Map events apart from the map: map_events/<map>/*.json of any mod merged by id (RpgMapEventResolver, RpgMapEventMerge); item Icon look for events; rpg_walk checks a pickup across leaving the map and loading a save

src/Data/RpgMap.cs

@@ -16,7 +16,10 @@ namespace Cthangover.Mods.Rpg
     /// <para/>
     /// Files declare <c>"Kind": "rpg_map"</c>. Layers are parsed by
     /// <see cref="RpgMapGrid"/>; a dependent mod replaces a whole map by id, the
-    /// usual entity override.
+    /// usual entity override. The map file holds only the ground: what stands on it
+    /// (NPCs, doors, chests, pickups) are events in <c>map_events/&lt;id&gt;/</c> of any
+    /// mod, merged by <see cref="RpgMapEventResolver"/>, so a mod adds to another
+    /// mod's map without replacing it.
     /// </summary>
     [EntityKind("rpg_map")]
     public class RpgMap : IIdentifiable
@@ -49,8 +52,6 @@ namespace Cthangover.Mods.Rpg
         /// <summary>Where the player appears when entering the map without a teleport target.</summary>
         public RpgTeleport Spawn { get; set; } = new();
 
-        /// <summary>Events placed on the map.</summary>
-        public List<RpgMapEvent> Events { get; set; } = new();
 
         /// <summary>Random battles; null for a safe map.</summary>
         public RpgEncounterTable Encounters { get; set; }

src/Data/RpgMapEvent.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Text.Json.Serialization;
 
 namespace Cthangover.Mods.Rpg
 {
@@ -7,7 +8,7 @@ namespace Cthangover.Mods.Rpg
     /// RPG Maker events: an NPC, a sign, a chest, a door. What it looks like and
     /// what it does are independent:
     /// <list type="bullet">
-    /// <item>look — a charset <see cref="Sprite"/>, or one atlas <see cref="Tile"/>, or nothing (an invisible trigger);</item>
+    /// <item>look — a charset <see cref="Sprite"/>, or one atlas <see cref="Tile"/>, or an item <see cref="Icon"/>, or nothing (an invisible trigger);</item>
     /// <item>effect — a <see cref="Teleport"/>, handled natively, or a dialog built
     /// from a <see cref="Scenario"/> file followed by inline <see cref="Commands"/>
     /// (the full scenario DSL, so <c>action rpg.battle …</c>, <c>flag …</c>, quests).</item>
@@ -15,6 +16,9 @@ namespace Cthangover.Mods.Rpg
     /// A <see cref="Condition"/> in the scenario condition language hides the
     /// event while false; it is re-checked whenever game state changes, so a
     /// defeated boss (<c>flag boss_dead 1</c>) disappears at once.
+    /// <para/>
+    /// Events are stored apart from their map, in <c>map_events/&lt;map&gt;/*.json</c>
+    /// of any mod (<see cref="RpgMapEventResolver"/>).
     /// </summary>
     public class RpgMapEvent
     {
@@ -33,13 +37,19 @@ namespace Cthangover.Mods.Rpg
         /// <summary>Atlas index of the map's tileset drawn as the event when it has no sprite; -1 for none.</summary>
         public int Tile { get; set; } = -1;
 
+        /// <summary>
+        /// Picture in the <c>items</c> group (what an item's <c>Sprite</c> names), drawn fitted into the
+        /// cell when the event has neither a sprite nor a tile: an item lying on the ground.
+        /// </summary>
+        public string Icon { get; set; }
+
         /// <summary>Initial facing of a sprite.</summary>
         public RpgDirection Dir { get; set; } = RpgDirection.Down;
 
         /// <summary>When the event fires.</summary>
         public RpgEventTrigger Trigger { get; set; } = RpgEventTrigger.Action;
 
-        /// <summary>The event occupies its cell. Null means "solid when it is visible" (a sprite or a tile).</summary>
+        /// <summary>The event occupies its cell. Null means "solid when it is visible" (a sprite, a tile or an icon).</summary>
         public bool? Solid { get; set; }
 
