list view doesn't receive LBN_SELCHANGE messages

[eth0]

Hi all.

My list view is a child window of my main window created with the following

hListView = CreateWindowEx(0,
                   WC_LISTVIEW,
                   NULL,
                   WS_CHILD | WS_VISIBLE | LVS_REPORT | WS_BORDER |
                   LBS_NOTIFY | LVS_SORTASCENDING | LBS_NOREDRAW,
                   0, 0, 0, 0,
                   hwnd,
                   (HMENU) IDC_SERVLIST,
                   hInstance,
                   NULL);

when an item is selected, I'm not recieving any messages from my list box.
I thought that having the LBS_NOTIFY flag directed all list view messages to the parent window.

I do however receive WM_NOTIFY messages when an item is double clicked.

Any ideas what is going wrong? I'm use windows not dialogs.

For reference, here is my main window creation code

hMainWnd = CreateWindowEx(
	    0,
	    ClassName,
	    _T("Test List View"),
	    WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN,
	    CW_USEDEFAULT, CW_USEDEFAULT, 650, 450,
	    NULL, NULL, hInstance, NULL);

[anonytmouse]

LBN_SELCHANGE is received through the WM_COMMAND message. Does your code look something like this:

case WM_COMMAND:
{
    if (HIWORD(wParam) == LBN_SELCHANGE && LOWORD(wParam) == IDC_SERVLIST)
    {
          // do something...
    }
}

[eth0]

yes. Here is my code :

case WM_COMMAND:

    switch(LOWORD(wParam))
    {
        case IDC_SERVLIST:
            switch (HIWORD(wParam))
            {
                case LBN_SELCHANGE:
                    MessageBox(NULL, _T("sel changed"), _T("note"), MB_ICONEXCLAMATION | MB_OK);
            }
        break;
...

Putting a break point on WM_COMMAND doesn't fire up the debugger when changing seletion in the list view. WM_COMMAND messages do not seem to be getting to the parent window, or are not being generated by the list view.

[Cactus_Hugger]

Do list view controls generate LBN_* notifications? (And for that matter, do List View's accept LBS_* styles?) I'm unsing Spy++ on one of my apps with a list view (which I granted the LBS_NOTIFY style for testing), and it's not sending any WM_COMMANDs either. It is sending WM_NOTIFY's though, with some with LVN_ITEMCHANGED.

The LVN_ITEMCHANGED notification gives a NM_LISTVIEW structure, detailing the change. I get a bunch of them too... I assume one saying that the item isn't selected for the old selection, and one saying that the new selection is selected. The state member of the LV_ITEM structure contains info on whether or not that item is selected.
At any rate, LVN_ITEMCHANGED should tell you, with the NM_LISTVIEW.uChanged member being LVIS_SELECTED (hopefully...), but you might get two of these. (One when the original selection is deselected, etc. Might not matter.) Perhaps this is what you want...

Edit: My app also needs to check selection state as it turns out, so I tried my above method, no go. I get LVN_ITEMCHANGED notifications ok, but the uChanged member makes no sense... it's set to 8, which is LVIS_DROPHILITE, when I select things. (Hell, my ListView doesn't even let me drag & drop stuff...)

[anonytmouse]

Do list view controls generate LBN_* notifications?

Nice catch Cactus_Hugger! LBN_ notifications are obviously for list boxes.

My app also needs to check selection state as it turns out, so I tried my above method, no go. I get LVN_ITEMCHANGED notifications ok, but the uChanged member makes no sense... it's set to 8, which is LVIS_DROPHILITE, when I select things. (Hell, my ListView doesn't even let me drag & drop stuff...)

The uChanged member contains a mask of which members of the LVITEM structure for the item have changed. 0x0008 is LVIF_STATE, meaning that LVITEM.state has changed. When uChanged includes LVIF_STATE, you can look at uNewState and uOldState to check whether the selection has changed. A selected item will have the LVIS_SELECTED bit set.

Something like this:

case WM_NOTIFY:
{
	NMHDR* nm = (NMHDR*) lParam;

	if ( nm->idFrom == IDC_MYLISTVIEW &&
	     nm->code == LVN_ITEMCHANGED )
	{
		LPNMLISTVIEW pnmv = (LPNMLISTVIEW) lParam;

		if ( (pnmv->uChanged & LVIF_STATE) &&
		     (pnmv->uNewState & LVIS_SELECTED) != (pnmv->uOldState & LVIS_SELECTED) )
		{
			// pnmv->iItem has been selected or deselected.

			if (pnmv->uNewState & LVIS_SELECTED)
				PRINT("Item number %d has been selected\n", pnmv->iItem);
			else
				PRINT("Item number %d has been deselected\n", pnmv->iItem);
		}
	}
}

[Cactus_Hugger]

Ah, you're exactly right! I entirely misread the help on uChanged. I was expecting it to have the same flags as the state member (LVIS_*), when it says (in bold, admittidly...) same flags as the mask member... (LVIF_*). Problem solved for me, hopefully for eth0 too.

Thanks for that info! (Hope I didn't hijack your thread eth0... ;-) )

[eth0]

(Hope I didn't hijack your thread eth0... ;-) )

Nope, I got my answer and learned something else too.
Thanks guys