1046993 - Use more floating-point coordinates in Axis

Status: RESOLVED FIXED

(Core :: Panning and Zooming, defect)

Description

[Botond Ballo [:botond]]

Currently, gfx/layers/apz/src/Axis.{h,cpp} uses a mixture of integer and floating-point coordinates. This means we are doing rounding/truncating that could be avoided. It would be better to use floating-point coordinates throughout.

Comment 1

[Milan Sreckovic [:milan] (needinfo for best results)]

Any micro benchmarks to help us not regress performance?

Comment 2

[Botond Ballo [:botond]]

Attachment: bug1046993.patch

This patch modifies Axis to consistently use floating-point coordinates.

I also took the opportunity to modify GetFirstTouchScreenPoint(), which was returning by reference for no good reason, to return by value.

Comment 3

[Botond Ballo [:botond]]

Try push: https://tbpl.mozilla.org/?tree=Try&rev=c5bfa9ae12a8

Comment 4

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

Comment on attachment 8476265 [details] [diff] [review]
bug1046993.patch

Review of attachment 8476265 [details] [diff] [review]:
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Nice!

Comment 5

[Botond Ballo [:botond]]

(In reply to Milan Sreckovic [:milan] from comment #1)
> Any micro benchmarks to help us not regress performance?

The amount of computation we do with these values is a few operations per touch event, so I would expect any performance impact to be negligible. The new code might actually be faster (again, by a negligible amount) by avoiding some float -> int -> float round trips.

The value in this change is from the accuracy we gain by avoiding such round trips.

Comment 6

[Botond Ballo [:botond]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/85a95286b6cf

Comment 7

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/85a95286b6cf