Advanced MFC Programming

Chapter 5. Common Controls
}
The initially selected bitmap is IDC_BITMAP_SMILE_1. We should not load bitmaps for other states
(“down”, “focused” and “disabled”) because the purpose of this button is to display images rather than
executing commands. We need to change the currently loaded image upon receiving UDN_DELTAPOS
notification. To change button’s associated bitmap, in the sample application, a UDN_DELTAPOS message
handler is added for IDC_SPIN_BMP, which is implemented as follows:
void CCCtlDlg::OnDeltaposSpinBmp(NMHDR* pNMHDR, LRESULT* pResult)
{
int nNewPos;
NM_UPDOWN *pNMUpDown=(NM_UPDOWN*)pNMHDR;
}
nNewPos=pNMUpDown->iPos+pNMUpDown->iDelta;
switch(nNewPos)
{
case 0:
{
m_bmpBtn.LoadBitmaps(IDB_BITMAP_SMILE_1);
break;
}
case 1:
{
m_bmpBtn.LoadBitmaps(IDB_BITMAP_SMILE_2);
break;
}
case 2:
{
m_bmpBtn.LoadBitmaps(IDB_BITMAP_SMILE_3);
break;
}
case 3:
{
m_bmpBtn.LoadBitmaps(IDB_BITMAP_SMILE_4);
break;
}
}
m_bmpBtn.Invalidate();
*pResult=0;
Although we say that the bitmap button is the buddy of the spin control, in the above implementation
we see that they do not have special relationship. A spin control needs a buddy only in the case when we
want the text in the buddy window to be updated automatically. If we implement this in UDN_DELTAPOS
message handler, the buddy loses its meaning because we can actually set text for any control. Although
this is true, here we still treat the bitmap button as the buddy of spin control because the bitmap button is
under the control of the spin.
5.5 Slider
A slider is a control that allows the user to select a value from pre-defined range using mouse or
keyboard. A slider can be customized to have many different styles: we can put tick marks on it, set its
starting and ending ranges, make the tick marks distributed linearly or non-linearly. Besides these
attributes, we can also set the line size and page size of a slider, which decide the minimum distance the
slider moves when the user clicks mouse on slider’s rail or hit arrow keys of the keyboard.
Including Slider Control in the Application
Sample 5.5\CCtl demonstrates how to use the slider control. It is a standard dialog based application
generated by the Application Wizard. In the dialog box, three different sliders are implemented, they are
used to show how to set tick marks, page size, line size, and implement other customizations.
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