Update css and js for CDN

Author: oscarlevin via GitHub Actions

dist/_static/pretext/css/epub.css

@@ -1,17 +1,48 @@
-window.addEventListener('message', function(event) {
-    if (typeof event.data=='string' && event.data.match(/lti\.frameResize/)) {
-        var edata = JSON.parse(event.data);
+// SPLICE resize handling - https://cssplice.org/
+// Expected message format:
+// {
+//   subject: lti.frameResize',
+//   message_id: (a unique string ID),  // optional - not used
+//   height: ...,
+//   width: ...
+// }
+
+window.addEventListener('message', function (event) {
+    let edata = event.data;
+
+    //MoM sends event.data as a string instead of JSON
+    if (typeof event.data == 'string' && event.data.match(/lti\.frameResize/)) {
+        edata = JSON.parse(event.data);
+    }
+
+    if (edata.subject === "lti.frameResize") {
         if ("frame_id" in edata) {
+            // MoM may send frame_id
+            let el = document.getElementById(edata['frame_id']);
             document.getElementById(edata['frame_id']).style.height = edata.height + 'px';
             if (edata.wrapheight && document.getElementById(edata['frame_id'] + 'wrap')) {
                 document.getElementById(edata['frame_id'] + 'wrap').style.height = edata.wrapheight + 'px';
             }
         } else if ("iframe_resize_id" in edata) {
+            // MoM may send iframe_resize_id
             document.getElementById(edata['iframe_resize_id']).style.height = edata.height + 'px';
+        } else {
+            // No target element specified, so resize the iframe that sent the message
+            // event.source.frameElement is only accessible if the iframe is on the same domain
+            // so loop through iframes to find the one that sent the message
+            const iFrames = document.getElementsByTagName('iframe');
+            for(const iFrame of iFrames) {
+                if(iFrame.contentWindow === event.source) {
+                    if (edata.height) iFrame.height = edata.height;
+                    if (edata.width) iFrame.width = edata.width;
+                    break;
+                }
+            }
         }
     }
-});
+  });
 
-function sendResizeRequest(el) {
+  // Currently only used by My Open Math to request a resize after knowls open
+  function sendResizeRequest(el) {
     el.contentWindow.postMessage("requestResize", "*");
-}
+  }