         /// <summary>Scenario path inside the <c>scenarios</c> group (extension optional), played as a dialog.</summary>
@@ -54,7 +64,15 @@ namespace Cthangover.Mods.Rpg
         /// <summary>Scenario condition; the event exists only while it is true.</summary>
         public string Condition { get; set; }
 
+        /// <summary>Mod the event was read from (set by the event resolver, not stored).</summary>
+        [JsonIgnore]
+        public string ModId { get; set; }
+
+        /// <summary>Mod-relative path of the file the event was read from (set by the event resolver, not stored).</summary>
+        [JsonIgnore]
+        public string File { get; set; }
+
         /// <summary>Effective solidity: explicit value, else whether the event is drawn.</summary>
-        public bool IsSolid => Solid ?? (!string.IsNullOrEmpty(Sprite) || Tile >= 0);
+        public bool IsSolid => Solid ?? (!string.IsNullOrEmpty(Sprite) || Tile >= 0 || !string.IsNullOrEmpty(Icon));
     }
 }

src/Data/RpgMapEventFile.cs

@@ -0,0 +1,15 @@
+using System.Collections.Generic;
+
+namespace Cthangover.Mods.Rpg
+{
+    /// <summary>
+    /// One file of map events, <c>map_events/&lt;map id&gt;/&lt;any name&gt;.json</c>:
+    /// <c>{"Events": [ … ]}</c>. The folder names the map, so a file holds the events
+    /// of one map, and a mod may split them over as many files as it likes.
+    /// </summary>
+    public class RpgMapEventFile
+    {
+        /// <summary>The events of the file, in drawing order.</summary>
+        public List<RpgMapEvent> Events { get; set; } = new();
+    }
+}

src/Data/RpgMapEventMerge.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+
+namespace Cthangover.Mods.Rpg
+{
+    /// <summary>
+    /// Builds the event list of every map from event files read in mod load order.
+    /// A new id is appended; an id already present (ignoring case) is replaced in
+    /// place, so the later file wins and keeps the original's drawing order. Mods
+    /// load after their dependencies, so the engine's replacement rule holds:
+    /// ship the same event id and declare <c>depends</c> on the owner to replace
+    /// it, ship a new id to add to any mod's map.
+    /// <para/>
+    /// Pure data, so the merge rules are tested without a mod set.
+    /// </summary>
+    public class RpgMapEventMerge
+    {
+        /// <summary>Events per map id (case-insensitive).</summary>
+        public Dictionary<string, List<RpgMapEvent>> Maps { get; } = new(StringComparer.OrdinalIgnoreCase);
+
+        /// <summary>
+        /// Adds the events of one file of <paramref name="modId"/> for map <paramref name="map"/>;
+        /// each event gets <see cref="RpgMapEvent.ModId"/> and <see cref="RpgMapEvent.File"/>.
+        /// Returns the ids that replaced an earlier event.
+        /// </summary>
+        public List<string> Add(string map, string modId, string file, IEnumerable<RpgMapEvent> events)
+        {
+            var replaced = new List<string>();
+            if (!Maps.TryGetValue(map, out var list))
+            {
+                list = new List<RpgMapEvent>();
+                Maps[map] = list;
+            }
+
+            foreach (var mapEvent in events ?? Array.Empty<RpgMapEvent>())
+            {
+                if (mapEvent == null || string.IsNullOrWhiteSpace(mapEvent.Id))
+                    continue;
+                mapEvent.ModId = modId;
+                mapEvent.File = file;
+                var index = list.FindIndex(e => string.Equals(e.Id, mapEvent.Id, StringComparison.OrdinalIgnoreCase));
+                if (index < 0)
+                {
+                    list.Add(mapEvent);
+                    continue;
+                }
+                list[index] = mapEvent;
+                replaced.Add(mapEvent.Id);
+            }
+            return replaced;
+        }
+    }
+}

