InvalidateRgn
The InvalidateRgn
function invalidates the client area within the specified region by adding it
to the current update region of a window. The invalidated region, along with
all other areas in the update region, is marked for painting when the next WM_PAINT message occurs.
BOOL InvalidateRgn(
|
HWND hWnd, |
// handle of window
with changed update region |
|
HRGN hRgn, |
// handle of region
to add |
|
BOOL bErase |
// erase-background
flag |
|
); |
|
Parameters
hWnd
Identifies
the window with an update region that is to be modified.
hRgn
Identifies
the region to be added to the update region. The region is assumed to have
client coordinates. If this parameter is NULL, the entire client area is added
to the update region.
bErase
Specifies
whether the background within the update region should be erased when the
update region is processed. If this parameter is TRUE, the background is erased
when the BeginPaint
function is called. If the parameter is FALSE, the background remains
unchanged.
Return Values
The return
value is always nonzero.
Remarks
Invalidated
areas accumulate in the update region until the next WM_PAINT message is
processed 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.
The specified
region must have been created by using one of the region functions.
If the bErase
parameter is TRUE for any part of the update region, the background in the
entire region is erased, not just in the specified part.
See Also