export}" DockPanel.Dock="Right" VerticalAlignment="Center" Click="ExportButtonClick"/>
+        <Button Style="{StaticResource MaterialDesignFlatMidBgButton}" Content="{x:Static properties:Resources.Import}" Margin="10,0,10,0"  DockPanel.Dock="Right" VerticalAlignment="Center" Click="ImportButtonClick"/>
         <TextBox x:Name="ConfigFile" Text="{}{CONFIG_FILE}" IsReadOnly="True"  DockPanel.Dock="Left"/>
       </DockPanel>
 

src/Soloplan.WhatsON.GUI/Configuration/View/ConfigWindow.xaml.cs

@@ -162,7 +162,6 @@ protected override void OnContentRendered(EventArgs e)
       }
 
       this.windowShown = true;
-      ((App)Application.Current).ApplyTheme(this.configurationSource.DarkThemeEnabled);
     }
 
     /// <summary>

src/Soloplan.WhatsON.GUI/Configuration/Wizard/WizardWindow.xaml.cs

@@ -91,8 +91,6 @@ protected override void OnContentRendered(EventArgs e)
       }
 
       this.windowShown = true;
-      var app = (App)Application.Current;
-      app.ApplyTheme(app.IsDarkThemeEnabled);
     }
 
     /// <summary>

src/Soloplan.WhatsON.GUI/TrayHandler.cs

@@ -73,11 +73,6 @@ public TrayHandler(ObservationScheduler scheduler, ApplicationConfiguration conf
       {
         this.VisualSettings = SerializationHelper.Load<MainWindowSettings>(Path.Combine(SerializationHelper.Instance.ConfigFolder, MainWindow.VisualSettingsFile));
       }
-
-      if (!this.configuration.OpenMinimized)
-      {
-        this.ShowOrHideWindow();
-      }
     }
 
     public MainWindowSettings VisualSettings { get; private set; }
@@ -219,7 +214,7 @@ private void OnCloseApplicationClick(object sender, EventArgs e)
     /// <summary>
     /// Handles showing and hiding main window.
     /// </summary>
-    private void ShowOrHideWindow()
+    public void ShowOrHideWindow()
     {
       if (this.MainWindowVisible)
       {