don't allow players to pick up items if they are too far away

src/CommonFileFormats.hh

@@ -37,6 +37,14 @@ struct VectorXZF {
   inline double norm2() const {
     return ((this->x * this->x) + (this->z * this->z));
   }
+  inline double dist(const VectorXZF& other) const {
+    return sqrt(this->dist2(other));
+  }
+  inline double dist2(const VectorXZF& other) const {
+    double x = this->x - other.x;
+    double z = this->z - other.z;
+    return ((x * x) + (z * z));
+  }
 
   inline VectorXZF rotate_y(double angle) const {
     double s = sin(angle);

src/ReceiveSubcommands.cc

@@ -2264,6 +2264,15 @@ static asio::awaitable<void> on_pick_up_item_generic(
       co_return;
     }
 
+    // TODO: Figure out what the actual max range is; 30 is an overestimate
+    double dist2 = fi->pos.dist2(c->pos);
+    if (dist2 > 900.0) {
+      l->log.warning_f("Player {} requests to pick up {:08X}, but it is too far away (dist2={})",
+          client_id, item_id, dist2);
+      l->add_item(floor, fi);
+      co_return;
+    }
+
     try {
       p->add_item(fi->data, *s->item_stack_limits(c->version()));
     } catch (const out_of_range&) {