kobo/powerd, kobo/nickel_conf: Support reading/setting natural light

Nickel stores the 'warmth' values as 'ColorSetting' in a linear
mapping from '1500' to '6400'.

frontend/device/kobo/nickel_conf.lua

@@ -3,17 +3,23 @@
     Only PowerOptions:FrontLightLevel is currently supported .
 ]]
 
+local dbg = require("dbg")
+
 local NickelConf = {}
 NickelConf.frontLightLevel = {}
 NickelConf.frontLightState = {}
+NickelConf.colorSetting = {}
 
 local kobo_conf_path = '/mnt/onboard/.kobo/Kobo/Kobo eReader.conf'
 local front_light_level_str = "FrontLightLevel"
 local front_light_state_str = "FrontLightState"
+local color_setting_str = "ColorSetting"
 -- Nickel will set FrontLightLevel to 0 - 100
 local re_FrontLightLevel = "^" .. front_light_level_str .. "%s*=%s*([0-9]+)%s*$"
 -- Nickel will set FrontLightState to true (light on) or false (light off)
 local re_FrontLightState = "^" .. front_light_state_str .. "%s*=%s*(.+)%s*$"
+-- Nickel will set ColorSetting to 1500 - 6400
+local re_ColorSetting = "^" .. color_setting_str .. "%s*=%s*([0-9]+)%s*$"
 local re_PowerOptionsSection = "^%[PowerOptions%]%s*"
 local re_AnySection = "^%[.*%]%s*"
 
@@ -69,6 +75,14 @@ function NickelConf.frontLightState.get()
     return new_state
 end
 
+function NickelConf.colorSetting.get()
+    local new_colorsetting = NickelConf._read_kobo_conf(re_ColorSetting)
+    if new_colorsetting then
+        return tonumber(new_colorsetting)
+    end
+    return nil
+end
+
 function NickelConf._write_kobo_conf(re_Match, key, value, dont_create)
     local kobo_conf = io.open(kobo_conf_path, "r")
     local lines = {}
@@ -143,4 +157,16 @@ function NickelConf.frontLightState.set(new_state)
                                        true)
 end
 
+function NickelConf.colorSetting.set(new_color)
+    return NickelConf._write_kobo_conf(re_ColorSetting,
+                                       color_setting_str,
+                                       new_color)
+end
+
+dbg:guard(NickelConf.colorSetting, 'set',
+          function(self, new_color)
+              assert(new_color >= 1500 and new_color <= 6400,
+                     "Wrong colorSetting value given!")
+          end)
+
 return NickelConf

frontend/device/kobo/powerd.lua

@@ -23,6 +23,7 @@ local KoboPowerD = BasePowerD:new{
 function KoboPowerD:_syncKoboLightOnStart()
     local new_intensity = nil
     local is_frontlight_on = nil
+    local new_warmth = nil
     local kobo_light_on_start = tonumber(KOBO_LIGHT_ON_START)
     if kobo_light_on_start then
         if kobo_light_on_start > 0 then
@@ -34,6 +35,14 @@ function KoboPowerD:_syncKoboLightOnStart()
         elseif kobo_light_on_start == -2 then -- get values from NickelConf
             new_intensity = NickelConf.frontLightLevel.get()
             is_frontlight_on = NickelConf.frontLightState:get()
+            if self.fl_warmth ~= nil then
+                local new_color = NickelConf.colorSetting.get()
+                if new_color ~= nil then
+                    -- ColorSetting is in [1500,6400], with '1500'
+                    -- being maximum warmth, so normalize this to [0,100]
+                    new_warmth = (100 - math.floor((new_color - 1500) / 49))
+                end
+            end
             if is_frontlight_on == nil then
                 -- this device does not support frontlight toggle,
                 -- we set the value based on frontlight intensity.
@@ -54,6 +63,9 @@ function KoboPowerD:_syncKoboLightOnStart()
             -- stored in koreader settings
             new_intensity = G_reader_settings:readSetting("frontlight_intensity")
             is_frontlight_on = G_reader_settings:readSetting("is_frontlight_on")
+            if self.fl_warmth ~= nil then
+                new_warmth = G_reader_settings:readSetting("frontlight_warmth")
+            end
         end
     end
 
@@ -64,6 +76,9 @@ function KoboPowerD:_syncKoboLightOnStart()
         -- will only be used to give initial state to BasePowerD:_decideFrontlightState()
         self.initial_is_fl_on = is_frontlight_on
     end
+    if new_warmth ~= nil then
+        self.fl_warmth = new_warmth
+    end
 
     -- In any case frontlight is off, ensure intensity is non-zero so untoggle works
     if self.initial_is_fl_on == false and self.hw_intensity == 0 then
@@ -103,9 +118,13 @@ function KoboPowerD:saveSettings()
         -- untoggled intensity and toggle state at next startup)
         local cur_intensity = self.fl_intensity
         local cur_is_fl_on = self.is_fl_on
+        local cur_warmth = self.fl_warmth
         -- Save intensity to koreader settings
         G_reader_settings:saveSetting("frontlight_intensity", cur_intensity)
         G_reader_settings:saveSetting("is_frontlight_on", cur_is_fl_on)
+        if cur_warmth ~= nil then
+            G_reader_settings:saveSetting("frontlight_warmth", cur_warmth)
+        end
         -- And to "Kobo eReader.conf" if needed
         if KOBO_SYNC_BRIGHTNESS_WITH_NICKEL then
             if NickelConf.frontLightState.get() ~= nil then
@@ -120,6 +139,12 @@ function KoboPowerD:saveSettings()
             if NickelConf.frontLightLevel.get() ~= cur_intensity then
                 NickelConf.frontLightLevel.set(cur_intensity)
             end
+            if cur_warmth ~= nil then
+                local warmth_rescaled = (100 - cur_warmth) * 49 + 1500
+                if NickelConf.colorSetting.get() ~= warmth_rescaled then
+                    NickelConf.colorSetting.set(warmth_rescaled)
+                end
+            end
         end
     end
 end