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RedrawWindow The RedrawWindow function updates the specified rectangle or region in a window’s client area.
VB4-32,5,6
Declare Function RedrawWindow Lib "user32" Alias "RedrawWindow" (ByVal hwnd As Long, lprcUpdate As RECT, ByVal hrgnUpdate As Long, ByVal fuRedraw As Long) As Long |
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Operating Systems Supported |
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Requires Windows NT 3.1 or later; Requires Windows 95 or later |
- hWnd
Identifies the window to be redrawn. If this parameter is NULL, the desktop window is updated.
- lprcUpdate
Points to a RECT structure containing the coordinates of the update rectangle. This parameter is ignored if the hrgnUpdate parameter identifies a region.
- hrgnUpdate
Identifies the update region. If both the hrgnUpdate and lprcUpdate parameters are NULL, the entire client area is added to the update region.
- flags
Specifies one or more redraw flags. This parameter can be a combination of flags that invalidate or validate a window, control repainting, and control which windows are affected by RedrawWindow.
The following flags are used to invalidate the window:
RDW_ERASE
Causes the window to receive a WM_ERASEBKGND message when the window is repainted. The RDW_INVALIDATE flag must also be specified; otherwise, RDW_ERASE has no effect.
RDW_FRAME
Causes any part of the nonclient area of the window that intersects the update region to receive a WM_NCPAINT message. The RDW_INVALIDATE flag must also be specified; otherwise, RDW_FRAME has no effect. The WM_NCPAINT message is typically not sent during the execution of RedrawWindow unless either RDW_UPDATENOW or RDW_ERASENOW is specified.
RDW_INTERNALPAINT
Causes a WM_PAINT message to be posted to the window regardless of whether any portion of the window is invalid.
RDW_INVALIDATE
Invalidates lprcUpdate or hrgnUpdate (only one may be non-NULL). If both are NULL, the entire window is invalidated.
The following flags are used to validate the window:
RDW_NOERASE
Suppresses any pending WM_ERASEBKGND messages.
RDW_NOFRAME
Suppresses any pending WM_NCPAINT messages. This flag must be used with RDW_VALIDATE and is typically used with RDW_NOCHILDREN. RDW_NOFRAME should be used with care, as it could cause parts of a window to be painted improperly.
RDW_NOINTERNALPAINT
Suppresses any pending internal WM_PAINT messages. This flag does not affect WM_PAINT messages resulting from a non-NULL update area.
RDW_VALIDATE
Validates lprcUpdate or hrgnUpdate (only one may be non-NULL). If both are NULL, the entire window is validated. This flag does not affect internal WM_PAINT messages.
The following flags control when repainting occurs. RedrawWindow will not repaint unless one of these flags is specified.
RDW_ERASENOW
Causes the affected windows (as specified by the RDW_ALLCHILDREN and RDW_NOCHILDREN flags) to receive WM_NCPAINT and WM_ERASEBKGND messages, if necessary, before the function returns. WM_PAINT messages are received at the ordinary time.
RDW_UPDATENOW
Causes the affected windows (as specified by the RDW_ALLCHILDREN and RDW_NOCHILDREN flags) to receive WM_NCPAINT, WM_ERASEBKGND, and WM_PAINT messages, if necessary, before the function returns.
By default, the windows affected by RedrawWindow depend on whether the given window has the WS_CLIPCHILDREN style. Child windows that are not the WS_CLIPCHILDREN style are unaffected; non-WS_CLIPCHILDREN windows are recursively validated or invalidated until a WS_CLIPCHILDREN window is encountered. The following flags control which windows are affected by the RedrawWindow function:
RDW_ALLCHILDREN
Includes child windows, if any, in the repainting operation.
RDW_NOCHILDREN
Excludes child windows, if any, from the repainting operation. |
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, call GetLastError. |
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