fundamental design issues with trips and dives

[Dirk Hohndel]

> On Nov 7, 2019, at 2:02 PM, Linus Torvalds <torvalds at linux-foundation.org> wrote:
> 
> On Thu, Nov 7, 2019 at 12:14 PM Berthold Stoeger
> <bstoeger at mail.tuwien.ac.at> wrote:
>> 
>> It doesn't have to. Just like you defined a proxy model on top of the
>> DiveListModel, one could implement a proxy model on top of the tree model that
>> "linearizes" it.
> 
> Maybe we should do that in general, even for the desktop case.
> 
> I don't think there is any major reason why the model should contain
> all the dives. In many ways it would be much better if the model only
> contains the *visible* dives, and we'd have a totally flat model,
> where a trip (whether it's a collapsed header only, or the header for
> a list of dives that has been exposed) is just a special model entry.
> 
> That would mean that we'd handle collapsing and exposing trips by just
> removing/inserting the dives in the trip into that flat model.
> 
> IOW, get rid of the tree model entirely, and make that "proxy" model
> be "the" model.
> 
> Yes, yes, we have this very clever code to keep dives selected even
> when they're not visible. It's a pain. it's probably not worth it.
> 
> And it might be truly *lovely* for startup if we didn't populate the
> whole model at all. For the git format, we could literally avoid even
> parsing the dives that are in a collapsed trip and this not visible.

So we'd have a dive_table that isn't populated? That sounds entertaining.
And some magic code that figures out when we need a dive and then
quickly parses the information from git? But if loading XML we don't?
And statistics functions would trigger fully populating the dive_table?

Maybe it's the jet lag, but that sounds like a LOT of work and a lot of
new corner cases - and I'm not 100% sure what we'd gain.

I have only 640 dives in my dive list, so maybe that's not a good
benchmark, but even in a very low end VM with a single core and
not a lot of memory (2GB) I have never had issues with the Subsurface
startup speed on the desktop. Our mobile startup speed is terrible,
but that has other reasons.

/D