navigator mission block fix get_time_inside() and cleanup helpers

src/modules/navigator/mission_block.cpp

@@ -477,10 +477,14 @@ MissionBlock::issue_command(const mission_item_s &item)
 }
 
 float
-MissionBlock::get_time_inside(const struct mission_item_s &item)
+MissionBlock::get_time_inside(const mission_item_s &item) const
 {
-	if (item.nav_cmd != NAV_CMD_TAKEOFF) {
-		return item.time_inside;
+	if ((item.nav_cmd == NAV_CMD_WAYPOINT && _navigator->get_vstatus()->is_rotary_wing) ||
+	    item.nav_cmd == NAV_CMD_LOITER_TIME_LIMIT ||
+	    item.nav_cmd == NAV_CMD_DELAY) {
+
+		// a negative time inside would be invalid
+		return math::max(item.time_inside, 0.0f);
 	}
 
 	return 0.0f;
@@ -510,7 +514,7 @@ MissionBlock::mission_item_to_position_setpoint(const mission_item_s &item, posi
 
 	sp->lat = item.lat;
 	sp->lon = item.lon;
-	sp->alt = item.altitude_is_relative ? item.altitude + _navigator->get_home_position()->alt : item.altitude;
+	sp->alt = get_absolute_altitude_for_item(item);
 	sp->yaw = item.yaw;
 	sp->yaw_valid = PX4_ISFINITE(item.yaw);
 	sp->loiter_radius = (fabsf(item.loiter_radius) > NAV_EPSILON_POSITION) ? fabsf(item.loiter_radius) :
@@ -736,7 +740,7 @@ MissionBlock::mission_apply_limitation(mission_item_s &item)
 }
 
 float
-MissionBlock::get_absolute_altitude_for_item(struct mission_item_s &mission_item) const
+MissionBlock::get_absolute_altitude_for_item(const mission_item_s &mission_item) const
 {
 	if (mission_item.altitude_is_relative) {
 		return mission_item.altitude + _navigator->get_home_position()->alt;

src/modules/navigator/mission_block.h

@@ -115,13 +115,13 @@ protected:
 	/**
 	 * General function used to adjust the mission item based on vehicle specific limitations
 	 */
-	void	mission_apply_limitation(mission_item_s &item);
+	void mission_apply_limitation(mission_item_s &item);
 
 	void issue_command(const mission_item_s &item);
 
-	float get_time_inside(const struct mission_item_s &item);
+	float get_time_inside(const mission_item_s &item) const ;
 
-	float get_absolute_altitude_for_item(struct mission_item_s &mission_item) const;
+	float get_absolute_altitude_for_item(const mission_item_s &mission_item) const;
 
 	mission_item_s _mission_item{};