[Webkit-unassigned] [Bug 93002] webkit_dom_document_create_tree_walker impossible to use due to WebKitDOMNodeFilter

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Mon Jun 16 05:40:31 PDT 2014


Carlos Garcia Campos <cgarcia at igalia.com> changed:

           What    |Removed                     |Added
                 CC|                            |cgarcia at igalia.com,
                   |                            |gns at gnome.org,
                   |                            |mrobinson at webkit.org

--- Comment #2 from Carlos Garcia Campos <cgarcia at igalia.com>  2014-06-16 05:40:53 PST ---
(In reply to comment #0)
> As per http://lists.webkit.org/pipermail/webkit-gtk/2012-August/001186.html, the following bug (incomplete functionality) exists with the WebKitDOMTreeWalker API:
> webkit_dom_document_create_tree_walker is not possible to use, because:
> 1) It requires a non-NULL WebKitDOMNodeFilter pointer
> As per the usage of document.createTreeWalker in Javascript, this is a bug because you are allowed to pass "null" for the Filter parameter in Javascript.  In WebKitDOMDocument.cpp, in the function body for webkit_dom_document_create_tree_walker, the line g_return_val_if_fail(filter, 0) should be removed, because WebCore::Document::createTreeWalker() will accept a NULL filter.  The Document::createTreeWalker() function will convert the null raw pointer to a smart pointer, and pass it to a WebCore::Traversal instance.  WebCore::Traversal will then check for a NULL filter in Traversal::acceptNode.  So there is no reason for the GTK layer to check for a NULL with g_return_val_if_fail(filter, 0).

We should add this method to canBeNullParams variable to indicate that the node filter can be NULL.

> 2) The Webkit GTK API does not expose any means to create a WebKitDOMNodeFilter object.  (The header file WebKitDOMNodeFilter.h does not expose a constructor.)
> In combination with (1), this second bug makes WebKitDOMTreeWalker impossible to use at all, since the Webkit GTK API exposes no way to instantiate a WebKitDOMNodeFilter instance.  In WebKitDOMNodeFilter.h there needs to be a constructor function exposed, which wraps a WebCore::NodeFilter object.  It's also unclear how the WebKit GTK API handles user-provided Node Filters (which are handled using the virtual function NodeFilterCondition::acceptNode() in WebCore.)  Presumably, a derived class of webCore::NodeFilterCondition would need to be created which just defers to a wrapped C function provided at the Webkit-GTK layer.

The problem is that WebKitDOMNodeFilter shouldn't be a class but an interface, since the method accept_node needs to be implemented by the user.

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