TEMPORARY: restore style elements removed by hostile sites

apply.js

@@ -7,8 +7,11 @@ var disableAll = false;
 var styleElements = new Map();
 var retiredStyleIds = [];
 var iframeObserver;
+var styleObserverSymbol = Symbol('Stylus.styleObserver');
+var orphanCheckTimer;
 
 initObserver();
+initStyleObserver();
 requestStyles();
 chrome.runtime.onMessage.addListener(applyOnMessage);
 
@@ -134,10 +137,7 @@ function applyStyleState(id, enabled, doc) {
 
 function removeStyle(id, doc) {
   styleElements.delete('stylus-' + id);
-  const el = doc.getElementById('stylus-' + id);
-  if (el) {
-    el.remove();
-  }
+  removeStyleElements([doc.getElementById('stylus-' + id)]);
   if (doc == document && !styleElements.size) {
     iframeObserver.disconnect();
   }
@@ -193,6 +193,24 @@ function applyStyles(styleHash) {
     } else {
       document.addEventListener('DOMContentLoaded', onDOMContentLoaded);
     }
+
+    if (!location.href.startsWith('chrome-extension:')) {
+      const t0 = performance.now();
+      let counter = 0;
+      console.warn(location.href, 'START');
+      const interval = setInterval(() => {
+        counter++;
+        for (const [id, el] of styleElements.entries()) {
+          if (!document.getElementById(id)) {
+            document.documentElement.appendChild(el);
+            console.log(location.href, el);
+          } else if (performance.now() - t0 > 1000) {
+            console.warn(location.href, 'watchdog fired', counter, 'times');
+            clearInterval(interval);
+          }
+        }
+      }, 10);
+    }
   }
 
   if (retiredStyleIds.length) {
@@ -259,6 +277,7 @@ function addDocumentStylesToIFrame(iframe) {
       addStyleElement(el, doc);
     }
   }
+  initStyleObserver(doc);
 }
 
 
@@ -327,16 +346,38 @@ function replaceAll(newStyles, doc) {
 function replaceAllpass2(newStyles, doc) {
   const oldStyles = [...doc.querySelectorAll('STYLE.stylus[id$="-ghost"]')];
   processDynamicIFrames(doc, replaceAllpass2, newStyles);
-  oldStyles.forEach(style => style.remove());
+  removeStyleElements(oldStyles);
+}
+
+
+function removeStyleElements(elements) {
+  if (!elements[0]) {
+    return;
+  }
+  const styleObserver = elements[0].ownerDocument[styleObserverSymbol];
+  if (styleObserver) {
+    styleObserver.disconnect();
+  }
+  for (const el of elements) {
+    el.remove();
+  }
+  if (styleObserver) {
+    styleObserver.start();
+  }
 }
 
 
 // Observe dynamic IFRAMEs being added
 function initObserver() {
-  let orphanCheckTimer;
   const iframesCollection = document.getElementsByTagName('iframe');
 
-  iframeObserver = new MutationObserver(function(mutations) {
+  iframeObserver = Object.assign(new MutationObserver(observer), {
+    start() {
+      this.observe(document, {childList: true, subtree: true});
+    }
+  });
+
+  function observer(mutations) {
     // MutationObserver runs as a microtask so the timer won't fire
     // until all queued mutations are fired
     clearTimeout(orphanCheckTimer);
@@ -355,15 +396,16 @@ function initObserver() {
     // because some same-domain (!) iframes fail to load when their 'contentDocument' is accessed (!)
     // namely gmail's old chat iframe talkgadget.google.com
     setTimeout(process, 0, mutations);
-  });
+  }
 
   function process(mutations) {
-    /* eslint-disable no-var # var is slightly faster and MutationObserver may run a lot */
     for (var m = 0, mutation; (mutation = mutations[m++]);) {
       var added = mutation.addedNodes;
       for (var n = 0, node; (node = added[n++]);) {
         // process only ELEMENT_NODE
-        if (node.nodeType == 1) {
+        if (node.nodeType != 1) {
+          continue;
+        }
         var iframes = node.localName === 'iframe' ? [node] :
           node.children.length && node.getElementsByTagName('iframe');
         for (var i = 0, iframe; (iframe = iframes[i++]);) {
@@ -374,13 +416,57 @@ function initObserver() {
       }
     }
   }
-    /* eslint-enable no-var */
 }
 
