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Re: [css-transitions] interpolating animation of the 'order' property

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Sun, 27 Mar 2016 15:50:43 -0700
Message-ID: <CAAWBYDBNaDh9F9r=es7VZo_4TK6Vjm4YaPLtW6UqLJYFp=5s_g@mail.gmail.com>
To: Jared Wein <jaws@mozilla.com>
Cc: www-style <www-style@w3.org>
On Fri, Mar 25, 2016 at 11:35 AM, Jared Wein <jaws@mozilla.com> wrote:
> The flex spec introduced the 'order' property as an animatable property.
> This is supported and implemented in Gecko, but the implementation doesn't
> interpolate the position of the element that is moving.
>
> In the CSS Grid implementation, elements moved via a transition on the
> 'order' property jump from grid-area to grid-area. It would be ideal if we
> could "slide" the elements instead of jumping them.
>
> See https://bugzilla.mozilla.org/attachment.cgi?id=8734793 for a reduced
> testcase.
>
> What are some complicated cases that make this a fundamentally hard problem?

The fundamentally hard part is right in the basic case - the order
property has a specific meaning, and no part of that can be
interpreted as "position these elements so they partially overlap", or
are otherwise flying between the positions they'd occupy at integer
values.

I spent some time 2 or 3 years ago trying to work out "layout
transitions" to handle this, along with my peers at Chrome, and it's a
super-hard problem to make work correctly and efficiently.

~TJ
Received on Sunday, 27 March 2016 22:51:31 UTC

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