Closed Bug 1254424 Opened 7 years ago Closed 5 years ago

Animations using em-based units should respond to changes in the font-size on the parent


(Core :: CSS Parsing and Computation, defect)

Not set



Tracking Status
firefox48 --- affected


(Reporter: birtles, Unassigned)


(Blocks 1 open bug)


(Keywords: dev-doc-complete)


(1 file)

Attached file Test case
In the attached test case, two elements have a CSS animation that animates the margin-left from '0em' to '10em'. After the first iteration, the font-size is updated.

For the green box, the font-size on the element itself is updated.
For the red box, the font-size on the parent element is updated.

Expected results:
After the first iteration both animations start animating "further" to the right, due to the increased font-size.

Actual results:
Only the green box (the element whose specified style was updated, as opposed to its parent's) updates its animation. However, some actions such as opening DevTools inspector can cause the red box to suddenly update.

This is a subset of the work needed to bring our CSS animations implementation into line with the behavior resolved by the CSS WG regarding liveness[1] but which has yet to be edited into the spec[2].

Bug 1245748 should make us start storing the specified values so that we can re-resolve them into (computed) StyleAnimationValues when we detect a situation where the meaning of context-sensitive values might have changed.

[1] item 1a
Depends on: 1338944
Note that in stylo this bug will be fixed by bug 1350754.
See Also: → 1350754
Marking as part of documentation plan for intentional stylo differences
Keywords: dev-doc-needed
Closing this works as expected on our new style system (i.e. stylo), and we already dropped the old style system.
Closed: 5 years ago
Resolution: --- → WONTFIX
You need to log in before you can comment on or make changes to this bug.