1486409 - Font editor: guard against zero as value for font properties

Status: VERIFIED FIXED

(DevTools :: Inspector, defect, P2)

Description

[Razvan Caliman [:rcaliman]]

The CSS `font-size` value may be zero and that causes unexpected results when using it for unit conversion or line-height computation.

Steps:
- go to https://news.google.com/
- inspect a headline, select its parent `<article>` element
- observe the font editor in the Fonts panel


Expected:
Size should be shown as 0px (same as from Computed panel). Line height should show 0. 

Result:
Size field is not populated. Line height is shown as NaN because of the division by zero.

A few other cases are impacted by `font-size: 0`, such as converting between relative units which use the font-size value, for example converting from 'px' to 'em'.

Comment 1

[Razvan Caliman [:rcaliman]]

Attachment: font-size: 0

Comment 2

[Razvan Caliman [:rcaliman]]

Attachment: Bug 1486409 - Guard against a font property value of zero. Catch NaN and Infinity in unit conversion. r=gl

Comment 3

[Gabriel Luong [:gl] (ΦωΦ)]

Comment on attachment 9004189 [details]
Bug 1486409 - Guard against a font property value of zero. Catch NaN and Infinity in unit conversion. r=gl

Gabriel [:gl] (ΦωΦ) has approved the revision.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f10df314fc4d
Guard against a font property value of zero. Catch NaN and Infinity in unit conversion. r=gl

Comment 5

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/f10df314fc4d

Comment 6

[Catalin Sasca, Desktop QA [:csasca]]

I successfully reproduced the issue on Firefox Nightly 63.0a1 (2018-08-27) under Windows 10 (x64) using the STR from Comment 0.

The issue is no longer reproducible on Firefox Beta 63.0b13 and latest Firefox 64.0a1 (2018-10-09). Tests were performed on Windows 10 (x64), macOS 10.13 and Ubuntu 16.04 (x64).