Re: [webkit-gtk] GObject API for JavaScriptCore

[Carlos Garcia Campos]

El mar, 18-10-2016 a las 13:29 +, tev...@gmail.com escribió:
[...]
> > It doesn't need to be just a wrapper, because to wrap the JSC API
> > you
> > can just use the existing API. As I said, this depends on how we
> > design
> > the value object for example, if we use a different subtype for
> > every
> > value type, we definitely want to use GObjects. I really don't
> > think
> > there's that much overhead in using GObject, compared to boxed
> > types.
> > And it also depends on whether we want to use floating references,
> > especially for the JSCValue it could be interesting to make it
> > initially unowned.
> > 
> 
> Well... I don't really see a point on having subtypes for every kind
> of value... maybe code maintainability, but I don't think this will
> be hurt if we use only one type for values (yet). Feel free to
> convince me though. And it's a good idea to make JSCValues initially
> unowned.

I'm afraid it works the other way around :-) you have to convince us
that using boxed types is better, or prove that the GObject overhead is
so high that it's worth not using them. We could implement the desired
features for a boxed type (ref counting, floating refs, weak refs,
etc.) but we would be reinventing GObject in the end. Note that we can
have a single JSCValue for everything but still make it a GObject
instead of a boxed type.
 
> > > >  * Error handling: I'm not sure GError is enough to handle js
> > > > exceptions. They can happen at any time and have additional
> > > > information
> > > > like line number, column, etc. that can't be represented by
> > GError.
> > > > The
> > > > Objc API allows to set a callback per context to handle the
> > > > exceptions.
> > > >
> > >
> > > We can use a boxed type here too (simpler) or subclass GError to
> > add
> > > the details... 
> > 
> > I wouldn't use GError, but a custom exception object (boxed type or
> > whatever), because it's not that we want extra info, but that maybe
> > we
> > don't really need the error code and quark.
> >  
> > > > I would start the API with the wrappers needed to setup a js
> > > > context
> > > > and then the JSValueRef wrapper with methods to set an retrieve
> > > > simple
> > > > values (string, bool, number, array, object/dictionary, date),
> > > > leaving
> > > > the handling of custom objects out for now. We could probably
> > use a
> > > > bug
> > > > report or a dedicated thread in this list to decide about this
> > > > specific
> > > > part of the API (whether we want to expose it as a single Value
> > > > type or
> > > > have a different type per value type, whether to use GObjects
> > or
> > > > boxed
> > > > types, whether to make it initially unowned, etc.)
> > > >
> > >
> > > I'll wait for your comments on the namespace and types to open
> > that
> > > bug report. This way, I can upload the initial patch.
> > 
> > Ok, note that it's not just me, for public API in WebKitGTK+ we
> > hace a
> > rule that it needs to be approved by two reviewers, so maybe you
> > want
> > to wait ot hear the opinion of other people. Also, I would at least
> > send a proposal here with the types you are going to add and
> > propotypes
> > of methods before spending too much time with the actual
> > implementation, just in case.
> 
> So, considering your previous comments, we can do something like this
> for a start:
> 
> Objects:
> o JSCContext
> o JSCValue
> o JSCObject
>   * JSCError (JSCArray, JSCDate and other stuff should come here too)

Why is Object special? So, we use a single JSValue for everything
except Object? I think we should be consistent here. I know that's what
the C API does, but this is what I meant when I said that our API
doesn't necessarily need match the C API 1 to 1.

And then JSCError is also a JSCObject? why is this a different object
too? I think it should be named JSCException, btw.

> Methods:
> JSCContext* jsc_context_new();
> JSCObject* jsc_context_get_global_object(JSCContext*);

If we add convenient methods to JSCContext to deal with the global
object we can leave this for now. For example, the Objc API allows to
do something like this:

context["foo"] = @"bar";

This means, create a string value with "bar" contents and set it to the
global object of context as property "foo". And the same to get a
value;

JSValue *foo = context["foo"];

This is super convenient, we can't do the same in C, but we can still
add convenient methods to do that, for example:

jsc_context_set_object (context, "foo", jsc_value_new_string ("bar"));
JSCValue *foo = jsc_context_get_object (context, "foo");

Note that we can pass the returned value of jsc_value_new_string (or
jsc_string_new if we use subtypes) if we make them initially unowned
and the context consumes the floating reference.

