[RESOLVED] UserControl Terminate event not firing

[fafalone]

User sabbath69 pointed out that with my Shell Tree Control, when the control is on a secondary form and that form unloads, the UserControl_Terminate event does not fire; it doesn't until the whole program is exiting. This is not the case with any of the other UCs I checked (besides my other UC, ucShellBrowse, which has the same issue). It seems like something that would happen because something needs to be freed; but cleanup can't occur if the terminate event isn't even fired.
Any thoughts?

[dz32]

[...]

[LaVolpe]

Just curious, does the form actually unload, or stays loaded, but hidden? Might want to place a Debug.Print in the form's terminate event.

Also, in that other thread, the OP mentioned modality. Does this happen only when the secondary form is modal?

You'd say Terminate does occur, but when the entire project is unloaded?

Edited: dz32 & I posted about same time. Sounds like you have a starting point. Ignore above.

[dz32]

[...]

[Eduardo-]

Hello, as dz32 already said I also traced the problem to the reference in the RegisterDragDrop API call.
This reference needs to be freed in order to allow the UserControl to terminate.

My suggestion is:

in References

Private Const WM_SHOWWINDOW As Long = &H18

in pvCreate

'    If hTVD Then Attach hTVD

(the line was commented or removed)

in ucWinProc

Select Case uMsg
    Case WM_SHOWWINDOW
        If Ambient.UserMode Then
            If wParam = 1 Then
                If hTVD Then Attach hTVD
            Else
                Detach
            End If
        End If

It registers the dragdrop when the form is shown and unregister it when the form is unloaded.

[fafalone]

Yup that did it for both controls. Thanks, very much appreciated everyone.

ps- modality didn't matter.

Edit: pps- You don't need to define WM_ constants in ucShellTree or ucShellBrowse, or any oleexp project, as all of the documented ones are supplied in the WindowMessages enum since v3.7.

[sabbath69]

Eduardo/dz32 How were you guys able to trace the issue to that particular call. Did you use a tool to see open references? Very interested in how this was done, to assist me with future coding.

[dz32]

[...]

[Eduardo-]

Eduardo/dz32 How were you guys able to trace the issue to that particular call. Did you use a tool to see open references? Very interested in how this was done, to assist me with future coding.

Hello. I didn't use any tool. I used sucesive aproximations logic and temporarily removing lines of code.
First I removed all the code in the ReadProperties event and checked if the Terminate event happened (it did).
Then traced the problem to pvCreate, then to the line If hTVD Then Attach hTVD (always removing all, some, few or just one line of code and checking if the Terminate event happened or not when closing the form). Then, traced it to Attach, then to the RegisterDragDrop API call, and I saw the word Me there. Me was the reference that prevented the control to terminate.
That reference had to be freed in order to allow the control to terminate.

[sabbath69]

Thanks dz32 and Eduardo!