The GET_X_LPARAM macro retrieves the signed x-coordinate from the given LPARAM value.
int GET_X_LPARAM(
LPARAM lParam // value from which the signed x-coordinate is retrieved
);
The return value is the low-order int of the specified value.
The GET_X_LPARAM macro is defined as follows:
#define GET_X_LPARAM(lp) ((int)(short)LOWORD(lp))
Windows Overview, Window Macros, GET_Y_LPARAM, HIWORD, LOWORD