CB_GETDROPPEDCONTROLRECT
wParam = 0; /* not used, must be zero */
lParam = (LPARAM) (RECT FAR*) lprc; /* address of RECT structure */
An application sends a CB_GETDROPPEDCONTROLRECT message to retrieve the screen coordinates of the visible (dropped-down) list box of a combo box.
lprc
Value of lParam. Points to the RECT structure that is to receive the coordinates. The RECT structure has the following form:
typedef struct tagRECT { /* rc */
LONG left;
LONG top;
LONG right;
LONG bottom;
} RECT;
This message always returns CB_OKAY.