Few bugs and a feature req from testing Subsurface

[Linus Torvalds]

On Sat, Mar 15, 2014 at 12:26 PM, Dirk Hohndel <dirk at hohndel.org> wrote:
>
> So here's what I'm proposing to fix the current implementation
>
> a) if no default cylinder is set, don't just use AL80. Disable the
> default cylinder logic
>
> b) if a default cylinder is set, ONLY use it for the first cylinder of a
> DC
>
> Linus, will this address your issues?

Yes, that works for me, and I think is more sensible. The whole
"default cylinder" concept doesn't really make sense if you carry
multiple cylinders, since even if you do have defaults, they would
likely not be a single default cylinder (ie a recreational diver might
have a tiny 3cuft spare-air thing (0.4l cylinder), and a tech diver
might have a default 40cuft (5.8l) deco bottle).

So I don't think it ever makes sense to fill in the default for all
cylinders, unless you make that default cylinder config option be a
_list_ of cylinders to be used by default.

>> Anyway, what we probably *should* do (after the two bugs above get
>> sorted out) is likely to say that when you delete a cylinder, you
>> delete all gas change events associated with it too. That would give
>> us a way to fix up the above issue by the user just saying "I really
>> only had the first cylinder, so delete that bogus second cylinder",
>> and everything would work out right. But right now, deleting that
>> second cylinder has bigger problems than "the gas change event
>> remains".
>
> I like this. When I understood what caused the odd situation Miika was
> seeing I was wondering what to do about it after the fact. This seems
> like a clean solution.

Well, there are issues with that model too, and there are more complex
cases that we simply don't handle well at all.

For example, a user might decide to "edit" a cylinder by deleting it
and creating a new one. That sounds like a bad idea ("don't do that
then"), but it's actually valid in some cases, notably if you want to
change the order of cylinders, so it's not *entirely* crazy. How would
we re-associate gases with dive computers and with pressure readings?

And with bad gasmix information (which isn't that uncommon, with
Miika's case as an example) _and_ multiple actual real cylinders, more
complex cases can happen.

I've fixed a few cases in my history by just editing things by hand.
And it's probably special enough that in the end that may be what we
have to have as a fallback. So the "delete cylinder" approach may work
for the really simple cases, but they are hopefully the only ones that
are common enough to worry about.

                  Linus