SpatialMap now uses unordered_multimap to allow for multiple items in a square, but they're also tagged to mark some with collision.

Makefile

@@ -37,7 +37,7 @@ tracy_build:
 	meson compile -j 10 -C builddir
 
 test: asset_build build
-	./builddir/runtests
+	./builddir/runtests "[collision]"
 
 run: build test
 ifeq '$(OS)' 'Windows_NT'
@@ -60,7 +60,7 @@ clean:
 	meson compile --clean -C builddir
 
 debug_test: build
-	gdb --nx -x .gdbinit --ex run --args builddir/runtests -e
+	gdb --nx -x .gdbinit --ex run --args builddir/runtests -e "[collision]"
 
 win_installer:
 	powershell 'start "C:\Program Files (x86)\solicus\InstallForge\bin\ifbuilderenvx86.exe" scripts\win_installer.ifp'

dinkyecs.hpp

@@ -14,6 +14,8 @@ namespace DinkyECS
 {
   using Entity = unsigned long;
 
+  const Entity NONE = 0;
+
   using EntityMap = std::unordered_map<Entity, size_t>;
 
   template <typename T>
@@ -30,7 +32,7 @@ namespace DinkyECS
   typedef std::queue<Event> EventQueue;
 
   struct World {
-    unsigned long entity_count = 0;
+    unsigned long entity_count = NONE+1;
     std::unordered_map<std::type_index, EntityMap> $components;
     std::unordered_map<std::type_index, std::any> $facts;
     std::unordered_map<std::type_index, EventQueue> $events;

spatialmap.cpp

@@ -6,46 +6,49 @@ using namespace fmt;
 using DinkyECS::Entity;
 
 void SpatialMap::insert(Point pos, Entity ent, bool has_collision) {
-  if(has_collision) {
-    dbc::check(!yes_collision.contains(pos), "YES_collision already has entity");
-    yes_collision.insert_or_assign(pos, ent);
-  } else {
-    dbc::check(!no_collision.contains(pos), "no_collision already has entity");
-    no_collision.insert_or_assign(pos, ent);
-  }
+  dbc::check(!occupied(pos), "attempt to insert an entity with collision in space with collision");
+
+  $collision.emplace(pos, CollisionData{ent, has_collision});
 }
 
-bool SpatialMap::remove(Point pos) {
-  if(yes_collision.contains(pos)) {
-    yes_collision.erase(pos);
-    return true;
-  } else {
-    dbc::check(no_collision.contains(pos), "remove of entity that's not in no_collision");
-    no_collision.erase(pos);
-    return false;
+CollisionData SpatialMap::remove(Point pos, Entity ent) {
+  auto [begin, end] = $collision.equal_range(pos);
+  for(auto it = begin; it != end; ++it) {
+    if(it->second.entity == ent) {
+      // does the it->second go invalid after erase?
+      auto copy = it->second;
+      $collision.erase(it);
+      return copy;
+    }
   }
+
+  dbc::sentinel("failed to find entity to remove");
 }
 
 void SpatialMap::move(Point from, Point to, Entity ent) {
-  dbc::check(!occupied(to), "attempt to move to point with an existing entity");
-  bool has_collision = remove(from);
-  insert(to, ent, has_collision);
+  auto data = remove(from, ent);
+  insert(to, ent, data.collision);
 }
 
 bool SpatialMap::occupied(Point at) const {
-  return yes_collision.contains(at);
+  auto [begin, end] = $collision.equal_range(at);
+  for(auto it = begin; it != end; ++it) {
+    if(it->second.collision) {
+      return true;
+    }
+  }
+
+  return false;
 }
 
 bool SpatialMap::something_there(Point at) const {
-  return yes_collision.contains(at) || no_collision.contains(at);
+  return $collision.count(at) > 0;
 }
 
 Entity SpatialMap::get(Point at) const {
-  if(yes_collision.contains(at)) {
-    return yes_collision.at(at);
-  } else {
-    return no_collision.at(at);
-  }
+  dbc::check($collision.contains(at), "attempt to get entity when none there");
+  auto [begin, end] = $collision.equal_range(at);
+  return begin->second.entity;
 }
 
 /*
@@ -63,7 +66,7 @@ inline void find_neighbor(const PointEntityMap &table, EntityList &result, Point
 
   auto it = table.find(cell);
   if (it != table.end()) {
-    result.insert(result.end(), it->second);
+    result.insert(result.end(), it->second.entity);
   }
 }
 
@@ -72,16 +75,16 @@ FoundEntities SpatialMap::neighbors(Point cell, bool diag) const {
 
