RedrawWindow

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Windows Embedded CE 6.0 R3

4/8/2010

This function updates the specified rectangle or region in the client area of a window.

Syntax

BOOL WINAPI RedrawWindow(
  HWND hwnd,
  CONST RECT* lprcUpdate,
  HRGN hrgnUpdate,
  UINT flags
);

Parameters

• hwnd
  [in] Handle to the window that you want to redraw.

  If this parameter is NULL, RedrawWindow updates the desktop window.

• lprcUpdate
  [in] Pointer to a RECT structure that contains the coordinates, in device units, of the update rectangle.

  RedrawWindow ignores this parameter if the hrgnUpdate parameter identifies a region.

• hrgnUpdate
  [in] Handle to the update region.

  If both the hrgnUpdate and lprcUpdate parameters are NULL, RedrawWindow adds the entire client area to the update region.

• flags
  [in] DWORD that specifies one or more redraw options.

  You can use this parameter to invalidate or validate a window, control when repainting occurs, and control the windows that RedrawWindow affects.

  The following table shows the values that invalidate the window.

  Value	Description
  RDW_ERASE	Causes the window to receive a WM_ERASEBKGND message when the window is repainted. Specify this value in combination with the RDW_INVALIDATE value; otherwise, RDW_ERASE has no effect.
  RDW_INTERNALPAINT	Causes the OS to post a WM_PAINT message to the window regardless of whether a portion of the window is invalid.
  RDW_INVALIDATE	Invalidates the rectangle or region that you specify in lprcUpdate or hrgnUpdate. You can set only one of these parameters to a non-NULL value. If both are NULL, RDW_INVALIDATE invalidates the entire window.

  The following table shows the values that validate the window.

  Value	Description
  RDW_NOERASE	Suppresses any pending WM_ERASEBKGND messages.
  RDW_VALIDATE	Validates the rectangle or region that you specify in lprcUpdate or hrgnUpdate. You can set only one of these parameters to a non-NULL value. If both are NULL, RDW_VALIDATE validates the entire window. This value does not affect internal WM_PAINT messages.

  The following table shows the values that control when repainting occurs. RedrawWindow does not repaint unless you specify one of these values.

  Value	Description
  RDW_ERASENOW	Causes the affected windows, which you specify by setting the RDW_ALLCHILDREN and RDW_NOCHILDREN values, to receive WM_ERASEBKGND messages before RedrawWindow returns, if necessary. The affected windows receive WM_PAINT messages at the ordinary time.
  RDW_UPDATENOW	Causes the affected windows, which you specify by setting the RDW_ALLCHILDREN and RDW_NOCHILDREN values, to receive WM_ERASEBKGND and WM_PAINT messages before the RedrawWindow returns, if necessary.

  By default, the set of windows that RedrawWindow affects depends on whether the windows have the WS_CLIPCHILDREN style.

  RedrawWindow does not affect child windows that do not have the WS_CLIPCHILDREN style.

  RedrawWindow recursively validates or invalidates non-WS_CLIPCHILDREN windows until RedrawWindow encounters a WS_CLIPCHILDREN window.

  The following table shows the values that control the windows that RedrawWindow affects.

  Value	Description
  RDW_ALLCHILDREN	Includes child windows, if any, in the repainting operation.
  RDW_NOCHILDREN	Excludes child windows, if any, from the repainting operation.

Return Value

A nonzero value indicates success. Zero indicates failure. To get extended error information, call GetLastError.

Requirements

See Also

Reference

WM_ERASEBKGND
WM_PAINT
RECT