Fix brightness slider - allow minimum value

ag/11455081 stopped the brightness slider from reaching the minimum value. This change reverts this but other changes in this topic also change the Walleye initial curves to start at 1 instead of 0.

Bug: 157838219

Test: manual - cover ambient light sensor - ensure brightness reduces
but not to 0. Move the slider to min and check that it stays there. grep for brightness splines too:
adb shell dumpsys display | grep -i "spline\|mConfig"

Change-Id: I26334986d299d297e6d1e320222566b22497b2ff

1 files changed, 4 insertions, 3 deletions

diff --git a/services/core/java/com/android/server/display/BrightnessMappingStrategy.java b/services/core/java/com/android/server/display/BrightnessMappingStrategy.java
index 787f7f398fcb..6f12155c5ec6 100644
--- a/services/core/java/com/android/server/display/BrightnessMappingStrategy.java
+++ b/services/core/java/com/android/server/display/BrightnessMappingStrategy.java
@@ -28,6 +28,7 @@ import android.util.Pair;
 import android.util.Slog;
 import android.util.Spline;
 
+import com.android.internal.BrightnessSynchronizer;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.Preconditions;
 import com.android.server.display.utils.Plog;
@@ -348,9 +349,9 @@ public abstract class BrightnessMappingStrategy {
 
     // Normalize entire brightness range to 0 - 1.
     protected static float normalizeAbsoluteBrightness(int brightness) {
-        brightness = MathUtils.constrain(brightness,
-                PowerManager.BRIGHTNESS_OFF, PowerManager.BRIGHTNESS_ON);
-        return (float) brightness / PowerManager.BRIGHTNESS_ON;
+        return BrightnessSynchronizer.brightnessIntToFloat(brightness,
+                PowerManager.BRIGHTNESS_OFF + 1, PowerManager.BRIGHTNESS_ON,
+                PowerManager.BRIGHTNESS_MIN, PowerManager.BRIGHTNESS_MAX);
     }
 
     private Pair<float[], float[]> insertControlPoint(