Issue 6437 - Skip styles-only patterns on DOM mutations

lib/content/elemHideEmulation.js

Index: lib/content/elemHideEmulation.js
===================================================================
--- a/lib/content/elemHideEmulation.js
+++ b/lib/content/elemHideEmulation.js
@@ -239,16 +239,17 @@
 
 function HasSelector(selectors)
 {
   this._innerSelectors = selectors;
 }
 
 HasSelector.prototype = {
   requiresHiding: true,
+  dependsOnDOM: true,

[Manish Jethani, 2018/03/01 17:18:11]

-abp-has and -abp-contains definitely, one hundred percent, depend on the DOM
(i.e. they should be considered for processing in response to DOM mutations).

 
   get dependsOnStyles()
   {
     return this._innerSelectors.some(selector => selector.dependsOnStyles);
   },
 
   get dependsOnCharacterData()
   {
@@ -301,16 +302,17 @@
 
 function ContainsSelector(textContent)
 {
   this._regexp = makeRegExpParameter(textContent);
 }
 
 ContainsSelector.prototype = {
   requiresHiding: true,
+  dependsOnDOM: true,
   dependsOnCharacterData: true,
 
   *getSelectors(prefix, subtree, stylesheet)
   {
     for (let element of this.getElements(prefix, subtree, stylesheet))
       yield [makeSelector(element, ""), subtree];
   },
 
@@ -378,16 +380,46 @@
 };
 
 function isSelectorHidingOnlyPattern(pattern)
 {
   return pattern.selectors.some(s => s.preferHideWithSelector) &&
     !pattern.selectors.some(s => s.requiresHiding);
 }
 
+function patternDependsOnStyles(pattern)
+{
+  return pattern.selectors.some(s => s.dependsOnStyles);
+}
+
+function patternDependsOnDOM(pattern)
+{
+  return pattern.selectors.some(s => s.dependsOnDOM);
+}
+
+function patternDependsOnBothStylesAndDOM(pattern)
+{
+  return pattern.selectors.some(s => s.dependsOnStyles && s.dependsOnDOM);
+}
+
+function shouldProcessPattern(pattern, stylesheets, mutations)
+{
+  if (!stylesheets && !mutations)
+    // Process everything.
+    return true;
+
+  if (!stylesheets && !patternDependsOnDOM(pattern))
+    return false;
+
+  if (!mutations && !patternDependsOnStyles(pattern))
+    return false;
+
+  return true;
+}
+
 function shouldObserveAttributes(patterns)
 {
   // Observe changes to attributes if either there's a plain selector that
   // looks like an ID selector, class selector, or attribute selector in one of
   // the patterns (e.g. "a[href='https://example.com/']")
   // or there's a properties selector nested inside a has selector
   // (e.g. "div:-abp-has(:-abp-properties(color: blue))")
   return patterns.some(
@@ -497,34 +529,60 @@
 
   /**
    * 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 {MutationRecord[]} [mutations]
+   *    The list of DOM mutations that have been applied to the document and
+   *    made reprocessing necessary. This parameter shouldn't be passed in for
+   *    the initial processing, the entire document will be considered
+   *    then and all rules, including the ones not dependent on the DOM.
    * @param {function} [done]
    *    Callback to call when done.
    */
-  _addSelectors(stylesheets, done)
+  _addSelectors(stylesheets, mutations, done)
   {
     let selectors = [];
     let selectorFilters = [];
 
     let elements = [];
     let elementFilters = [];
 
     let cssStyles = [];
 
-    let stylesheetOnlyChange = !!stylesheets;
-    if (!stylesheets)
+    let patterns = null;
+
+    // If neither any style sheets nor any DOM mutations have been specified,
+    // do full processing.
+    if (!stylesheets && !mutations)
+    {
+      patterns = this.patterns.slice();
+      stylesheets = this.document.styleSheets;
+    }
+    else
+    {
+      patterns = this.patterns.filter(
+        pattern => shouldProcessPattern(pattern, stylesheets, mutations)
+      );
+    }
+
+    // If there are any DOM mutations and any of the patterns depends on both
+    // style sheets and the DOM (e.g. -abp-has(-abp-properties)), find all the
+    // rules in every style sheet in the document, because we need to run
+    // querySelectorAll afterwards. On the other hand, if we only have patterns
+    // that depend on either styles or DOM both not both
+    // (e.g. -abp-properties or -abp-contains), we can skip this part.
+    if (mutations && patterns.some(patternDependsOnBothStylesAndDOM))
       stylesheets = this.document.styleSheets;
 
-    for (let stylesheet of stylesheets)
+    for (let stylesheet of stylesheets || [])
     {
       // Explicitly ignore third-party stylesheets to ensure consistent behavior
       // between Firefox and Chrome.
       if (!this.isSameOrigin(stylesheet))
         continue;
 
       let rules = stylesheet.cssRules;
       if (!rules)
@@ -534,17 +592,16 @@
       {
         if (rule.type != rule.STYLE_RULE)
           continue;
 
         cssStyles.push(stringifyStyle(rule));
       }
     }
 
-    let patterns = this.patterns.slice();
     let pattern = null;
     let generator = null;
 
     let processPatterns = () =>
     {
       let cycleStart = performance.now();
 
       if (!pattern)
@@ -555,22 +612,16 @@
           this.hideElemsFunc(elements, elementFilters);
           if (typeof done == "function")
             done();
           return;
         }
 
         pattern = patterns.shift();
 
-        if (stylesheetOnlyChange &&

[Manish Jethani, 2018/03/01 17:18:11]

This is taken care of in shouldProcessPattern now.

