fixup pan touch

pointer.js

@@ -43,6 +43,10 @@ export class Pointer {
       this.handlePointerUp({x: e.clientX, y: e.clientY});
     });
 
+    el.addEventListener('pointerleave', e => {
+      this.handlePointerUp({x: e.clientX, y: e.clientY});
+    });
+
     // Monitor wheel events
     el.addEventListener('wheel', e => {
       const factor = e.deltaY < 0 ? ZOOM_IN_FACTOR : ZOOM_OUT_FACTOR;
@@ -126,16 +130,19 @@ export class Pointer {
       // Set panning velocity
       if (this.panTouchStart && this.panTouchLatest) {
         const dt = (this.panTouchLatest.t - this.panTouchStart.t) / 1000;
-        const latest = this.panTouchLatest;
-        const start = this.panTouchStart;
-        // const speed = Math.sqrt((latest.x - start.x)**2 + (latest.y - start.y)**2) / dt;
-        const { scale } = this.sim.display;
-        this.panning = {
-          velocity: {
-            x: 2 * (latest.x - start.x) / scale / dt,
-            y: 2 * (latest.y - start.y) / scale / dt,
-          }
-        };
+        if (!dt) {
+          this.panning = undefined;
+        } else {
+          const { v } = this.pointerHistory[this.pointerHistory.length - 1];
+          // Convert pointer velocity to simulation scale
+          v.x /= this.sim.display.scale;
+          v.y /= this.sim.display.scale;
+
+          this.panning = {
+            velocity: v
+          };
+        }
+
         this.panTouchStart = undefined;
       }
     }
@@ -159,12 +166,14 @@ export class Pointer {
       this.sim.objects.handlePointerMove({x, y, vx: v.x, vy: v.y});
 
     } else if (this.sim.isCurrentMode(MODE_PAN_VIEW)) {
-      // Event loop should be able to read
-      this.panTouchLatest = {
-        x: clientX,
-        y: clientY,
-        t: document.timeline.currentTime,
-      };
+      if (this.panTouchStart) {
+        // Event loop should be able to read
+        this.panTouchLatest = {
+          x: clientX,
+          y: clientY,
+          t: document.timeline.currentTime,
+        };
+      }
     }
   }