Implement loading tile sets from JSON files

assets/tilesets/terrain.json

@@ -0,0 +1,26 @@
+{
+    "texture": "terrain.png",
+    "tile_size": 32,
+    "tiles": [
+        {
+            "x": 0,
+            "y": 0
+        },
+        {
+            "x": 0,
+            "y": 0
+        },
+        {
+            "x": 1,
+            "y": 0
+        },
+        {
+            "x": 2,
+            "y": 0
+        },
+        {
+            "x": 3,
+            "y": 0
+        }
+    ]
+}

src/rutile/core/resources/loaders/tile_set_loader.cppm

@@ -6,9 +6,11 @@ import std;
 import rutile.core.common;
 import rutile.core.resources.texture;
 import rutile.core.resources.tile_set;
-// import vendor.nlohmann.json;
+import wrappers.sdl;
+import vendor.nlohmann.json;
 
-// using json = nlohmann::json;
+namespace fs = std::filesystem;
+using json = nlohmann::json;
 
 namespace rutile
 {
@@ -38,20 +40,29 @@ export namespace rutile
 
             TileSet load_resource(const std::string& name) const
             {
-                return TileSet::create_from_texture(
-                    texture_load_callback_(name),
-                    // TODO: Load this from a JSON file
-                    32,
-                    {
-                        // Tile 0: No tile
-                        {0, 0},
-                        // Tile 1: Actual first tile in the texture
-                        {0, 0},
-                        {1, 0},
-                        {2, 0},
-                        {3, 0},
+                try {
+                    std::ifstream json_file(name);
+                    json data = json::parse(json_file);
+
+                    // Texture path is relative to JSON file
+                    fs::path texture_path = fs::path(name).replace_filename(data.at("texture"));
+
+                    std::vector<sdl::Point> tile_atlas_coords;
+                    for (auto tile : data.at("tiles")) {
+                        tile_atlas_coords.push_back({tile.at("x"), tile.at("y")});
                     }
-                );
+
+                    return TileSet::create_from_texture(
+                        texture_load_callback_(texture_path),
+                        data.at("tile_size"),
+                        tile_atlas_coords
+                    );
+                }
+                catch (const json::exception& e) {
+                    throw std::runtime_error(
+                        std::format("Error loading tile set from \"{}\": {}", name, e.what())
+                    );
+                }
             }
     };
 }

src/rutile/game/game.cppm

@@ -40,7 +40,7 @@ export namespace rutile
                   )
               },
               tile_map_{
-                  engine_.get_resource_server().load_tile_set("assets/tilesets/terrain.png"),
+                  engine_.get_resource_server().load_tile_set("assets/tilesets/terrain.json"),
                   32, 16, 12, {50, 50}
               }
         {