GetUpdateRect (Compact 2013)

3/28/2014

This function retrieves the coordinates of the smallest rectangle that completely encloses the update region of the specified window in client coordinates.

If there is no update region, GetUpdateRect retrieves an empty rectangle; it sets all coordinates to zero.

Syntax

BOOL GetUpdateRect( 
  HWND hWnd, 
  LPRECT lpRect, 
  BOOL bErase
); 

Parameters

• hWnd
  Handle to the window with an update region that is to be retrieved.

• lpRect
  Long pointer 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_PAINTmessage resulted from an invalid area.

• bErase
  Boolean that 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 Value

Nonzero indicates that the update region is not empty.

Zero indicates that there is no update region.

To get extended error information, call GetLastError.

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.

Requirements

Header	winuser.h
Library	coredll.lib, Winmgr.lib

See Also

Reference

GDI Functions
BeginPaint
GetUpdateRgn
InvalidateRect
UpdateWindow
ValidateRect
RECT