More descriptive types for Hammer.js events

This required adding @types/hammerjs; see https://stackoverflow.com/a/46011417/25507.

package.json

@@ -82,6 +82,7 @@
     "chart.js": ">=3.2.0"
   },
   "dependencies": {
+    "@types/hammerjs": "^2.0.45",
     "hammerjs": "^2.0.8"
   }
 }

types/options.d.ts

@@ -1,5 +1,5 @@
 import { Chart, Color, Point } from 'chart.js';
-
+import { Input as HammerInput } from 'hammerjs';
 
 type Mode = 'x' | 'y' | 'xy';
 type Key = 'ctrl' | 'alt' | 'shift' | 'meta';
@@ -167,9 +167,9 @@ export interface PanOptions {
    * Function called when pan fails because modifier key was not detected.
    * event is the a hammer event that failed - see https://hammerjs.github.io/api#event-object
    */
-  onPanRejected?: (context: { chart: Chart, event: Event }) => void;
+  onPanRejected?: (context: { chart: Chart, event: HammerInput }) => void;
 
-  onPanStart?: (context: { chart: Chart, event: Event, point: Point }) => boolean | undefined;
+  onPanStart?: (context: { chart: Chart, event: HammerInput, point: Point }) => boolean | undefined;
 }
 
 export interface ScaleLimits {

types/tests/exports.ts

@@ -34,7 +34,10 @@ const chart = new Chart('id', {
         },
         pan: {
           enabled: true,
-          mode: 'x'
+          mode: 'x',
+          onPanStart({ event }) {
+            return event.distance > 2;
+          }
         },
         zoom: {
           wheel: {