Timers without Ticking

[smessmer]

Both the Timer and Stopwatch APIs need you to tick them, i.e. periodically update them in one of your systems. Is this actually necessary?

Imagine a Timer class that - instead of storing a elapsed: Duration member just stores a start: Instant member. Such a timer wouldn't need to be ticked, but we'd have to change the elapsed() function to take a Time& argument so that we can calculate it on the fly. Because of that, it's not a clear win but it's a different way of doing this.

In my personal opinion, however, that's a better way because it is more explicit. You cannot accidentally forget to tick the timer or accidentally tick it twice and get weird behavior in your game. Also, it would likely be more accurate since we don't have as many floating point addition operations.

[akimakinai]

That said, real-time independent and explicitly ticked timers might work better when pausing the game, changing its speed, or saving, loading or rolling back the game state. Also, since duration is represented by (u64, u32), ticking by duration seems to be integer addition.

[smessmer]

You're right that the implementation details of the timer get a bit more complicated to handle pausing and speed changes but it's possible and the API should look the same.

[smessmer]

Oh actually the API would have to change. We'd have to pass in a &Time object to pause() and unpause() so pause can remember when it was paused and unpause can adjust the start member accordingly.

[smessmer]

I guess another option is to have timers automatically register themselves with a central timer registry and make that registry tick them automatically. But that comes with some overhead for creating timers.