🚀 go-pugleaf

"borland" <rogersmail@ntlworld.com> wrote in message
news:40d3e14f@newsgroups.borland.com...

> the only difference between the two programs is the listview
> that works fine is placed upon a form directly, whereas this
> one that i am having trouble with is place upon a TabSheet
> which in turn is on a PageControl.

That makes a *big* difference.  You are trying to catch the message in the
wrong place.  The Parent of the ListView is the one that always receives the
message.  In this case, the TabSheet, not the form, will be the one to
receive the message.  Since you are trying to catch it from the form itself,
you will never see the message when the ListView is on the TabSheet.

With that said, you should subclass the ListView's WindowProc property
directly and then look for CN_NOTIFY messages instead of WM_NOTIFY.  The VCL
is specifically set up to forward WM_NOTIFY and WM_COMMAND messages to
individual components so that they can handle their own messages directly
regardless of which Parent components received the original messages.

In other words, do the following instead:

    TWndMethod OldListViewProc = NULL;

    __fastcall TMainForm::TMainForm(TComponent *Owner)
        : TForm(Owner)
    {
        OldListViewProc = ListView1->WindowProc;
        ListView1->WindowProc = ListViewWndProc;
    }

    void __fastcall TMainForm::ListViewWndProc(TMessage &Message)
    {
        if( Message.Msg == CN_NOTIFY )
        {
            LPNM_LISTVIEW lpnm = (NM_LISTVIEW *)Message.LParam;
            if( lpnm->hdr.code == NM_CUSTOMDRAW )
            {
                // at this point, you already know the message belongs
                // to the ListView so just always handle it here as
needed...
                return;
            }
        }

        // default handling...
        OldListViewProc(Message);
    }


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