> JSCValue* jsc_context_evaluate_script(JSCContext *, gchar* script,
> JSCError* err);

Note that evalueScript is not the only function that can raise js
exceptions, other methods like jsc_value_ge_string() for example, can
also raise 

Re: [webkit-gtk] GObject API for JavaScriptCore

[tev...@gmail.com]

Em seg, 17 de out de 2016 às 14:24, Carlos Garcia Campos 
escreveu:

> El lun, 17-10-2016 a las 12:37 +, tev...@gmail.com escribió:
> >
> >
> > Em seg, 17 de out de 2016 às 04:31, Carlos Garcia Campos  > lia.com> escreveu:
> > > El lun, 10-10-2016 a las 01:19 +, tev...@gmail.com escribió:
> > > > Hello, everyone.
> > >
> > > Hi,
> > >
> > > > Some background first: my name is Estêvão and every now and the I
> > > try
> > > > to contribute to Gnome Web, AKA Epiphany. First time was back in
> > > > 2010. After the migration of Epiphany to WebKit, it stopped
> > > > identifying feed links on pages. I had to dig into JavaScriptCore
> > > to
> > > > call JavaScript functions to check for feed links on pages. DOM
> > > > bindings were only in TODO by then. Now what I need to do is a
> > > little
> > > > bit different, but also involves JavaScriptCore. We need to
> > > bridge
> > > > between JavaScript and C code so that an about page can be able
> > > to
> > > > list URLs to display. I was chocked that up to now JavaScriptCore
> > > is
> > > > untouched. So I started thinking about how could a GObject
> > > binding to
> > > > JSC be implemented.
> > > >
> > > > The proposal:
> > > >
> > > > I'm thinking about creating GObjects to warap JSC objects. For
> > > > instance: GJSCContext wrapping JSContextRef, GJSCObject wrapping
> > > > JSObjectRef and so on.
> > >
> > > We talked during the web engines hackfest about adding a GLib
> > > wrapper
> > > for JSC, not necessarily a 1 to 1 wrapper from JSC object to GLib
> > > objects, though.
> > >
> > > >  I implemented a POC of the API and a simple client to make my
> > > > intentions clearer. It's available on https://github.com/tevaum/j
> > > sc-
> > > > bindings.
> > >
> > > Thanks for working on this!
> > >
> > > > With that *not-so-gobject* partial API the client is able to
> > > bridge
> > > > javascript functions to native C callbacks and to execute
> > > javascript
> > > > code from C. Also the C function returns an array to the
> > > javascript
> > > > code. An example of error handling is also shown.
> > >
> > > I think error handling is a bit different in this case, we probably
> > > need a special way to handle JS exceptions.
> > >
> > > > I think that we have to start simple and add stuff incrementally,
> > > > based on what's already being used/requested by people. Please
> > > take
> > > > your time to dig into the example code provided, ask questions
> > > and
> > > > poit directions, so that we can buld a better WebKitGTK+.
> > >
> > > I agree with the idea of starting simple and going step by step,
> > > but
> > > before designing a new API there are a set of general things we
> > > should
> > > decide, and the most important thing, we should know what we want
> > > this
> > > new API to be used for. I think the API should allow:
> > >
> > >  * Easily run javascript snippets from C code in a web extension.
> > >  * Interact with javascript contexts, retrieve existing JS values
> > > in
> > > the context to the C code, and add values from C to the javascript
> > > context.
> > >  * Easily expose full objects to javascript
> > >
> > > That would cover the main uses cases, replacing the dom bindings
> > > and
> > > injecting custom code to JavaScript.
> > >
> > > Regarding the general things we should decide:
> > >
> > >  * Naming: we don't need a name for the library because it will be
> > > part
> > > of libjavascriptcoregtk (gtk is for gtk port, not because it uses
> > > gtk
> > > at all), but we need to use apublic header and a common prefix for
> > > methods and types. In your POC you are using javascript.h as the
> > > header
> > > name, jscore prefix for methods and GJSC for types. The API should
> > > be
> > > consistent in this regard.
> > >
> > >
> >
> > Yes, I really messed up the namespaces :P What about using
> > javascriptcoregtk.h for the header, JSCoreStuff for the objects and
> > jscore_stuff for the methods? Or maybe jsc-gtk.h JSCStuff for the
> > objects and jsc_stuff for the methods?
>
> We don't use gtk in any of our public headers, so maybe ,
> JSCFoo, jsc_foo. What do other people think?
>
> > >  * Memory management: this is very important to decide how to
> > > declare
> > > your objects, they could be GObject, boxed types with ref counting,
> > > etc. Note that javascript objects are garbage collected, so it's
> > > very
> > > important to have mechanisms, to prevent wrapped object from being
> > > destroyed by the garbage collector if we still have a wrapper
> > > alive.
> > > So, we will probably have to protect all js object when wrapped,
> > > which
> > > means API use will always have to manually unref every single
> > > wrapper.
> > > We might want to make it easier by making out wrappers initially
> > > unowned, for example. There might be cases in which we want to
> > > wrapper
> > > to be automatically destroyed when the wrapped object is garbage
> > > collected too. We need to 

[webkit-gtk] WebKitPluginProcess2 segfault on live feed Re: WebKitGTK+ 2.14.1 released!

