add multi-resolution icons to AppImage

Builders/LinuxBuilder.cs

@@ -34,14 +34,40 @@ public override Uploader CreateUploader()
             return new LinuxVelopackUploader(app_name, os_name, RuntimeIdentifier, RuntimeIdentifier, extraArgs: extra_args, stagingPath: stagingTarget);
         }
 
+        // https://learn.microsoft.com/en-us/dotnet/standard/io/how-to-copy-directories
+        static void CopyDirectory(string sourceDir, string destinationDir, bool recursive)
+        {
+            var dir = new DirectoryInfo(sourceDir);
+
+            if (!dir.Exists)
+                throw new DirectoryNotFoundException($"Source directory not found: {dir.FullName}");
+
+            DirectoryInfo[] dirs = dir.GetDirectories();
+
+            Directory.CreateDirectory(destinationDir);
+
+            foreach (FileInfo file in dir.GetFiles())
+            {
+                string targetFilePath = Path.Combine(destinationDir, file.Name);
+                file.CopyTo(targetFilePath);
+            }
+
+            if (recursive)
+            {
+                foreach (DirectoryInfo subDir in dirs)
+                {
+                    string newDestinationDir = Path.Combine(destinationDir, subDir.Name);
+                    CopyDirectory(subDir.FullName, newDestinationDir, true);
+                }
+            }
+        }
+
         public override void Build()
         {
             if (Directory.Exists(stagingTarget))
                 Directory.Delete(stagingTarget, true);
-            Directory.CreateDirectory(stagingTarget);
 
-            foreach (var file in Directory.GetFiles(Path.Combine(Program.TemplatesPath, app_dir)))
-                new FileInfo(file).CopyTo(Path.Combine(stagingTarget, Path.GetFileName(file)));
+            CopyDirectory(Path.Combine(Program.TemplatesPath, app_dir), stagingTarget, true);
 
             Program.RunCommand("chmod", $"+x {stagingTarget}/AppRun");
 

templates/osu!.AppDir/osu!.desktop

@@ -4,7 +4,7 @@ Version=1.5
 Type=Application
 Name=osu!
 Comment=A free-to-win rhythm game. Rhythm is just a *click* away!
-Icon=osu!
+Icon=osu
 Exec=osu! %u
 Terminal=false
 MimeType=application/x-osu-beatmap-archive;application/x-osu-skin-archive;application/x-osu-beatmap;application/x-osu-storyboard;application/x-osu-replay;x-scheme-handler/osu;