[Webkit-unassigned] [Bug 214230] New: font-weight should always serialize as a number

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=214230

            Bug ID: 214230
           Summary: font-weight should always serialize as a number
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: taken.spc at gmail.com

Created attachment 404087

  --> https://bugs.webkit.org/attachment.cgi?id=404087&action=review

Test case

The font-weight should always serialize as a number (400, 700 and so on). 

WebKit uses keyword ("normal" or "bold") when possible and number otherwise (300, 600 and son on). This behavior has some drawbacks:


1. It is a bit harder to get differences of computed values in animations


```
const {fontWeight: oldFontWeight} = window.getComputedStyle(element);
// do some stuff
const {fontWeight} = window.getComputedStyle(element));
const diff = parseInt(oldFontWeight, 10) - parseInt(fontWeight, 10);
```


Expected behavior
If oldFontWeight is "300" and fontWeight is "600" then the diff is 300.
If oldFontWeight is "400" and fontWeight is "700" then the diff is 300.

Actual behavior
If oldFontWeight is "300" and fontWeight is "600" then the diff  is 300.�� 
If oldFontWeight is "normal" and fontWeight is "bold" then the diff is NaN.��


2. Inconsistency with specs

CSS Fonts Module Level 3 defines computed value of font-weight is "numeric"
https://www.w3.org/TR/2018/REC-css-fonts-3-20180920/#propdef-font-weight

CSS Fonts Module Level 4 defines computed value of font-weight is "number"
https://drafts.csswg.org/css-fonts/#propdef-font-weight


3. Inconsistency with other browsers

- IE 11: always use a number
- Chrome: always uses a number
- Firefox always uses a number

WebKit should always use number for font-weight.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20200712/56c82111/attachment.htm>