CODEWITHSUNDEEP
c++mfcscrollbar
Alpha_33
Alpha_33

Reputation: 97

OnVScroll : invoked from CSpinButtonCtrl or Vertical ScrollBar?

I have a derived MFC CFormView class (CMyFormView) and I must implement my own OnVScroll function.

My CMyFormView is used for several dialog box resources, mainly, to re-implement the OnCtlColor() function. Some dialogs contain a CSpinButtonCtrl control.

My problem:
When the OnVScroll function is invoked, I am unable to know if the Windows message comes from a CSpinButtonCtrl or from the scrollbar.

void CMyFormView :: OnVScroll (UINT nSBCode, UINT nPos, CScrollBar * pScrollBar)
{
// message comes from CSpinButtonCtrl or VscrollBare ?
}

I cannot use the CSpinButtonCtrl IDs (dlgitem) of the controls because they are very numerous.

Question:
How to know if the message comes from a CSpinButtonCtrl or the scrollbar?

Environment details:

Upvotes: 1

Views: 309

Answers (1)

Adrian Mole
Adrian Mole

Reputation: 51825

If the OnVScroll handler is called via actions in a window's (framework-provided) scrollbar, then the pScrollBar parameter will be NULL; if it is from a control, then it will not be NULL. From the CWnd Documentation:

pScrollBar
If the scroll message came from a scroll-bar control, contains a pointer to the control. If the user clicked a window's scroll bar, this parameter is NULL. The pointer may be temporary and should not be stored for later use.

So, you can simply check for a NULL value:

void CMyFormView :: OnVScroll (UINT nSBCode, UINT nPos, CScrollBar * pScrollBar)
{
    if (!pScrollBar) {
        // From window's scrollbar...
    }
    else {
        // From a control...
    }
}

Upvotes: 1

Related Questions