sdk: Stop using lerp for night/day mode transitions

* This makes it clear what the desired behavior is
* In order to make the logic more clear, also start
  scaling into night mode before civil sunset so that
  we finish by civil sunset -- this makes sure that
  by the time there's no light out for practical
  purposes, we are in night mode
* While we're at it, add a few comments about what
  each return is supposed to do, for the future

Change-Id: I4ec0f8eec6b0129a37e99f9e3a2b3f124aeeb4f2

1 files changed, 9 insertions, 6 deletions

diff --git a/lineage/lib/main/java/org/lineageos/platform/internal/display/ColorTemperatureController.java b/lineage/lib/main/java/org/lineageos/platform/internal/display/ColorTemperatureController.java
index 7dbd2874..27b86d9a 100644
--- a/lineage/lib/main/java/org/lineageos/platform/internal/display/ColorTemperatureController.java
+++ b/lineage/lib/main/java/org/lineageos/platform/internal/display/ColorTemperatureController.java
@@ -293,20 +293,23 @@ public class ColorTemperatureController extends LiveDisplayFeature {
      */
     private static float adj(long now, long sunset, long sunrise) {
         if (sunset < 0 || sunrise < 0
-                || now < sunset || now > (sunrise + TWILIGHT_ADJUSTMENT_TIME)) {
+                || now < (sunset - TWILIGHT_ADJUSTMENT_TIME)
+                || now > (sunrise + TWILIGHT_ADJUSTMENT_TIME)) {
+            // More than 1hr after civil sunrise or before civil sunset
             return 1.0f;
         }
 
-        if (now <= (sunset + TWILIGHT_ADJUSTMENT_TIME)) {
-            return MathUtils.lerp(1.0f, 0.0f,
-                    (float) (now - sunset) / TWILIGHT_ADJUSTMENT_TIME);
+        // Scale the transition into night mode in 1hr before civil sunset
+        if (now <= sunset) {
+            return (float) (sunset - now) / TWILIGHT_ADJUSTMENT_TIME;
         }
 
+        // Scale the transition into day mode in 1hr after civil sunrise
         if (now >= sunrise) {
-            return MathUtils.lerp(1.0f, 0.0f,
-                    (float) ((sunrise + TWILIGHT_ADJUSTMENT_TIME) - now) / TWILIGHT_ADJUSTMENT_TIME);
+            return (float) (now - sunrise) / TWILIGHT_ADJUSTMENT_TIME;
         }
 
+        // More than 1hr past civil sunset
         return 0.0f;
     }