fix: classify sprite-sheet tilesets by their image source

fxgl-core/src/main/kotlin/com/almasb/fxgl/entity/level/tiled/Tileset.kt

@@ -28,10 +28,17 @@ data class Tileset(
 ) {
 
     /**
+     * Tilesets are either a sprite sheet (one atlas image) or a collection of images
+     * (each [Tile] owns its image). Tiled still emits `<tile>` entries on sprite sheets
+     * when tiles have custom properties; those metadata-only entries do not replace the
+     * tileset image. Classification therefore follows the independently parsed tileset
+     * image source, not whether [tiles] is empty. [image] is a non-null [String], so
+     * emptiness is tested with [String.isNotEmpty] rather than a null check.
+     *
      * @return true if tileset is a sprite sheet, false if tileset is a collection of images
      */
     val isSpriteSheet: Boolean
-        get() = tiles.isEmpty()
+        get() = image.isNotEmpty()
 }
 
 data class Tile(

fxgl-core/src/test/kotlin/com/almasb/fxgl/entity/level/tiled/TMXLevelLoaderTest.kt

@@ -220,6 +220,93 @@ class TMXLevelLoaderTest {
         assertTrue(e.message!!.isNotEmpty())
     }
 
+    @Test
+    fun `Parse sprite sheet tileset with metadata-only tile entries`() {
+        val map = javaClass.getResourceAsStream("map_with_tile_properties.tmx").use {
+            TMXLevelLoader().parse(it)
+        }
+
+        val tileset = map.tilesets[0]
+
+        assertThat(tileset.image, `is`("tileset_black.png"))
+        assertThat(tileset.tiles.size, `is`(2))
+        assertTrue(tileset.isSpriteSheet)
+
+        val tile83 = tileset.tiles.find { it.id == 83 }!!
+        val tile220 = tileset.tiles.find { it.id == 220 }!!
+
+        assertThat(tile83.image, `is`(""))
+        assertThat(tile83.imagewidth, `is`(0))
+        assertThat(tile83.imageheight, `is`(0))
+
+        assertThat(tile220.image, `is`(""))
+        assertThat(tile220.imagewidth, `is`(0))
+        assertThat(tile220.imageheight, `is`(0))
+
+        // gid 11 (tile id 10) is used by the layer but has no metadata entry
+        assertTrue(tileset.tiles.none { it.id == 10 })
+    }
+
+    @Test
+    fun `Load tmx level with sprite sheet tile properties`() {
+        val world = GameWorld()
+        world.addEntityFactory(MyEntityFactory())
+
+        val level = TMXLevelLoader().load(javaClass.getResource("map_with_tile_properties.tmx"), world)
+
+        assertThat(level.width, `is`(16 * 2))
+        assertThat(level.height, `is`(16 * 1))
+
+        // 1 tile layer + 1 gid object
+        assertThat(level.entities.size, `is`(1 + 1))
+
+        val view = level.entities[0].viewComponent.children[0] as ImageView
+
+        assertThat(view.image.width, `is`(32.0))
+        assertThat(view.image.height, `is`(16.0))
+
+        // Decorated sprite-sheet tile (gid 221 / id 220)
+        assertThat(view.image.pixelReader.getColor(0, 0), `is`(Color.TRANSPARENT))
+        assertThat(view.image.pixelReader.getColor(0, 15), `is`(Color.BLACK))
+        assertThat(view.image.pixelReader.getColor(8, 8), `is`(Color.BLACK))
+
+        // Undecorated atlas tile (gid 11 / id 10) must still be addressable
+        assertThat(view.image.pixelReader.getColor(16, 0), `is`(Color.BLACK))
+        assertThat(view.image.pixelReader.getColor(16, 15), `is`(Color.BLACK))
+        assertThat(view.image.pixelReader.getColor(31, 0), `is`(Color.BLACK))
+
+        val gidObject = level.entities.drop(1).find { it.getInt("id") == 1 }!!
+        val gidView = gidObject.viewComponent.children[0] as ImageView
+
+        assertThat(gidView.image.width, `is`(16.0))
+        assertThat(gidView.image.height, `is`(16.0))
+        assertThat(gidView.image.pixelReader.getColor(0, 0), `is`(Color.TRANSPARENT))
+        assertThat(gidView.image.pixelReader.getColor(0, 15), `is`(Color.BLACK))
+        assertThat(gidView.image.pixelReader.getColor(8, 8), `is`(Color.BLACK))
+    }
+
+    @Test
+    fun `Tileset image ownership classifies sprite sheets independently of tile metadata`() {
+        val tileset = Tileset(image = "tileset_black.png")
+        assertTrue(tileset.isSpriteSheet)
+
+        tileset.tiles += Tile(id = 1)
+        tileset.tiles += Tile(id = 2, image = "")
+        assertTrue(tileset.isSpriteSheet)
+
+        tileset.image = ""
+        tileset.tiles.clear()
+        tileset.tiles += Tile(id = 0, image = "tank1.png", imagewidth = 64, imageheight = 64)
+        tileset.tiles += Tile(id = 1, image = "tank2.png", imagewidth = 64, imageheight = 64)
+        assertFalse(tileset.isSpriteSheet)
+
+        tileset.image = "tileset_black.png"
+        assertTrue(tileset.isSpriteSheet)
+
+        tileset.image = ""
+        assertFalse(tileset.isSpriteSheet)
+    }
+
     @ParameterizedTest
     @CsvSource("sewers_v1_1_2.tmx", "sewers_v1_2_3.tmx", "sewers_v1_9_0.tmx")
     fun parse(mapName: String) {

fxgl-core/src/test/resources/com/almasb/fxgl/entity/level/tiled/map_with_tile_properties.tmx

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<map version="1.9" tiledversion="1.9.0" orientation="orthogonal" renderorder="right-down" width="2" height="1" tilewidth="16" tileheight="16" infinite="0" nextlayerid="3" nextobjectid="2">
+ <tileset firstgid="1" name="tileset_black" tilewidth="16" tileheight="16" tilecount="256" columns="16">
+  <image source="tileset_black.png" width="256" height="256"/>
+  <tile id="83">
+   <properties>
+    <property name="collectible" type="bool" value="true"/>
+    <property name="kind" value="coin"/>
+   </properties>
+  </tile>
+  <tile id="220">
+   <properties>
+    <property name="solid" type="bool" value="false"/>
+    <property name="label" value="slash"/>
+   </properties>
+  </tile>
+ </tileset>
+ <layer id="1" name="Tile Layer 1" width="2" height="1">
+  <data encoding="csv">
+221,11
+</data>
+ </layer>
+ <objectgroup id="2" name="Object layer 1">
+  <object id="1" type="Player" gid="221" x="0" y="16" width="16" height="16"/>
+ </objectgroup>
+</map>