RE: [litwindow-users] Re: m_current as a pointer

[yrs90 <yr...@ya...>]

Oh, I didn't explain the failure mode for the m_current as pointer
implementation.  I have to paraphrase this because I don't have the stack
trace at hand.  When there was a rule defined using Current and data changed
(I presume this involved something like NotifyChanged("m_List");) then I
would see function calls related to find_scope that were sometimes seeking
...Current... and sometimes seeking the underlying data m_List.  Anyway I
stepped through watching iterations of find_scope until I got a heap
failure.

I rationalized this by thinking that recursing m_current and getting an
m_List member must have triggered Current to be evaluated and so on.
However, I didn't stay with it long to pinpoint the propagation mechanism.
(Lots of loops...) Instead I did a combination of tracing and sitting on
breakpoints until I confirmed I had localized the failure.

Regards,
Joel


-----Original Message-----
Sent: Thursday, April 28, 2005 4:46 AM
To: lit...@li...
Subject: RE: [litwindow-users] Re: m_current as a pointer

> Can you post the relevant code? m_current declaration, and where you 
> call NotifyChanged and other relevant places.

Let's see.  This is a little hard to boil down. I presume (perhaps wrongly)
that you prefer the narrative explanation over a diff.

lwListAdapterBase header was changed so
     mutable accessor    m_current;
became
     mutable accessor    *m_current;
     mutable accessor     m_empty;

m_current was initialized to &m_empty in lwListAdapterBase constructor.
m_empty.destroy() is called in the lwListAdapterBase destructor.

The biggest changes were to CalcCurrent where empty is assigned an empty
object if not !is_valid and m_current either points to the the_item or
m_empty accessor depending on whether the container index indicated an item
was selected.

void lwListAdapterBase::CalcCurrent(int containerIndex) const {
    if (m_items.is_valid() && m_items.is_container()) {
        // the const_accessor points to the end item which is invalid
        // but the type of the item is valid.
        container c=m_items.get_container();
        container::iterator i=containerIndex>=0 ?
m_items.get_container().at(containerIndex) : m_items.get_container().end();
        accessor the_item=*i;
        prop_t type=the_item.get_type();
        if (!m_empty.is_valid())
            m_empty=create_object(type);
        if (i!=c.end())
            m_current = &the_item;
        else {
            m_current = &m_empty;
        }
        g_rapidUI->ValueChanged(*m_current, true);
    }
}


Commands to destroy m_current were removed.  All ValueChanged() calls in
wxListObject were changed to reference *m_current rather than m_current.



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