feat: Support for compressed MusicXML files

src.csharp/AlphaTab/Core/TypeHelper.cs

@@ -30,6 +30,11 @@ public static void Add<T>(this IList<T> list, IList<T> newItems)
             }
         }
 
+        public static T Find<T>(this IList<T> list, Func<T, bool> predicate)
+        {
+            return list.FirstOrDefault(predicate);
+        }
+
         public static IList<T> Splice<T>(this IList<T> data, double start, double deleteCount)
         {
             var items = data.GetRange((int) start, (int) deleteCount);

src/importer/MusicXmlImporter.ts

@@ -27,6 +27,8 @@ import { ModelUtils } from '@src/model/ModelUtils';
 import { XmlDocument } from '@src/xml/XmlDocument';
 import { XmlNode, XmlNodeType } from '@src/xml/XmlNode';
 import { IOHelper } from '@src/io/IOHelper';
+import { ZipReader } from '@src/zip/ZipReader';
+import { ZipEntry } from '@src/zip/ZipEntry';
 
 export class MusicXmlImporter extends ScoreImporter {
     private _score!: Score;
@@ -54,7 +56,8 @@ export class MusicXmlImporter extends ScoreImporter {
         this._tieStarts = [];
         this._tieStartIds = new Map<number, boolean>();
         this._slurStarts = new Map<string, Note>();
-        let xml: string = IOHelper.toString(this.data.readAll(), this.settings.importer.encoding);
+
+        let xml: string = this.extractMusicXml();
         let dom: XmlDocument = new XmlDocument();
         try {
             dom.parse(xml);
@@ -73,6 +76,65 @@ export class MusicXmlImporter extends ScoreImporter {
         return this._score;
     }
 
+    extractMusicXml(): string {
+        const zip = new ZipReader(this.data);
+        let entries: ZipEntry[];
+        try {
+            entries = zip.read();
+        } catch (e) {
+            entries = [];
+        }
+
+        // no compressed MusicXML, try raw 
+        if(entries.length === 0) {
+            this.data.reset();
+            return IOHelper.toString(this.data.readAll(), this.settings.importer.encoding);
+        }
+
+        const container = entries.find(e => e.fullName === 'META-INF/container.xml');
+        if (!container) {
+            throw new UnsupportedFormatError('No compressed MusicXML');
+        }
+
+        const containerDom = new XmlDocument();
+        try {
+            containerDom.parse(IOHelper.toString(container.data, this.settings.importer.encoding));
+        } catch (e) {
+            throw new UnsupportedFormatError('Malformed container.xml, could not parse as XML', e as Error);
+        }
+
+        let root: XmlNode | null = containerDom.firstElement;
+        if (!root || root.localName !== "container") {
+            throw new UnsupportedFormatError("Malformed container.xml, root element not 'container'");
+        }
+
+        const rootFiles = root.findChildElement("rootfiles");
+        if(!rootFiles) {
+            throw new UnsupportedFormatError("Malformed container.xml, 'container/rootfiles' not found");
+        }
+
+        let uncompressedFileFullPath:string = "";
+        for(const c of rootFiles.childNodes) {
+            if(c.nodeType == XmlNodeType.Element && c.localName === "rootfile") {
+                // The MusicXML root must be described in the first <rootfile> element.
+                // https://www.w3.org/2021/06/musicxml40/tutorial/compressed-mxl-files/
+                uncompressedFileFullPath = c.getAttribute("full-path");
+                break;
+            }
+        }
+
+        if(!uncompressedFileFullPath) {
+            throw new UnsupportedFormatError("Unsupported compressed MusicXML, missing rootfile");
+        }
+
+        const file = entries.find(e => e.fullName === uncompressedFileFullPath);
+        if(!file) {
+            throw new UnsupportedFormatError(`Malformed container.xml, '${uncompressedFileFullPath}' not contained in zip`);
+        }
+
+        return IOHelper.toString(file.data, this.settings.importer.encoding); 
+    }
+
     private mergePartGroups(): void {
         let anyMerged: boolean = false;
         for (const tracks of this._partGroups.values()) {

test/importer/MusicXmlImporter.test.ts

@@ -94,4 +94,14 @@ describe('MusicXmlImporterTests', () => {
         expect(score.tracks[0].staves[0].bars[0].voices[0].beats[0].chord!.strings[4]).to.equal(3);
         expect(score.tracks[0].staves[0].bars[0].voices[0].beats[0].chord!.strings[5]).to.equal(-1);
     });
+
+    it('compressed', async () => {
+        const score: Score = await MusicXmlImporterTestHelper.testReferenceFile(
+            'test-data/musicxml3/compressed.mxl'
+        );
+
+        expect(score.title).to.equal("Title");
+        expect(score.tracks.length).to.equal(1);
+        expect(score.masterBars.length).to.equal(1);
+    });
 });