Fix dive trip merging logic

We used to have very spotty logic for picking the dive trip when
merging two dives. It turns out that that spotty logic almost never
really matters, because in practice you'll never hit the situation of
merging two dives with different dive trips, but it *can* happen.

In particular, it happens when you use multiple dive computers, and
end up loading the dives from one computer on top of the dives of your
other computer. If the clocks of the dive computers was set
sufficiently close to each other, the dive merging logic will kick in
and you may now have slightly different times for the dives that get
merged, and the trip merging logic got *really* confused.

The trip management also depends on the trip dates being updated
correctly when the dives associated with a trip are updated (whether
added or removed), and the trip merging code did none of that.

This fixes it all up. Hopefully correctly.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Process ceiling events and store ceiling data in plot_info

This just creates the infrastructure but doesn't yet do anything useful
with the data.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add plotting of the deco ceiling

Plot a red-shaded area on top of the depth profile to indicate the deco
ceiling (i.e., the area into which it isn't save to ascend at this point
of the dive.

So far this is of very limited use as libdivecomputer doesn't give us the
necessary information to plot this. I have sent patches for the OSTC to
Jef, hoping that he will include them in an update. I don't know how many
other dive computers will make this data available - I still need to add
this to our native Uemis support.

This commit also fixes two cut and paste errors in the previous commit
6540be9bd924 "Process ceiling events and store ceiling data in plot_info".

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Ignore last dive read from Uemis when starting with empty divelist

When the user closes the divelist and starts with an empty file it makes
no sense to assume that she only wants to download new dives since the
last time dives have been downloaded. So if the current divelist is empty
we ignore that information and start from the beginning again.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Instead of the ugly red boxes make the surface come down to ceiling

Based on suggestions from Linus (and a few iterations) we now simply have
the surface (i.e., background color / pattern) come down to where the
ceiling is. And we only do the angry red shading when the diver violates
the ceiling.

I think this looks much better.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Create the correct ceiling events for Uemis Zurich

The hold_depth field is rather misleading as it normally gives the safety
stop depth and only when the p_amb_tol goes "below the surface" does it
switch to showing the first deco stop depth.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Use correct surface pressure to detect ceiling with Uemis Zurich

The dive data contains the surface pressure prior to the dive, and that is
what we need to compare p_amb_tol to, not the standard 1013mbar.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix cut and paste error in an error message

This has been around for a loooong time, I just happened to stamble across
it when reading the code...

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Convert Uemis deco stop hold time to seconds

This is actually stored in minutes (which seems odd, given they allocate
16 bits for it... how much deco do these people want to be prepared for??)

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Improve logic handling events

We now throw away redundant events, just as we throw away other redundant
data coming from the dive computer. Events are considered redundant if
they are less than 61 seconds apart and identical.

This also improves the display of the remaining events in the profile as
we now show the value of the event, if it is present (for example for a
deco event we show the duration of the deepest stop).

Finally, for events that define a range (so they set the beginning flag
and assume and end flag some time later) we no loger show the triangle but
assume that some other code handles visualizing them (as happens for the
ceiling events).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Merge branch 'ceiling-plot'

This enables plotting the ceiling in deco dives and also adds the
necessary code to the uemis importer. The only other dive computer this
has been tested with the OSTC and that needs a libdivecomputer patch in
order to provide the deco/ceiling information to Subsurface.

Fixes #5
Try to find optimal dive sample merge offset

When we merge dives where the samples have come from different dive
computers, the samples may be offset from each other due to the dive
computers not having decided that the dive starts at quite the same
time.

For example, some dive computers may take a while to wake up when
submerged, or there may be differences in exactly when the dive
computer decides that a dive has started. Different computers tend to
have different depths that they consider the start of a real dive.

So when we merge two dives, look for differences in the sample data,
and search for the sample time offset that minimizes the differences
(logic: minimize the sum-of-square of the depth differences over a
two-minute window at the start of the dive).

This still doesn't really result in perfect merges, since different
computers will give slightly different values anyway, but it improves
the dive merging noticeably. To the point that this seems to have
found a bug in our Uemis data import (it looks like the Uemis importer
does an incorrect saltwater pressure conversion, and the data is
actually in centimeter, not in pressure).

