feat: spawn active items on mapgen (#4283)

* Documentation

* Give `place_item` an `active` argument.

Now you can spawn grenades active in houses, or you know, atomic lights

* `item_groups` can spawn `active` items

* revert active grenades on roof

* fix: msvc does not like auto return types

* fix: move pointer explicitly

Co-authored-by: joveeater <joveasarus@gmail.com>

* style(autofix.ci): automated formatting

* docs(mapgen): class fields

Co-authored-by: Coolthulhu <Coolthulhu@gmail.com>

* docs(item_spawn): be more explicit, add examples

Co-authored-by: Coolthulhu <Coolthulhu@gmail.com>

---------

Co-authored-by: KheirFerrum <102964889+KheirFerrum@users.noreply.github.com>
Co-authored-by: joveeater <joveasarus@gmail.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Coolthulhu <Coolthulhu@gmail.com>

doc/src/content/docs/en/mod/json/reference/items/item_spawn.md

@@ -94,6 +94,7 @@ item(s):
 "charges": <number>|<array>,
 "charges-min": <number>,
 "charges-max": <number>,
+"active": "<bool>"
 "contents-item": "<item-id>" (can be a string or an array of strings),
 "contents-group": "<group-id>" (can be a string or an array of strings),
 "ammo-item": "<ammo-item-id>",
@@ -111,6 +112,33 @@ item. This allows water, that contains a book, that contains a steel frame, that
 or ammo/magazine capacity. Setting max too high will decrease it to maximum capacity. Not setting
 min will set it to 0 when max is set.
 
