1209493 - [New-Homescreen] Icon dragging performance is not as good as it could be

Status: RESOLVED FIXED

(Firefox OS Graveyard :: Gaia::Homescreen, defect)

Description

[Chris Lord [:cwiiis]]

When dragging icons around, the animation of the icons underneath the dragged icon can cause the dragged icon to lag behind the position of the finger very obviously and cause the animation to be a bit janky. This is especially evident in 4-column mode.

The performance of this varies wildly depending on what Gecko builds you use, but there are still optimisations here that haven't been employed that could make it considerably better.

Comment 1

[Chris Lord [:cwiiis]]

So, employed the optimisation I was thinking of which has markedly improved consistency, but it's still a bit laggy - it seems that applying the class change that makes the icons move out of the way is quite expensive in and of itself...

Seeing if I can get it better - may have to just apply the style directly, which seems a shame...

Comment 2

[GitHub Autolander Bot]

Attachment: [gaia] Cwiiis:bug1209493-new-homescreen-icon-drag-perf > mozilla-b2g:master

Comment 3

[Chris Lord [:cwiiis]]

Comment on attachment 8667380 [details] [review]
[gaia] Cwiiis:bug1209493-new-homescreen-icon-drag-perf > mozilla-b2g:master

I'm not pleased that I couldn't get this better, but I think further improvements may be down to platform. The remaining jank appears to be entirely from setting the style on the icons that move out of the way - doing all the work that it currently does, but omitting that step results in silky smooth movement (but obviously no feedback). I tried setting style directly on the icons, but it didn't appear to be appreciably less expensive than setting the class list.

This patch basically just sticks 'will-change: transform' on all the currently visible icons, which removes the cost of layerisation/repainting and smooths out the transitions a bit.

Comment 4

[Guillaume Marty [:gmarty]]

Comment on attachment 8667380 [details] [review]
[gaia] Cwiiis:bug1209493-new-homescreen-icon-drag-perf > mozilla-b2g:master

LGTM.
Did you open a specific bug to enquire the platform side of things?

Comment 5

[Chris Lord [:cwiiis]]

Merged: https://github.com/mozilla-b2g/gaia/commit/1d2d0ba06fb1665981cf3229d5fa73551dd89dcd

Not opening a platform bug just yet, WebIDE isn't working right now and I'd like to get a profile to know exactly where the time is going. Leaving n?me to follow up on this.

Comment 6

[Chris Lord [:cwiiis]]

I don't think there's any specific platform thing to do here, except just be faster. Maybe bug 1154825. I think our displayport sizes could probably do with tweaking again at some point too.