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Verify event is not null on touch.js #13

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Verify event is not null on touch.js #13

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1dfc86d
Verify event is not null on touch.js
as0ler Mar 3, 2023
2cbb96e
Tweak style
oleavr Mar 3, 2023
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95 changes: 47 additions & 48 deletions lib/touch.js
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Original file line number Diff line number Diff line change
Expand Up @@ -129,58 +129,57 @@ const Injector = ObjC.registerClass({

const app = UIApplication.sharedApplication();
const event = app['- _touchesEvent'].call(app);
event['- _clearTouches'].call(event);

const absoluteTime = mach_absolute_time();

const timestamp = [
absoluteTime.shr(32).toNumber(),
absoluteTime.and(0xffffffff).toNumber()
];

touch.setTimestamp_(CFGetSystemUptime());

const eventMask = (phase === UITouchPhaseMoved)
? kIOHIDDigitizerEventPosition
: (kIOHIDDigitizerEventRange | kIOHIDDigitizerEventTouch);
const isRangeAndTouch = (phase !== UITouchPhaseEnded) ? 1 : 0;

const hidEvent = IOHIDEventCreateDigitizerFingerEvent(
kCFAllocatorDefault,
timestamp,
0,
2,
eventMask,
point[0],
point[1],
0,
0,
0,
isRangeAndTouch,
isRangeAndTouch,
0);

if ('- _setHidEvent:' in touch) {
touch['- _setHidEvent:'].call(touch, hidEvent);
}

event['- _setHIDEvent:'].call(event, hidEvent);
event['- _addTouch:forDelayedDelivery:'].call(event, touch, false);

const pool = NSAutoreleasePool.alloc().init();
try {
app.sendEvent_(event);
} finally {
pool.release();
if (event !== null) {
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@oleavr oleavr Mar 3, 2023 •
edited
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Oh wait, sorry, I'm not sure I understand what happens here. Does -[UIApplication _touchesEvent] keep returning nil or is it a random glitch? If it's the latter I'm wondering if we should make the _touchesEvent() call earlier, before we do pending.shift(), and simply return there -- that way dispatchTouch: gets called again on the next frame, and might succeed that time and keep going. (But if this is a permanent failure, I suppose we should call onComplete() with an Error so it can reject the Promise?)

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It occurs when the application goes to the background for any reason and comes back. So I would say it's happening on a non-predictable manner.

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@oleavr oleavr Mar 3, 2023 •
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Interesting. I guess the tap down event instantly triggers backgrounding, and in this failure case we get the next dispatchTouch: just after the app has gone off screen -- whereas in the happy case we get it after it is back on the screen again.

If that is correct, I think we have two options:

  1. Keep trying, by returning early, before we do pending.shift(). In this way we will eventually move it through the different phases.
  2. Complete the touch right away, as if pending.length === 0. In that case we will have to release priv.touch if we already created it.

It seems to me that 1) is the right solution, since we will keep going once the app is back on the screen. This is also what happens when we are luckier -- the app goes to the background and dispatchTouch: does not get called until it's back on the screen.

What do you think, @mrmacete?

event['- _clearTouches'].call(event);
const absoluteTime = mach_absolute_time();

const timestamp = [
absoluteTime.shr(32).toNumber(),
absoluteTime.and(0xffffffff).toNumber()
];

touch.setTimestamp_(CFGetSystemUptime());

const eventMask = (phase === UITouchPhaseMoved)
? kIOHIDDigitizerEventPosition
: (kIOHIDDigitizerEventRange | kIOHIDDigitizerEventTouch);
const isRangeAndTouch = (phase !== UITouchPhaseEnded) ? 1 : 0;

const hidEvent = IOHIDEventCreateDigitizerFingerEvent(
kCFAllocatorDefault,
timestamp,
0,
2,
eventMask,
point[0],
point[1],
0,
0,
0,
isRangeAndTouch,
isRangeAndTouch,
0);

if ('- _setHidEvent:' in touch) {
touch['- _setHidEvent:'].call(touch, hidEvent);
}

CFRelease(hidEvent);
event['- _setHIDEvent:'].call(event, hidEvent);
event['- _addTouch:forDelayedDelivery:'].call(event, touch, false);

priv.previous = point;
if (isLastTouch) {
touch.release();
priv.touch = null;
const pool = NSAutoreleasePool.alloc().init();
try {
app.sendEvent_(event);
} finally {
pool.release();
CFRelease(hidEvent);
}
}
priv.previous = point;
if (isLastTouch) {
touch.release();
priv.touch = null;
}
}
}
}
Expand Down