I've got a treeview listing files that are dropped upon it.
When I make a new treeview item, I'd like to store the address of the file as a string in that item, and retrieve it for various nefarious purposes at a later point in time.
Looking at the TVITEM structure in Microsoft docs, apparently LPARAM is the place to store a value:
lParam
Type: LPARAM A value to associate with the item.
So, I have gone ahead and done that:
TVITEM tvi;
tvi.mask = TVIF_TEXT;
tvi.pszText = const_cast<char *> (str0.c_str());
tvi.cchTextMax = sizeof(tvi.pszText);
tvi.lParam = (LPARAM) foo; // SETTING LPARAM HERE, foo IS A const char *
TVINSERTSTRUCT tvis;
tvis.item = tvi;
tvis.hInsertAfter = 0;
tvis.hParent = hti0;
// Send message to update tree, and return tree item.
return TreeView_InsertItem(tvw_filelist_, &tvis);
Then, when I try to retrieve my value...
HTREEITEM htiSel = TreeView_GetSelection(tvw_filelist_);
TVITEM tvItem;
tvItem.hItem = htiSel;
TreeView_GetItem(tvw_filelist_, &tvItem);
const char * info = (const char *) tvItem.lParam;
MessageBox(NULL, info, "Alert", MB_OK);
...I just get garbage, indicating my pointer went out of scope or is taking a nap or something. The size of that pointer is always 4.
Is this the right way to do what I'm trying to do? If so, what's going on?
Of course, take the time to post a question after a long time trying to figure it out, and the answer shows up in seconds.
Turns out the TVITEM mask needs to include TVIF_PARAM, similar to this question.
If I change the above code to:
tvi.mask = TVIF_TEXT | TVIF_PARAM;
it works as expected.
I'm still not sure if this is the recommended use for LPARAM, though.