Gases in divelist

[Dirk Hohndel]

"Robert C. Helling" <helling at atdotde.de> writes:

> Hi,
>
> I received a "bug report" on the list of gases in the dive list (which is determined in the function nitrox_data_func()). It turned out, there is no bug, the list is as intended (as in the comments in the source): If there is any helium, report only gas with largest amount of helium, otherwise report only O2 percentages either as a range or as one value (and the column-heading "O2%" does not exactly reflect that). In addition, the 'strongest' trimix in my friends' dive was not used at all during the dive but still that was the only gas reported.
>
> This is based on code that was written by Linus in September 2011. Maybe this is the time to rethink if this logic still applies. I guess it was dictated by concerns about the column width. What do people think, shouldn't we 
>
> a) a report a more complete gas list there
> b) maybe exclude gases that have not been used (e.g. starting pressure == end pressure)?

I find this a rather difficult problem to get right.

Not all dive computers report the gas(es) used. Even fewer report
starting and and pressure.

So if we get exactly one gas from the computer, no gas is added manually
and there are no gas change events, either, this is all straight forward
and works correctly today.

If we get more than one gas from the computer or the user added a tank
then things start getting complicated. What do we do with the second (or
third...) gas if there is no gas change event? Forget using starting and
end pressure - those you only have with air integrated computers and
even with those usually just for the first tank (I'll finally do my
first multi tank diving with multiple transmitters connected to the same
computer next week). We definitely don't want to delete tanks that
aren't "used" (especially since we are still missing a manual way to add
gas change events - on my infinite todo list). Do we want to ignore them
when calculating the gas data shown in the dive list? Maybe. But I
promise the moment we implement this we get bug reports "I added my
Trimix tank and it doesn't show up in the dive list...".

And of course there are the computers like the OSTC that always give you
all defined gases and aren't air integrated. What do do for that? Show
all? Show only those that have a gas change event?

As I said - complicated.

/D