GetUpdateRect
The GetUpdateRect
function retrieves the coordinates of the smallest rectangle that completely
encloses the update region of the specified window. If the window was created
with the CS_OWNDC style and the mapping mode is not MM_TEXT, GetUpdateRect
retrieves the rectangle in logical coordinates. Otherwise, it retrieves the
rectangle in client coordinates. If there is no update region, GetUpdateRect
retrieves an empty rectangle (sets all coordinates to zero).
BOOL GetUpdateRect(
|
HWND hWnd, |
// handle
of window |
|
LPRECT lpRect, |
// address
of update rectangle coordinates |
|
BOOL bErase |
// erase
flag |
|
); |
|
Parameters
hWnd
Identifies
the window with an update region that is to be retrieved.
lpRect
Points to the
RECT
structure that receives the coordinates of the enclosing rectangle.
An
application can set this parameter to NULL to determine whether an update
region exists for the window. If this parameter is NULL, GetUpdateRect
returns nonzero if an update region exists, and zero if one does not. This provides
a simple and efficient means of determining whether a WM_PAINT message resulted
from an invalid area.
bErase
Specifies
whether the background in the update region is to be erased. If this parameter
is TRUE and the update region is not empty, GetUpdateRect sends a
WM_ERASEBKGND message to the specified window to erase the background.
Return Values
If the update
region is not empty, the return value is nonzero.
If there is
no update region, the return value is zero.
Remarks
The update
rectangle retrieved by the BeginPaint function is identical to that retrieved by GetUpdateRect.
BeginPaint automatically validates the update region, so any
call to GetUpdateRect made immediately after the call to BeginPaint
retrieves an empty update region.
See Also