On Thu, May 10, 2018 at 8:42 AM, Anoop R. S. <anoop....@gmail.com> wrote:
> Ok. I figured out that if v8::IndexedPropertyHandlerConfiguration is set,
> and IndexedPropertyEnumeratorCallback is implemented, I can configure what
> is displayed on mouse over action (Debugger.evaluateOnCallFrame is passed
> from devtools on doing that operation.)
>
> The implementation is provided below.
> void IndexedPropertyEnumeratorCallbackFunction(
> const v8::PropertyCallbackInfo<v8::Array>& p_callbackInfo)
> {
> v8::Local<v8::Array> IndexArray =
> v8::Array::New(p_callbackInfo.GetIsolate(), 2);
> IndexArray->Set(
> v8::Integer::New(p_callbackInfo.GetIsolate(), 0),
> v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"x"));
> IndexArray->Set(
> v8::Integer::New(p_callbackInfo.GetIsolate(), 1),
> v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"y"));
> p_callbackInfo.GetReturnValue().Set(IndexArray);
> }
>
> From reading the embedder's guide, my understanding is that
>>
>> indexed property interceptors - called when accessing indexed properties.
>> An example of this, in a browser environment, is document.forms.elements[0].
>
>
> Why is it called on evaluateOnCallFrame action? Also, I tried with other
> callback s of v8::IndexedPropertyHandlerConfiguration, but they are not
> called. Can I know why? Also, since the signature of callback is as below :
>
> void (*IndexedPropertyEnumeratorCallback)( const
> PropertyCallbackInfo<Array>& info);
>
> I can set only arrays into the result and nothing else.
> I am not an expert in v8, hence these questions. Please let me know about
> it/ point me to some documentation regarding this.
>
> regards,
> Anoop R. S.
IndexedPropertyEnumeratorCallback - is called for Object.keys()-like
operations; i.e., to list the enumerable properties of the object but
not non-enumerable or prototype properties. The 'Indexed' refers to
the fact that it's intended for numeric keys, i.e., array-like
objects. Instead of v8::IndexedPropertyHandlerConfiguration, you may
want to use v8::NamedPropertyHandlerConfiguration.
evaluateOnCallFrame - V8 cannot know whether your callback has any
side effects (it could create objects, call into JS code, etc.), hence
it evaluates it as if it were a snippet of regular JS code. Newer
versions of V8 let you register callbacks with kHasNoSideEffect but as
far as I know that has no effect (hah!) on whether or not
evaluateOnCallFrame is used. Maybe in the future.
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