Mats Palmgren (inactive) Reporter
	Description • 7 years ago

https://drafts.csswg.org/css-grid/#track-sizing
"
Animatable: 	as a simple list of length, percentage, or calc, provided the only differences are the values of the length, percentage, or calc components in the list 
"

It's worth noting in this context that these properties are kind of
special in that the computed values are the resolved values:
https://drafts.csswg.org/css-grid/#resolved-track-list

	Mats Palmgren (inactive) Reporter
	Comment 1 • 7 years ago

Here's some advice from Brian Birtles (:birtles) (bug 1348500 comment 5):

For the second question about how to implement animation of new types, it basically just involves adding the necessary handling to StyleAnimationValue. I think you might find the implementation of animation of the background-position and background-size properties a helpful reference: https://hg.mozilla.org/mozilla-central/rev/eb947f317c42ec7168e44ace57714af65472cfe6

The trouble with the last point is that we're currently working on replacing StyleAnimationValue as part of the stylo project. As a result, any code you add to StyleAnimationValue will also need to be added to Servo's interpolation functions.

	Mats Palmgren (inactive) Reporter
	Comment 2 • 6 years ago

Still kind of blocked on moving animation to Stylo (bug 1288269).
(b/c it seems like a waste of time to implement it in the old style system
only to have to port/re-implement it in stylo later)

	Emilio Cobos Álvarez (:emilio)
	Comment 3 • 6 years ago

(In reply to Mats Palmgren (:mats) from comment #2)
> Still kind of blocked on moving animation to Stylo (bug 1288269).
> (b/c it seems like a waste of time to implement it in the old style system
> only to have to port/re-implement it in stylo later)

StyleAnimationValue is mostly gone, there's some tasks to clean it up completely, but there would be no need to implement anything there afaict.

	Mats Palmgren (inactive) Reporter
	Comment 4 • 6 years ago

Awesome!  I guess we should try to implement this then. :-)

	Boris Chiou [:boris] Assignee
	Comment 5 • 6 years ago

I think it's time to do this bug. Take this.

	Mats Palmgren (inactive) Reporter
	Comment 6 • 6 years ago

FYI, the "Animation type" link in the Grid spec is wrong,
it should link here:
https://www.w3.org/TR/web-animations-1/#animating-properties
which describes the "by computed value" type.

I think we should probably relax the conditions for when to
fall back to "discrete" animation for these properties.
For example, I think we should try to handle <line-names>
as "discrete" while animating track sizing functions normally,
e.g. "1px [a] 2px" -> "3px [b c] 5px" could just switch
the 2nd component from "[a]" to "[b c]" halfway through.

I also don't see a problem with handling some <track-size>
components as "discrete" and others not.  E.g.
"minmax(1px, 500px)" -> "minmax(100px, max-content)"
could animate the min track-sizing function normally while
animating "500px" -> "max-content" discretely.  IIRC, our
internal computed value always has both a min and a max value
which we can treat as "components" of the overall value.

A mismatch in list length is probably harder to do something
sane for.  Likewise for any "repeat(auto-fit/auto-fill, ...)"
values.  We should probably fall back to discrete animation
of the whole list when that happens, at least in the initial
implementation.

FTR, there's a spec issue where we can give feedback here:
https://github.com/w3c/csswg-drafts/issues/3201

	Boris Chiou [:boris] Assignee
	Comment 7 • 6 years ago

Move this into CSS Transitions and Animations Component.

	Boris Chiou [:boris] Assignee
	Comment 8 • 5 years ago

(In reply to Mats Palmgren (:mats) from comment #6)
> FTR, there's a spec issue where we can give feedback here:
> https://github.com/w3c/csswg-drafts/issues/3201

Good news, the spec issue has been resolved. :)

	Boris Chiou [:boris] Assignee
	Comment 9 • 5 years ago

Based on https://bugzilla.mozilla.org/show_bug.cgi?id=1348519#c6 and
https://github.com/w3c/csswg-drafts/issues/3201:

Currently grid-template-rows/columns interpolate “per computed value”, which
means that if the number of tracks differs, or any track changes to/from a
particular keyword value to any other value, or if a line name is added/removed
at any position, the entire track listing is interpolated as “discrete”.
But we "agree" with two more granular options:

1. Check interpolation type per track, rather than for the entire list, before
   falling back to discrete. I.e. a length-percentage track can animate between
   two values while an adjacent auto track flips discretely to min-content.
2. Allow discrete interpolation of line name changes independently of track
   sizes.

Besides, for the repeat() function, it's complicated to support interpolation
between different repeat types (i.e. auto-fill, auto-fit) and different repeat
counts, so we always fall-back to discrete if the first parameter of repeat()
is different.

	Boris Chiou [:boris] Assignee
	Comment 10 • 5 years ago

Add wpt for testing interpolation result on grid-template-{columns|rows}.

Depends on D16129

	Boris Chiou [:boris] Assignee
	Comment 13 • 5 years ago

SO we can derive Animate on more generic types.

	Pulsebot
	Comment 14 • 5 years ago

Pushed by boris.chiou@gmail.com:
https://hg.mozilla.org/integration/autoland/rev/37838b3650fd
Part 1: Support field_bound on Animate. r=emilio
https://hg.mozilla.org/integration/autoland/rev/bd4efc854419
Part 2: Implement Animate for track lists on grid-template-{columns|rows}. r=emilio
https://hg.mozilla.org/integration/autoland/rev/80dc7df104e6
Part 3: Add web platform tests for grid-template-{columns|rows}. r=mats

	Web Platform Test Sync Bot (Matrix: #interop:mozilla.org)
	Comment 16 • 5 years ago

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/14849 for changes under testing/web-platform/tests