Issue 5438 - Observer DOM changes to reapply filters.

chrome/content/elemHideEmulation.js

Index: chrome/content/elemHideEmulation.js
===================================================================
--- a/chrome/content/elemHideEmulation.js
+++ b/chrome/content/elemHideEmulation.js
@@ -152,26 +152,27 @@
   }
   styles.sort();
   return {
     style: styles.join(" "),
     subSelectors: splitSelector(rule.selectorText)
   };
 }
 
-function* evaluate(chain, index, prefix, subtree, styles)
+function* evaluate(chain, index, prefix, subtree, styles, map)
 {
   if (index >= chain.length)
   {
     yield prefix;
     return;
   }
   for (let [selector, element] of
-       chain[index].getSelectors(prefix, subtree, styles))
-    yield* evaluate(chain, index + 1, selector, element, styles);
+       chain[index].getSelectors(prefix, subtree, styles,
+                                 chain.slice(index), map))
+    yield* evaluate(chain, index + 1, selector, element, styles, map);
 }
 
 function PlainSelector(selector)
 {
   this._selector = selector;
 }
 
 PlainSelector.prototype = {
@@ -199,36 +200,43 @@
 HasSelector.prototype = {
   requiresHiding: true,
 
   get dependsOnStyles()
   {
     return this._innerSelectors.some(selector => selector.dependsOnStyles);
   },
 
-  *getSelectors(prefix, subtree, styles)
+  *getSelectors(prefix, subtree, styles, chain, map)
   {
-    for (let element of this.getElements(prefix, subtree, styles))
+    for (let element of this.getElements(prefix, subtree, styles, chain, map))
       yield [makeSelector(element, ""), element];
   },
 
   /**
    * Generator function returning selected elements.
    * @param {string} prefix the prefix for the selector.
    * @param {Node} subtree the subtree we work on.
    * @param {StringifiedStyle[]} styles the stringified style objects.
+   * @param {Array} chain the chain of selectors including this.
+   * @param {WeakMap} map of the elements and chain for re-evaluation.
    */
-  *getElements(prefix, subtree, styles)
+  *getElements(prefix, subtree, styles, chain, map)
   {
     let actualPrefix = (!prefix || incompletePrefixRegexp.test(prefix)) ?
         prefix + "*" : prefix;
     let elements = subtree.querySelectorAll(actualPrefix);
     for (let element of elements)
     {
-      let iter = evaluate(this._innerSelectors, 0, "", element, styles);
+      let e = map.get(element);
+      if (e == undefined)
+        map.set(element, [chain]);
+      else
+        e.push(chain);
+      let iter = evaluate(this._innerSelectors, 0, "", element, styles, map);
       for (let selector of iter)
       {
         if (relativeSelector.test(selector))
           selector = ":scope" + selector;
         if (element.querySelector(selector))
           yield element;
       }
     }
@@ -238,23 +246,24 @@
 function ContainsSelector(textContent)
 {
   this._text = textContent;
 }
 
 ContainsSelector.prototype = {
   requiresHiding: true,
 
-  *getSelectors(prefix, subtree, stylesheet)
+  *getSelectors(prefix, subtree, stylesheet, chain, map)
   {
-    for (let element of this.getElements(prefix, subtree, stylesheet))
+    for (let element of this.getElements(prefix, subtree, stylesheet,
+                                         chain, map))
       yield [makeSelector(element, ""), subtree];
   },
 
-  *getElements(prefix, subtree, stylesheet)
+  *getElements(prefix, subtree, stylesheet, chain, map)
   {
     let actualPrefix = (!prefix || incompletePrefixRegexp.test(prefix)) ?
         prefix + "*" : prefix;
     let elements = subtree.querySelectorAll(actualPrefix);
     for (let element of elements)
       if (element.textContent.includes(this._text))
         yield element;
   }
@@ -305,23 +314,30 @@
 
   *getSelectors(prefix, subtree, styles)
   {
     for (let selector of this.findPropsSelectors(styles, prefix, this._regexp))
       yield [selector, subtree];
   }
 };
 
