Dash touch scrolling is slower (more laggy) than web browser touch scrolling

[Daniel van Vugt]

Dash touch scrolling is slower than web browser touch scrolling. But obviously it should not be.

This has been an issue for as long as I remember. Just upgraded mako to xenial and it's still there.

Am I imagining things? Is this simply explained by the web browser using a different toolkit? Could it just be a side-effect of bug 1494795?

[Michael Zanetti (mzanetti)]

The difference is explained by the different toolkits, yes. The reason why the dash (and everything else) is slower is very likely because we still haven't landed the Qt pixel-independence branches which causes Qt to calculate the max flickVerlocy based on high density pixel ratio of mako, instead of our virtual grid unit ratio.

[Daniel van Vugt (vanvugt)]

Awesome. Glad it's no my imagination at least.

[Daniel van Vugt (vanvugt)]

Although I'm surprised you would use either the pixel density or grid unit calculations. Accurate scrolling is all about exact pixels.

[Daniel van Vugt (vanvugt)]

Hmm, maybe this is just a natural consequence of bug 1494795

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

Oh... could this just be a logic problem in that we're throttling the dash scroll speed all the time? I know the scroll speed is throttled if you fling it and let go, but it feels like the problem might just be that we're throttling the scroll speed even while a finger is still touching, which of course would make it artificially more laggy. The throttling should only kick in after the user has let go.