1615858 - Improve precision of touch velocity computation by taking "historical" events into account

Status: RESOLVED FIXED

(Core :: Panning and Zooming, enhancement, P3)

Description

[Markus Stange [:mstange]]

On Android, MotionEvent lets you access "historical" event data for the original events that were batched into one MotionEvent. Chrome makes use of these events in its velocity tracker, and we should probably do the same.

Comment 1

[Kartikaya Gupta (email:[e-mail])]

Is this something that came up while you were working on bug 1458653? If so, are you planning to take this bug, or are you spinning it out for somebody else to tackle?

Comment 2

[Markus Stange [:mstange]]

It is something that I stumbled over as part of the investigation into that bug, but it's probably not essential to do for that bug. I'm not planning to work on this.

Comment 3

[Markus Stange [:mstange]]

I'm going to take a quick stab at it. It seems that my Moto G5 samples the touch screen at a rate of 100Hz. Since vsync happens at 60Hz, and touch events are dispatched in alignment with vsync, that means that each touch event is the result of one or two touch screen samples. An increase of 50% touch data would definitely make it easier for the AndroidVelocityTracker to compute accurate velocities.

Comment 4

[Markus Stange [:mstange]]

Attachment: Bug 1615858 - Add MultiTouchInput::SingleTouchData::mHistoricalCoords to store historical touch data. r=kats

Comment 5

[Markus Stange [:mstange]]

Attachment: Bug 1615858 - Propagate historical touch data from Java to C++. r=kats

Comment 6

[Markus Stange [:mstange]]

Attachment: Bug 1615858 - Take historical touch positions into account when estimating touch velocity. r=kats

This also adds a test. The velocities computed in the test are the following:

SimpleVelocityTracker: 0.65 with full data, 0.467 with partial data
AndroidVelocityTracker: 1.225 with full data, 0.833 with partial data

Depends on D95645

Comment 7

[Markus Stange [:mstange]]

Attachment: Bug 1615858 - Add MultiTouchInput::SingleTouchData::mHistoricalData. r=kats

Comment 8

[Markus Stange [:mstange]]

Attachment: Bug 1615858 - Propagate historical touch data from Java to C++. r=kats

Depends on D95649

Comment 9

[Markus Stange [:mstange]]

Attachment: Bug 1615858 - Take historical touch positions into account when estimating touch velocity. r=kats

This also adds a test. The velocities computed in the test are the following:

SimpleVelocityTracker: 0.65 with full data, 0.467 with partial data
AndroidVelocityTracker: 1.225 with full data, 0.833 with partial data

Depends on D95650

Comment 10

[Markus Stange [:mstange]]

https://treeherder.mozilla.org/jobs?repo=try&revision=e64ec3f85c91be54d7da23f85d01f4d1b765f58b

Comment 11

[Markus Stange [:mstange]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=4eb3427e7a0cc0e33f2f608d5f8df612dee045aa

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4c5fdaab5f27
Add MultiTouchInput::SingleTouchData::mHistoricalData. r=kats
https://hg.mozilla.org/integration/autoland/rev/b4f668a31f18
Propagate historical touch data from Java to C++. r=kats,geckoview-reviewers,agi
https://hg.mozilla.org/integration/autoland/rev/bf8313268c20
Take historical touch positions into account when estimating touch velocity. r=kats

Comment 13

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/4c5fdaab5f27
https://hg.mozilla.org/mozilla-central/rev/b4f668a31f18
https://hg.mozilla.org/mozilla-central/rev/bf8313268c20