1524319 - Alpha values in #RRGGBBAA format can lose accuracy

Status: RESOLVED FIXED

(DevTools :: Inspector: Rules, defect, P2)

Description

[Michał Gołębiowski-Owczarek [:mgol]]

Bug 1271191 added support for the #RRGGBBAA hexadecimal with alpha color format:
https://drafts.csswg.org/css-color/#hex-notation

However, when set via DevTools CSS Rules pane, the value is converted in a lossy way, losing the opacity precision.

To reproduce:

1. Open DevTools.
2. Focus some element.
3. In the CSS Rules pane, add a new property: color: #fefefef0.
4. Notice the browser changes it to color: #fefefee6.

The weird thing is this looks only as a representation problem - CSSOM APIs return the correct value:

document.body.style.color; // "rgba(254, 254, 254, 0.94)"

If you set the Firefox-modified value via CSSOM, you can see it's different:

document.body.style.color = '#fefefee6';
document.body.style.color; // "rgba(254, 254, 254, 0.90)"

Comment 1

[Mike Ratcliffe [:miker] [:mratcliffe] [:mikeratcliffe]]

Adding to the above STR:

You must first set the default color unit to "Hex" in settings.

Comment 2

[Mike Ratcliffe [:miker] [:mratcliffe] [:mikeratcliffe]]

Attachment: Bug 1524319 - Alpha values in #RRGGBBAA format can lose accuracy r?nchevobbe!

Comment 3

[Michał Gołębiowski-Owczarek [:mgol]]

(In reply to Mike Ratcliffe [:miker] [:mratcliffe] [:mikeratcliffe] from comment #1)

Adding to the above STR:

You must first set the default color unit to "Hex" in settings.

You don't have to, it also works with the default "As authored". If you changed that to a non-hex format then yes, my STR won't work.

Comment 4

[Mike Ratcliffe [:miker] [:mratcliffe] [:mikeratcliffe]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=e51b137ed66d9905e14a6e371f633ed9cddf6a60

Comment 5

[Mike Ratcliffe [:miker] [:mratcliffe] [:mikeratcliffe]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=50337c88a371cefecd805687583dd9c8a00aba2d

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2a4f6bb7524a
Alpha values in #RRGGBBAA format can lose accuracy r=nchevobbe

Comment 7

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/2a4f6bb7524a