AP_Mission: 2of3 add loiter_xtrack option flag for post-loiter navigation via param4

0 to crosstrack from center of waypoint, 1 to crosstrack from tangent exit location

libraries/AP_Mission/AP_Mission.cpp

@@ -536,6 +536,7 @@ MAV_MISSION_RESULT AP_Mission::mavlink_int_to_mission_cmd(const mavlink_mission_
         uint16_t radius_m = fabsf(packet.param3);        // param 3 is radius in meters is held in high p1
         cmd.p1 = (radius_m<<8) | (num_turns & 0x00FF);   // store radius in high byte of p1, num turns in low byte of p1
         cmd.content.location.flags.loiter_ccw = (packet.param3 < 0);
+        cmd.content.location.flags.loiter_xtrack = (packet.param4 > 0); // 0 to xtrack from center of waypoint, 1 to xtrack from tangent exit location
     }
         break;
 
@@ -543,6 +544,7 @@ MAV_MISSION_RESULT AP_Mission::mavlink_int_to_mission_cmd(const mavlink_mission_
         copy_location = true;
         cmd.p1 = packet.param1;                         // loiter time in seconds uses all 16 bits, 8bit seconds is too small. No room for radius.
         cmd.content.location.flags.loiter_ccw = (packet.param3 < 0);
+        cmd.content.location.flags.loiter_xtrack = (packet.param4 > 0); // 0 to xtrack from center of waypoint, 1 to xtrack from tangent exit location
         break;
 
     case MAV_CMD_NAV_RETURN_TO_LAUNCH:                  // MAV ID: 20
@@ -571,6 +573,7 @@ MAV_MISSION_RESULT AP_Mission::mavlink_int_to_mission_cmd(const mavlink_mission_
         copy_location = true;
         cmd.p1 = fabsf(packet.param2);                  // param2 is radius in meters
         cmd.content.location.flags.loiter_ccw = (packet.param2 < 0);
+        cmd.content.location.flags.loiter_xtrack = (packet.param4 > 0); // 0 to xtrack from center of waypoint, 1 to xtrack from tangent exit location
         break;
 
     case MAV_CMD_NAV_SPLINE_WAYPOINT:                   // MAV ID: 82
@@ -950,6 +953,7 @@ bool AP_Mission::mission_cmd_to_mavlink_int(const AP_Mission::Mission_Command& c
         if (cmd.content.location.flags.loiter_ccw) {
             packet.param3 = -packet.param3;
         }
+        packet.param4 = cmd.content.location.flags.loiter_xtrack; // 0 to xtrack from center of waypoint, 1 to xtrack from tangent exit location
         break;
 
     case MAV_CMD_NAV_LOITER_TIME:                       // MAV ID: 19
@@ -960,6 +964,7 @@ bool AP_Mission::mission_cmd_to_mavlink_int(const AP_Mission::Mission_Command& c
         } else {
             packet.param3 = 1;
         }
+        packet.param4 = cmd.content.location.flags.loiter_xtrack; // 0 to xtrack from center of waypoint, 1 to xtrack from tangent exit location
         break;
 
     case MAV_CMD_NAV_RETURN_TO_LAUNCH:                  // MAV ID: 20
@@ -990,6 +995,7 @@ bool AP_Mission::mission_cmd_to_mavlink_int(const AP_Mission::Mission_Command& c
         if (cmd.content.location.flags.loiter_ccw) {
             packet.param2 = -packet.param2;
         }
+        packet.param4 = cmd.content.location.flags.loiter_xtrack; // 0 to xtrack from center of waypoint, 1 to xtrack from tangent exit location
         break;
 
     case MAV_CMD_NAV_SPLINE_WAYPOINT:                   // MAV ID: 82