Fix iterator issues

distribution/openrct2.d.ts

@@ -1165,15 +1165,26 @@ declare global {
 
     interface TrackIterator {
         /**
-         * The position and direction of the current track segment, from the first element.
+         * The position and direction of the current track segment. Usually this is the position of the
+         * element of the segment, however for some segments, it may be offset.
          */
          readonly position: CoordsXYZD;
 
         /**
-         * The current track segment or undefined if at the beginning or end of a disconnected circuit.
+         * The current track segment.
          */
         readonly segment: TrackSegment | undefined;
 
+        /**
+         * Gets the position of where the previous track element should start.
+         */
+        readonly previousPosition: CoordsXYZD | undefined;
+
+        /**
+         * Gets the position of where the next track element should start.
+         */
+        readonly nextPosition: CoordsXYZD | undefined;
+
         /**
          * Moves the iterator to the previous track segment.
          * @returns true if there is a previous segment, otherwise false.

src/openrct2/scripting/bindings/ride/ScTrackIterator.cpp

@@ -42,6 +42,8 @@ void ScTrackIterator::Register(duk_context* ctx)
 {
     dukglue_register_property(ctx, &ScTrackIterator::position_get, nullptr, "position");
     dukglue_register_property(ctx, &ScTrackIterator::segment_get, nullptr, "segment");
+    dukglue_register_property(ctx, &ScTrackIterator::previousPosition_get, nullptr, "previousPosition");
+    dukglue_register_property(ctx, &ScTrackIterator::nextPosition_get, nullptr, "nextPosition");
     dukglue_register_method(ctx, &ScTrackIterator::previous, "previous");
     dukglue_register_method(ctx, &ScTrackIterator::next, "next");
 }
@@ -64,28 +66,69 @@ DukValue ScTrackIterator::segment_get() const
     return GetObjectAsDukValue(ctx, std::make_shared<ScTrackSegment>(_type));
 }
 
+DukValue ScTrackIterator::previousPosition_get() const
+{
+    auto& scriptEngine = GetContext()->GetScriptEngine();
+    auto ctx = scriptEngine.GetContext();
+
+    auto& ted = GetTrackElementDescriptor(_type);
+    auto& seq0 = ted.Block;
+    auto pos = _position + CoordsXYZ(seq0->x, seq0->y, seq0->z);
+
+    auto el = map_get_track_element_at_of_type_seq(pos, _type, 0);
+    if (el == nullptr)
+        return ToDuk(ctx, undefined);
+
+    auto posEl = CoordsXYE(pos.x, pos.y, reinterpret_cast<TileElement*>(el));
+    track_begin_end tbe{};
+    track_block_get_previous(posEl, &tbe);
+    CoordsXYZD result(tbe.end_x, tbe.end_y, tbe.begin_z, tbe.begin_direction);
+    return ToDuk(ctx, result);
+}
+
+DukValue ScTrackIterator::nextPosition_get() const
+{
+    auto& scriptEngine = GetContext()->GetScriptEngine();
+    auto ctx = scriptEngine.GetContext();
+
+    auto& ted = GetTrackElementDescriptor(_type);
+    auto& seq0 = ted.Block;
+    auto pos = _position + CoordsXYZ(seq0->x, seq0->y, seq0->z);
+
+    auto el = map_get_track_element_at_of_type_seq(pos, _type, 0);
+    if (el == nullptr)
+        return ToDuk(ctx, undefined);
+
+    auto posEl = CoordsXYE(_position.x, _position.y, reinterpret_cast<TileElement*>(el));
+    CoordsXYE next;
+    int32_t z{};
+    int32_t direction{};
+    track_block_get_next(&posEl, &next, &z, &direction);
+    CoordsXYZD result(next.x, next.y, z, direction);
+    return ToDuk(ctx, result);
+}
+
 bool ScTrackIterator::previous()
 {
     auto& ted = GetTrackElementDescriptor(_type);
     auto& seq0 = ted.Block;
     auto pos = _position + CoordsXYZ(seq0->x, seq0->y, seq0->z);
 
-    auto el = map_get_track_element_at(pos);
+    auto el = map_get_track_element_at_of_type_seq(pos, _type, 0);
     if (el == nullptr)
         return false;
 
     auto posEl = CoordsXYE(pos.x, pos.y, reinterpret_cast<TileElement*>(el));
     track_begin_end tbe{};
-    auto value = track_block_get_previous(posEl, &tbe);
-    if (tbe.begin_element != nullptr)
+    if (track_block_get_previous(posEl, &tbe))
     {
-        auto prev = CoordsXYE(tbe.begin_x, tbe.begin_y, tbe.begin_element);
+        auto prev = CoordsXYE(tbe.end_x, tbe.end_y, tbe.begin_element);
         auto origin = GetTrackSegmentOrigin(prev);
         if (origin)
         {
             _position = *origin;
             _type = prev.element->AsTrack()->GetTrackType();
-            return value;
+            return true;
         }
     }
     return false;
@@ -97,23 +140,22 @@ bool ScTrackIterator::next()
     auto& seq0 = ted.Block;
     auto pos = _position + CoordsXYZ(seq0->x, seq0->y, seq0->z);
 
-    auto el = map_get_track_element_at(pos);
+    auto el = map_get_track_element_at_of_type_seq(pos, _type, 0);
     if (el == nullptr)
         return false;
 
     auto posEl = CoordsXYE(_position.x, _position.y, reinterpret_cast<TileElement*>(el));
     CoordsXYE next;
     int32_t z{};
-    int32_t direction = -1;
-    auto value = track_block_get_next(&posEl, &next, &z, &direction);
-    if (next.element != nullptr)
+    int32_t direction{};
+    if (track_block_get_next(&posEl, &next, &z, &direction))
     {
         auto origin = GetTrackSegmentOrigin(next);
         if (origin)
         {
             _position = *origin;
             _type = next.element->AsTrack()->GetTrackType();
-            return value;
+            return true;
         }
     }
     return false;

src/openrct2/scripting/bindings/ride/ScTrackIterator.h

@@ -35,6 +35,9 @@ namespace OpenRCT2::Scripting
     private:
         DukValue position_get() const;
         DukValue segment_get() const;
+        DukValue previousPosition_get() const;
+        DukValue nextPosition_get() const;
+
         bool previous();
         bool next();
     };