Mouse-wheel scrolling smoothness

Vladan Djeric vdjeric at
Thu Aug 27 21:12:51 UTC 2015

I would like us to look into mouse-wheel scrolling smoothness as part of
content-perf. I noticed that IE and Edge scroll much smoother than Firefox
on a variety of Windows machines. I think this might be down to our
smooth-scroll implementation/configs.

I'd like others to reproduce my impressions, and if we can confirm them,
then I'd like to request the gfx team to make the changes. Of course, we
should wrap up our current content-perf investigations first.

Evaluation procedure:

1. Start e10s Nightly with APZ=on smoothscroll=on (defaults) on a Windows
7/8.1/10 machine
2. Load the following URL :
3. Scroll the page down to a text-heavy part of the article, position the
cursor over text.
4. Using the mouse-wheel:

   - scroll up or down over the article text by a single mouse-wheel
   "click" at a time. Does the scroll animation for one mouse-wheel click look
   "bad" to you?
      - Compare vs IE or Edge
      - scroll up or down over the article text by rolling the mouse-wheel
   by about 3 clicks. How does the animation look?
      - Compare vs IE or Edge

Post back on this mailing list with your observations. I tested with the
Win 8.1 HP 14t reference laptop, Win7 Lenovo W520, Win 8.1 Lenovo X1
Carbon, and a Win 10 desktop with an Nvidia GTS 450 GPU. The single-click
and three-click mouse-wheel scrolls consistently looked smoother in IE and
Edge. Others I showed it to around the office agreed with my assesment. I
also tested against Chrome, but there wasn't a consensus on Firefox vs

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