Library cannot be used in iOS v13 and older

[bowozer]

It happened ever since using event emitter that merged by this PR #567

i setup a simple html script that opened from iPhone (iOS 13.6) emulator. The script pretty much the same with the fiddler on the README.md (https://jsfiddle.net/szimek/jq9cyzuc/), but i wrapped the SignaturePad object creation with try-catch to see the error.

Original Code:

var signaturePad = new SignaturePad(canvas, {
  backgroundColor: 'rgb(255, 255, 255)' // necessary for saving image as JPEG; can be removed is only saving as PNG or SVG
});

Modified to:

var signaturePad;
try {
    signaturePad = new SignaturePad(canvas, {
        backgroundColor: 'rgb(255, 255, 255)' // necessary for saving image as JPEG; can be removed is only saving as PNG or SVG
    });
} catch (error) {
    alert(`oh no '${error.message}', it means current browser does not have EventTarget() constructor..`);
}

Here is the error:

I think it is because the SignaturePad inherits from EventTarget and call EventTarget constructor. Hence the "super()" error.
iOS only start support EventTarget constructor from iOS 14....
https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/eventTarget

[bowozer]

oh yeah i probably should say: user cannot stroke any lines in the canvas after that error. I guess it is pretty much breaking the pad.

I think it is important to make it runs on iOS 13 because many devices still works on them.

[bowozer]

i hope this PR #581 suffices to solve this issue. Just awaiting for approval

[welsh]

I noticed on Android 6.0.1 that also upgrading it stopped working, reverting back to v3.0.0-beta.3 resolved the problem.

The error was about an illegal constructor typescript, I wonder if this is the same issue that you're running into.

[bowozer]

@welsh well luckily on Android OS, the browser engine actually decoupled with the OS itself. So you just need to upgrade the browser to the latest and it would have the newest browser engine, and thus it would work with the latest library.

Unfortunately, it is different with iOS, though. No matter the browser in iOS, it always uses webkit engine . The engine (webkit) is coupled with the iOS. That is why to upgrade browser engine, you would need to upgrade iOS as well.. It doesn't sit really well because it would make this library unusable in many devices that currently being used.

[strivelen]

For the current problem, my solution is to introduce an EventTarget polyfill in the head tag of html.
It is recommended to use it in transition or in emergencies. I still hope that this library can be compatible with the IOS13 version. There are indeed many people who use this version.

[UziTech]

fixed by #581