bug in xml merging code.

[Mathieu Lacage <mathieu eazel com>]

hi,

I have been trying to fix some misc bugs in nautilus related to the bonobo
new menu merging code.. One of them involves changing the icon of a toplevel
'submenu' item. (although hte problem as described below is not related to 
icon since changing the label name of any toplevel 'submenu' item has the 
same effect)

If you change an attribute of a toplevel 'submenu' item, (ie: 
bonobo_ui_component_set_attr (component, "attrname", "value")), 
bonobo will do 2 things:

        - during the xml merging of the main xml tree and the small
        xml fragment resulting from this function call (in bonobo-ui-xml.c
        function (merge)), it replaces the original toplevel 'submenu' item
        by the 'submenu' item of the xml fragment. ie: it actually
        switches pointers so that the original toplevel 'submenu' items
        have a new sibbling pointer.

        - after xml merging, and during the updating of the widget tree from
        the xml tree, the code behaves as folows: if it finds a widget which
        has a pointer to an xmlNode which is not in the xml tree (yes, each 
        widget holds a pointer to its corresponding xml node and vice-versa)
        it decides to rebuild the widget from scratch and then reinserts it 
        in the widget hierarchy. This has the side effect here of leaving 
        the old toplevel 'submenu' item in the menu tree and duplicating 
        the widgets since the code does not destroy the old widget.
        The relevant code for this is in (bonobo-win.c, function
        sync_generic_widgets. The important line is :
        same = (b != NULL) && (widget_get_node (b->data) == a);

        this piece of code tests if the current widget (b->data) has an xml 
        Node pointer (widget_get_node (b->data)) equal to the current xml 
        node (a). In our case, it does not happen because we changed the 
        pointer to the relevant xml node in teh xml tree although the data
        has not fundamentaly changed.


I am not clear what the correct behaviour should be but my feeling is that the
xml merging code should be more conservative and it should not overide the
xmlNode pointer but it should move the attributes of the new node into the 
old one...

So, I am sorry but I have been unable to fix this bug since I could not figure
out how the current code works: the 'merge' function and 'overide_with_node'
function are really misterious... Rewriting all the xml menu merging code is 
probably what I will do if no one fixes this problem but I hope someone will
find the bug here :)



Mathieu

-- 
Mathieu Lacage <mathieu eazel com>