This message is sent when a window is to be hidden or shown. A window is hidden or shown when the ShowWindow function is called; when an overlapped window is maximized or restored; or when an overlapped or pop-up window is closed (made iconic) or opened (displayed on the screen). When an overlapped window is closed, all pop-up windows associated with that window are hidden.
wParam
Specifies whether a window is being shown. It is TRUE if the window is being shown. It is FALSE if the window is being hidden.
lParam
Specifies the status of the window being shown. It is zero if the message is sent because of a ShowWindow function call. Otherwise, the lParam parameter is one of the following values:
| Value | Description |
| SW_PARENTCLOSING | Parent window is closing (being made iconic) or a pop-up window is being hidden. |
| SW_PARENTOPENING | Parent window is opening (being displayed) or a pop-up window is being shown. |
The DefWindowProc function hides or shows the window as specified by the message.
ShowWindow