When a main window is created with the WS_MAXIMIZE or WS_MINIMIZE styleWM_SHOWWINDOW
fShow = (BOOL) wParam; /* show/hide flag */
fnStatus = LOWORD(lParam); /* status flag */The WM_SHOWWINDOW message is sent to a window when it is about 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 minimized or displayed on the screen. When an overlapped window is minimized, all pop-up windows associated with that window are hidden.
fShow
Value of 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.
fnStatus
Value of the low-order word of lParam. Specifies the status of the window being shown. The fnStatus parameter is zero if the message is sent because of a ShowWindow function call; otherwise, fnStatus is one of the following values:
| Value | Description |
| SW_PARENTCLOSING | Parent window is being minimized, or a pop-up window is being hidden. |
| SW_PARENTOPENING | Parent window is opening (being displayed) or a pop-up window is being shown. |
An application should return zero if it processes this message.
The DefWindowProc function hides or shows the window as specified by the message.
The WM_SHOWWINDOW message is not sent under the following circumstances:
When a main window is created with the WS_MAXIMIZE or WS_MINIMIZE style
When the SW_SHOWNORMAL flag is specified in the call to the ShowWindow function