How to find QWebFrame calling C++ API from Javascript

willc

Hi,
new here - working on a port of an application from Webkit/GTK to Webkit/QT 4.7.

is it possible to find a reference to the frame that is executing a JS call to a custom QObject API in C++ via slot function?

the page has multiple frames which may be calling the C++ API. I would like to store the frame reference so that I can call frame->evaluateJavaScript() later.

tried using page->currentFrame() but this returns the frame with focus, not the frame executing the JS.

any help would be appreciated,
thanks.

benjamin.poulain

I cannot think of any direct way. But objects are added by frames right? It is convoluted but couldn't you have a caller-proxy objects that keep a reference to the frame it has been added, and pass that as argument to the object executing javascript?

willc

Hi Benjamin - thanks for the suggestion.

I would need to create a new custom qobject for each new frame and use these to store the frame reference. The object would have to be deleted on a frame delete - do you know if there a signal/event for a frame delete, I can't see any in the docs?

I seen there is an 'own' parameter for QWebFrame::addToJavaScriptWindowObject() to set the ownership - maybe if I set this to script then the delete would be handled?

benjamin.poulain

Yep, that is what I would do, set the ownership to the script engine itself.

DavidGOrtega

Adding the QObject using ScriptOwnership is really a bad idea, the destructor is never called!! I'm figuring that this is not working at least in Qt 4.5.3

benjamin.poulain

[quote author="DavidGOrtega" date="1294760299"]Adding the QObject using ScriptOwnership is really a bad idea, the destructor is never called!! I'm figuring that this is not working at least in Qt 4.5.3[/quote]

I know about at least one big project using ScriptOwnership with 4.7 for security check on tear down. I think they would have complained if that was not working :)

willc

I will test in 4.7 and let you know..

willc

fyi - using ScriptOwnership worked ok for me for simple test with 4.7.

ie. frame->addToJavaScriptWindowObject( "objectName", pObject, QScriptEngine::ScriptOwnership );

pObject gets deleted before frame is deleted.

willc

after some further test I did find something funny using QScriptEngine::ScriptOwnership - on a page reload the object I attached to the main frame gets garbage collected!

as an alternative I set the custom object parent to the frame and use default ownership when calling addToJavaScriptWindowObject(). This way the object gets deleted when the frame is deleted which is what I want.

dangelog

[quote author="willc" date="1294934025"]after some further test I did find something funny using QScriptEngine::ScriptOwnership - on a page reload the object I attached to the main frame gets garbage collected!

as an alternative I set the custom object parent to the frame and use default ownership when calling addToJavaScriptWindowObject(). This way the object gets deleted when the frame is deleted which is what I want.
[/quote]

Or, you can call addToJavaScriptWindowObject in a slot connected to the javaScriptWindowObjectCleared signal.

benjamin.poulain

@willc, yep, that is intended. Custom objects are not supposed to live past the lifetime of the content. You can do as peppe says to get them from page to page.

willc

yeah - I am doing that too..

does anyone know the expected behaviour when an new frame (iframe) is created?

I have connected a function to the page "frameCreated" signal - this is called for the new frame and I call newFrame->addToJavaScriptWindowObject() to add my custom object.

I also connect to the javaScriptWindowObjectCleared signal for the new frame.

Sometimes this signal goes off immediately resulting in a second call to addToJavaScriptWindowObject() - is this expected?