[TS] WebKit 602 disappearing graphics bug (#1093)

* Added a fix for the iOS 10 issue described at http://esotericsoftware.com/forum/iOS-10-disappearing-graphics-10109

* Renamed uselessFunction and updated documentation

spine-ts/core/src/AnimationState.ts

@@ -172,8 +172,11 @@ module spine {
 						let pose = timelineData[ii] >= AnimationState.FIRST ? MixPose.setup : currentPose;
 						if (timeline instanceof RotateTimeline) {
 							this.applyRotateTimeline(timeline, skeleton, animationTime, mix, pose, timelinesRotation, ii << 1, firstFrame);
-						} else
+						} else {
+							// This fixes the WebKit 602 specific issue described at http://esotericsoftware.com/forum/iOS-10-disappearing-graphics-10109
+							Utils.webkit602BugfixHelper(mix, pose);
 							timeline.apply(skeleton, animationLast, animationTime, events, mix, pose, MixDirection.in);
+						}
 					}
 				}
 				this.queueEvents(current, animationTime);
@@ -242,6 +245,8 @@ module spine {
 				if (timeline instanceof RotateTimeline)
 					this.applyRotateTimeline(timeline, skeleton, animationTime, alpha, pose, timelinesRotation, i << 1, firstFrame);
 				else {
+					// This fixes the WebKit 602 specific issue described at http://esotericsoftware.com/forum/iOS-10-disappearing-graphics-10109
+					Utils.webkit602BugfixHelper(alpha, pose);
 					timeline.apply(skeleton, animationLast, animationTime, events, alpha, pose, MixDirection.out);
 				}
 			}

spine-ts/core/src/Utils.ts

@@ -259,6 +259,11 @@ module spine {
 		static toSinglePrecision (value: number) {
 			return Utils.SUPPORTS_TYPED_ARRAYS ? Math.fround(value) : value;
 		}
+
+		// This function is used to fix WebKit 602 specific issue described at http://esotericsoftware.com/forum/iOS-10-disappearing-graphics-10109
+		static webkit602BugfixHelper (alpha: number, pose: MixPose) {
+
+		}
 	}
 
 	export class DebugUtils {