src/Data/RpgMapEventResolver.cs

@@ -0,0 +1,93 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.Json;
+using Cthangover.Core.Mods;
+using Cthangover.Core.Mods.Resolvers;
+using Cthangover.Core.Utils;
+
+namespace Cthangover.Mods.Rpg
+{
+    /// <summary>
+    /// Collects map events from <c>map_events/&lt;map id&gt;/**/*.json</c> of every
+    /// loaded mod in load order (files of one mod sorted by path), then from the
+    /// studio overlays, and merges them per map with <see cref="RpgMapEventMerge"/>.
+    /// <para/>
+    /// Events live apart from the map file (<c>maps/&lt;id&gt;.json</c> holds only
+    /// tiles, collision, spawn and encounters) so that any mod can put its own NPC,
+    /// chest or quest trigger on another mod's map without replacing the map, and
+    /// so that drawing and placing do not fight over one big file. Events of a map
+    /// no mod defines are kept and simply never shown.
+    /// </summary>
+    public class RpgMapEventResolver : ModAssetResolver
+    {
+        /// <summary>Group folder of event files.</summary>
+        public const string Directory = "map_events";
+
+        private Dictionary<string, List<RpgMapEvent>> cache;
+
+        /// <inheritdoc />
+        public override string Id => "rpg_map_events";
+
+        /// <summary>Events per map id, merged; cached until the next mod reload or <see cref="ClearCache"/>.</summary>
+        public Dictionary<string, List<RpgMapEvent>> Collect()
+        {
+            Context.Initialize();
+            if (cache != null)
+                return cache;
+
+            var merge = new RpgMapEventMerge();
+            foreach (var modId in Context.GetOrderedModIds())
+                CollectMod(Context.Mods[modId].FileProvider, modId, merge);
+            foreach (var overlay in ModOverlays.All)
+                CollectMod(overlay.Value, overlay.Key, merge);
+
+            cache = merge.Maps;
+            GameLogger.Log("RPG", $"map events: {cache.Values.Sum(l => l.Count)} event(s) on {cache.Count} map(s)");
+            return cache;
+        }
+
+        /// <inheritdoc />
+        public override void ClearCache() => cache = null;
+
+        private void CollectMod(IModFileProvider provider, string modId, RpgMapEventMerge merge)
+        {
+            foreach (var mapDir in provider.ListFiles(Directory).Where(e => e.EndsWith("/")).OrderBy(e => e, System.StringComparer.Ordinal))
+            {
+                var map = mapDir.TrimEnd('/');
+                map = map.Substring(map.LastIndexOf('/') + 1);
+                var files = new List<string>();
+                ListJson(provider, mapDir.TrimEnd('/'), files);
+                foreach (var file in files.OrderBy(f => f, System.StringComparer.Ordinal))
+                    ReadFile(provider, modId, map, file, merge);
+            }
+        }
+
+        private static void ListJson(IModFileProvider provider, string dir, List<string> files)
+        {
+            foreach (var entry in provider.ListFiles(dir))
+            {
+                if (entry.EndsWith("/"))
+                    ListJson(provider, entry.TrimEnd('/'), files);
+                else if (entry.EndsWith(".json", System.StringComparison.OrdinalIgnoreCase))
+                    files.Add(entry);
+            }
+        }
+
+        private void ReadFile(IModFileProvider provider, string modId, string map, string file, RpgMapEventMerge merge)
+        {
+            var text = Context.ReadResolvedText(modId, file, provider);
+            if (string.IsNullOrWhiteSpace(text))
+                return;
+            try
+            {
+                var data = JsonSerializer.Deserialize<RpgMapEventFile>(text, JsonOptionsProvider.ReadOptions);
+                foreach (var id in merge.Add(map, modId, file, data?.Events))
+                    GameLogger.Log("RPG", $"map '{map}': event '{id}' replaced by mod '{modId}' ({file})");
+            }
+            catch (JsonException ex)
+            {
+                GameLogger.Log("RPG", $"map events '{modId}/{file}': broken JSON: {ex.Message}", LogLevel.Error);
+            }
+        }
+    }
+}

src/Data/RpgMapEvents.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using Cthangover.Core.Mods;
+
+namespace Cthangover.Mods.Rpg
+{
+    /// <summary>Access to the merged map events of <see cref="RpgMapEventResolver"/>.</summary>
+    public static class RpgMapEvents
+    {
+        /// <summary>The events of a map (an empty list when it has none); the list is shared, do not change it.</summary>
+        public static IReadOnlyList<RpgMapEvent> Of(string map)
+        {
+            var maps = ModManager.Instance.GetResolver<RpgMapEventResolver>()?.Collect();
+            return map != null && maps != null && maps.TryGetValue(map, out var list) ? list : new List<RpgMapEvent>();
+        }
+
+        /// <summary>Forgets the collected events, so the next <see cref="Of"/> reads the files again (after an editor save).</summary>
+        public static void Invalidate() => ModManager.Instance.GetResolver<RpgMapEventResolver>()?.ClearCache();
+    }
+}

src/World/RpgActor.cs

@@ -79,6 +79,25 @@ namespace Cthangover.Mods.Rpg
             AddChild(sprite);
         }
 
