Bug 214230

Created attachment 404087 [details] 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.