+`active`: If true, activates the item on spawn. Note that this _does not work_ for itemgroups, only
+individual items _within_ itemgroups.
+
+#### `active` Usage example
+
+```json
+[
+  {
+    "id": "test_grenade",
+    "type": "item_group",
+    "subtype": "collection",
+    "items": [{ "item": "grenade_act", "prob": 100, "active": true }]
+  },
+  {
+    "type": "mapgen",
+    "method": "json",
+    "om_terrain": "shelter_roof",
+    "weight": 100,
+    "object": {
+      // ...
+      "place_items": [{ "item": "test_grenade", "x": 12, "y": 12, "chance": 100, "repeat": 1 }],
+      "place_item": [{ "item": "grenade_act", "x": 15, "y": 15, "chance": 100, "active": true }]
+    }
+  }
+]
+```
+
 ```json
 "damage-min": 0,
 "damage-max": 3,

src/item_factory.cpp

@@ -3121,6 +3121,22 @@ bool Item_factory::load_string( std::vector<std::string> &vec, const JsonObject
     return result;
 }
 
+namespace
+{
+auto load_active( std::vector<ItemFn> &xs, const JsonObject &obj ) -> bool
+{
+    const bool result = obj.has_bool( "active" ) && obj.get_bool( "active" );
+    if( result ) {
+        xs.emplace_back( []( detached_ptr<item> &&it ) {
+            it->activate();
+            return std::move( it );
+        } );
+    }
+    return result;
+}
+
+} // namespace
+
 void Item_factory::add_entry( Item_group &ig, const JsonObject &obj )
 {
     std::unique_ptr<Item_group> gptr;
@@ -3164,6 +3180,7 @@ void Item_factory::add_entry( Item_group &ig, const JsonObject &obj )
     use_modifier |= load_sub_ref( modifier.ammo, obj, "ammo", ig );
     use_modifier |= load_sub_ref( modifier.container, obj, "container", ig );
     use_modifier |= load_sub_ref( modifier.contents, obj, "contents", ig );
+    use_modifier |= load_active( modifier.postprocess_fns, obj );
 
     std::vector<std::string> custom_flags;
     use_modifier |= load_string( custom_flags, obj, "custom-flags" );

src/item_group.cpp

@@ -374,6 +374,10 @@ detached_ptr<item> Item_modifier::modify( detached_ptr<item> &&new_item ) const
     for( const flag_id &flag : custom_flags ) {
         new_item->set_flag( flag );
     }
+
+    for( const auto &fn : postprocess_fns ) {
+        new_item = fn( std::move( new_item ) );
+    }
     return std::move( new_item );
 }
 

src/item_group.h

@@ -144,6 +144,9 @@ class Item_spawn_data
         /** probability, used by the parent object. */
         int probability;
 };
+
+using ItemFn = std::function < detached_ptr<item> ( detached_ptr<item> &&it ) >;
+
 /**
  * Creates a single item, but can change various aspects
  * of the created item.
@@ -186,6 +189,11 @@ class Item_modifier
          */
         std::vector<flag_id> custom_flags;
 
+        /**
+         * Custom functions to be applied to the item after its creation.
+         */
+        std::vector<ItemFn> postprocess_fns;
+
         Item_modifier();
         Item_modifier( Item_modifier && ) = default;
 

src/map.cpp

@@ -4303,6 +4303,10 @@ std::vector<detached_ptr<item>> map::i_clear( const tripoint &p )
 detached_ptr<item> map::spawn_an_item( const tripoint &p, detached_ptr<item> &&new_item,
                                        const int charges, const int damlevel )
 {
+    if( one_in( 3 ) && new_item->has_flag( flag_VARSIZE ) ) {
+        new_item->set_flag( flag_FIT );
+    }
+
     if( charges && new_item->charges > 0 ) {
         //let's fail silently if we specify charges for an item that doesn't support it
         new_item->charges = charges;
@@ -4364,9 +4368,6 @@ void map::spawn_item( const tripoint &p, const itype_id &type_id,
     for( size_t i = 0; i < quantity; i++ ) {
         // spawn the item
         detached_ptr<item> new_item = item::spawn( type_id, birthday );
-        if( one_in( 3 ) && new_item->has_flag( flag_VARSIZE ) ) {
-            new_item->set_flag( flag_FIT );
-        }
 
         spawn_an_item( p, std::move( new_item ), charges, damlevel );
     }

src/mapgen.cpp

@@ -2164,24 +2164,21 @@ class jmapgen_vehicle : public jmapgen_piece
             type.check( oter_name, parameters );
         }
 };
-/**
- * Place a specific item.
- * "item": id of item type to spawn.
- * "chance": chance of spawning it (1 = always, otherwise one_in(chance)).
- * "amount": amount of items to spawn.
- * "repeat": number of times to apply this piece
- */
+
+/// Place a specific item.
 class jmapgen_spawn_item : public jmapgen_piece
 {
     public:
-        mapgen_value<itype_id> type;
-        jmapgen_int amount;
-        jmapgen_int chance;
+        mapgen_value<itype_id> type; //< id of item type to spawn.
+        jmapgen_int amount;          //< amount of items to spawn.
+        jmapgen_int chance;          //< chance of spawning it (1 = always, otherwise one_in(chance)).
+        bool activate_on_spawn;      //< whether to activate the item on spawn.
         jmapgen_spawn_item( const JsonObject &jsi ) :
             type( jsi.get_member( "item" ) )
             , amount( jsi, "amount", 1, 1 )
             , chance( jsi, "chance", 100, 100 ) {
             repeat = jmapgen_int( jsi, "repeat", 1, 1 );
+            activate_on_spawn = jsi.get_bool( "active", false );
         }
         void apply( const mapgendata &dat, const jmapgen_int &x, const jmapgen_int &y
                   ) const override {
@@ -2193,13 +2190,28 @@ class jmapgen_spawn_item : public jmapgen_piece
             // individual items here.
             chosen_id = item_controller->migrate_id( chosen_id );
 
+            if( item_is_blacklisted( chosen_id ) ) {
+                return;
+            }
+
             const int c = chance.get();
 
             // 100% chance = exactly 1 item, otherwise scale by item spawn rate.
             const float spawn_rate = get_option<float>( "ITEM_SPAWNRATE" );
-            int spawn_count = ( c == 100 ) ? 1 : roll_remainder( c * spawn_rate / 100.0f );
+            const int spawn_count = ( c == 100 ) ? 1 : roll_remainder( c * spawn_rate / 100.0f );
+            const int quantity = amount.get();
+
+            const point p = { x.get(), y.get() };
+
             for( int i = 0; i < spawn_count; i++ ) {
-                dat.m.spawn_item( point( x.get(), y.get() ), chosen_id, amount.get() );
+                for( int j = 0; j < quantity; j++ ) {
+                    detached_ptr<item> new_item = item::spawn( chosen_id, calendar::start_of_cataclysm );
+                    if( activate_on_spawn ) {
+                        new_item->activate();
+                    }
+
+                    dat.m.spawn_an_item( p, std::move( new_item ), 0, 0 );
+                }
             }
         }