Helicopter bugfixes : allow descending into open air while moving, an…

…d disallow roof teleporting (#39275)

src/vehicle_move.cpp

@@ -980,6 +980,8 @@ bool vehicle::check_heli_descend( player &p )
         debugmsg( "A vehicle is somehow flying without being an aircraft" );
         return true;
     }
+    int count = 0;
+    int air_count = 0;
     for( const tripoint &pt : get_points( true ) ) {
         tripoint below( pt.xy(), pt.z - 1 );
         if( g->m.has_zlevels() && ( pt.z < -OVERMAP_DEPTH ||
@@ -993,8 +995,12 @@ bool vehicle::check_heli_descend( player &p )
                                  _( "It would be unsafe to try and land when there are obstacles below you." ) );
             return false;
         }
+        if( g->m.has_flag_ter_or_furn( TFLAG_NO_FLOOR, below ) ) {
+            air_count++;
+        }
+        count++;
     }
-    if( velocity > 0 ) {
+    if( velocity > 0 && air_count != count ) {
         p.add_msg_if_player( m_bad, _( "It would be unsafe to try and land while you are moving." ) );
         return false;
     }
@@ -1012,6 +1018,16 @@ bool vehicle::check_heli_ascend( player &p )
         p.add_msg_if_player( m_bad, _( "It would be unsafe to try and take off while you are moving." ) );
         return false;
     }
+    for( const tripoint &pt : get_points( true ) ) {
+        tripoint above( pt.xy(), pt.z + 1 );
+        const optional_vpart_position ovp = g->m.veh_at( above );
+        if( g->m.impassable_ter_furn( above ) || ovp || g->critter_at( above ) || !g->m.is_outside( pt ) ||
+            !g->m.is_outside( above ) ) {
+            p.add_msg_if_player( m_bad,
+                                 _( "It would be unsafe to try and ascend when there are obstacles above you." ) );
+            return false;
+        }
+    }
     return true;
 }