InvalidateRect

This function adds a rectangle to the specified windows update region. The update region represents the portion of the windows 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 this parameter is NULL, the system invalidates and redraws all windows, and sends the WM_ERASEBKGND message to the window procedure before the function returns.
• 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

Note   This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.

See Also

BeginPaint, GetLastError, ValidateRect, WM_ERASEBKGND, WM_PAINT, RECT

 Last updated on Tuesday, July 13, 2004

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