W3C home > Mailing lists > Public > www-style@w3.org > February 2009

Re: Comments on CSS Transitions

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 27 Feb 2009 12:24:43 -0600
Message-ID: <dd0fbad0902271024g34aaf32cg7df7e0572753e343@mail.gmail.com>
To: Giovanni Campagna <scampa.giovanni@gmail.com>
Cc: www-style@w3.org, www-svg@w3.org
On Fri, Feb 27, 2009 at 12:05 PM, Giovanni Campagna
<scampa.giovanni@gmail.com> wrote:
> If the specified value is "inherit", or is a percentage (in some
> properties like line-height) / relative unit (em, rem, ex, ch...), or
> the computed depends on other properties (like the computed value for
> top in relative positioned elements), then the latter may change with
> the same specified value. This should trigger transitions.
> That is, answering also to David Hyatt, if I say :root { width: 100% }
> I should not have a transition on width when the window is resized,
> but if I say :root { width: 100vw; } I should have.

See, I'm not liking that either.  I want transitions to fire *only*
when an actual rule change occurs.  Any incidental changes, such as
from the user resizing the window, are completely out of my control.
The user probably doesn't want such changes to animate, either - when
I resize a window, I expect everything to resize in sync.

In my mental model of transitions, animations only get triggered when
the specified value changes, but *operate on* the used values.  This
means that transitioning from a percentage to a px value is completely
possible.  Is there anything fundamentally wrong with this?  I think
it's how us authors are generally going to think of it - it's
difficult to consider the inability to animate from 50% to 100px as
being anything other than a bug.

Received on Friday, 27 February 2009 18:25:22 UTC

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