[Solved] How to activate scroll wheel for scrollable graphic?

[qwert]

I use a child GUI to display a graphic that often exceeds the height of that control, so I've defined a vertical scroll bar. Everything about the scroll bar works fine -- except that the graphic doesn't scroll when I try to use the mouse scroll wheel. (The wheel works fine with all other applications.)

I've searched with no success for anything to indicate that a separate "enable scroll wheel" step is needed. These are the WM_VSCROLL entries I have defined:

Switch $nScrollCode
        Case $SB_TOP ; user clicked the HOME keyboard key
            DllStructSetData($tSCROLLINFO, "nPos", $Min)

        Case $SB_BOTTOM ; user clicked the END keyboard key
            DllStructSetData($tSCROLLINFO, "nPos", $Max)

        Case $SB_LINEUP ; user clicked the top arrow
            DllStructSetData($tSCROLLINFO, "nPos", $Pos - 1)

        Case $SB_LINEDOWN ; user clicked the bottom arrow
            DllStructSetData($tSCROLLINFO, "nPos", $Pos + 1)

        Case $SB_PAGEUP ; user clicked the scroll bar shaft above the scroll box
            DllStructSetData($tSCROLLINFO, "nPos", $Pos - $Page)

        Case $SB_PAGEDOWN ; user clicked the scroll bar shaft below the scroll box
            DllStructSetData($tSCROLLINFO, "nPos", $Pos + $Page)

        Case $SB_THUMBTRACK ; user dragged the scroll box
            DllStructSetData($tSCROLLINFO, "nPos", $TrackPos)
    EndSwitch

I will appreciate a nudge in the right direction.

Thanks.

Edited September 2, 2009 by qwert

[bolthead]

This should help

#710515

[qwert]

Excellent reference. Thank you.

Just to clarify for others, the technique is to register a separate function to detect a scroll wheel movement ... and then send a message to the (previously-defined) WM_VSCROLL function to invoke an up or down shift:

GUIRegisterMsg($WM_MOUSEWHEEL, 'WM_MOUSEWHEEL')
;
;
Func WM_MOUSEWHEEL($hWnd, $iMsg, $iwParam, $ilParam)
    Local $iDelta = BitShift($iwParam, 16)
    If $iDelta > 0 Then
        _SendMessage($GUI, $WM_VSCROLL, $SB_LINEUP)
    Else
        _SendMessage($GUI, $WM_VSCROLL, $SB_LINEDOWN)
    EndIf
    Return 'GUI_RUNDEFMSG'
EndFunc