It was nice that this was happening asynchronously, but I don't think it matter
so much in practice. On the other hand it's nice to filter out the unnecessary
patterns up front.

-            !pattern.selectors.some(selector => selector.dependsOnStyles))
-        {
-          pattern = null;
-          return processPatterns();
-        }
         generator = evaluate(pattern.selectors, 0, "",
                              this.document, cssStyles);
       }
       for (let selector of generator)
       {
         if (selector != null)
         {
           if (isSelectorHidingOnlyPattern(pattern))
@@ -615,85 +666,107 @@
   _filteringInProgress: false,
   _lastInvocation: -MIN_INVOCATION_INTERVAL,
   _scheduledProcessing: null,
 
   /**
    * Re-run filtering either immediately or queued.
    * @param {CSSStyleSheet[]} [stylesheets]
    *    new stylesheets to be processed. This parameter should be omitted
-   *    for DOM modification (full reprocessing required).
+   *    for full reprocessing.
+   * @param {MutationRecord[]} [mutations]
+   *    new DOM mutations to be processed. This parameter should be omitted
+   *    for full reprocessing.
    */
-  queueFiltering(stylesheets)
+  queueFiltering(stylesheets, mutations)

[Manish Jethani, 2018/03/01 17:18:11]

The addition of the mutations parameter here is mainly just for passing it on to
_addSelectors. It is treated exactly like the stylesheets parameter.

   {
     let completion = () =>
     {
       this._lastInvocation = performance.now();
       this._filteringInProgress = false;
       if (this._scheduledProcessing)
       {
         let newStylesheets = this._scheduledProcessing.stylesheets;
+        let newMutations = this._scheduledProcessing.mutations;
         this._scheduledProcessing = null;
-        this.queueFiltering(newStylesheets);
+        this.queueFiltering(newStylesheets, newMutations);
       }
     };
 
     if (this._scheduledProcessing)
     {
-      if (!stylesheets)
+      if (!stylesheets && !mutations)
+      {
         this._scheduledProcessing.stylesheets = null;
-      else if (this._scheduledProcessing.stylesheets)
-        this._scheduledProcessing.stylesheets.push(...stylesheets);
+        this._scheduledProcessing.mutations = null;
+      }
+      else
+      {
+        if (stylesheets)
+        {
+          if (!this._scheduledProcessing.stylesheets)
+            this._scheduledProcessing.stylesheets = [];
+          this._scheduledProcessing.stylesheets.push(...stylesheets);
+        }
+        if (mutations)
+        {
+          if (!this._scheduledProcessing.mutations)
+            this._scheduledProcessing.mutations = [];
+          this._scheduledProcessing.mutations.push(...mutations);
+        }
+      }
     }
     else if (this._filteringInProgress)
     {
-      this._scheduledProcessing = {stylesheets};
+      this._scheduledProcessing = {stylesheets, mutations};
     }
     else if (performance.now() - this._lastInvocation < MIN_INVOCATION_INTERVAL)
     {
-      this._scheduledProcessing = {stylesheets};
+      this._scheduledProcessing = {stylesheets, mutations};
       setTimeout(() =>
       {
         let newStylesheets = this._scheduledProcessing.stylesheets;
+        let newMutations = this._scheduledProcessing.mutations;
         this._filteringInProgress = true;
         this._scheduledProcessing = null;
-        this._addSelectors(newStylesheets, completion);
+        this._addSelectors(newStylesheets, newMutations, completion);
       },
       MIN_INVOCATION_INTERVAL - (performance.now() - this._lastInvocation));
     }
     else if (this.document.readyState == "loading")
     {
-      this._scheduledProcessing = {stylesheets};
+      this._scheduledProcessing = {stylesheets, mutations};
       let handler = () =>
       {
         document.removeEventListener("DOMContentLoaded", handler);
         let newStylesheets = this._scheduledProcessing.stylesheets;
+        let newMutations = this._scheduledProcessing.mutations;
         this._filteringInProgress = true;
         this._scheduledProcessing = null;
-        this._addSelectors(newStylesheets, completion);
+        this._addSelectors(newStylesheets, newMutations, completion);
       };
       document.addEventListener("DOMContentLoaded", handler);
     }
     else
     {
       this._filteringInProgress = true;
-      this._addSelectors(stylesheets, completion);
+      this._addSelectors(stylesheets, mutations, completion);
     }
   },
 
   onLoad(event)
   {
     let stylesheet = event.target.sheet;
     if (stylesheet)
       this.queueFiltering([stylesheet]);
   },
 
   observe(mutations)
   {
-    this.queueFiltering();
+    this.queueFiltering(null, mutations);
   },
 
   apply(patterns)
   {
     this.patterns = [];
     for (let pattern of patterns)
     {
       let selectors = this.parseSelector(pattern.selector);