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4/8/2010

This 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.

Syntax 

BOOL InvalidateRect( 
  HWND 
hWnd, 
  const RECT* 
lpRect, 
  BOOL 
bErase
);

Parameters

hWnd

Handle to the window whose update region has changed.

If you pass a NULL value for this parameter InvalidateRecttakes no action and returns FALSE.

lpRect

Long pointer to a RECTstructure 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

Boolean that 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 BeginPaintfunction is called.

If this parameter is FALSE, the background remains unchanged.

Return Value

Nonzero indicates success.

Zero indicates failure.

To get extended error information, call GetLastError.

To get extended error information, call GetLastError.

Remarks

The hWndparameter cannot be NULL.

The invalidated areas accumulate in the update region until the region is processed when the next WM_PAINTmessage occurs or until the region is validated by using the ValidateRectfunction.

The system sends a WM_PAINTmessage 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 bEraseparameter is TRUE for any part of the update region, the background is erased in the entire region, not just in the given part.

Requirements

Header winuser.h
Library coredll.lib, Winmgr.lib
Windows Embedded CE Windows CE 1.0 and later
Windows Mobile Windows Mobile Version 5.0 and later

See Also