Issue 2395 - Added content script for CSS property filters

chrome/content/cssProperties.js

+CSSPropertyFilters = {
+  stringifyStyle: function(style)
+  {
+    var styles = [];
+    for (var i = 0; i < style.length; i++)
+    {
+      var property = style.item(i);
+      var value    = style.getPropertyValue(property);
+      var priority = style.getPropertyPriority(property);
+      styles.push(property + ": " + value + (priority ? " !" + priority : "") + ";");
+    }
+    styles.sort();
+    return styles.join(" ");
+  },
+
+  findSelectors: function(stylesheet, selectors)
+  {
+    var rules = stylesheet.cssRules;
+    if (!rules)
+      return;
+
+    for (var i = 0; i < rules.length; i++)
+    {
+      var rule = rules[i];
+      if (rule.type != CSSRule.STYLE_RULE)
+        continue;
+
+      var style = this.stringifyStyle(rule.style);
+      for (var j = 0; j < this.patterns.length; j++)
+      {
+        var pattern = this.patterns[j];
+        var regexp = pattern.regexp;
+
+        if (typeof regexp == "string")
+          regexp = pattern.regexp = new RegExp(regexp);

[Wladimir Palant, 2015/10/23 18:36:37]

What about invalid regexps? new RegExp() can throw.

[Sebastian Noack, 2015/10/23 20:49:31]

The regular expression is generated by our code. See 
CSSPropertyFilter.regexpString in lib/filterClasses.js

+
+        if (regexp.test(style))
+          selectors.push(pattern.prefix + rule.selectorText + pattern.suffix);
+      }
+    }
+  },
+
+  addSelectors: function(stylesheets)
+  {
+    var selectors = [];
+    for (var i = 0; i < stylesheets.length; i++)
+      this.findSelectors(stylesheets[i], selectors);
+    addElemHideSelectors(selectors);
+  },
+
+  onLoad: function(event)
+  {
+    var stylesheet = event.target.sheet;
+    if (stylesheet)
+      CSSPropertyFilters.addSelectors([stylesheet]);
+  },
+
+  load: function(callback)
+  {
+    ext.backgroundPage.sendMessage(
+      {
+        type: "filters.get",
+        what: "cssproperties"
+      },
+      function(patterns)
+      {
+        this.patterns = patterns;
+        callback();
+      }.bind(this)
+    );
+  },
+
+  apply: function()
+  {
+    if (patterns.length > 0)
+    {
+      this.addSelectors(document.styleSheets);
+      document.addEventListener("load", this.onLoad, true);

[Wladimir Palant, 2015/10/23 18:36:36]

Are you sure that the "load" event is being triggered for stylesheets while the
page is still loading?

[Sebastian Noack, 2015/10/23 20:49:31]

Seems so. Tested using https://pastebin.mozilla.org/8850267 on Chrome 46 and
Firefox 38.

+    }
+  },
+
+  init: function()
+  {
+    this.load(this.apply.bind(this));
+  }
+};
+
+CSSPropertyFilters.init();

[Wladimir Palant, 2015/10/23 18:36:37]

As I said earlier, CSSPropertyFilters should ideally be a class. So this should
be:

  if (typeof window == "object")
    new CSSPropertyFilters(window);

In non-window context (Firefox) the class will be instantiated by outside code.

[Sebastian Noack, 2015/10/23 20:49:31]

I've added the check. Do we have to use a constructor? It's not that passing
around instances seems to make sense. But maybe I miss something.

[Wladimir Palant, 2015/10/23 21:04:40]

In Firefox there will be more than one window/document handled in the same
scope. So - yes, having one instance per window should be the simplest way.

[Sebastian Noack, 2015/10/23 21:23:22]

Gotya.