What is meaning by "pause"?

[desmeit]

I try to have a simple timer and need to pause it:

late final PausableTimer timer;

timer = PausableTimer(Duration(seconds: 1), () {
    print('Fired!');
    timer
        ..reset()
       ..start();
    });
    timer.start();

now I want to pause it:

timer!.pause();

But after starting again with timer!.start(); it starts from millisecond 0.
This is not good because I never hit exactly at millisecond 0 when pausing, but maybe at 323 millisecond or similar.

How can I restart the timer from the exact position where i paused it?

[llucax]

Hi @desmeit,

I'm not sure why are you observing this behaviour, it might be useful to provide a full test case to reproduce it.

The timer should continue from where it was paused, have a look at the source code:

pausable_timer/lib/pausable_timer.dart

Line 63 in d7253c1

_timer = _zone.createTimer(_originalDuration - _stopwatch!.elapsed, () {

This is also being tested in the tests:

pausable_timer/test/pausable_timer_test.dart

Lines 79 to 121 in d7253c1

	test('pause()', () {
	fakeAsync((fakeTime) {
	final timer = PausableTimer(oneSecond, callback);
	timer.start();
	expectState(timer, oneSecond, active);
	// Wait for half the duration, it should be still running
	fakeTime.elapse(oneSecond ~/ 2);
	expectState(timer, oneSecond, active, elapsed: oneSecond ~/ 2);
	var elapsed = timer.elapsed;
	// Pause it
	timer.pause();
	expectState(timer, oneSecond, paused, elapsed: elapsed);
	elapsed = timer.elapsed;
	// Wait for a couple more seconds, nothing should happen
	fakeTime.elapse(oneSecond * 2);
	expectState(timer, oneSecond, paused, elapsed: elapsed);
	// pause should do nothing either, even if more time passes
	timer.pause();
	fakeTime.elapse(oneSecond * 2);
	expectState(timer, oneSecond, paused, elapsed: elapsed);
	// Resume the timer, it should be active again
	timer.start();
	expectState(timer, oneSecond, active, elapsed: elapsed);
	// Wait for the remaining time, then it should be expired
	fakeTime.elapse(oneSecond - timer.elapsed);
	expectState(timer, oneSecond, expired, elapsed: oneSecond, withCalls: 1);
	// Wait for a couple more seconds, nothing should happen
	fakeTime.elapse(oneSecond * 2);
	expectState(timer, oneSecond, expired, elapsed: oneSecond, withCalls: 1);
	// pause when it's already expired should do nothing
	timer.pause();
	expectState(timer, oneSecond, expired, elapsed: oneSecond, withCalls: 1);
	});
	});

If there is really a bug, I won't be able to look at it sadly, as I haven't worked with Dart for years now, I don't even have Dart installed anymore. I'm looking for a maintainer to take over.

[llucax]

Can you please try out this example and let me know if it works or not for you?

https://github.com/llucax/pausable_timer/blob/main/example/countdown.dart

[llucax]

BTW, I will convert to a discussion until we can confirm this is a bug.

[llucax]

@desmeit I just found my dart environment I use to make releases and tried the countdown example (with a small modification to make it more obvious) which pauses the timer and it works fine:

$ dart --version
Dart SDK version: 3.0.2 (stable) (Tue May 23 08:26:58 2023 +0000) on "linux_x64"
$ git diff | cat
diff --git a/example/countdown.dart b/example/countdown.dart
index c26429e..0eb1ea7 100644
--- a/example/countdown.dart
+++ b/example/countdown.dart
@@ -27,10 +27,10 @@ void main() async {
     },
   )..start();
 
-  print('And wait 2.1 seconds...');
+  print('And wait 2.5 seconds...');
   print('(0.1 extra to make sure there is no race between the timer and the '
       'waiting here)');
-  await Future<void>.delayed(timer.duration * 2.1);
+  await Future<void>.delayed(timer.duration * 2.5);
   print('By now 2 events should have fired: 4, 3\n');
 
   print('We can pause it now');
$ dart countdown.dart | while read l; do echo "$(date +'%T.%N' | cut -c-11) $l"; done
14:16:06.86 Create a periodic timer that fires every 1 second and starts it
14:16:06.87 And wait 2.5 seconds...
14:16:06.87 (0.1 extra to make sure there is no race between the timer and the waiting here)
14:16:07.89 4
14:16:08.89 3     <----------------------------- LAST TICK AT ~8.9
14:16:09.38 By now 2 events should have fired: 4, 3
14:16:09.39 
14:16:09.40 We can pause it now   <--------- PAUSED AT 9.4 (0.5 seconds after the last tick)
14:16:09.41 And we wait for 2 more seconds...  <---- 2 SECONDS Paused
14:16:11.38 But our timer doesn't care while it's paused
14:16:11.39 
14:16:11.40 So we start it again   <-------- RESUMED AT 11.4
14:16:11.41 And wait for 3.1 seconds more...
14:16:11.89 2         <------------------ NEXT TICK AT 11.9 (0.5 seconds after resumed)
14:16:12.89 1
14:16:13.89 0
14:16:14.48 And we are done: 2, 1 and 0 should have been printed
14:16:14.49 The timer should be unpaused, inactive, expired and not cancelled
14:16:14.50 isPaused: false
14:16:14.51 isActive: false
14:16:14.52 isExpired: true
14:16:14.53 isCancelled: false
14:16:14.54 We can now reset it and start it again, now for 3 seconds
14:16:14.55 And wait for 3.1 seconds...
14:16:15.49 2
14:16:16.49 1
14:16:17.49 0
14:16:17.59 And it should be done printing: 2, 1 and 0

As you can see, the timer is resumed where it was left when paused.

[desmeit]

okay thanks, maybe I made a mistake.