IsWindowVisible function (winuser.h)

Determines the visibility state of the specified window.

BOOL IsWindowVisible(
  [in] HWND hWnd
);

[in] hWnd

Type: HWND

A handle to the window to be tested.

Type: BOOL

If the specified window, its parent window, its parent's parent window, and so forth, have the WS_VISIBLE style, the return value is nonzero. Otherwise, the return value is zero.

Because the return value specifies whether the window has the WS_VISIBLE style, it may be nonzero even if the window is totally obscured by other windows.

The visibility state of a window is indicated by the WS_VISIBLE style bit. When WS_VISIBLE is set, the window is displayed and subsequent drawing into it is displayed as long as the window has the WS_VISIBLE style.

Any drawing to a window with the WS_VISIBLE style will not be displayed if the window is obscured by other windows or is clipped by its parent window.

Conceptual

Reference

ShowWindow

Windows