WM_GETMINMAXINFO
lpmmi = (LPMINMAXINFO) lParam; /* address of structure */
The WM_GETMINMAXINFO message is sent to a window whenever Windows needs the maximized position or dimensions of the window or needs the maximum or minimum tracking size of the window. The maximized size of a window is the size of the window when its borders are fully extended. The maximum tracking size of a window is the largest window size that can be achieved by using the borders to size the window. The minimum tracking size of a window is the smallest window size that can be achieved by using the borders to size the window.
Win32 fills in a MINMAXINFO data structure, specifying default values for the various positions and dimensions. The application may change these values if it processes this message.
lpmmi
Value of lParam. Points to a MINMAXINFO data structure. The MINMAXINFO structure has the following form:
typedef struct tagMINMAXINFO { /* mmi */
POINT ptReserved;
POINT ptMaxSize;
POINT ptMaxPosition;
POINT ptMinTrackSize;
POINT ptMaxTrackSize;
} MINMAXINFO, *LPMINMAXINFO;
An application should return zero if it processes this message.