How to handle click events on a Windows treeview items - windows

Question

How can I handle individual items being clicked in a MS Windows treeview ?
My windows proc has :
LRESULT CALLBACK WndProcTreeView(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
PAINTSTRUCT paintStruct;
HDC hDC;
switch (message)
{
case WM_PAINT:
{
hDC = BeginPaint(hwnd, &paintStruct);
EndPaint(hwnd, &paintStruct);
break;
}
case WM_NOTIFY:
{
switch (reinterpret_cast<LPNMHDR>(lParam)->code) {
case NM_CLICK:
MessageBox(nullptr, "click", "click", MB_OK);
}
}
default:
{
return DefWindowProc(hwnd, message, wParam, lParam);
break;
}
}
Which outputs a message box when I click on the treeview control. How can I handle individual elements ?
Example of a treeview item being added to the list :
std::string vTxt = std::string("Vertex count : ") + std::to_string(mesh.v.size());
tvinsert.hInsertAfter = mesh_items[mesh_items.size() - 1];
tvinsert.hParent = mesh_items[mesh_items.size() - 1];
tvinsert.item.mask = TVIF_TEXT;
tvinsert.item.pszText = (LPSTR)vTxt.c_str();
mesh_items_sub.push_back((HTREEITEM)SendMessage(hwnd, TVM_INSERTITEM, 0, (LPARAM)&tvinsert));
I have seen using SendDlgItemMessage instead (which gives an ID as LOWORD(wParam) inside the windows proc) but it requires IDs set in a resource file - which I don't know how to create.

Answer 1

Two things I needed for my code to work : first give each item a lparam value and changing TVIF_TEXT as item's mask to TVIF_TEXT | TVIF_IMAGE | TVIF_SELECTEDIMAGE | TVIF_PARAM (TVIF_PARAM allowing for an lparam to be passed to the window proc thus identifying the controller).
Working code excerpt :
TV_INSERTSTRUCT tvinsert;
// ...
tvinsert.hInsertAfter = Root;
tvinsert.hParent = Root;
tvinsert.item.pszText = std::string("some text...").c_str();
tvinsert.item.lParam = ID_SOME_ID; // << #defined constant or plain int
tvinsert.item.mask = TVIF_TEXT | TVIF_IMAGE | TVIF_SELECTEDIMAGE | TVIF_PARAM;
root_sub.push_back((HTREEITEM)SendMessage(hwnd, TVM_INSERTITEM, 0, (LPARAM)&tvinsert));
// window proc code below
LRESULT CALLBACK WndProcTreeView(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
PAINTSTRUCT paintStruct;
HDC hDC;
switch (message)
{
case WM_PAINT:
{
hDC = BeginPaint(hwnd, &paintStruct);
EndPaint(hwnd, &paintStruct);
break;
}
case WM_NOTIFY:
{
LPNM_TREEVIEW pntv = (LPNM_TREEVIEW)lParam;
if (pntv->hdr.code == TVN_SELCHANGED) {
switch (pntv->itemNew.lParam) {
case ID_SOME_ID:
std::cout << "ID_SOME_ID selected caught here..." << std::endl;
break;
}
}
}
default:
{
return DefWindowProc(hwnd, message, wParam, lParam);
break;
}
}
return 0;
}
Good explanation/example here (in french) http://chgi.developpez.com/windows/treeview/