GetWindowRgn function (winuser.h)

Article
10/13/2021

The GetWindowRgn function obtains a copy of the window region of a window. The window region of a window is set by calling the SetWindowRgn function. 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 GetWindowRgn(
  [in] HWND hWnd,
  [in] HRGN hRgn
);

Parameters

[in] hWnd

Handle to the window whose window region is to be obtained.

[in] hRgn

Handle to the region which will be modified to represent the window region.

Return value

The return value specifies the type of the region that the function obtains. It can be one of the following values.

Return code	Description
NULLREGION	The region is empty.
SIMPLEREGION	The region is a single rectangle.
COMPLEXREGION	The region is more than one rectangle.
ERROR	The specified window does not have a region, or an error occurred while attempting to return the region.

Remarks

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.

To set the window region of a window, call the SetWindowRgn function.

Examples

The following code shows how you pass in the handle of an existing region.


HRGN hrgn = CreateRectRgn(0,0,0,0);
int regionType = GetWindowRgn(hwnd, hrgn);
if (regionType != ERROR) 
{ 
/* hrgn contains window region */ 
}
DeleteObject(hrgn); /* finished with region */

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winuser.h (include Windows.h)
Library	User32.lib
DLL	User32.dll
API set	ext-ms-win-ntuser-draw-l1-1-2 (introduced in Windows 10, version 10.0.10240)