Uncompress drawio XML for better chainpad patches

bower.json

@@ -49,7 +49,9 @@
     "requirejs-plugins": "^1.0.3",
     "dragula.js": "3.7.2",
     "MathJax": "3.0.5",
-    "drawio": "jgraph/drawio#v20.8.18"
+    "drawio": "jgraph/drawio#v20.8.18",
+    "js-base64": "^3.7.5",
+    "pako": "^2.1.0"
   },
   "resolutions": {
     "bootstrap": "^v4.0.0",

www/drawio/empty.drawio

@@ -1 +0,0 @@
-<mxfile host="app.diagrams.net" modified="2023-02-09T14:31:26.715Z" agent="5.0 (X11)" version="20.8.3" etag="vZrRUdoCIbYwi7awANB8" type="device"><diagram id="B2HR0nVHLojD-jhrMkZj" name="Seite-1">dZFNE4IgEIZ/DXeFvjyb1aWTh86MbMIMug7SaP36dICMsU4sz77vLrsQljfj2fBOXlGAJjQRI2FHQmmaZMl0zOTpyGGzdaA2SnjRAkr1guD09KEE9JHQImqruhhW2LZQ2YhxY3CIZXfUcdeO17ACZcX1mt6UsNJPQfcLv4CqZeic7jKXaXgQ+0l6yQUOX4gVhOUG0bqoGXPQ8/LCXpzv9Cf7eZiB1v4wTMFSe7pEP8SKNw==</diagram></mxfile>

www/drawio/inner.js

@@ -2,26 +2,36 @@
 define([
     '/common/sframe-app-framework.js',
     '/customize/messages.js', // translation keys
-    'text!/drawio/empty.drawio',
+    '/bower_components/pako/dist/pako.min.js',
+    '/bower_components/js-base64/base64.js',
     'less!/drawio/app.less',
     'css!/drawio/drawio.css',
 ], function (
     Framework,
     Messages,
-    emptyDrawioXml) {
+    pako,
+    base64) {
 
+    console.log('XXX base64', base64);
 
     // This is the main initialization loop
     var onFrameworkReady = function (framework) {
         const drawioFrame = document.querySelector('#cp-app-drawio-content');
-        let lastContent = emptyDrawioXml;
+        let lastContent = '';
+        let drawIoInitalized = false;
 
         const postMessageToDrawio = function(msg) {
+            if (!drawIoInitalized) {
+                return;
+            }
+
             console.log('XXX postMessageToDrawio', msg);
             drawioFrame.contentWindow.postMessage(JSON.stringify(msg), '*');
         };
 
         const onDrawioInit = function(data) {
+            drawIoInitalized = true;
+
             postMessageToDrawio({
                 action: 'load',
                 xml: lastContent,
@@ -30,6 +40,7 @@ define([
         };
 
         const onDrawioChange = function(newXml) {
+            newXml = decompressDrawioXml(newXml);
             if (lastContent != newXml) {
                 lastContent = newXml;
                 framework.localChange();
@@ -71,7 +82,18 @@ define([
         // starting the CryptPad framework
         framework.start();
 
-        drawioFrame.src = '/bower_components/drawio/src/main/webapp/index.html?pages=0&dev=1&stealth=1&embed=1&drafts=0&noSaveBtn=1&modified=unsavedChanges&proto=json';
+        drawioFrame.src = '/bower_components/drawio/src/main/webapp/index.html?'
+            + new URLSearchParams({
+                // pages: 0,
+                dev: 1,
+                test: 1,
+                stealth: 1,
+                embed: 1,
+                drafts: 0,
+                noSaveBtn: 1,
+                modified: 'unsavedChanges',
+                proto: 'json',
+            });
 
         window.addEventListener("message", (event) => {
             if (event.source == drawioFrame.contentWindow) {
@@ -86,6 +108,40 @@ define([
         }, false);
     };
 
+    // As described here: https://drawio-app.com/extracting-the-xml-from-mxfiles/
+    let decompressDrawioXml = function(xmlDocStr) {
+        const TEXT_NODE = 3;
+
+        const parser = new DOMParser();
+        const doc = parser.parseFromString(xmlDocStr, "application/xml");
+
+        doc.firstChild.removeAttribute('modified');
+        doc.firstChild.removeAttribute('agent');
+        doc.firstChild.removeAttribute('etag');
+
+        const errorNode = doc.querySelector("parsererror");
+        if (errorNode) {
+            console.error("error while parsing", errorNode);
+            return xmlStr;
+        }
+
+        const diagrams = doc.querySelectorAll('diagram');
+
+        diagrams.forEach((diagram) => {
+            if (diagram.firstChild && diagram.firstChild.nodeType == TEXT_NODE)  {
+                const innerText = diagram.firstChild.nodeValue;
+                const bin = base64.toUint8Array(innerText);
+                const xmlUrlStr = pako.inflateRaw(bin, {to: 'string'});
+                const xmlStr = decodeURIComponent(xmlUrlStr);
+                const diagramDoc = parser.parseFromString(xmlStr, "application/xml");
+                diagram.replaceChild(diagramDoc.firstChild, diagram.firstChild);
+            }
+        });
+
+
+        return new XMLSerializer().serializeToString(doc);
+    }
+
     // Framework initialization
     Framework.create({
         toolbarContainer: '#cme_toolbox',