Advanced MFC Programming

Chapter 5. Common Controls
((CSpinButtonCtrl *)GetDlgItem(IDC_SPIN_HOR))->SetRange(50, 0);
((CSpinButtonCtrl *)GetDlgItem(IDC_SPIN_HOR))->SetBase(10);
((CSpinButtonCtrl *)GetDlgItem(IDC_SPIN_HOR))->SetPos(25);
}
return TRUE;
5.3 Displaying Text Strings in the Buddy Window
Sometimes we want the buddy to display text strings rather than numerical numbers. For example, we
may prefer the text displayed in the buddy window to be “One”, “Two”, “Three”… rather than “1”, “2”,
“3”…. To customize this style, we could not use “Set buddy integer” style anymore. Instead, we need to
write our own message handlers and set the buddy control’s text by ourselves.
When the position of a spin has changed, the parent window of the spin control will receive a
UDN_DELTAPOS message. From this message, we can get the current position of the spin control, along with
the proposed change to the current position. Based on this information, we can decide what we should
display in the buddy control window.
Sample 5.3\CCtl demonstrates how to display text strings in a buddy window. It is based on sample
5.2\CCtl, with a new spin control IDC_SPIN_STR and an edit box IDC_EDIT_STR added to the application.
The edit control will display text strings “Zero”, “One”, “Two”,…, “Nine” instead of integers. The buddy
of spin IDC_SPIN_STR is set automatically.
The UDN_DELTAPOS message handler can be added through following steps: 1) Invoke Class Wizard,
click “Messages Maps” tab. 2) Select “CCCtlDlg” class from “Class name” window, then highlight
“IDC_SPIN_STR” in “Object IDs” window. 3) There will be two messages contained in “Messages”
window, we need to highlight “UDN_DELTAPOS” and press “Add function” button. The newly added
function will look like follows:
void CCCtlDlg::OnDeltaposSpinStr(NMHDR* pNMHDR, LRESULT* pResult)
{
NM_UPDOWN* pNMUpDown = (NM_UPDOWN*)pNMHDR;
}
*pResult = 0;
The first parameter here is a NMHDR type pointer. This is a structure that contains Windows
notification messages. A notification message is sent to the parent window of a common control to notify
the changes on that control. It is used to handle events such as mouse left button clicking, left button double
clicking, mouse right button clicking, and right button double clicking performed on a common control.
Many types of common controls use this message to notify the parent window. For spin control, after
receiving this message, we need to cast the pointer type from NMHDR to NM_UPDOWN. Here structure
MN_UPDOWN is defined as follows:
typedef struct _NM_UPDOWN { nmud
NMHDR hdr; // notification message header
int iPos; // current position
int iDelta; // proposed change in position
} NM_UPDOWNW;
In the structure, member iPos specifies the current position of the spin control, and iDelta indicates
the proposed change on spin’s position. We can calculate the new position of the spin control by adding up
these two members.
The following function shows how the buddy’s text is set after receiving the message:
void CCCtlDlg::OnDeltaposSpinStr(NMHDR* pNMHDR, LRESULT* pResult)
{
int nNewPos;
char szNumber[][16]=
{
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