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Re: [css3-images] Reintroduce object-fit: none

From: Simon Fraser <smfr@me.com>
Date: Wed, 26 Jan 2011 19:59:38 -0800
Cc: "L. David Baron" <dbaron@dbaron.org>, Leif Arne Storset <lstorset@opera.com>, www-style@w3.org, Philip Jägenstedt <philipj@opera.com>, "Simon Pieters (zcorpan)" <simonp@opera.com>
Message-id: <384A43F3-D356-4427-8B26-D40974F8C527@me.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
On Jan 26, 2011, at 5:15 PM, Tab Atkins Jr. wrote:

> On Wed, Jan 26, 2011 at 4:50 PM, L. David Baron <dbaron@dbaron.org> wrote:
>> On Wednesday 2011-01-26 11:50 +0100, Leif Arne Storset wrote:
>>> I was asked recently whether and why 'object-fit: none' was removed
>>> from the spec. Digging in the archives, it seems the proposal to
>>> keep/revive it was forgotten amid other issues. So this is a request
>>> to re-introduce 'none' as a value for 'object-fit'. The definition
>>> would be "Render the content at its intrinsic dimensions,
>>> overflowing if necessary."
>>> 
>>> The use case is easy centering or positioning images without scaling
>>> them. Centering images vertically in a box can be a PITA today,
>>> especially if you don't know the dimensions. With image-fit:none, it
>>> is super-easy. Have a look at the attached demo (only supported in
>>> Opera 11, AFAIK).
>>> 
>>> (To avoid any confusion: There were objections to our proposal of
>>> another value, 'object-fit: auto', because the proposal was that
>>> behavior depend on content type. These issues do not affect the
>>> current proposal of 'object-fit: none', since no content-type
>>> negotation takes place for 'object-fit: none'.)
>> 
>> I think this is a bad idea.  (I think the 'object-fit: scale-down'
>> proposal later in the thread, however, is fine.)
>> 
>> 
>> The main things I don't like about it derive from the fact that it
>> causes replaced elements to overflow.  I now see that
>> object-fit:cover also does this, though I don't remember it doing
>> that the last time I read the proposal.  I'd really like to avoid
>> getting into a situation where overflow applies to replaced
>> elements; I'd prefer that they just never overflow their content
>> box.
>> 
>> (It's also quite inconsistent with what we ended up doing
>> about the interaction of border-radius and replaced elements, since
>> the border-radius is supposed to clip replaced elements.  What
>> happens with img { object-fit: cover; border-radius: 10px } ?)
>> 
>> I think making it easy to overflow is generally a bad thing:  layout
>> systems should make it easy for authors to do what they want in ways
>> that don't accidentally cause horrible layouts in a slightly
>> different situation (e.g., slightly different viewport size, font
>> size, etc.).  Having an object-fitting mode that overflows by
>> default fails this test (whereas 'scale-down' passes it).  This is
>> why I'd prefer that replaced elements not overflow their content
>> box.
> 
> So, you support removing 'cover' and 'none' entirely?  'cover' is
> indeed designed to overflow *by default*.
> 
> Another option is to simply disallow the overflow effect at all - that
> is, *always* hide overflow on replaced elements, and ignore the
> 'overflow' property.  That would solve your concern while still
> allowing whatever use-cases 'cover' allows.  (I'm not sure why 'cover'
> is useful, personally.)

I agree with David; the content of replaced elements should never overflow
their box, nor should the UA ever show scrollbars because of object-fit.

I still think 'cover' is useful, and that it's fine to always treat overflow
as hidden.

Simon
Received on Thursday, 27 January 2011 04:00:40 GMT

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