[unity] Unity Sprite slices for atlas textures.

The new "Apply Regions as Texture Sprite Slices" button adds Sprite slices to all atlas page Textures of an AtlasAsset in Unity Editor.
Clicking the button updates existing sprites if it detects name-matches. Adds ones that don't exist. It does not remove non-matches.

Sprite slices are not auto-applied on atlas import. Users have to opt-in by clicking the button.
This is also to communicate that spine-unity does not currently rely on the Unity sprite system. Unity 5.5 has promising API changes to this end but this cannot be a standard spine-unity feature yet.

This replaces the functionality of the old Region Baking as prefabs with mesh assets. Original functionality has been precompiler-defined out. Region baking code will be removed in a future version.

spine-unity/Assets/spine-unity/Asset Types/Editor/AtlasAssetInspector.cs

@@ -29,6 +29,7 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *****************************************************************************/
 //#define BAKE_ALL_BUTTON
+//#define REGION_BAKING_MESH
 
 using System;
 using System.Collections.Generic;
@@ -44,8 +45,6 @@ namespace Spine.Unity.Editor {
 	public class AtlasAssetInspector : UnityEditor.Editor {
 		private SerializedProperty atlasFile, materials;
 		private AtlasAsset atlasAsset;
-		private List<bool> baked;
-		private List<GameObject> bakedObjects;
 
 		void OnEnable () {
 			SpineEditorUtilities.ConfirmInitialization();
@@ -53,8 +52,14 @@ namespace Spine.Unity.Editor {
 			materials = serializedObject.FindProperty("materials");
 			materials.isExpanded = true;
 			atlasAsset = (AtlasAsset)target;
+			#if REGION_BAKING_MESH
 			UpdateBakedList();
+			#endif
 		}
+			
+		#if REGION_BAKING_MESH
+		private List<bool> baked;
+		private List<GameObject> bakedObjects;
 
 		void UpdateBakedList () {
 			AtlasAsset asset = (AtlasAsset)target;
@@ -78,13 +83,72 @@ namespace Spine.Unity.Editor {
 				}
 			}
 		}
+		#endif
+
+		static public void UpdateSpriteSlices (Texture texture, Atlas atlas) {
+			string texturePath = AssetDatabase.GetAssetPath(texture.GetInstanceID());
+			var t = (TextureImporter)TextureImporter.GetAtPath(texturePath);
+			t.spriteImportMode = SpriteImportMode.Multiple;
+			var spriteSheet = t.spritesheet;
+			var sprites = new List<SpriteMetaData>(spriteSheet);
+
+			FieldInfo field = typeof(Atlas).GetField("regions", BindingFlags.Instance | BindingFlags.NonPublic);
+			var regions = (List<AtlasRegion>)field.GetValue(atlas);
+			int textureHeight = texture.height;
+			char[] FilenameDelimiter = {'.'};
+			int updatedCount = 0;
+			int addedCount = 0;
+
+			foreach (var r in regions) {
+				int width, height;
+				if (r.rotate) {
+					width = r.height;
+					height = r.width;
+				} else {
+					width = r.width;
+					height = r.height;
+				}
+
+				int x = r.x;
+				int y = textureHeight - height - r.y;
+
+				string pageName = r.page.name.Split(FilenameDelimiter, StringSplitOptions.RemoveEmptyEntries)[0];
+				string textureName = texture.name;
+				bool pageMatch = string.Equals(pageName, textureName,StringComparison.Ordinal);
+				int spriteIndex = pageMatch ? sprites.FindIndex(
+					(s) => string.Equals(s.name, r.name, StringComparison.Ordinal)
+				) : -1;
+				bool matchFound = spriteIndex >= 0;
+
+				if (matchFound) {
+					var s = sprites[spriteIndex];
+					s.rect = new Rect(x, y, width, height);
+					sprites[spriteIndex] = s;
+					updatedCount++;
+				} else {
+					if (pageMatch) {
+						sprites.Add(new SpriteMetaData {
+							name = r.name,
+							pivot = new Vector2(0.5f, 0.5f),
+							rect = new Rect(x, y, width, height)
+						});
+						addedCount++;
+					}
+				}
+			}
+
+			t.spritesheet = sprites.ToArray();
+			EditorUtility.SetDirty(t);
+			AssetDatabase.ImportAsset(texturePath, ImportAssetOptions.ForceUpdate);
+			Debug.Log(string.Format("Applied sprite slices to {2}. {0} added. {1} updated.", addedCount, updatedCount, texture.name));
+		}
 
 		override public void OnInspectorGUI () {
 			serializedObject.Update();
-			AtlasAsset asset = (AtlasAsset)target;
-
+			atlasAsset = atlasAsset ?? (AtlasAsset)target;
 			EditorGUI.BeginChangeCheck();
 			EditorGUILayout.PropertyField(atlasFile);
+
 			EditorGUILayout.PropertyField(materials, true);
 			if (EditorGUI.EndChangeCheck())
 				serializedObject.ApplyModifiedProperties();
@@ -103,6 +167,22 @@ namespace Spine.Unity.Editor {
 				}
 			}
 
+			if (atlasFile.objectReferenceValue != null) {
+				if (GUILayout.Button(
+					new GUIContent(
+						"Apply Regions as Texture Sprite Slices",
+						"Adds Sprite slices to atlas texture(s). " +
+						"Updates existing slices if ones with matching names exist. \n\n" +
+						"If your atlas was exported with Premultiply Alpha, " +
+						"your SpriteRenderer should use the generated Spine _Material asset (or any Material with a PMA shader) instead of Sprites-Default.")
+					, GUILayout.Height(70f))) {
+					var atlas = atlasAsset.GetAtlas();
+					foreach (var m in atlasAsset.materials)
+						UpdateSpriteSlices(m.mainTexture, atlas);
+				}
+			}
+
+			#if REGION_BAKING_MESH
 			if (atlasFile.objectReferenceValue != null) {
 				Atlas atlas = asset.GetAtlas();
 				FieldInfo field = typeof(Atlas).GetField("regions", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.NonPublic);
@@ -206,13 +286,14 @@ namespace Spine.Unity.Editor {
 
 				}
 				#endif
-
+				
 			}
+			#endif
 
 			if (serializedObject.ApplyModifiedProperties() ||
 				(UnityEngine.Event.current.type == EventType.ValidateCommand && UnityEngine.Event.current.commandName == "UndoRedoPerformed")
 			) {
-				asset.Reset();
+				atlasAsset.Reset();
 			}
 		}
 	}