Bug 152482 – [WK2] Looping in testcase: fast/dom/Window/property-access-on-cached-window-after-frame-removed.html

• Status: RESOLVED
• Resolution: FIXED
• Component: WebKit2

[Jiewen Tan]

WK2 will keep looping in fast/dom/Window/property-access-on-cached-window-after-frame-removed.html while WK1 won't.
Investigate why it keeps looping.

[Jiewen Tan]

The looping path is:
accessibilityController,rootElement,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,verticalScrollbar,endTextMarker

[Jiewen Tan]

The looping can be explained as follow:
The testcase is trying to do a DFS of window object's properties. Since verticalScrollbar itself is an AcessibilityUIElement, and AcessibilityUIElement class by default has verticalScrollbar property, DFS will be stuck.

Actually, the class abstract is the same for both WebkitTestRunner and DumpRenderTree for AcessibilityUIElement. The difference is how they implement it.

In WebkitTestRunner:
PassRefPtr<AccessibilityUIElement> AccessibilityUIElement::verticalScrollbar() const
{
    BEGIN_AX_OBJC_EXCEPTIONS
    return AccessibilityUIElement::create([m_element accessibilityAttributeValue:NSAccessibilityVerticalScrollBarAttribute]);
    END_AX_OBJC_EXCEPTIONS        

    return nullptr;
}

PassRefPtr<AccessibilityUIElement> AccessibilityUIElement::create(PlatformUIElement uiElement)
{
    return adoptRef(new AccessibilityUIElement(uiElement));
}
Therefore, every time when the property is accessed, an new AccessibilityUIElement is created and returned. I am not sure which constructor it calls. I am assuming the follows:
AccessibilityUIElement::AccessibilityUIElement(PlatformUIElement element)
    : m_element(element)
    , m_notificationHandler(0)
{
    // FIXME: [e-mail] says ObjC objects need to be CFRetained/CFRelease to be GC-compliant on the mac.
    [m_element retain];
}

In DumpRenderTree:
AccessibilityUIElement AccessibilityUIElement::verticalScrollbar() const
{
    BEGIN_AX_OBJC_EXCEPTIONS
    return AccessibilityUIElement([m_element accessibilityAttributeValue:NSAccessibilityVerticalScrollBarAttribute]);
    END_AX_OBJC_EXCEPTIONS        

    return nullptr;
}

AccessibilityUIElement::AccessibilityUIElement(PlatformUIElement element)
    : m_element(element)
    , m_notificationHandler(0)
{
    // FIXME: [e-mail] says ObjC objects need to be CFRetained/CFRelease to be GC-compliant on the mac.
    [m_element retain];
}
Here, a ref will be returned directly.

In fact, the DumpRenderTree will loop as well, but it stops after the second try. Therefore, I am not sure whether it is due to some reasons specific to the language itself cause the problem. I suggest to handover the bug to the accessibility guy.

[Jiewen Tan]

Created attachment 267765 [details]
Test Case

[Jiewen Tan]

Created attachment 267766 [details]
Test Case Resource

[chris fleizach]

Created attachment 267781 [details]
patch

[Jiewen Tan]

Comment on attachment 267781 [details]
patch

Could you please remove the skip statement for the test case under LayoutTests/platform/mac-wk2/TestExpectations  L344 as well?

[chris fleizach]

Created attachment 267782 [details]
patch

[Brent Fulgham]

Comment on attachment 267781 [details]
patch

Thanks for fixing this so quickly! r=me.

[WebKit Commit Bot]

Comment on attachment 267782 [details]
patch

Clearing flags on attachment: 267782

Committed r194364: <http://trac.webkit.org/changeset/194364>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.