+function isSelectorHidingOnlyPattern(pattern)
+{
+  return pattern.selectors.some(s => s.preferHideWithSelector) &&
+    !pattern.selectors.some(s => s.requiresHiding);
+}
+
 function ElemHideEmulation(window, getFiltersFunc, addSelectorsFunc,
                            hideElemsFunc)
 {
   this.window = window;
   this.getFiltersFunc = getFiltersFunc;
   this.addSelectorsFunc = addSelectorsFunc;
   this.hideElemsFunc = hideElemsFunc;
+  this.observer = new window.MutationObserver(this.observe.bind(this));
 }
 
 ElemHideEmulation.prototype = {
   isSameOrigin(stylesheet)
   {
     try
     {
       return new URL(stylesheet.href).origin == this.window.location.origin;
@@ -398,39 +414,43 @@
         new SyntaxError("Failed to parse Adblock Plus " +
                         `selector ${selector}, can't ` +
                         "have a lonely :-abp-contains()."));
       return null;
     }
     return selectors;
   },
 
+  _observerMap: new WeakMap(),
+
   _lastInvocation: 0,
 
   /**
    * Processes the current document and applies all rules to it.
    * @param {CSSStyleSheet[]} [stylesheets]
    *    The list of new stylesheets that have been added to the document and
    *    made reprocessing necessary. This parameter shouldn't be passed in for
    *    the initial processing, all of document's stylesheets will be considered
    *    then and all rules, including the ones not dependent on styles.
+   * @param {boolean} [domUpdate]
+   *    Indicate this is a DOM update.
    */
-  addSelectors(stylesheets)
+  addSelectors(stylesheets, domUpdate)
   {
     this._lastInvocation = Date.now();
 
     let selectors = [];
     let selectorFilters = [];
 
     let elements = [];
     let elementFilters = [];
 
     let cssStyles = [];
 
-    let stylesheetOnlyChange = !!stylesheets;
+    let stylesheetOnlyChange = !!stylesheets && !domUpdate;
     if (!stylesheets)
       stylesheets = this.window.document.styleSheets;
 
     // Chrome < 51 doesn't have an iterable StyleSheetList
     // https://issues.adblockplus.org/ticket/5381
     for (let i = 0; i < stylesheets.length; i++)
     {
       let stylesheet = stylesheets[i];
@@ -456,21 +476,20 @@
     for (let pattern of this.patterns)
     {
       if (stylesheetOnlyChange &&
           !pattern.selectors.some(selector => selector.dependsOnStyles))
       {
         continue;
       }
 
-      for (let selector of evaluate(pattern.selectors,
-                                    0, "", document, cssStyles))
+      for (let selector of evaluate(pattern.selectors, 0, "", document,
+                                    cssStyles, this._observerMap))
       {
-        if (pattern.selectors.some(s => s.preferHideWithSelector) &&
-            !pattern.selectors.some(s => s.requiresHiding))
+        if (isSelectorHidingOnlyPattern(pattern))
         {
           selectors.push(selector);
           selectorFilters.push(pattern.text);
         }
         else
         {
           for (let element of document.querySelectorAll(selector))
           {
@@ -482,38 +501,96 @@
     }
 
     this.addSelectorsFunc(selectors, selectorFilters);
     this.hideElemsFunc(elements, elementFilters);
   },
 
   _stylesheetQueue: null,
 
+  /** Filtering reason
+   * @typedef {Object} FilteringReason
+   * @property {boolean} dom Indicate the DOM changed (tree or attributes)
+   * @property {CSSStyleSheet[]} [stylesheets]
+   *    Indicate the stylesheets that needs refresh
+   * @property {WeakSet} subtrees The subtrees affected we were watching.
+   */
+
+  /** Re-run filtering either immediately or queued.
+   * @param {FilteringReason} reason why the filtering must be queued.
+   */
+  queueFiltering(reason)
+  {
+    if (!this._stylesheetQueue &&
+        (Date.now() - this._lastInvocation < MIN_INVOCATION_INTERVAL ||
+         reason.dom))
+    {
+      this._stylesheetQueue = [];
+      this.window.setTimeout(() =>
+      {
+        let stylesheets = this._stylesheetQueue;
+        this._stylesheetQueue = null;
+        let domUpdate = reason.dom;

[hub, 2017/08/03 16:28:18]

I realise this should have been moved up, out of the lambda to only capture
domUpdate. Will be in the next iteration.

