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SetWindowRgn function

The SetWindowRgn function sets the window region of a window. The window region determines the area within the window where the system permits drawing. The system does not display any portion of a window that lies outside of the window region

Syntax


int SetWindowRgn(
  _In_  HWND hWnd,
  _In_  HRGN hRgn,
  _In_  BOOL bRedraw
);

Parameters

hWnd [in]

A handle to the window whose window region is to be set.

hRgn [in]

A handle to a region. The function sets the window region of the window to this region.

If hRgn is NULL, the function sets the window region to NULL.

bRedraw [in]

Specifies whether the system redraws the window after setting the window region. If bRedraw is TRUE, the system does so; otherwise, it does not.

Typically, you set bRedraw to TRUE if the window is visible.

Return value

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero.

Remarks

When this function is called, the system sends the WM_WINDOWPOSCHANGING and WM_WINDOWPOSCHANGING messages to the window.

The coordinates of a window's window region are relative to the upper-left corner of the window, not the client area of the window.

Note  If the window layout is right-to-left (RTL), the coordinates are relative to the upper-right corner of the window. See Window Layout and Mirroring.

After a successful call to SetWindowRgn, the system owns the region specified by the region handle hRgn. The system does not make a copy of the region. Thus, you should not make any further function calls with this region handle. In particular, do not delete this region handle. The system deletes the region handle when it no longer needed.

To obtain the window region of a window, call the GetWindowRgn function.

Requirements

Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

Header

Winuser.h (include Windows.h)

Library

User32.lib

DLL

User32.dll

See also

Painting and Drawing Overview
Painting and Drawing Functions
GetWindowRgn
WM_WINDOWPOSCHANGING

 

 

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