Issue 4125 - [emscripten] Convert filter classes to C++

compiled/Filter.h

 #pragma once
 
 #include <vector>
 
 #include "String.h"
 #include "intrusive_ptr.h"
 #include "debug.h"
 
 class Filter : public ref_counted
 {
 protected:
   OwnedString mText;
 
 public:
   enum Type
   {
     UNKNOWN = 0,
     INVALID = 1,
     COMMENT = 2,
     BLOCKING = 3,
     WHITELIST = 4,
     ELEMHIDE = 5,
     ELEMHIDEEXCEPTION = 6,
     CSSPROPERTY = 7,
   };
 
   explicit Filter(Type type, const String& text);

[sergei, 2017/01/10 15:57:46]

Just observation:
Before C++11 the compiler was allowed to implicitly construct some class only
for one argument case, but starting with C++11 it may also decide to construct a
class when initializer-list like expression is used, e.g. {arg1, arg2, ...},
including also the case with one argument, {arg}. It also seems a bit
complicated how and when a particular constructor is chosen, so, it seems now it
makes sense to use explicit for all constructors just in case and drop it in
rare cases, when it's getting annoying and we are sure it won't conflict with
something else.

[Wladimir Palant, 2017/03/13 17:42:03]

I see. Here it rather seems to be a left-over from a previous version but I'm
fine with making all constructors explicit. That's a lot of them however.

-  virtual ~Filter();

[sergei, 2017/01/10 15:57:48]

I'm not sure that we need to say virtual here because we already know that the
destructor is virtual because ref_counted has a virtual destructor.

[Wladimir Palant, 2017/03/13 17:42:08]

Done.

+  ~Filter();
 
   Type mType;

[sergei, 2017/01/10 15:57:44]

I guess it's a public member only for the sake of performance. In JS it should
be at least two times faster to simply read the member of object than to call a
method which returns the value of the member. Right?

[Wladimir Palant, 2017/03/13 17:42:06]

Yes, we were calling a function originally in order to differentiate between
subclasses. Reading out a value from memory is considerably faster and it also
happens to be simpler to implement in our bindings.

 
   /* TODO
   std::vector<Subscription> mSubscriptions;
   */
 
   EMSCRIPTEN_KEEPALIVE const String& GetText() const
   {
     return mText;
   }
 
   EMSCRIPTEN_KEEPALIVE OwnedString Serialize() const;
 
-  static EMSCRIPTEN_KEEPALIVE Type GetType(Filter* filter)

[sergei, 2017/01/10 15:57:42]

It seems we don't need this method anymore.

[Wladimir Palant, 2017/03/13 17:42:01]

Done.

-  {
-    return filter->mType;
-  }
-
   static EMSCRIPTEN_KEEPALIVE Filter* FromText(DependentString& text);
 };
 
 typedef intrusive_ptr<Filter> FilterPtr;