sf_mcheckpress_area   Returns .t. if mouse pressed in given area
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 *  function logical sf_mcheckpress_area prototype
      parameters value int valid_button,;
                 value int lr,;
                 value int lc,;
                 value int rr,;
                 value int rc

    Returns logical .t. if the given mouse button was pressed in the given
    area.

#define  MOUSE_NONE    0
#define  MOUSE_LEFT    1
#define  MOUSE_MIDDLE  3
#define  MOUSE_RIGHT   2