[wpe-webkit] Web Extension Support In WPE

[Munez Bn]

Hello Again,

I was trying to use jsc_class_add_constructor() like it was used in
*TestJSC.cpp.* Earlier I tried only registering JSC class and adding
method/properties to JSC class which worked fine for me.
With constructor  approach, when I call  getPath(), it says G_IS_FILE(file)
check failed. Not sure who is freeing this GFile object. I tried this in
both javascript and *jsc_context_evaluate()* but same issue.  Instead of
returning GFile object, if I return ref of GFile object  in constructor
callback, then it works fine. But in TestJSC.cpp. we do not return ref the
GFile in constructor callback.

    JSCClass* gFileClass = jsc_context_register_class(js_context, "GFile",
nullptr, nullptr, nullptr);
    jsc_class_add_method (gFileClass, "getPath", G_CALLBACK
(js_get_gfile_path), NULL, NULL, G_TYPE_STRING, 0);

    JSCValue *constructor = jsc_class_add_constructor(gFileClass, nullptr,
G_CALLBACK(createGFile), nullptr, nullptr, G_TYPE_OBJECT, 1, G_TYPE_STRING);
    jsc_context_set_value(js_context, jsc_class_get_name(gFileClass),
constructor);

  static GFile* createGFile(const char* path, gpointer user_data)
 {
    GFile* file = g_file_new_for_path(path);
    return file;
    //return G_FILE(g_object_ref(file));    *---> If i return like this
then it works as expected.*
 }

static char* js_get_gfile_path (GFile* file, gpointer usr_data)
{
    char *path = nullptr;
    if(G_IS_FILE(file))                      ------>* this is false if I
don't ref and return in  createGFile  *
        path = g_file_get_path (file);
     return path;
}

Thanks & Regards
Munez

On Thu, Jun 20, 2019 at 11:29 PM Munez Bn <munezbn.dev at gmail.com> wrote:

> Thanks Michael & Carlos for all your suggestions. It was very helpful. I
> am able to return native objects and have better understanding of JSC APi
> now :)
> I will update my stack-overflow post.
>
> Please note that when I tried initially, my sample extension was stored in
> *Tools/MiniBrowser/gtk/TestExtension/CMakeLists.tx*t and in Extension's
> *CMakeLists.tx*t I had exported all the internal include paths. Also Some
> function I declaration locally in extension file. I will do all the cleanup
> and do it in a clean way now.
>
> Cheers..
> Munez
>
> On Thu, Jun 20, 2019 at 12:55 PM Carlos Garcia Campos <cgarcia at igalia.com>
> wrote:
>
>> El mié, 19-06-2019 a las 15:33 -0500, Michael Catanzaro escribió:
>> > Hi Munez,
>> >
>> > On Wed, Jun 19, 2019 at 2:10 PM, Munez Bn <munezbn.dev at gmail.com>
>> > wrote:
>> > > I didn't do any changes in webkit or makefiles to install internal
>> > > headers.
>> >
>> > I'm really confused then. You are using multiple internal APIs that
>> > are
>> > not defined in any public headers, so you must have somehow made
>> > some
>> > major changes to WebKit to gain access to these APIs.
>> >
>> > On Wed, Jun 19, 2019 at 2:10 PM, Munez Bn <munezbn.dev at gmail.com>
>> > wrote:
>> > > 1. The API description of jsc_value_new_function() says that, If
>> > > we
>> > > really want to return a new copy of the boxed type in the callback
>> > > function passed as argument to jsc_value_new_function(), then use
>> > > #JSC_TYPE_VALUE and return a #JSCValue created with
>> > > jsc_value_new_object() that receives the copy as instance
>> > > parameter.
>> > > But jsc_value_new_object() also needs a context so when I tried to
>> > > passed jsc_context as user data to callback function, the callback
>> > > function threw following error.
>> > >
>> > > JSCValue* jsc_value_new_undefined(JSCContext*): assertion
>> > > 'JSC_IS_CONTEXT(context)' failed
>> > >
>> > > Please let me know if i am missing anything. I was planing to
>> > > register class in callback function getTestExtObjec().
>> >
>> > OK, this at least looks straightforward. You correctly noticed that
>> > the
>> > JSCContext returned by
>> > webkit_frame_get_js_context_for_script_world()
>> > is returned transfer full, so your code is responsible for taking
>> > ownership. You used g_autoptr to hold that ownership, which is good.
>> > But you're failing to transfer the ownership from your
>> > windowObjectCleared function to the getTestExtObject callback. The
>> > fix
>> > would be to use g_steal_pointer():
>> >
>> > g_autoptr(JSCValue) function = jsc_value_new_function(jsContext,
>> > "getTestExtObject", G_CALLBACK(getTestExtObject),
>> > g_steal_pointer(&jsContext), NULL, JSC_TYPE_VALUE, 1, G_TYPE_STRING);
>> >
>> > Otherwise, it's deleted before your getTestExtObject() is called.
>> > Using
>> > g_steal_pointer() makes the ownership clear. You could also just not
>> > use g_autoptr at all, but then the ownership will not be obvious in
>> > the
>> > code. Either way, once that is fixed you will need to unref it in
>> > getTestExtObject() to avoid leaking it.
>>
>> Right, you are passing the context as callback data, but it's freed at
>> the time the callback is called. I don't think it's a good idea to pass
>> the context, though. You can simply use jsc_context_get_current(). That
>> always work inside function callbacks. The JSCContext won't be the same
>> as the one you got in window_object_cleared, but the wrapped
>> JSGlobalObjectRef is.
>>
>> You have an example of that in the unit tests too, in the function to
>> get the parent of a GFile (we need to create a new wrapped GFile in the
>> callback, see:
>>
>>
>> https://trac.webkit.org/browser/webkit/trunk/Tools/TestWebKitAPI/Tests/JavaScriptCore/glib/TestJSC.cpp#L1640
>>
>> > Hope that helps,
>> >
>> > Michael
>> >
>> >
>> >
>> --
>> Carlos Garcia Campos
>> http://pgp.rediris.es:11371/pks/lookup?op=get&search=0xF3D322D0EC4582C3
>>
>
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