-  iframeObserver.start = () => {
-    // subsequent calls are ignored if already started observing
-    iframeObserver.observe(document, {childList: true, subtree: true});
-  };
+
+function initStyleObserver(doc = document) {
+  const observer = Object.assign(new MutationObserver(styleObserver), {
+    counters: new Map(),
+    start() {
+      this.observe(doc.documentElement, {childList: true});
+    }
+  });
+  doc[styleObserverSymbol] = observer;
+  observer.start();
+}
+
+
+function styleObserver(mutations, observer) {
+  //console.log(location.href,
+  //  [].concat.apply([], mutations.map(m => [...m.addedNodes])),
+  //  [].concat.apply([], mutations.map(m => [...m.removedNodes]))
+  //);
+  for (var m = 0, mutation; (mutation = mutations[m++]);) {
+    var removed = mutation.removedNodes;
+    for (var n = 0, node; (node = removed[n++]);) {
+      let id = node.id;
+      var ourElement = styleElements.get(id);
+      if (!ourElement) {
+        for (const [elId, el] of styleElements.entries()) {
+          if (el == node) {
+            node.id = id = elId;
+            ourElement = el;
+            break;
+          }
+        }
+      }
+      if (!ourElement) {
+        continue;
+      }
+      const counter = observer.counters.get(id) || 0;
+      if (counter > 10) {
+        continue;
+      }
+      observer.counters.set(id, counter + 1);
+      if (ourElement.ownerDocument != node.ownerDocument) {
+        ourElement = node.ownerDocument.importNode(ourElement, true);
+      }
+      node.ownerDocument.documentElement.appendChild(ourElement);
+      //console.log('Restoring style', ourElement);
+    }
+  }
+}
+
 
 function orphanCheck() {
   orphanCheckTimer = 0;
@@ -395,12 +481,23 @@ function initObserver() {
   iframeObserver.takeRecords();
   iframeObserver.disconnect();
   iframeObserver = null;
+  document[styleObserverSymbol].disconnect();
+  document[styleObserverSymbol] = null;
+  (function removeStyleObservers(doc) {
+    getDynamicIFrames(doc).forEach(iframe => {
+      const styleObserver = iframe.contentDocument[styleObserverSymbol];
+      if (styleObserver) {
+        styleObserver.disconnect();
+        document[styleObserverSymbol] = null;
+      }
+      removeStyleObservers(iframe.contentDocument);
+    });
+  })(document);
   // we can detach event listeners
   document.removeEventListener('DOMContentLoaded', onDOMContentLoaded);
   // we can't detach chrome.runtime.onMessage because it's no longer connected internally
-
-    // we can destroy global functions in this context to free up memory
-    [
+  // we can destroy our globals in this context to free up memory
+  [ // functions
     'addDocumentStylesToAllIFrames',
     'addDocumentStylesToIFrame',
     'addStyleElement',
@@ -414,14 +511,17 @@ function initObserver() {
     'iframeIsDynamic',
     'iframeIsLoadingSrcDoc',
     'initObserver',
+    'initStyleObserver',
+    'orphanCheck',
     'removeStyle',
     'replaceAll',
     'replaceAllpass2',
     'requestStyles',
-      'retireStyle'
+    'retireStyle',
+    'styleObserver',
+    // variables
+    'styleElements',
+    'iframeObserver',
+    'retiredStyleIds',
   ].forEach(fn => (window[fn] = null));
-
-    // we can destroy global variables
-    styleElements = iframeObserver = retiredStyleIds = null;
-  }
 }