   // just unroll the loop since we only check four directions
   // this also solves the problem that it was detecting that the cell was automatically included as a "neighbor" but it's not
-  find_neighbor(yes_collision, result, cell, 0, 1); // north
-  find_neighbor(yes_collision, result, cell, 0, -1); // south
-  find_neighbor(yes_collision, result, cell, 1, 0); // east
-  find_neighbor(yes_collision, result, cell, -1, 0); // west
+  find_neighbor($collision, result, cell, 0, 1); // north
+  find_neighbor($collision, result, cell, 0, -1); // south
+  find_neighbor($collision, result, cell, 1, 0); // east
+  find_neighbor($collision, result, cell, -1, 0); // west
 
   if(diag) {
-    find_neighbor(yes_collision, result, cell, 1, -1); // south east
-    find_neighbor(yes_collision, result, cell, -1, -1); // south west
-    find_neighbor(yes_collision, result, cell, 1, 1); // north east
-    find_neighbor(yes_collision, result, cell, -1, 1); // north west
+    find_neighbor($collision, result, cell, 1, -1); // south east
+    find_neighbor($collision, result, cell, -1, -1); // south west
+    find_neighbor($collision, result, cell, 1, 1); // north east
+    find_neighbor($collision, result, cell, -1, 1); // north west
   }
 
   return {!result.empty(), result};
@@ -94,7 +97,7 @@ inline void update_sorted(SortedEntities& sprite_distance, PointEntityMap& table
         (from.y - sprite.y) * (from.y - sprite.y);
 
     if(inside < max_dist) {
-      sprite_distance.push_back({inside, rec.second});
+      sprite_distance.push_back({inside, rec.second.entity});
     }
   }
 }
@@ -102,8 +105,7 @@ inline void update_sorted(SortedEntities& sprite_distance, PointEntityMap& table
 SortedEntities SpatialMap::distance_sorted(Point from, int max_dist) {
   SortedEntities sprite_distance;
 
-  update_sorted(sprite_distance, yes_collision, from, max_dist);
-  update_sorted(sprite_distance, no_collision, from, max_dist);
+  update_sorted(sprite_distance, $collision, from, max_dist);
 
   std::sort(sprite_distance.begin(), sprite_distance.end(), std::greater<>());
 

spatialmap.hpp

@@ -5,10 +5,14 @@
 #include "dinkyecs.hpp"
 #include "point.hpp"
 
-typedef std::vector<DinkyECS::Entity> EntityList;
+struct CollisionData {
+  DinkyECS::Entity entity = DinkyECS::NONE;
+  bool collision = false;
+};
 
 // Point's has is in point.hpp
-using PointEntityMap = std::unordered_map<Point, DinkyECS::Entity>;
+using EntityList = std::vector<DinkyECS::Entity>;
+using PointEntityMap = std::unordered_multimap<Point, CollisionData>;
 using SortedEntities = std::vector<std::pair<int, DinkyECS::Entity>>;
 
 struct FoundEntities {
@@ -19,18 +23,17 @@ struct FoundEntities {
 class SpatialMap {
   public:
     SpatialMap() {}
-    PointEntityMap yes_collision;
-    PointEntityMap no_collision;
+    PointEntityMap $collision;
 
     void insert(Point pos, DinkyECS::Entity obj, bool has_collision);
     void move(Point from, Point to, DinkyECS::Entity ent);
     // return value is whether the removed thing has collision
-    bool remove(Point pos);
+    CollisionData remove(Point pos, DinkyECS::Entity entity);
     bool occupied(Point pos) const;
     bool something_there(Point at) const;
     DinkyECS::Entity get(Point at) const;
     FoundEntities neighbors(Point position, bool diag=false) const;
 
     SortedEntities distance_sorted(Point from, int max_distance);
-    size_t size() { return yes_collision.size(); }
+    size_t size() { return $collision.size(); }
 };

systems.cpp

@@ -214,7 +214,7 @@ void System::death(GameLevel &level) {
     auto pos = world.get<Position>(ent);
 
     // need to remove _after_ getting the position
-    level.collision->remove(pos.location);
+    level.collision->remove(pos.location, ent);
 
     // distribute_loot is then responsible for putting something there
     System::distribute_loot(level, pos);
@@ -327,7 +327,7 @@ void System::collision(GameLevel &level) {
  */
 void System::remove_from_world(GameLevel &level, Entity entity) {
   auto& item_pos = level.world->get<Position>(entity);
-  level.collision->remove(item_pos.location);
+  level.collision->remove(item_pos.location, entity);
   level.world->remove<Tile>(entity);
   // if you don't do this you get the bug that you can pickup
   // an item and it'll also be in your inventory

tests/spatialmap.cpp

@@ -37,7 +37,7 @@ TEST_CASE("confirm basic collision operations", "[collision]") {
   REQUIRE(nearby[0] == player);
 
   { // removed
-    collider.remove({11,11});
+    collider.remove({11,11}, player);
     auto [found, nearby] = collider.neighbors({10,10}, true);
     REQUIRE(!found);
     REQUIRE(nearby.empty());
@@ -141,7 +141,7 @@ TEST_CASE("check all diagonal works", "[collision]") {
   }
 }
 
-TEST_CASE("confirm can iterate through all", "[spatialmap-sort]") {
+TEST_CASE("confirm can iterate through all", "[collision]") {
   DinkyECS::World world;
   SpatialMap collider;
   Point player{10,10};
@@ -154,8 +154,10 @@ TEST_CASE("confirm can iterate through all", "[spatialmap-sort]") {
       size_t y = Random::uniform<size_t>(0, 251);
 
       Entity ent = world.entity();
+      if(!collider.occupied({x, y})) {
         collider.insert({x,y}, ent, true);
       }
+    }
 
     auto sprite_distance = collider.distance_sorted(player, 1000);