Add support for async plugins

src/DesktopMagic/BuiltInPlugins/WeatherPlugin.cs

@@ -11,7 +11,7 @@ using System.Threading.Tasks;
 
 namespace DesktopMagic.BuiltInPlugins;
 
-public class WeatherPlugin : Plugin
+public class WeatherPlugin : AsyncPlugin
 {
     [Setting("city-name", "City Name")]
     private readonly TextBox cityInput = new TextBox("Berlin");
@@ -74,12 +74,12 @@ public class WeatherPlugin : Plugin
         };
     }
 
-    public override Bitmap Main()
+    public override async Task<Bitmap?> MainAsync()
     {
         // Periodic background update
         if (!isLoading && cachedLat != null && cachedLon != null)
         {
-            _ = UpdateWeatherOnly(cachedLat, cachedLon);
+            await UpdateWeatherOnly(cachedLat, cachedLon);
         }
 
         Bitmap bmp = new Bitmap(1200, 800);

src/DesktopMagic/GlobalSuppressions.cs

@@ -12,3 +12,4 @@ using System.Diagnostics.CodeAnalysis;
 [assembly: SuppressMessage("Major Code Smell", "S3885:\"Assembly.Load\" should be used", Justification = "Assembly.Load does not load dependencies", Scope = "member", Target = "~M:DesktopMagic.PluginWindow.ExecuteSource")]
 [assembly: SuppressMessage("Minor Code Smell", "S2325:Methods and properties that don't access instance data should be static", Justification = "<Pending>", Scope = "member", Target = "~M:DesktopMagic.MainWindow.OpenPluginsFolderButton_Click(System.Object,System.Windows.RoutedEventArgs)")]
 [assembly: SuppressMessage("Minor Code Smell", "S2325:Methods and properties that don't access instance data should be static", Justification = "<Pending>", Scope = "member", Target = "~M:DesktopMagic.MainWindow.ScrollViewer_PreviewMouseWheel(System.Object,System.Windows.Input.MouseWheelEventArgs)")]
+[assembly: SuppressMessage("Major Code Smell", "S6966:Awaitable method should be used", Justification = "Breaks stuff", Scope = "member", Target = "~M:DesktopMagic.PluginWindow.UpdateTimer_Elapsed(System.Object,System.Timers.ElapsedEventArgs)")]

src/DesktopMagic/Plugins/PluginWindow.xaml.cs

@@ -401,13 +401,22 @@ public partial class PluginWindow : Window, IPluginWindow
         }
     }
 
-    private void UpdateTimer_Elapsed(object? sender, ElapsedEventArgs? e)
+    private async void UpdateTimer_Elapsed(object? sender, ElapsedEventArgs? e)
     {
         try
         {
             if (IsRunning && pluginClassInstance is not null)
             {
-                Bitmap? result = pluginClassInstance.Main();
+                Bitmap? result;
+
+                if (pluginClassInstance is AsyncPlugin asyncPlugin)
+                {
+                    result = await asyncPlugin.MainAsync();
+                }
+                else
+                {
+                    result = pluginClassInstance.Main();
+                }
 
                 if (pluginClassInstance.UpdateInterval > 0)
                 {

src/DesktopMagicPluginAPI/AsyncPlugin.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Drawing;
+using System.Threading.Tasks;
+
+namespace DesktopMagic.Api;
+
+/// <summary>
+/// Provides an abstract base class for plugins that execute asynchronously. Derive from this class to implement plugins
+/// whose main logic runs in a non-blocking manner using asynchronous operations.
+/// </summary>
+/// <remarks>AsyncPlugin is intended for scenarios where plugin execution should not block the calling thread.
+/// Override the MainAsync method to implement asynchronous plugin behavior. The synchronous Main method is sealed and
+/// obsolete; it cannot be used for execution and will always throw an exception. Use MainAsync for all plugin logic.
+/// The MainAsync method is typically invoked when the UpdateInterval elapses, allowing periodic asynchronous
+/// execution.</remarks>
+public abstract class AsyncPlugin : Plugin
+{
+    /// <summary>
+    /// Occurs when the <see cref="Plugin.UpdateInterval"/> elapses.
+    /// </summary>
+    /// <returns></returns>
+    public abstract Task<Bitmap?> MainAsync();
+
+    /// <summary>
+    /// This method should not be called directly! Override and use <see cref="MainAsync"/> for asynchronous plugin operations.
+    /// </summary>
+    /// <remarks>This method only exists to fulfill base class requirements.</remarks>
+    /// <returns>Calling it will always result in an <see cref="InvalidOperationException"/>.</returns>
+    /// <exception cref="InvalidOperationException">Thrown if this method is called directly. Use MainAsync for plugin execution instead.</exception>
+    public sealed override Bitmap? Main()
+    {
+        throw new InvalidOperationException($"AsyncPlugin.Main() should not be called directly. Override {nameof(MainAsync)} instead.");
+    }
+}