Issue 4394 - Create a filter class for element hiding emulation filters [WIP]

chrome/content/cssProperties.js

 function splitSelector(selector)
 {
   if (selector.indexOf(",") == -1)
     return [selector];
 
   var selectors = [];
   var start = 0;
   var level = 0;
   var sep = "";
 
@@ skipping 110 matching lines @@
   {
     var stylesheet = event.target.sheet;
     if (stylesheet)
       this.addSelectors([stylesheet]);
   },
 
   load: function(callback)
   {
     this.getFiltersFunc(function(patterns)
     {
-      this.patterns = patterns;
+      // We currently don't support any element hiding emulation feature except

[kzar, 2016/09/25 14:52:06]

Shouldn't it be up to the callback to decide which filters are used? (Since
that's in adblockpluschrome / adblockplus and support might depend on the
platform.)

[Felix Dahlke, 2016/09/30 10:22:26]

Yeah, that's a good point. My thinking was that we can avoid duplication and
make things more robust by making sure the cssProperties content script ignores
all other filters, whether the platform specific code hands any in or not. Since
this content script will be replaced by one that can both handle :has and
property selectors, that seems to be the best option until we get there.

[kzar, 2016/10/05 11:58:14]

How about adding an extra parameter to the CSSPropertyFilters constructor called
something like `features`? That way the platform code gets to pass in an array
of supported features and we can check the filters are supported here before
returning them.

[Felix Dahlke, 2016/11/03 16:14:13]

My thinking on this was that we don't have to pass anything in, we can just do
feature detection in ElemHideBase.fromText. But for now this is a theoretical
discussion anyway, since it'll take quite a while before :has will be supported
natively...

+      // for property selectors, so we remove rules that use other features.
+      // See https://issues.adblockplus.org/ticket/3143.
+      this.patterns = [];
+      for (var i = 0; i < patterns.length; i++)
+      {
+        var pattern = patterns[i];
+        if (pattern.features.length == 1 &&
+            pattern.features[0] == "PROPERTY_SELECTOR")
+          this.patterns.push(pattern);
+      }
+
       callback();
     }.bind(this));
   },
 
   apply: function()
   {
     if (this.patterns.length > 0)
     {
       var document = this.window.document;
       this.addSelectors(document.styleSheets);
       document.addEventListener("load", this.onLoad.bind(this), true);
     }
   }
 };