Fix rotation calculation to prevent 90 degree jump

Based on hammerjs#982
squadette · Aug 24, 2019 · 5c53476 · 5c53476
1 parent a0eb000
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,8 @@
 
 - Fix rotation calculation to prevent 90 degree jump.
 
+Based on https://github.com/hammerjs/hammer.js/pull/982
+
 ### 2.1.0pre0
 
 No functional changes, prepare baseline for future changes.

diff --git a/hammer.js b/hammer.js
@@ -1679,7 +1679,7 @@ function getScale(start, end) {
  * @return {Number} rotation
  */
 function getRotation(start, end) {
-  return getAngle(end[1], end[0], PROPS_CLIENT_XY) + getAngle(start[1], start[0], PROPS_CLIENT_XY);
+  return getAngle(end[1], end[0], PROPS_CLIENT_XY) - getAngle(start[1], start[0], PROPS_CLIENT_XY);
 }
 
 /**

diff --git a/hammer.min.js b/hammer.min.js
diff --git a/src/inputjs/get-rotation.js b/src/inputjs/get-rotation.js
@@ -9,5 +9,5 @@ import { PROPS_CLIENT_XY } from './input-consts';
  * @return {Number} rotation
  */
 export default function getRotation(start, end) {
-  return getAngle(end[1], end[0], PROPS_CLIENT_XY) + getAngle(start[1], start[0], PROPS_CLIENT_XY);
+  return getAngle(end[1], end[0], PROPS_CLIENT_XY) - getAngle(start[1], start[0], PROPS_CLIENT_XY);
 }