+        /// <summary>
+        /// Shows an item picture fitted into three quarters of the cell and centred on it,
+        /// so an icon of any size lies on the ground like a tile-sized object.
+        /// </summary>
+        public void UseIcon(Texture2D texture)
+        {
+            if (texture == null)
+                return;
+            var fit = tileSize * 0.75f / Mathf.Max(1, Mathf.Max(texture.GetWidth(), texture.GetHeight()));
+            sprite = new Sprite2D
+            {
+                Texture = texture,
+                Position = new Vector2(tileSize, tileSize) / 2f,
+                Scale = new Vector2(fit, fit),
+                TextureFilter = TextureFilterEnum.Linear,
+            };
+            AddChild(sprite);
+        }
+
         /// <summary>Puts the actor on a cell at once, stopping any step.</summary>
         public void Place(Vector2I cell, RpgDirection facing)
         {

src/World/RpgTextures.cs

@@ -8,7 +8,8 @@ namespace Cthangover.Mods.Rpg
     /// Image lookup of the RPG world: tileset atlases in the <c>tilesets</c> file
     /// group, charsets in <c>charsets</c>. Both are file groups (last mod wins),
     /// not texture groups, so their names never collide with backgrounds or
-    /// icons. Decoded textures are kept for the life of one world, which builds
+    /// icons; item pictures for <see cref="RpgMapEvent.Icon"/> come from the
+    /// <c>items</c> group the inventory uses. Decoded textures are kept for the life of one world, which builds
     /// and owns an instance; the editor keeps its own.
     /// </summary>
     public class RpgTextures
@@ -19,6 +20,9 @@ namespace Cthangover.Mods.Rpg
         /// <summary>File group of charset images.</summary>
         public const string CharsetGroup = "charsets";
 
+        /// <summary>File group of item pictures (an item's <c>Sprite</c>).</summary>
+        public const string IconGroup = "items";
+
         private readonly Dictionary<string, Texture2D> cache = new();
 
         /// <summary>Tileset atlas image, or null (logged by the loader).</summary>
@@ -27,6 +31,9 @@ namespace Cthangover.Mods.Rpg
         /// <summary>Charset image, or null.</summary>
         public Texture2D Charset(string path) => Load(CharsetGroup, path);
 
+        /// <summary>Item picture, or null.</summary>
+        public Texture2D Icon(string path) => Load(IconGroup, path);
+
         private Texture2D Load(string group, string path)
         {
             if (string.IsNullOrWhiteSpace(path))

src/World/RpgWorldView.cs

@@ -66,7 +66,7 @@ namespace Cthangover.Mods.Rpg
             AddChild(actorLayer);
             AddChild(BuildLayer(RpgLayer.Front, tileSet));
 
-            foreach (var mapEvent in map.Events ?? new List<RpgMapEvent>())
+            foreach (var mapEvent in RpgMapEvents.Of(map.ID))
                 AddEventActor(mapEvent);
             RefreshEvents();
 
@@ -227,6 +227,8 @@ namespace Cthangover.Mods.Rpg
                 actor.UseCharset(textures.Charset(mapEvent.Sprite));
             else if (mapEvent.Tile >= 0 && Tileset != null)
                 actor.UseTile(atlas, RpgTileSetBuilder.AtlasCoords(Tileset, mapEvent.Tile));
+            else if (!string.IsNullOrEmpty(mapEvent.Icon))
+                actor.UseIcon(textures.Icon(mapEvent.Icon));
             actor.Place(new Vector2I(mapEvent.X, mapEvent.Y), mapEvent.Dir);
             actorLayer.AddChild(actor);
             eventActors[mapEvent.Id] = actor;