1865810 - [css-properties-values-api] getPropertyValue returns old value when iframe is resized

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[Zach Hoffman [:zrhoffman]]

Attachment: getpropertyvalue-not-updating.html

Steps to reproduce:

• Make an iframe with width 200px, containing registered <length> custom property --my-property with initial value 50vw
• Observe that --my-property's computed value is 100px
• Use CSSOM to change the iframe's width to 300px
• Check --my-property's computed value again

Expected result: --my-property's computed value is 150px

Actual result: --my-property's computed value is 100px

See attached testcase.

WPT: https://wpt.fyi/results/css/css-properties-values-api/at-property-viewport-units-dynamic.html

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Yeah, we need to track whether any custom property uses viewport units in its initial value, and either mark all elements with USES_VIEWPORT_UNITS or, most likely simpler, trigger a subtree recascade around here...

Comment 2

[Zach Hoffman [:zrhoffman]]

Attachment: Bug 1865810 - [css-properties-values-api] Keep track of flags that were set when computing initial values r=zsun,fredw,#style

This will be useful later to check whether the registered property
initial values contained viewport units.

Comment 3

[Zach Hoffman [:zrhoffman]]

Attachment: Bug 1865810 - [css-properties-values-api] Recompute initial values when viewport changes r=zsun,fredw,#style

If the initial values of custom property registrations contain viewport
units, changing the viewport will result in recomputing the initial
values.

Depends on D194667

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/931685329b50
[css-properties-values-api] Keep track of flags that were set when computing initial values r=firefox-style-system-reviewers,emilio
https://hg.mozilla.org/integration/autoland/rev/0cd5e7d76f8a
[css-properties-values-api] Recompute initial values when viewport changes r=firefox-style-system-reviewers,emilio

Comment 5

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/mozilla-central/rev/931685329b50
https://hg.mozilla.org/mozilla-central/rev/0cd5e7d76f8a