ScrollDC
The ScrollDC
function scrolls a rectangle of bits horizontally and vertically.
BOOL ScrollDC(
|
HDC hDC, |
// handle of device
context |
|
int dx, |
// horizontal
scroll units |
|
int dy, |
// vertical scroll
units |
|
CONST RECT *lprcScroll, |
// address of
structure for scrolling rectangle |
|
CONST RECT *lprcClip, |
// address of
structure for clipping rectangle |
|
HRGN hrgnUpdate, |
// handle of
scrolling region |
|
LPRECT lprcUpdate |
// address of
structure for update rectangle |
|
); |
|
Parameters
hDC
Identifies
the device context that contains the bits to be scrolled.
dx
Specifies the
amount, in device units, of horizontal scrolling. This parameter must be a
negative value to scroll to the left.
dy
Specifies the
amount, in device units, of vertical scrolling. This parameter must be a
negative value to scroll up.
lprcScroll
Points to the
RECT
structure containing the coordinates of the scrolling rectangle.
lprcClip
Points to the
RECT structure containing the coordinates of the clipping rectangle.
Only device bits within the clipping rectangle are affected. Bits scrolled from
the outside of the rectangle to the inside are painted; bits scrolled from the
inside of the rectangle to the outside are not painted.
hrgnUpdate
Identifies
the region uncovered by the scrolling process. ScrollDC defines this
region; it is not necessarily a rectangle.
lprcUpdate
Points to the
RECT structure that receives the coordinates of the rectangle bounding
the scrolling update region. This is the largest rectangular area that requires
repainting. When the function returns, the values in the structure are in
client coordinates, regardless of the mapping mode for the specified device
context. This allows applications to use the update region in a call to the InvalidateRgn function, if required.
Return Values
If the
function succeeds, the return value is nonzero.
If the
function fails, the return value is zero. To get extended error information,
call GetLastError.
Remarks
If the lprcUpdate
parameter is NULL, Windows does not compute the update rectangle. If both the hrgnUpdate
and lprcUpdate parameters are NULL, Windows does not compute the update
region. If hrgnUpdate is not NULL, Windows proceeds as though it
contains a valid handle of the region uncovered by the scrolling process
(defined by ScrollDC).
When you must
scroll the entire client area of a window, use the ScrollWindow function;
otherwise, use ScrollDC.
See Also