1225137 - ScrollbarActivity segfaults on a division-by-zero if the scrollbar fade pref is set to zer0

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

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

In bug 1223928 I enabled the gecko scrollbar for Fennec and copied over the relevant prefs from B2G. However it crashed because of the division-by-zero at [1]. This same line runs on B2G also, but the division by zero returns infinity instead. I assume this is because TimeDuration is kept as an int on Fennec but turned into a float on B2G. Still, this seems bad and we should avoid the division by zero.

[1] https://dxr.mozilla.org/mozilla-central/rev/bc74dbdea094059d5f1d353a2585b4f6352b6ec4/layout/generic/ScrollbarActivity.cpp#366

Comment 1

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

Attachment: Patch

Comment 2

[Stephen A Pohl [:spohl]]

Comment on attachment 8687953 [details] [diff] [review]
Patch

Review of attachment 8687953 [details] [diff] [review]:
-----------------------------------------------------------------

::: layout/generic/ScrollbarActivity.cpp
@@ +366,5 @@
> +  // Avoid division by zero if mScrollbarFadeDuration is zero, just jump
> +  // to the end of the fade animation
> +  double progress = mScrollbarFadeDuration
> +    ? ((aTime - mFadeBeginTime) / FadeDuration())
> +    : 1.0f;

nit: we can drop the 'f' here

Comment 3

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/8fa1bffbfeaf

Comment 4

[Timothy Nikkel (:tnikkel)]

(In reply to Kartikaya Gupta (email:[e-mail]) from comment #0)
\> at [1]. This same line runs on B2G also, but the division by zero returns
> infinity instead. I assume this is because TimeDuration is kept as an int on
> Fennec but turned into a float on B2G. Still, this seems bad and we should
> avoid the division by zero.

I had pushed this same pref flip to try a while back when I looked into fennec scrollbars. I had assumed the div by zero was because the scrollbars are styled display: none on fennec, but I never looked into it, so I could be totally wrong.

Comment 5

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

In my case I made the gecko scrollbars display on fennec, so I don't think it's related to display:none.

Comment 6

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

https://hg.mozilla.org/mozilla-central/rev/8fa1bffbfeaf