variants vs separate ports

[Ryan Schmidt]

On May 24, 2010, at 12:38, Daniel J. Luke wrote:

> On May 24, 2010, at 1:30 PM, Ryan Schmidt wrote:
>> GraphicsMagick uses:
>> 
>> if {![variant_isset q16] && ![variant_isset q32]} {
>>   default_variants +q8
>> }
>> 
>> This ensures that if the user does not specify +q8, +q16 or +q32, it selects +q8. 
>> 
>> The one thing this does not handle is if the user specifically tries to install "GraphicsMagick -q8"; in this case no variant will be selected. I've never been entirely comfortable with that. Perhaps we should indeed be using variant_set instead:
>> 
>> if {![variant_isset q16] && ![variant_isset q32]} {
>>   variant_set q8
>> }
>> 
>> I'm not certain why we haven't been doing that.
> 
> I still don't understand why you set up some of your ports this way instead of the more straightforward method (have the +q8 configure args in the default configure args, and have the variants just remove the +q8 stuff and add their appropriate args).
> 
> To me, Portfiles are always clearer if they can avoid using variant_isset.

Because we are talking about a choice between three mutually-exclusive options, three settings: q8, q16, and q32. In a GUI, these would be represented as radio buttons. It makes no sense to me that two of these options should be implemented as variants and one of them would not be.