Massive stutters in firefox in 0.29.0-beta, 0.29.1-beta and master (games)

[cybersoulK]

I spent the last several hours debugging this.
My game Normal behaviour in firefox is 120 fps stable

I finally troubleshooted that 0.29.0-beta was causing issues in comparison with what i had previously: ed14254.
Then i tested all of the versions including the current master 399edf5.

The master is by far the worst. 0.29.0-beta and 0.29.1-beta was 120 fps 90% of the time and then stutters down to 20 fps. The master stays at 25fps most of the time and occasionally freezes for 1 Second!!

Here is a video of the issue in current master: https://youtu.be/VCMHpYqanMg

I tested with the latest stable firefox.

[kchibisov]

Given that we have no idea what you're doing, I'd suggest to at least try to ask for redraw_requested on the window. There were also some different polling modes added for the web.

Maybe you just do Poll and draw, but we have no idea.

[cybersoulK]

i tried window.redraw_requested at the end of RedrawRequested, and also tried it inside AboutToWait.
is there something that i am missing?

I also don't touch ControlFlow at all, it says it's Poll by default

[daxpedda]

i tried window.redraw_requested at the end of RedrawRequested, and also tried it inside AboutToWait.
is there something that i am missing?

It really doesn't matter where you call redraw_requested() from.

I also don't touch ControlFlow at all, it says it's Poll by default

Using Poll in Firefox will currently just not work. But Winit can't do anything about that, it's just an issue with Firefox: requestAnimationFrame() will get throttled under pressure (Bugzilla).

The reason it was working before is Poll was using rAF, which was incorrect. If you really need Poll in Firefox, consider using PollStrategy::IdleCallback from #3084, as @kchibisov already mentioned.

@kchibisov I would like to know how Poll is used in practice on other backends: because it just loops as fast as possible it will basically consume 100% CPU. For that reason I've never used Poll in practice except when testing stuff in Winit.

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In any case, I will close this as it isn't really actionable from our side. @cybersoulK we are also guessing at your problem here because we don't have any information. If you can put together something reproducable it would be ideal.

[kchibisov]

@kchibisov I would like to know how Poll is used in practice on other backends: because it just loops as fast as possible it will basically consume 100% CPU. For that reason I've never used Poll in practice except when testing stuff in Winit.

From what I can say, it's used with some blocking mechanism in the main loop, like vsync, but I'm not sure myself why you'd use poll. The only reason is to render as fast as possible, so you draw every time you wake up trying to blast frames per second.

I guess the use case for web in this issue is the same, they want to blast FPS.

[daxpedda]

From what I can say, it's used with some blocking mechanism in the main loop, like vsync, but I'm not sure myself why you'd use poll. The only reason is to render as fast as possible, so you draw every time you wake up trying to blast frames per second.

I guess the use case for web in this issue is the same, they want to blast FPS.

Fun. Did we ever consider switching the default to Wait?

[kchibisov]

We could, will default of Wait work on the web?

[daxpedda]

Yes. Are you thinking of any specific reason why it wouldn't?

[cybersoulK]

It's firefox fault? But like i said ed14254 works normal.

It's not only about the good fps, but also like you saw in the video, the alpha versions + master have massive stuttering, this is unusable. Can you guys switch like it was before, because it worked well

[kchibisov]

@cybersoulK have you read what we replied? Don't use Poll, use Wait, because Poll now follows other platforms and it's what web can't do.

[daxpedda]

It's firefox fault? But like i said ed14254 works normal.

From #3105 (comment):

The reason it was working before is Poll was using rAF, which was incorrect. If you really need Poll in Firefox, consider using PollStrategy::IdleCallback from #3084, as @kchibisov already mentioned.

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Can you guys switch like it was before, because it worked well

Using rAF for Poll is simply incorrect, so we can't switch back to that. In any case, if you are using Window::request_redraw() in every event loop cycle with Wait, you get the exact same behavior as before.

If this doesn't fulfill your requirements, you should point out exactly why so we can figure out how to proceed.

[cybersoulK]

Okay i am not really sure, i reverted all of my codes back and i can't try it right now. I also had people in gamedev community having issues with the newest versions. I will try it on the next non-alpha version of winit.

I have no idea of Poll vs Wait, but my game works on windows + mac + linux well, and a simple request_redraw loop works on firefox. Maybe make another controlFlow called Render instead of Poll or Wait? and just give it as default, it's confusing to me

If it's firefox issue, we still need to accommodate for its shortcomings, it's a major browser

[kchibisov]

But those a basics of control flow, winit also doesn't render anything. It's also documented which control flow does. Poll means spin the loop as fast as it can, the Wait means, wait for the actual event to arrive. Web can't spin as fast as it can on firefox, due to linked issue.

[cybersoulK]

Uhm, i had several major devs telling me to use Poll.
their quotes:

Dev Name X

"Poll if you're doing continuous rendering/animation on the same thread as your event handling (typical for games)
Wait[Until] if you're only updating on the same thread in response to events and don't want to pointlessly drain your user's battery (typicalish for business apps) "

Dev Name Y

"as I understand it Wait + request_redraw is mainly meant to be used when you only want to redraw the window in reaction to events or something happening in your program
whereas for a game where stuff is changing every frame, you'd want to  Poll and let vsync (or some other accurate frame timing mechanism) decide when to draw"

So it seems common sense between game devs to use the default ControlFLow in winit which is Poll