Re: Bug 23935 - Proposal: New syntax for constraints

On 12/3/13 3:53 PM, Jim Barnett wrote:
>
> Sorry, I wasn’t clear.  I was referring to the request for new values 
> ‘max’, ‘min’ and ‘mid’, where {width: max} would mean “make it as wide 
> as you can”.  “min” would ask for the minimum possible value, and 
> ‘mid’ would mean “try for something in the middle of the range”.
>

As with anything in life, asking for the maximum without knowing what it 
is strikes me as a very bad idea. Would you ask the Hulk to hit you as 
hard as he can? Amount of Advil? Your app can already specify any number 
of absolute values or ranges of values it knows about (and hopefully has 
been tested with) Can you give me a use-case where this is not sufficient?

If expressiveness is a problem, we should address this directly, which 
is what I believe my syntax proposal does. I can say:

[ { width: 4096, height: 2160 },
{ width: 3840, height: 2160 },
   { width: 2880, height: 1800 },
   { width: { min: 1024, max: 4096 }, height: { min: 768, max: 2160 }, 
aspect: { min: 1.6, max: 1.9 } ]

In this example, I prefer certain resolutions I have tested with (even 
when higher ones are available), and only if I cannot get one of those 
exact ones will I accept a range, but no less than 1024x768. How would 
you express that today?

PS: In the above example, a clever UA could deduce that higher 
resolutions are probably preferred in the range.

PPS: Note how readable that was. I'll bet you intuitively understood 
what that meant. Try that with mandatory/optional.

.: Jan-Ivar :.

>   We haven’t introduced these yet, but there seemed to be interest in 
> them.  I think that the semantics would have to be that anything the 
> UA chose counted as correct.  Just because the property ‘foo’ defines 
> its range to be 0-1000 doesn’t mean that  the UA can actually set a 
> value of 1000 in every case (particularly if there are other 
> interacting properties), so whatever the UA gives you has to count as 
> “as good as I could do”.
>
> -Jim
>
> *From:*Jan-Ivar Bruaroey [mailto:jib@mozilla.com]
> *Sent:* Tuesday, December 03, 2013 3:47 PM
> *To:* Jim Barnett; public-media-capture@w3.org
> *Subject:* Re: Bug 23935 - Proposal: New syntax for constraints
>
> On 11/27/13 10:55 AM, Jim Barnett wrote:
>
>     I prefer the current syntax.  It is more compact and makes
>     back-off easier.  Furthermore, it makes the semantics of ‘best
>     effort’ values like min/max/mid easy to understand, at least in
>     the case of optional constraints.  Suppose we have optional
>     constraints  “prop1 max, prop2 max, prop3 max”.  This would 
>     mean:  set prop1 to the largest value you can, the set prop2 to
>     the largest value you can without changing prop1, then set prop3
>     to the largest value you can get without changing  prop1 or prop2.
>     The ordering of the constraints specifies the ordering of the
>     optimizations.
>
>
> I don't understand your use of min and max (what is mid?) - Can you 
> please use actual syntax?
>
> Are you saying that { width: { max: 2880 } } must return the highest 
> value possible, up to and including 2880? If so, that doesn't match my 
> understanding. Where in the spec do you read that?
>
> My interpretation is that there is no such guarantee, and that, given 
> no lower bound, browsers can return anything from the lowest possible 
> value and up to and including 2880.
>
> .: Jan-Ivar :.
>