Compute can_holser once per save to speed up d: filter from ~20s to ~5s

src/item.cpp

@@ -5994,15 +5994,7 @@ void item::final_info( std::vector<iteminfo> &info, const iteminfo_query *parts,
     }
 
     // does the item fit in any holsters?
-    std::vector<const itype *> holsters = Item_factory::find( [this]( const itype & e ) {
-        if( !e.can_use( "holster" ) ) {
-            return false;
-        }
-        const holster_actor *ptr = dynamic_cast<const holster_actor *>
-                                   ( e.get_use( "holster" )->get_actor_ptr() );
-        const item holster_item( &e );
-        return ptr->can_holster( holster_item, *this ) && !item_is_blacklisted( holster_item.typeId() );
-    } );
+    std::vector<const itype *> holsters = item_controller->find_holster_for( *type );
 
     if( !holsters.empty() && parts->test( iteminfo_parts::DESCRIPTION_HOLSTERS ) ) {
         insert_separation_line( info );

src/item_factory.cpp

@@ -4832,6 +4832,7 @@ void Item_factory::reset()
 void Item_factory::clear()
 {
     m_template_groups.clear();
+    type_contained_in_holsters.clear();
 
     iuse_function_list.clear();
 
@@ -5469,6 +5470,27 @@ std::vector<const itype *> Item_factory::find( const std::function<bool( const i
     return res;
 }
 
+const std::vector<const itype *> &Item_factory::find_holster_for( const itype &it )
+{
+    const itype_id iid = it.get_id();
+    if( type_contained_in_holsters.count( iid ) > 0 ) {
+        return type_contained_in_holsters.at( iid );
+    }
+    const item itm( &it );
+
+    type_contained_in_holsters[iid] = Item_factory::find( [&itm]( const itype & e ) {
+        if( !e.can_use( "holster" ) ) {
+            return false;
+        }
+        const holster_actor *ptr = dynamic_cast<const holster_actor *>
+                                   ( e.get_use( "holster" )->get_actor_ptr() );
+        const item holster_item( &e );
+        return ptr->can_holster( holster_item, itm );
+    } );
+
+    return type_contained_in_holsters[iid];
+}
+
 std::list<itype_id> Item_factory::subtype_replacement( const itype_id &base ) const
 {
     std::list<itype_id> ret;

src/item_factory.h

@@ -266,6 +266,14 @@ class Item_factory
 
         /** Find all item templates (both static and runtime) matching UnaryPredicate function */
         static std::vector<const itype *> find( const std::function<bool( const itype & )> &func );
+        /**
+         * Find all holsters for itype. Uses type_contained_in_holsters cache, so it's much faster
+         * than constructing the result on the fly.
+         *
+         * This internally constructs an empty item from the itype. It should not be used as replacement
+         * for item::can_holster (for non-empty items). Ignores blacklist too.
+         */
+        const std::vector<const itype *> &find_holster_for( const itype & );
 
         std::list<itype_id> subtype_replacement( const itype_id & ) const;
 
@@ -285,6 +293,9 @@ class Item_factory
         std::unordered_map<itype_id, ammotype> migrated_ammo;
         std::unordered_map<itype_id, itype_id> migrated_magazines;
 
+        // cache for holsters
+        std::unordered_map<itype_id, std::vector<const itype *>> type_contained_in_holsters;
+
         /** Checks that ammo is listed in ammunition_type::name().
          * At least one instance of this ammo type should be defined.
          * If any of checks fails, prints a message to the msg stream.