1858848 - [css-properties-values-api] Compute initial value

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement)

Description

[Zach Hoffman [:zrhoffman]]

Now that registered custom properties are computed, the initial value can also be computed.

Tests that should pass: https://wpt.fyi/results/css/css-properties-values-api/registered-property-initial.html

In order to use computed <length> and <length-percentage> values before bug 1856524 is resolved, a new generic computed value type would need to be added, like ComputedValueComponent added in bug 1857716, which uses computed::Length and computed::LengthPercentage instead of specified::Length and specified::LengthPercentage like ComputedValueComponent does until bug 1856524 is resolved.

Comment 1

[Zach Hoffman [:zrhoffman]]

This will probably require passing a computed::Context all the way to PropertyRegistration::validate_initial_value, similar to the Stylist passing in bug 1840478 and bug 1850370.

Comment 2

[Zach Hoffman [:zrhoffman]]

Attachment: Bug 1858848 - [css-properties-values-api] Compute initial value r=zsun,fredw,#style

This patch computes initial value when initial values are collected. The
initial value cannot be computed earlier (for example, at parse time)
without breaking intended behavior, since CSSOM expects the initial
value string of a CSSPropertyRule to remain uncomputed.

Although <length> and <length-percentage> can be accurately computed
already for initial values since valid initial values are always
font-indepent, this patch leaves <length> and <length-percentage>
uncomputed for simplicity (until bug 1856524 is implemented).

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ab1916269c71
[css-properties-values-api] Compute initial value r=firefox-style-system-reviewers,layout-reviewers,emilio

Comment 4

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/ab1916269c71