So there is room for improvement, but this is at least a reasonable
approximation and starting point.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
gtk spinbuttons are crazy - fix possible divide-by-zero

When we fill the cylinder information in an imperial unit world, a
working pressure of zero is a special case, and forces us to use the
actual physical size of the cylinder in liter, despite the fact that
we normally would use cuft.

However, we compare that value against zero in a 'double', and in
between going through the gtk spinbutton logic, the zero we have
filled in then gets read out as some very tiny epsilon value from the
gtk spinbuttons (typically in the 10**-317 range). This causes us to
think that the zero isn't actually a zero, because gtk has done odd
things with it.

Fix this by calculating the millibar value (as an integer) first, and
check that *integer* against zero. Any crazy epsilon values will have
been rounded away, and our logic works again.

There's a good reason why subsurface does everything using integers
(ie the afore-mentioned "convert to integer millibar" etc) and doesn't
use floating point for any core data structures, only for conversion.
FP rounding and inexact behavior can be really subtle.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix default filename handling errors

The default filename handling is broken in two different ways:

 (a) if we start subsurface with a non-existing file, we warn about
the inability to read that file, and then we exit without setting the
default filename.

This is broken because it means that if the user (perhaps by mistake,
by pressing ^S) now saves the file, he will overwrite the default
filename, even though that was *not* the file we read, and *not* the
file that subsurface was started with.

So just set the default filename even for a failed file open.

The exact same logic is true of a failed parse of an XML file that we
successfully opened. We do *not* want to leave the old default
filename in place just because the XML parsing failed, and possibly
then overwriting some file that was never involved with that failure
in the first place. So just get rid of all the logic to push the
filename saving into the XML parsing layer, it has zero relevance at
that point.

 (b) if we do replace the default filename with a NULL file, we need
to set that even if we cannot do a strdup() on the NULL.

This fixes both errors.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add threshold feature for partial pressure graphs

The tec diving preference pane now allows us to set a partial pressure
threshold for each of the three gases. When the partial pressure surpasses
that value, the graph becomes red.

Fixes #12

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add support for obtaining salinity from libdivecomputer

This requires a patched libdivecomputer that can return salinity of the
water the dive was conducted in. Experimental patches exist that implement
this for the OSTC. The code is designed so that it simply defaults to salt
water if libdivecomputer doesn't include the feature.

The patch also fixes the dive merge code to merge two other recent
additions to the dive structure (surface_pressure and visibility).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Simplify and clean up dive trip management

This adds a couple of helper functions to manage dive trips
("add_dive_to_trip()" and "remove_dive_from_trip()") and makes those
functions do the trip statistics maintenance (trip beginning times,
number of dives, etc).

This was needed because the dive merge cases for multiple dive
computers showed some rather nasty special cases: especially if the
new dive information has been loaded into an XML file with trips
auto-generated, merging several of these kinds of xml files with
multiple dives in several overlapping trips would completely confuse
our previous code.

In particular, auto-generated trips that had the exact same date as
previous trips (because they were generated from the same dive
computer) really confused the code that used the trip timestamp to
manage the trips.

Adding the helper functions allows us to get the general case right
without having to have each piece of code that handles trip
information having to bother about all the odd rules. It will
eventually also allow us to make the dive trip data structures more
logical: right now the dive trip list is largely designed around the
odd gtk model handling, rather than some more higher-level conceptual
relationship with the actual dives.

But for now, this keeps all the data structures unchanged, and just
modifies them using the new helper functions.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Don't simplify 'bookmark' and 'heading' events

Add the bookmark and heading events to the list of events not to be
simplified just because they are redundant - in both cases they are
about the user doing something explicit (like the gaschange), so even
if the data is otherwise identical, they should likely be saved.

That said, both events are kind of pointless (we don't actually seem
to save the heading value for the heading events, and bookmarks are
universally just due to user error in at least my case). But still..

This overly aggressive filtering was introduced in commit 6ad73a8f043b
("Improve logic handling events").

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add depth to mbar helper function

This ensures that we use consistent math to get the absolute pressure at a
certain depth.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Merge branch 'pressure'

Make depth to absolute pressure conversions consistent.