Display ETA and distance for destination

+don't overrun our iterators

src/do_turn.cpp

@@ -654,7 +654,7 @@ bool do_turn()
     // consider a stripped down cache just for monsters.
     m.build_map_cache( levz, true );
     monmove();
-    if( calendar::once_every( 5_minutes ) ) {
+    if( calendar::once_every( time_between_npc_OM_moves ) ) {
         overmap_npc_move();
     }
     if( calendar::once_every( 10_seconds ) ) {

src/game_constants.h

@@ -4,6 +4,7 @@
 
 #include <map>
 #include <string>
+#include "calendar.h"
 #include "units.h"
 
 // Fixed window sizes.
@@ -145,6 +146,9 @@ constexpr int BIO_CQB_LEVEL = 5;
 // Minimum size of a horde to show up on the minimap.
 constexpr int HORDE_VISIBILITY_SIZE = 3;
 
+// How often a NPC can move one tile on the overmap
+constexpr time_duration time_between_npc_OM_moves = 5_minutes;
+
 /**
  * Average annual temperature in Kelvin used for climate, weather and temperature calculation.
  * Average New England temperature = 43F/6C rounded to int.

src/npctalk_funcs.cpp

@@ -373,7 +373,7 @@ void talk_function::goto_location( npc &p )
         camps.push_back( temp_camp );
     }
     for( const basecamp *iter : camps ) {
-        //~ %1$s: camp name, %2$d and %3$d: coordinates
+        //~ %1$s: camp name, %2$s: coordinates of the camp
         selection_menu.addentry( i++, true, MENU_AUTOASSIGN, pgettext( "camp", "%1$s at %2$s" ),
                                  iter->camp_name(), iter->camp_omt_pos().to_string() );
     }
@@ -410,7 +410,12 @@ void talk_function::goto_location( npc &p )
     g->follower_path_to_show = &p; // Necessary for overmap display in tiles version...
     ui::omap::display_npc_path( p.global_omt_location(), p.omt_path );
     g->follower_path_to_show = nullptr;
-    if( !query_yn( _( "Is this path and destination acceptable?" ) ) ) {
+    int tiles_to_travel = p.omt_path.size();
+    time_duration ETA = time_between_npc_OM_moves * tiles_to_travel;
+    ETA = ETA * rng_float( 0.8, 1.2 ); // Add +-20% variance in our estimate
+    if( !query_yn(
+            _( "Estimated time to arrival: %1$s  \nTiles to travel: %2$s  \nIs this path and destination acceptable?" ),
+            to_string_approx( ETA ), tiles_to_travel ) ) {
         p.goal = npc::no_goal_point;
         p.omt_path.clear();
         return;

src/overmap_ui.cpp

@@ -1895,9 +1895,9 @@ static tripoint_abs_omt display( const tripoint_abs_omt &orig,
             // We go faster per-tile the more we have to go
             cursor_advance_time = std::chrono::milliseconds( 1000 ) / display_path.size();
             cursor_advance_time = std::max( cursor_advance_time, std::chrono::milliseconds( 1 ) );
-            curs = *display_path_iter;
             if( now > last_advance + cursor_advance_time ) {
                 if( display_path_iter != display_path.rend() ) {
+                    curs = *display_path_iter;
                     last_advance = now;
                     display_path_iter++;
                 } else if( now > last_advance + cursor_advance_time * 10 ) {