Guide doesn't explain variants very well

[myrrhlin@…]

There are some obvious questions about variants which are not answered in the guide (and also not in the FAQ). I only began to figure out the answers by trying things and finding out what worked and what didn't. The guide should be expanded to answer these questions.

• Can multiple variant options be selected at install time? (yes)
• Do variant options sometimes conflict, and how would I know? (??)
• Can two variants be installed at the same time? (yes, but only one can be active at a given time. use port deactivate on the first variant, then install the second)
• Can an existing variant be modified to add or remove variant options? (no)
• What if I need to add a new option to a variant (or remove one)? (uninstall it, then reinstall with the desired options)
• Is the 'universal' variant considered to be exclusive of all other options? That is, if there is an option that enables liba52 support, am I to assume the universal install doesn't have this support? (??)
• The documentation mentions turning off 'default' variant options with the minus sign syntax -- how do I find out which are the default ones, if any (other than reading the portfile)? (??)

I might add that the short descriptions of the variants are quite unclear to me, and insufficient. They're the sort of description which are adequate if you already know what the options mean. If you don't, it doesn't help much in making wise choices. I hope you consider support for greater documentation of these choices in the portfiles or elsewhere, more than a fraction of a line. The wiki would also be a great place for further documentation of this kind, if it was expanded to include pages for every port with variants. Please make it easier somehow for the documentation of variants to be expanded.

Here's an example. Whats the difference between darwin7, darwin8, macosx options as opposed to universal? I know 10.4 is darwin 8 (you should explain that too), but just when do I need to specify that? Anytime I see it given as a variant? Are darwin7 and darwin8 exclusive? Are darwin8 and macosx exclusive? How would I know?

Another example. I see that ffmpeg includes native support for vorbis and xvid, but there are variant options to use external libraries instead. What are the advantages to each choice? Which provides greater speed/flexibility/etc?

[raimue@…]

I opened #15628 as a spinoff of this issue. Some of these things here should be displayed by port variants.