InvalidateRect
The InvalidateRect
function adds a rectangle to the specified window s update region. The update
region represents the portion of the window s client area that must be redrawn.
BOOL InvalidateRect(
|
HWND hWnd, |
// handle of window
with changed update region |
|
CONST RECT *lpRect, |
// address of
rectangle coordinates |
|
BOOL bErase |
// erase-background
flag |
|
); |
|
Parameters
hWnd
Identifies
the window whose update region has changed. If this parameter is NULL, Windows
invalidates and redraws all windows, and sends the WM_ERASEBKGND and WM_NCPAINT messages to the window procedure
before the function returns.
lpRect
Points to a RECT structure that contains the
client coordinates of the rectangle to be added to the update region. If this
parameter is NULL, the entire client area is added to the update region.
bErase
Specifies
whether the background within the update region is to be erased when the update
region is processed. If this parameter is TRUE, the background is erased when
the BeginPaint
function is called. If this parameter is FALSE, the background remains
unchanged.
Return Values
If the
function succeeds, the return value is nonzero.
If the function
fails, the return value is zero.
Remarks
The
invalidated areas accumulate in the update region until the region is processed
when the next WM_PAINT
message occurs or until the region is validated by using the ValidateRect or ValidateRgn function.
Windows sends
a WM_PAINT message to a window whenever its update region is not empty and
there are no other messages in the application queue for that window.
If the bErase
parameter is TRUE for any part of the update region, the background is erased
in the entire region, not just in the given part.
See Also