[Amit Kachroo]

  
  
Hi 
  
  I am running a custom WebKitGtk based browser and if I switch the
  URLs or restart playback in quick succession, the
  WebKitPluginProcess2 occasionally fails with segfault.
  
https://www.youtube.com/v/y60wDzZt8yg?version=3=hd720=1
  
  Appended is gdb output. Any pointers on where I should be looking
  for fixing this will be much appreciated. 
  
  Regards,
  Amit
  
  Thread 4 (Thread 0x7fc0cfbff700 (LWP 1368)):
  #0  0x7fc11ed3cc8d in poll () at
  ../sysdeps/unix/syscall-template.S:81
  #1  0x7fc122f41b34 in g_main_context_iterate
  (priority=2147483647, n_fds=1, fds=0x7fc0c0001370, timeout=-1,
  context=0x7fc0c900) at gmain.c:4076
      poll_func = 0x7fc122f50f60 
      max_priority = 2147483647
      timeout = -1
      some_ready = 
      nfds = 1
      allocated_nfds = 2
      fds = 0x7fc0c0001370
  #2  0x7fc122f41b34 in g_main_context_iterate
  (context=0x7fc0c900, block=block@entry=1,
  dispatch=dispatch@entry=1, self=) at
  gmain.c:3776
      max_priority = 2147483647
      timeout = -1
      some_ready = 
      nfds = 1
      allocated_nfds = 2
      fds = 0x7fc0c0001370
  #3  0x7fc122f41ec2 in g_main_loop_run (loop=0x7fc0c0001240) at
  gmain.c:3975
      __FUNCTION__ = "g_main_loop_run"
  #4  0x7fc129e103c0 in WTF::RunLoop::run() () at
  /usr/src/debug/webkitgtk-2.14.1/Source/WTF/wtf/glib/RunLoopGLib.cpp:94
      runLoop = 
      @0x7fc116df7528: { =
  {
  = { = {m_refCount =
  { = {_M_i = 1}, }}, }, _vptr.FunctionDispatcher =
  0x7fc129ff0890 },
  m_functionQueueLock = {m_mutex = {__data = {__lock = 0, __count =
  0, __owner = 0, __nusers = 0, __kind = 512, __spins = 0, __elision
  = 0, __list = {__prev = 0x0, __next = 0x0}}, __size = '\000'
  , "\002", '\000' ,
  __align = 0}}, m_functionQueue = {m_start = 12, m_end = 12,
  m_buffer =
  { >>
  = {m_buffer = 0x7fc116dfaf80, m_capacity = 16, m_size = 0}, }}, m_mainContext = {m_ptr = 0x7fc0c900},
  m_mainLoops =
  {,
  0ul>> =
  {
  >> = {m_buffer = 0x7fc116dfa600, m_capacity = 16, m_size =
  1}, }, }, m_source =
  {m_ptr = 0x7fc0c0001260}}
      nestedMainLoop = 
  #5  0x7fc129e0eeac in std::_Function_handler
  >::_M_invoke(const std::_Any_data &) (__closure=0x55756b0)
      at
/usr/src/debug/webkitgtk-2.14.1/Source/WTF/wtf/generic/WorkQueueGeneric.cpp:58
      this = 0x7fc116dfb5f0
  #6  0x7fc129e0eeac in std::_Function_handler
  >::_M_invoke(const std::_Any_data &) (__functor=...)
      at /usr/include/c++/4.9.2/functional:2039
  #7  0x7fc129de93f5 in WTF::threadEntryPoint(void*)
  (this=0x7fc0cfbfebc0) at /usr/include/c++/4.9.2/functional:2439
      context = 0x7fc116df25f0
      entryPoint = 
   
  { =
  {},  = {static
  _M_max_size = 16, static _M_max_align = 8, _M_functor = {_M_unused
  = {_M_object = 0x55756b0, _M_const_object = 0x55756b0,
  _M_function_pointer = 0x55756b0, _M_member_pointer = (void
  (std::_Undefined_class::*)(std::_Undefined_class * const))
  0x55756b0, this adjustment 72671264}, _M_pod_data =
  "\260VW\005\000\000\000\000 \340T\004\000\000\000"}, _M_manager =
  0x7fc129e0ec30
  
  >::_M_manager(std::_Any_data &, const std::_Any_data &,
  std::_Manager_operation)>}, _M_invoker = 0x7fc129e0ee30
  
  >::_M_invoke(const std::_Any_data &)>}
  #8  0x7fc129de93f5 in WTF::threadEntryPoint(void*)
  (contextData=0x7fc116df25f0) at
  /usr/src/debug/webkitgtk-2.14.1/Source/WTF/wtf/Threading.cpp:60
      context = 0x7fc116df25f0
      entryPoint = 
   
  { =
  {},  = {static
  _M_max_size = 16, static _M_max_align = 8, _M_functor = {_M_unused
  = {_M_object = 0x55756b0, _M_const_object = 0x55756b0,
  _M_function_pointer = 0x55756b0, _M_member_pointer = (void