[Webkit-unassigned] [Bug 119654] New: [Qt] Avoid calling QWebPage's virtual functions during deletion of QWebPage

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=119654

           Summary: [Qt] Avoid calling QWebPage's virtual functions during
                    deletion of QWebPage
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Critical
          Priority: P2
         Component: WebKit Qt
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: arurajku at cisco.com
                CC: allan.jensen at digia.com, hausmann at webkit.org,
                    jocelyn.turcotte at digia.com, noam at webkit.org,
                    ararunprasad at gmail.com


What is the problem ?
--------------------
class UnLoadTestPage : public QWebPage
{
    Q_OBJECT
public:
    virtual void javaScriptAlert(QWebFrame *originatingFrame, const QString& msg)
    {
        qDebug()<<"alert:"<<msg;
    }
};


UnLoadTestPage* tstPage = new UnLoadTestPage();
tstPage->mainFrame()->evaluateJavaScript("window.onunload=function(){alert('hello');}");
delete tstPage;

In the above sample code my overriden javaScriptAlert(..) won't be called, because onunload event is fired from ~QWebPage during that time overriden UnLoadTestPage is already destroyed.

What is the solution?
---------------------
1. Provide C++ API to send "unload" event(as like Blackberry port's WebPage::prepareToDestroy, http://trac.webkit.org/browser/trunk/Source/WebKit/blackberry/Api/WebPage.h#L114), so it is the responsibility of the QtWebKit embedder to call this new C++ API in their destructors(or before deleting their QWebPage instance).
(ex: tstPage->prepareToDestroy)

2. Provide C++ API to delete any QWebPage instance, which will take care of sending "unload" event before destroying any QWebPage instance.
(ex: tstPage->deletePage(); or QWebPage::deletePage(tstPage); //static C++ API)

3. Provide both #1 & #2.

Any Side effects?
-----------------
No.Existing flow is unaffected, if embedder didn't call QWebPage::prepareToDestroy then unload event will be generated as like the current flow.


I prefer solution #3 and will upload the fix soon.

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