From 21ab3c7f3d8c545a3ad4d9c92682000628019b08 Mon Sep 17 00:00:00 2001
From: Joe Schafer <joe.schafer@delta46.us>
Date: Sun, 17 Jul 2022 19:30:40 -0700
Subject: [PATCH] fix: check for event.cancelable in touch events (#634)

Co-authored-by: Tony Brix <tony@brix.ninja>
---
 src/signature_pad.ts        | 13 +++++--
 tests/signature_pad.test.ts | 77 +++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 4 deletions(-)

diff --git a/src/signature_pad.ts b/src/signature_pad.ts
index 473196f7..5b608ad4 100644
--- a/src/signature_pad.ts
+++ b/src/signature_pad.ts
@@ -236,7 +236,9 @@ export default class SignaturePad extends SignatureEventTarget {
 
   private _handleTouchStart = (event: TouchEvent): void => {
     // Prevent scrolling.
-    event.preventDefault();
+    if (event.cancelable) {
+      event.preventDefault();
+    }
 
     if (event.targetTouches.length === 1) {
       const touch = event.changedTouches[0];
@@ -246,7 +248,9 @@ export default class SignaturePad extends SignatureEventTarget {
 
   private _handleTouchMove = (event: TouchEvent): void => {
     // Prevent scrolling.
-    event.preventDefault();
+    if (event.cancelable) {
+      event.preventDefault();
+    }
 
     const touch = event.targetTouches[0];
     this._strokeMoveUpdate(touch);
@@ -255,8 +259,9 @@ export default class SignaturePad extends SignatureEventTarget {
   private _handleTouchEnd = (event: TouchEvent): void => {
     const wasCanvasTouched = event.target === this.canvas;
     if (wasCanvasTouched) {
-      event.preventDefault();
-
+      if (event.cancelable) {
+        event.preventDefault();
+      }
       const touch = event.changedTouches[0];
       this._strokeEnd(touch);
     }
diff --git a/tests/signature_pad.test.ts b/tests/signature_pad.test.ts
index 6f2e07d1..c1a2938e 100644
--- a/tests/signature_pad.test.ts
+++ b/tests/signature_pad.test.ts
@@ -167,6 +167,83 @@ describe('user interactions', () => {
   });
 });
 
+describe(`touch events.`, () => {
+  let signpad: SignaturePad;
+
+  function createTouchEvents(cancelable: boolean) {
+    const touchStartEvent = new TouchEvent('touchstart', {
+      cancelable,
+      targetTouches: [{} as Touch],
+      changedTouches: [
+        {
+          clientX: 50,
+          clientY: 30,
+          force: 1,
+        } as Touch,
+      ],
+    });
+    const touchMoveEvent = new TouchEvent('touchmove', {
+      cancelable,
+      targetTouches: [
+        {
+          clientX: 55,
+          clientY: 35,
+          force: 1,
+        } as Touch,
+      ],
+    });
+    const touchEndEvent = new TouchEvent('touchend', {
+      cancelable,
+      changedTouches: [
+        {
+          clientX: 55,
+          clientY: 35,
+          force: 1,
+        } as Touch,
+      ],
+    });
+    jest.spyOn(touchStartEvent, 'preventDefault');
+    jest.spyOn(touchMoveEvent, 'preventDefault');
+    jest.spyOn(touchEndEvent, 'preventDefault');
+
+    return {
+      touchStartEvent,
+      touchMoveEvent,
+      touchEndEvent,
+    };
+  }
+
+  beforeEach(() => {
+    signpad = new SignaturePad(canvas);
+    signpad.off();
+    signpad['_handleTouchEvents']();
+  });
+
+  it('the event should not be prevented.', () => {
+    const { touchStartEvent, touchMoveEvent, touchEndEvent } =
+      createTouchEvents(false);
+    canvas.dispatchEvent(touchStartEvent);
+    canvas.dispatchEvent(touchMoveEvent);
+    canvas.dispatchEvent(touchEndEvent);
+
+    expect(touchStartEvent.preventDefault).not.toHaveBeenCalled();
+    expect(touchMoveEvent.preventDefault).not.toHaveBeenCalled();
+    expect(touchEndEvent.preventDefault).not.toHaveBeenCalled();
+  });
+
+  it('the event should be prevented.', () => {
+    const { touchStartEvent, touchMoveEvent, touchEndEvent } =
+      createTouchEvents(true);
+    canvas.dispatchEvent(touchStartEvent);
+    canvas.dispatchEvent(touchMoveEvent);
+    canvas.dispatchEvent(touchEndEvent);
+
+    expect(touchStartEvent.preventDefault).toHaveBeenCalled();
+    expect(touchMoveEvent.preventDefault).toHaveBeenCalled();
+    expect(touchEndEvent.preventDefault).toHaveBeenCalled();
+  });
+});
+
 describe('Signature events.', () => {
   let signpad: SignaturePad;
   let eventDispatched: Event | undefined;