Deal with setpoints in samples when switching a dive from CCR to OC

For some dive computers (at least the Shearwater Predator, I haven't
checked if there are others), libdivecomputer used to return setpoint
values in each sample even if the dive computer was in OC mode. Those
setpoint values are redundant and confuse our algorithm that tries to
detect if a dive is OC or CCR. So when manually switching from CCR to
OC we make sure that there are no setpoint values in the samples.

This is a destructive change - if the user switches to OC by mistake and
accepts that change, even when switching back to CCR the setpoint changes
during the dive are lost.

I rewrote the code dealing with the events as it was rather confused.
Looping over the events that way didn't make any sense since
get_next_event() is guaranteed to give you the first (if any) event of the
requested name.

See #826

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 21 insertions, 13 deletions

diff --git a/dive.c b/dive.c
index 7b3ab21ef..c120dde0e 100644
--- a/dive.c
+++ b/dive.c
@@ -872,25 +872,33 @@ int explicit_first_cylinder(struct dive *dive, struct divecomputer *dc)
 		return 0;
 }
 
+/* this gets called when the dive mode has changed (so OC vs. CC)
+ * there are two places we might have setpoints... events or in the samples
+ */
 void update_setpoint_events(struct divecomputer *dc)
 {
-	struct event *ev = get_next_event(dc->events, "SP change");
-	bool changed = false;
+	struct event *ev;
 	int new_setpoint = 0;
 
 	if (dc->divemode == CCR)
-	    new_setpoint = prefs.defaultsetpoint;
-
-	while (ev) {
-		if (ev->time.seconds == 0) {
-			ev->value = new_setpoint;
-			changed = true;
-		}
-		ev = get_next_event(ev->next, "SP change");
-	}
-	if (!changed) {
+		new_setpoint = prefs.defaultsetpoint;
+
+	if (dc->divemode == OC)
+		// make sure there's no setpoint in the samples
+		// this is an irreversible change - so switching a dive to OC
+		// by mistake when it's actually CCR is _bad_
+		for (int i = 0; i < dc->samples; i++)
+			dc->sample[i].setpoint.mbar = 0;
+
+	// an "SP change" event at t=0 is currently our marker for OC vs CCR
+	// this will need to change to a saner setup, but for now we can just
+	// check if such an event is there and adjust it, or add that event
+	ev = get_next_event(dc->events, "SP change");
+	if (ev && ev->time.seconds == 0) {
+		ev->value = new_setpoint;
+	} else {
 		if (!add_event(dc, 0, SAMPLE_EVENT_PO2, 0, new_setpoint, "SP change"))
-			printf("Could not add setpoint change event\n");
+			fprintf(stderr, "Could not add setpoint change event\n");
 	}
 }