How to capture which treeview node is clicked - c

Question

I created a tree view controls using WinApi. I want to capture mouse click on checkboxes. The notification message NM_CLICK contains NMHDR, which has no information about the node being clicked. since the clicked node may be different from the selected node, there should be a way to find which node has been checked or unchecked, It could be HTREEITEM, or lParam Inserted when adding items to tree view. I want to capture the checking/unchecking in real time. How can I specify which Node being checked/unchecked? any help or link appreciated.
mr.abzadeh

Answer 1

I want to capture the checking/unchecking in real time. How can I
specify which Node being checked/unchecked?
for this exist notification TVN_ITEMCHANGING and TVN_ITEMCHANGED - look for uStateNew and uStateOld members of NMTVITEMCHANGE - when tree view have checkboxes (TVS_CHECKBOXES style) it used as state image list with 2 images - unchecked and checked.
so state & TVIS_STATEIMAGEMASK will be 0 when no checkbox, INDEXTOSTATEIMAGEMASK(1) for unchecked and INDEXTOSTATEIMAGEMASK(2) for checked. based on this info we can and capture mouse click on checkboxes
by using TVN_ITEMCHANGING you can also prevent the change when you return TRUE for this notification. if you need only notify - use TVN_ITEMCHANGED
case WM_NOTIFY:
{
union {
LPARAM lp;
NMTVITEMCHANGE *pnm;
NMHDR* phdr;
};
lp = lParam;
switch (phdr->code)
{
case TVN_ITEMCHANGING:
{
UINT CheckStateOld = pnm->uStateOld & TVIS_STATEIMAGEMASK;
UINT CheckStateNew = pnm->uStateNew & TVIS_STATEIMAGEMASK;
if (CheckStateNew != CheckStateOld)
{
PCSTR szstate = "??";
switch (CheckStateNew)
{
case INDEXTOSTATEIMAGEMASK(1):
szstate = "uncheck";
break;
case INDEXTOSTATEIMAGEMASK(2):
szstate = "check";
break;
}
DbgPrint("%p>%s\n", pnm->lParam, szstate);
}
}
return FALSE;
}
}
also read How to Work With State Image Indexes
// Image 1 in the tree-view check box image list is the unchecked box.
// Image 2 is the checked box.
tvItem.state = INDEXTOSTATEIMAGEMASK((fCheck ? 2 : 1));
notification TVN_ITEMCHANGING and TVN_ITEMCHANGED is available begin from Windows Vista. if you need XP support too - on xp only option use #IInspectable solution

Answer 2

You can send a TVM_HITTEST message (or use the TreeView_HitTest macro) to find the tree view item, given a client-relative coordinate.
To get the cursor position at the time the NM_CLICK message was generated, use the GetMessagePos API.
This allows you do monitor any mouse click in the client area of the control. If you are interested in the state changes as the result of the standard tree view control implementation, you can handle the TVN_ITEMCHANGING or TVN_ITEMCHANGED notifications instead. Both supply an NMTVITEMCHANGE structure, where the hItem identifies the item being changed, and lParam carries application specific data.