[unity] Added an additional warning when `Alpha Is Transparency` is enabled at PMA textures, which causes incorrect light ghosting in transparent areas. See #1266.

spine-unity/Assets/Spine/Editor/spine-unity/Editor/SpineEditorUtilities.cs

@@ -167,6 +167,8 @@ namespace Spine.Unity.Editor {
 		public static string editorGUIPath = "";
 		public static bool initialized;
 
+		static int STRAIGHT_ALPHA_PARAM_ID = Shader.PropertyToID("_StraightAlphaInput");
+
 		// Preferences entry point
 		[PreferenceItem("Spine")]
 		static void PreferencesGUI () {
@@ -270,6 +272,18 @@ namespace Spine.Unity.Editor {
 			if (texImporter.sRGBTexture && texImporter.mipmapEnabled) {
 				Debug.LogWarningFormat("`{0}` : Incorrect Texture Settings found: When enabling `Generate Mip Maps`, it is strongly recommended to disable `sRGB (Color Texture)`. Otherwise you will receive white border artifacts on an atlas exported with default `Premultiply alpha` settings.\n(You can disable this warning in `Edit - Preferences - Spine`)", texturePath);
 			}
+			if (texImporter.alphaIsTransparency) {
+				int extensionPos = texturePath.LastIndexOf('.');
+				string materialPath = texturePath.Substring(0, extensionPos) + "_Material.mat";
+				Material material = AssetDatabase.LoadAssetAtPath<Material>(materialPath);
+				if (material != null) {
+					int straightAlphaValue = material.GetInt(STRAIGHT_ALPHA_PARAM_ID);
+					if (straightAlphaValue == 0) {
+						string materialName = System.IO.Path.GetFileName(materialPath);
+						Debug.LogWarningFormat("`{0}` and material `{1}` : Incorrect Texture / Material Settings found: It is strongly recommended to disable `Alpha Is Transparency` on `Premultiply alpha` textures.\nAssuming `Premultiply alpha` texture because `Straight Alpha Texture` is disabled at material). (You can disable this warning in `Edit - Preferences - Spine`)", texturePath, materialName);
+					}
+				}
+			}
 			return true;
 		}
 		#endregion