Graphics Reference
In-Depth Information
.
// removed content similar to that from
Listing 2.6 (Tutorial 2.2)
.
void
CTutorialDlg::DoDataExchange(CDataExchange
*
pDX) {
A2:
DDX
_
Text(pDX, IDC
_
H
_
SLIDER
_
ECHO, m
_
HSliderEcho);
DDX
_
Text(pDX, IDC
_
V
_
SLIDER
_
ECHO, m
_
VSliderEcho);
B2:
DDX
_
Control(pDX, IDC
_
V
_
SLIDER
_
BAR, m
_
VSliderBar);
DDX
_
Control(pDX, IDC
_
H
_
SLIDER
_
BAR, m
_
HSliderBar);
.
BEGIN
_
MESSAGE
_
MAP(CTutorialDlg, CDialog)
C2:
ON
_
WM
_
HSCROLL()
ON
_
WM
_
VSCROLL()
.
BOOL
CTutorialDlg::
OnInitDialog
() {
A3:
m
_
VSliderEcho.Format("
%
d", 0); m
_
HSliderEcho.Format("
%
d", 0);
B3:
m
_
VSliderBar.SetRange(0, 100, TRUE); m
_
VSliderBar.SetPos(0);
.
B4:
UpdateData(
false
);
.
C3:
This is the
Horizontal
scroll bar serviceroutine we override from MFC.
void
CTutorialDlg::OnHScroll(UINT nSBCode, UINT nPos, CScrollBar
*
pScrollBar) {
// check to make sure we know which slider bar is generating the events
if
(pScrollBar == (CScrollBar
*
)&m
_
HSliderBar) {
C4:
int
value = m
_
HSliderBar.GetPos();
C5:
m
_
HSliderEcho.Format("
%
d", value);
C6:
UpdateData(
false
);
.
C7:
This is the
Vertical
scroll bar serviceroutine we override from MFC.
void
CTutorialDlg::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar
*
pScrollBar) {
// content complements that of
OnHScroll
Listing 2.7.
(cont.)
HandV.
To avoid repeating
every sentence with an “
H
”
for horizontal and an “
V
”for
vertical, we omit the “
H/V
”
characters and use one iden-
tifier to refer to both. For
example,
OnScroll()
is re-
ferring to
On
H
Scroll()
and
On
V
Scroll
.
•
Slider bar service routines (C).
At label C1, we declare
OnScroll()
for
servicing all horizontal and vertical scroll bars. Notice that before the ser-
vice registration at label C2, these two are just simple functions. At label
C2, we register for the
ON
_
WM
_
SCROLL
(on window scroll) event. Notice
that no callback functions are passed in. The horizontal and vertical scroll
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