Hmmm. I have an idea. In my situation, I just need to stop the width
from going below zero.
In C I'd do something like this...
width = (parentwidth-20} * (parentwidth-20 > 0);
Is there some mathematical trickery I can use to convert true/false to
1/0 in a constraint?
The best I can come up with is the ternary operator...
width="${(parent.width-20) * (parent.width-20 > 0)?1:0}"
Quoting P T Withington <[EMAIL PROTECTED]>:
> If I wanted to be a pedant (ok, I do) I would tell you that
> [functions](http://en.wikipedia.org/wiki/
> Functional_programming#Pure_functions) are just fine in constraints,
> it is 'procedures' that are not.
>
> On 2006-09-25, at 16:21 EDT, John Sundman wrote:
>
>> Please consult the Developer's Guide on the hazards of using
>> functions within constraints.
>>
>> http://labs.openlaszlo.org/trunk-nightly/docs/guide/
>> constraints.html#d0e13355
>>
>> It can sometimes be done, but there be dangers there, and you do so
>> at your own risk.
>>
>> jrs
>>
>> On Sep 23, 2006, at 2:48 PM, Benjamin Shine wrote:
>>
>>>
>>> Constraints can hold complex javascript. To cap constraints to a
>>> range (100-500 in this example), I use something like
>>> width="{max(100, min(500, sizeslider.value))}"
>>>
>>> A nest of trinary ? expressions would probably be faster by avoiding
>>> two function calls. With whitespace added for clarity:
>>> width="${ sizeslider.value < 100
>>> ? 100
>>> : ( sizeslider.value > 500 ?
>>> 500
>>> : sizeslider.value)) }"
>>>
>>> It is sometimes clearer to express this as a handler for
>>> sizeslider.onvalue, something like this:
>>> <handler reference="sizeslider" event="onvalue"
>>> method="setClampedSize" />
>>> <method name="setClampedSize" args="x">
>>> var xclamp = min(100, max(500, x));
>>> mybox.setAttribute("width", xclamp);
>>> </method>
>>>
>>> The compiler probably turns the first and third forms above into the
>>> same thing; if the compiler has an optimization for min and max (but
>>> I don't think it does) then all three forms would be equivalent.
>>>
>>> -ben
>>>
>>> On Sep 22, 2006, at 10:25 PM, [EMAIL PROTECTED] wrote:
>>>
>>>> In my example below, I create a view with a smaller nested view.
>>>> The
>>>> inner view gets its size from constraints based on the its parent.
>>>> The problem is, when the parent is resized too small, the
>>>> constraints
>>>> on the inner view become negative. If you run my app, you can
>>>> adjust
>>>> the size with the slider and see what happens. Basically, I need
>>>> some
>>>> way to have a constraint that tracks the parent, but cannot become
>>>> negative. Is there some way to do this in a contstraint? Or
>>>> possibly
>>>> a different solution that doesn't have the negative constraint
>>>> problem?
>>>>
>>>>
>>>> <canvas>
>>>>
>>>> <view x="20" y="20" layout="axis:y">
>>>> <view layout="axis:x">
>>>> <text text="outer view size: "/>
>>>> <slider id="sizeslider" width="100" showvalue="true"
>>>> value="50"/>
>>>> </view>
>>>> <view layout="axis:x">
>>>> <text text="inner view size: "/>
>>>> <text text="${box.subviews[0].height}" bgcolor="silver"/>
>>>> </view>
>>>> </view>
>>>>
>>>> <view id="box" x="20" y="80" bgcolor="blue"
>>>> width="${sizeslider.value}" height="${sizeslider.value}">
>>>> <view bgcolor="green" x="10" y="10"
>>>> width="${parent.width - 20}" height="${parent.height -
>>>> 20}"/>
>>>> </view>
>>>>
>>>>
>>>> </canvas>
>>>>
>>>>
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