Yes, the WM_WindowPosChanging approach has worked in all my tests.
I’ve now written a ctQ_ComboTracker singleton with a syncobject around a queue. The class takes care of the hooking in a WndProc, and can send notification messages for show & hide, as well as tracking .IsShowing
I have read about CB_ShowDropDown, but it sounds like that used to ASK the combo to drop down. That said, I just wrote a quick testbed, and I did NOT get it to show the combo
The following works to show a combo,drop(n)
SETKEYCODE(DownKey)
FORWARDKEY(?UI:Combo)
There is also doc on CBN_DropDown as part of a WM_COMMAND message
But I haven’t seen WM_COMMAND appear.
You recently showed a demo which shows when the drop down is hidden or visible
ANN: Combo drop-down state - marketplace / Templates - ClarionHub
May I ask what approach you took ?