NM_UPDOWN* pNMUpDown = (NM_UPDOWN*)pNMHDR;
// TODO: Add your control notification handler code here
pNMUpDown->iDelta > 0 ---> increase
pNMUpDown->iDelta < 0 ---> decrease
// TODO: Add your control notification handler code here
pNMUpDown->iDelta > 0 ---> increase
pNMUpDown->iDelta < 0 ---> decrease
pNMUpDown->iDelta > 0 ---> decreasep
pNMUpDown->iDelta < 0 ---> increase
为什么?