fix(tilemap): anchor tile objects at their bottom-left corner

modules/tilemap/src/tile_map_renderer.cpp

@@ -168,7 +168,13 @@ namespace moth::tilemap {
                         scale.y = object.size.y / static_cast<float>(sourceRect.h());
                     }
 
-                    drawTileImage(*tileset, resolvedId, object.tile, object.position + offset, object.rotation, scale);
+                    // Tiled anchors a tile object at its bottom-left corner, where a plain
+                    // rectangle object is anchored top-left. Shift up by the drawn height so
+                    // the tile lands where the editor shows it.
+                    FloatVec2 topLeft = object.position + offset;
+                    topLeft.y -= static_cast<float>(sourceRect.h()) * scale.y;
+
+                    drawTileImage(*tileset, resolvedId, object.tile, topLeft, object.rotation, scale);
                 }
             };
 

modules/tilemap/tests/src/test_renderer.cpp

@@ -43,6 +43,7 @@ namespace {
             FloatVec2 position;
             IntRect sourceRect;
             FloatVec2 pivot;
+            FloatVec2 scale;
             float rotation = 0.0f;
             bool flipX;
             bool flipY;
@@ -72,6 +73,7 @@ namespace {
             call.position = transform.position;
             call.sourceRect = image.GetSourceRect();
             call.pivot = pivot;
+            call.scale = transform.scale;
             call.rotation = transform.rotation;
             call.flipX = flipX;
             call.flipY = flipY;
@@ -361,10 +363,36 @@ TEST_CASE("Renderer: draws tile objects from object layers, skipping shapes", "[
     REQUIRE(graphics.drawCalls.size() == 2);
     auto const& objectCall = graphics.drawCalls.back();
     REQUIRE(objectCall.position.x == Catch::Approx(8.0f));
-    REQUIRE(objectCall.position.y == Catch::Approx(8.0f));
+    // A tile object is anchored at its bottom-left corner, so a 16px tile placed
+    // at y = 8 draws from y = -8.
+    REQUIRE(objectCall.position.y == Catch::Approx(-8.0f));
     REQUIRE(objectCall.sourceRect == MakeRect(0, 0, 16, 16));
 }
 
+TEST_CASE("Renderer: a resized tile object is anchored at its scaled bottom-left", "[tilemap][renderer]") {
+    TileMap map = MakeMap(4, 4);
+
+    ObjectLayer objectLayer;
+    MapObject tileObject;
+    tileObject.tile = TileId::FromGid(1);
+    tileObject.position = { 8.0f, 48.0f };
+    tileObject.size = { 32.0f, 32.0f }; // a 16px tile drawn at double size
+    objectLayer.objects.push_back(tileObject);
+    map.objectLayers.push_back(objectLayer);
+
+    MockGraphics graphics;
+    std::vector<Image> tilesetImages{ Image(std::make_shared<MockTexture>()) };
+
+    DrawTileMap(graphics, map, tilesetImages, MakeRect(0.0f, 0.0f, 64.0f, 64.0f));
+
+    REQUIRE(graphics.drawCalls.size() == 1);
+    auto const& objectCall = graphics.drawCalls.back();
+    REQUIRE(objectCall.position.x == Catch::Approx(8.0f));
+    // The anchor shift follows the drawn height, not the tile's natural height.
+    REQUIRE(objectCall.position.y == Catch::Approx(16.0f));
+    REQUIRE(objectCall.scale.y == Catch::Approx(2.0f));
+}
+
 TEST_CASE("Renderer: applies layer parallax offset", "[tilemap][renderer]") {
     TileMap map = MakeMap(1, 1);
     AddLayer(map, { 1 });