From 4db8e85edd440f534fca25d7d7b1361a0fe8224b Mon Sep 17 00:00:00 2001
From: Michael Wright <michaelwr@google.com>
Date: Wed, 7 Mar 2018 14:27:34 +0000
Subject: [PATCH] Update the documentation for brightness configuration.

This should always match the documentation in frameworks/base, since
that's the canonical document.

Bug: 74328541
Test: N/A
Change-Id: I7b3266bb3c07631f13fe295ee883909ce24aff79
---
 .../base/core/res/res/values/config.xml       | 22 ++++++++++++++-----
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/overlay/frameworks/base/core/res/res/values/config.xml b/overlay/frameworks/base/core/res/res/values/config.xml
index b7a7593..d0831b0 100644
--- a/overlay/frameworks/base/core/res/res/values/config.xml
+++ b/overlay/frameworks/base/core/res/res/values/config.xml
@@ -26,14 +26,24 @@
     <!-- MMS user agent prolfile url -->
     <string name="config_mms_user_agent_profile_url" translatable="false">http://www.gstatic.com/android/sms/G011C.xml</string>
 
-    <!-- Array of light sensor LUX values to define our levels for auto backlight brightness support.
-         The N entries of this array define N  1 zones as follows:
+    <!-- Array of light sensor lux values to define our levels for auto backlight brightness support.
+         The N entries of this array define N + 1 control points as follows:
+         (1-based arrays)
 
-         Zone 0:        0 <= LUX < array[0]
-         Zone 1:        array[0] <= LUX < array[1]
+         Point 1:            (0, value[1]):             lux <= 0
+         Point 2:     (level[1], value[2]):  0        < lux <= level[1]
+         Point 3:     (level[2], value[3]):  level[2] < lux <= level[3]
          ...
-         Zone N:        array[N - 1] <= LUX < array[N]
-         Zone N + 1     array[N] <= LUX < infinity
+         Point N+1: (level[N], value[N+1]):  level[N] < lux
+
+         The control points must be strictly increasing.  Each control point
+         corresponds to an entry in the brightness backlight values arrays.
+         For example, if lux == level[1] (first element of the levels array)
+         then the brightness will be determined by value[2] (second element
+         of the brightness values array).
+
+         Spline interpolation is used to determine the auto-brightness
+         backlight values for lux levels between these control points.
 
          Must be overridden in platform specific overlays -->
     <integer-array name="config_autoBrightnessLevels">