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InvalidateRect

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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.

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 then InvalidateRect will take no action and return FALSE.
  • lpRect
    Long pointer 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
    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 BeginPaint function is called. If this parameter is FALSE, the background remains unchanged.

Return Values

Nonzero indicates success. Zero indicates failure. To get extended error information, call GetLastError.

To get extended error information, call GetLastError.

Remarks

The hWnd parameter cannot be NULL.

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 function.

The system 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.

Requirements

OS Versions: Windows CE 1.0 and later.
Header: Winuser.h.
Link Library: Coredll.lib, Winmgr.lib.

See Also

BeginPaint | ValidateRect | WM_ERASEBKGND | WM_PAINT | RECT

Last updated on Wednesday, April 13, 2005

© 2005 Microsoft Corporation. All rights reserved.