color: Allow night light to be always on

Currently if the user configures the "from" and "to" times for the night
light schedule to be close together or equal, g-s-d gets confused as it
still tries to smear the transition over a full hour period.

To fix this, first make sure that the smearing period is short enough to
fit between sunrise and sunset. Also redefine equal start/end times when
calculating whether a time falls into a range as the full 24h period.

This effectively means that we will smear over the full day or night
time when the sunrise and sunset are closer than an hour to each other.
It also means that we always enable night light when the times are
equal.

Based on a patch by Matthew Leeds <matthew.leeds@endlessm.com>.

3 files changed, 42 insertions, 22 deletions

diff --git a/plugins/color/gcm-self-test.c b/plugins/color/gcm-self-test.c
index 5cdcf987..46171fc9 100644
--- a/plugins/color/gcm-self-test.c
+++ b/plugins/color/gcm-self-test.c
@@ -338,17 +338,21 @@ gcm_test_frac_day (void)
         g_assert_cmpfloat (fd, <, fd_actual + 0.01);
 
         /* test same day */
-        g_assert (gsd_night_light_frac_day_is_between (12, 6, 20));
-        g_assert (!gsd_night_light_frac_day_is_between (5, 6, 20));
-        g_assert (gsd_night_light_frac_day_is_between (12, 0, 24));
-        g_assert (gsd_night_light_frac_day_is_between (12, -1, 25));
+        g_assert_true (gsd_night_light_frac_day_is_between (12, 6, 20));
+        g_assert_false (gsd_night_light_frac_day_is_between (5, 6, 20));
+        g_assert_true (gsd_night_light_frac_day_is_between (12, 0, 24));
+        g_assert_true (gsd_night_light_frac_day_is_between (12, -1, 25));
 
         /* test rollover to next day */
-        g_assert (gsd_night_light_frac_day_is_between (23, 20, 6));
-        g_assert (!gsd_night_light_frac_day_is_between (12, 20, 6));
+        g_assert_true (gsd_night_light_frac_day_is_between (23, 20, 6));
+        g_assert_false (gsd_night_light_frac_day_is_between (12, 20, 6));
 
         /* test rollover to the previous day */
-        g_assert (gsd_night_light_frac_day_is_between (5, 16, 8));
+        g_assert_true (gsd_night_light_frac_day_is_between (5, 16, 8));
+
+        /* test equality */
+        g_assert_true (gsd_night_light_frac_day_is_between (12, 0.5, 24.5));
+        g_assert_true (gsd_night_light_frac_day_is_between (0.5, 0.5, 0.5));
 }
 
 int
diff --git a/plugins/color/gsd-night-light-common.c b/plugins/color/gsd-night-light-common.c
index fe82bbf2..5fe756e7 100644
--- a/plugins/color/gsd-night-light-common.c
+++ b/plugins/color/gsd-night-light-common.c
@@ -115,16 +115,23 @@ gsd_night_light_frac_day_from_dt (GDateTime *dt)
 }
 
 gboolean
-gsd_night_light_frac_day_is_between (gdouble value, gdouble start, gdouble end)
+gsd_night_light_frac_day_is_between (gdouble  value,
+                                     gdouble  start,
+                                     gdouble  end)
 {
-        /* wraparound to the next day */
-        if (end < start)
+        /* wrap end to the next day if it is before start,
+         * considering equal values as a full 24h period
+         */
+        if (end <= start)
                 end += 24;
 
-        /* wraparound to the previous day */
+        /* wrap value to the next day if it is before the range */
         if (value < start && value < end)
                 value += 24;
 
-        /* test limits */
-        return value > start && value <= end;
+        /* Check whether value falls into range; together with the 24h
+         * wrap around above this means that TRUE is always returned when
+         * start == end.
+         */
+        return value >= start && value < end;
 }
diff --git a/plugins/color/gsd-night-light.c b/plugins/color/gsd-night-light.c
index d0349cc0..b5a55bc0 100644
--- a/plugins/color/gsd-night-light.c
+++ b/plugins/color/gsd-night-light.c
@@ -305,11 +305,12 @@ night_light_recheck (GsdNightLight *self)
                 if (time_span > (GTimeSpan) 24 * 60 * 60 * 1000000) {
                         g_debug ("night light disabled until tomorrow is older than 24h, resetting disabled until tomorrow");
                         reset = TRUE;
-                } else {
+                } else if (time_span > 0) {
                         /* Or if a sunrise lies between the time it was disabled and now. */
                         gdouble frac_disabled;
                         frac_disabled = gsd_night_light_frac_day_from_dt (self->disabled_until_tmw_dt);
-                        if (gsd_night_light_frac_day_is_between (schedule_to,
+                        if (frac_disabled != frac_day &&
+                            gsd_night_light_frac_day_is_between (schedule_to,
                                                                  frac_disabled,
                                                                  frac_day)) {
                                 g_debug ("night light sun rise happened, resetting disabled until tomorrow");
@@ -329,9 +330,14 @@ night_light_recheck (GsdNightLight *self)
                 }
         }
 
+        /* lower smearing period to be smaller than the time between start/stop */
+        smear = MIN (smear,
+                     MIN (     ABS (schedule_to - schedule_from),
+                          24 - ABS (schedule_to - schedule_from)));
+
         if (!gsd_night_light_frac_day_is_between (frac_day,
-                                                    schedule_from - smear,
-                                                    schedule_to)) {
+                                                  schedule_from - smear,
+                                                  schedule_to)) {
                 g_debug ("not time for night-light");
                 gsd_night_light_set_active (self, FALSE);
                 return;
@@ -348,15 +354,18 @@ night_light_recheck (GsdNightLight *self)
          *   \--------------------/
          */
         temperature = g_settings_get_uint (self->settings, "night-light-temperature");
-        if (gsd_night_light_frac_day_is_between (frac_day,
-                                                   schedule_from - smear,
-                                                   schedule_from)) {
+        if (smear < 0.01) {
+                /* Don't try to smear for extremely short or zero periods */
+                temp_smeared = temperature;
+        } else if (gsd_night_light_frac_day_is_between (frac_day,
+                                                        schedule_from - smear,
+                                                        schedule_from)) {
                 gdouble factor = 1.f - ((frac_day - (schedule_from - smear)) / smear);
                 temp_smeared = linear_interpolate (GSD_COLOR_TEMPERATURE_DEFAULT,
                                                    temperature, factor);
         } else if (gsd_night_light_frac_day_is_between (frac_day,
-                                                          schedule_to - smear,
-                                                          schedule_to)) {
+                                                        schedule_to - smear,
+                                                        schedule_to)) {
                 gdouble factor = (frac_day - (schedule_to - smear)) / smear;
                 temp_smeared = linear_interpolate (GSD_COLOR_TEMPERATURE_DEFAULT,
                                                    temperature, factor);