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Re: Additive vs absolute flexes

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 18 May 2010 10:12:10 -0700
Message-ID: <AANLkTinsS9LSj2CRgdkUsY9ZYm_1NRLlCTMqXPSu6RYt@mail.gmail.com>
To: robert@ocallahan.org
Cc: www-style <www-style@w3.org>, sylvain.spinelli@kelis.fr
On Tue, May 18, 2010 at 2:25 AM, Robert O'Callahan <robert@ocallahan.org> wrote:
> Sylvain Spinellli, a XUL developer, gave me some feedback on use-cases for
> additive flexes, and asked me to summarize for the list.
>
> Some example markup:
>    <slotSet height="650" orient="vertical" flex="5">
>            <slotContents id="contentsSlot" height="400" flex="5"/>
>            <slot id="bottomSlot" height="250" flex="1">
>                <simpleSearchView/>
>            </slot>
>    </slotSet>
> Goals:
> -- For very large windows, 'contentsSlot' should get approximately 5 times
> more vertical space than 'bottomSlot'
> -- But 'bottomSlot' has some controls and needs a reasonable amount of space
> to be readily usable. So when the window height is 650px, 'bottomSlot'
> should get 250px and the 'contentsSlot' should get 400px.
> -- However, if the window height gets very small then at least some of both
> 'bottomSlot' and 'contentsSlot' should be visible (so a nonzero min-height
> is not appropriate here).
>
> The attached images show the desired rendering for small windows and large
> windows.
>
> Further comments:
>>
>> There is something I don't understand. In xul, if you don't set an
>> explicit width, the intrinsic content width is used instead. Setting a width
>> is only an override of the " intrinsic content width". In the W3C
>> simplification idea "just size each child proportionally to its flex value",
>> intrinsic content width will not be take in account at all ? In this case I
>> think we can find many other problematic use cases :
>>
>> in classic dialog box, set flex=1 on 3 buttons in a hbox become unusable
>> (long labels will be cut prematurely),
>> in a tree or listbox columns width will not be auto-adapted correctly (If
>> I remember well, it was one of the big limit I found in extJs ui...),
>> etc.
>
> I followed up to clarify these comments, especially the first one. This
> use-case is a horizontal box containing three labeled buttons with different
> length labels. When the box is as wide as the sum of the lengths of the
> labels, he wants each button to be the width of its label. When it gets
> wider than the ideal width, I think he wants each button to get an equal
> share of the extra space. When it gets narrower than the ideal width, he
> wants each button to lose an equal amount of space. He does not want one or
> more buttons disappearing beyond the edge of the box.
>
> Thanks Sylvain!

Thanks Sylvain, and thanks Rob!  This is good.

So I just realized that my algorithm doesn't actually treat
calc(px+fl) as an additive flex; it instead translates it into a
min/max expression.  I'll have to revise it somewhat to make this work
correctly.

As well, this brings up an interesting possibility for what 'auto'
width/height should compute to.  Right now it computes to "1fl" as
long as the box isn't otherwise flexing in that axis.  Perhaps we
should have it compute to "calc(fit-content + 1fl)" instead? (That is,
have it act like the additive flex defined in the current module.)

/me goes to think on margin-collapsing some more.

~TJ
Received on Tuesday, 18 May 2010 17:13:02 GMT

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