From 9be30c44cd5fd8665f2727632e04ad4de80ab6de Mon Sep 17 00:00:00 2001
From: NathanSweet <nathan.sweet@gmail.com>
Date: Wed, 17 Oct 2018 14:52:15 +0200
Subject: [PATCH] [libgdx] Fixed tangents at position 0.

Calculating the tangent requires more precision than the position.

http://esotericsoftware.com/forum/Glitch-with-the-bones-constrained-to-the-path-10969

Repro:
http://n4te.com/x/173-path-tangent-precision.spine
---
 .../esotericsoftware/spine/PathConstraint.java    | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/PathConstraint.java b/spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/PathConstraint.java
index 377f034b3..e759d75e3 100644
--- a/spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/PathConstraint.java
+++ b/spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/PathConstraint.java
@@ -430,14 +430,23 @@ public class PathConstraint implements Constraint {
 
 	private void addCurvePosition (float p, float x1, float y1, float cx1, float cy1, float cx2, float cy2, float x2, float y2,
 		float[] out, int o, boolean tangents) {
-		if (p < epsilon || Float.isNaN(p)) p = epsilon;
+		if (p < epsilon || Float.isNaN(p)) {
+			out[o] = x1;
+			out[o + 1] = y1;
+			out[o + 2] = (float)Math.atan2(cy1 - y1, cx1 - x1);
+			return;
+		}
 		float tt = p * p, ttt = tt * p, u = 1 - p, uu = u * u, uuu = uu * u;
 		float ut = u * p, ut3 = ut * 3, uut3 = u * ut3, utt3 = ut3 * p;
 		float x = x1 * uuu + cx1 * uut3 + cx2 * utt3 + x2 * ttt, y = y1 * uuu + cy1 * uut3 + cy2 * utt3 + y2 * ttt;
 		out[o] = x;
 		out[o + 1] = y;
-		if (tangents)
-			out[o + 2] = (float)Math.atan2(y - (y1 * uu + cy1 * ut * 2 + cy2 * tt), x - (x1 * uu + cx1 * ut * 2 + cx2 * tt));
+		if (tangents) {
+			if (p < 0.001f)
+				out[o + 2] = (float)Math.atan2(cy1 - y1, cx1 - x1);
+			else
+				out[o + 2] = (float)Math.atan2(y - (y1 * uu + cy1 * ut * 2 + cy2 * tt), x - (x1 * uu + cx1 * ut * 2 + cx2 * tt));
+		}
 	}
 
 	public int getOrder () {