+        this.addSelectors(stylesheets, domUpdate);

[hub, 2017/08/02 04:10:55]

Here we don't use reason.subtree.

Actually I'm not convinced that it is a good idea to restrict only to the nodes
that we checked with :-abp-has() (scenario 2 in the issue). In that case
reason.subtree is irrelevant and we can simplify lot of the code removing it.

+      }, MIN_INVOCATION_INTERVAL - (Date.now() - this._lastInvocation));
+    }
+    if (reason.stylesheets)
+    {
+      if (this._stylesheetQueue)
+        this._stylesheetQueue.push(...reason.stylesheets);
+      else
+        this.addSelectors(reason.stylesheets);
+    }
+  },
+
   onLoad(event)
   {
     let stylesheet = event.target.sheet;
     if (stylesheet)
+      this.queueFiltering({stylesheets: [stylesheet]});
+  },
+
+  observe(mutations)
+  {
+    let reason = {};
+    reason.dom = true;
+    let stylesheets = [];
+    for (let mutation of mutations)
     {
-      if (!this._stylesheetQueue &&
-          Date.now() - this._lastInvocation < MIN_INVOCATION_INTERVAL)
+      if (mutation.type == "childList")
       {
-        this._stylesheetQueue = [];
-        this.window.setTimeout(() =>
+        for (let added of mutation.addedNodes)
+        {
+          if (added.nodeType == Node.ELEMENT_NODE &&
+              (added.tagName == "STYLE" || added.tagName == "style") &&
+              added.styesheet)
+            stylesheets.push(added.stylesheet);

[hub, 2017/08/02 04:10:54]

If we have a new style element, then we likely have a new stylesheet.

+        }
+        for (let removed of mutation.removedNodes)
         {
-          let stylesheets = this._stylesheetQueue;
-          this._stylesheetQueue = null;
-          this.addSelectors(stylesheets);
-        }, MIN_INVOCATION_INTERVAL - (Date.now() - this._lastInvocation));
+          this._observerMap.delete(removed);
+        }
       }
-
-      if (this._stylesheetQueue)
-        this._stylesheetQueue.push(stylesheet);
-      else
-        this.addSelectors([stylesheet]);
+      let currentNode = mutation.target;
+      while (currentNode)
+      {
+        let e = this._observerMap.has(currentNode);
+        if (e)
+        {
+          if (!(reason.subtrees instanceof Set))
+            reason.subtrees = new Set();
+          reason.subtrees.add(currentNode);
+          break;
+        }
+        currentNode = currentNode.parentNode;
+      }
     }
+    if (stylesheets.length > 0)
+      reason.stylesheets = stylesheets;
+    this.queueFiltering(reason);
   },
 
   apply()
   {
     this.getFiltersFunc(patterns =>
     {
       this.patterns = [];
       for (let pattern of patterns)
@@ -522,13 +599,22 @@
         if (selectors != null && selectors.length > 0)
           this.patterns.push({selectors, text: pattern.text});
       }
 
       if (this.patterns.length > 0)
       {
         let {document} = this.window;
         this.addSelectors();
+        this.observer.observe(
+          document,
+          {
+            childList: true,
+            attributes: true,
+            subtree: true,
+            attributeFilter: ["class", "id"]

[hub, 2017/08/02 04:10:54]

check for the obvious class and id attributes that directly impact filtering.

We could eventually when parsing the filters listing other attributes we might
be interested in.

+          }
+        );
         document.addEventListener("load", this.onLoad.bind(this), true);
       }
     });
   }
 };