Don't do a negative time step in recreational mode when beyond NDL

In recreational mode, we keep adding time at the last depth
until an ascent does violate the ceiling. Then we roll back
the last added time step and record the ascent. The test for
the ceiling violated was before adding the time so if it alreay
failed the first time we tried to unroll a time step that was
never added which resulted in a small kink in the pressure graph.

This patch corrects this logic by changin a while to a do {} while.

Furthermore, it removes the computation of deco state during the
final ascent since that is not used anywhere later.

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 12 insertions, 9 deletions

diff --git a/planner.c b/planner.c
index 05fd26e31..22d37165a 100644
--- a/planner.c
+++ b/planner.c
@@ -1070,15 +1070,21 @@ bool plan(struct diveplan *diveplan, char **cached_datap, bool is_planner, bool
 		bool safety_stop = prefs.safetystop && max_depth >= 10000;
 		track_ascent_gas(depth, &displayed_dive.cylinder[current_cylinder], avg_depth, bottom_time, safety_stop);
 		// How long can we stay at the current depth and still directly ascent to the surface?
-		while (trial_ascent(depth, 0, avg_depth, bottom_time, &displayed_dive.cylinder[current_cylinder].gasmix,
-				  po2, diveplan->surface_pressure / 1000.0) &&
-		       enough_gas(current_cylinder)) {
+		do {
 			add_segment(depth_to_bar(depth, &displayed_dive),
-						       &displayed_dive.cylinder[current_cylinder].gasmix,
-						       DECOTIMESTEP, po2, &displayed_dive, prefs.bottomsac);
+				    &displayed_dive.cylinder[current_cylinder].gasmix,
+				    DECOTIMESTEP, po2, &displayed_dive, prefs.bottomsac);
 			update_cylinder_pressure(&displayed_dive, depth, depth, DECOTIMESTEP, prefs.bottomsac, &displayed_dive.cylinder[current_cylinder], false);
 			clock += DECOTIMESTEP;
-		}
+		} while (trial_ascent(depth, 0, avg_depth, bottom_time, &displayed_dive.cylinder[current_cylinder].gasmix,
+				      po2, diveplan->surface_pressure / 1000.0) &&
+			 enough_gas(current_cylinder));
+
+		// We did stay one DECOTIMESTEP too many.
+		// In the best of all worlds, we would roll back also the last add_segment in terms of caching deco state, but
+		// let's ignore that since for the eventual ascent in recreational mode, nobody looks at the ceiling anymore,
+		// so we don't really have to compute the deco state.
+		update_cylinder_pressure(&displayed_dive, depth, depth, -DECOTIMESTEP, prefs.bottomsac, &displayed_dive.cylinder[current_cylinder], false);
 		clock -= DECOTIMESTEP;
 		plan_add_segment(diveplan, clock - previous_point_time, depth, gas, po2, true);
 		previous_point_time = clock;
@@ -1093,9 +1099,6 @@ bool plan(struct diveplan *diveplan, char **cached_datap, bool is_planner, bool
 			if (depth - deltad < 0)
 				deltad = depth;
 
-			add_segment(depth_to_bar(depth, &displayed_dive),
-				    &displayed_dive.cylinder[current_cylinder].gasmix,
-				    TIMESTEP, po2, &displayed_dive, prefs.decosac);
 			clock += TIMESTEP;
 			depth -= deltad;
 			if (depth <= 5000 && depth >= (5000 - deltad) && safety_stop) {