Clarify our OOP semantics across the codebase (#9586)

Basically:

* Use `extend` for class definitions
* Use `new` for object instantiations

That includes some minor code cleanups along the way:

* Updated `Widget`'s docs to make the semantics clearer.
* Removed `should_restrict_JIT` (it's been dead code since https://github.com/koreader/android-luajit-launcher/pull/283)
* Minor refactoring of LuaSettings/LuaData/LuaDefaults/DocSettings to behave (mostly, they are instantiated via `open` instead of `new`) like everything else and handle inheritance properly (i.e., DocSettings is now a proper LuaSettings subclass).
* Default to `WidgetContainer` instead of `InputContainer` for stuff that doesn't actually setup key/gesture events.
* Ditto for explicit `*Listener` only classes, make sure they're based on `EventListener` instead of something uselessly fancier.
* Unless absolutely necessary, do not store references in class objects, ever; only values. Instead, always store references in instances, to avoid both sneaky inheritance issues, and sneaky GC pinning of stale references.
  * ReaderUI: Fix one such issue with its `active_widgets` array, with critical implications, as it essentially pinned *all* of ReaderUI's modules, including their reference to the `Document` instance (i.e., that was a big-ass leak).
* Terminal: Make sure the shell is killed on plugin teardown.
* InputText: Fix Home/End/Del physical keys to behave sensibly.
* InputContainer/WidgetContainer: If necessary, compute self.dimen at paintTo time (previously, only InputContainers did, which might have had something to do with random widgets unconcerned about input using it as a baseclass instead of WidgetContainer...).
* OverlapGroup: Compute self.dimen at *init* time, because for some reason it needs to do that, but do it directly in OverlapGroup instead of going through a weird WidgetContainer method that it was the sole user of.
* ReaderCropping: Under no circumstances should a Document instance member (here, self.bbox) risk being `nil`ed!
* Kobo: Minor code cleanups.

frontend/device/kobo/device.lua

@@ -18,6 +18,7 @@ require("ffi/posix_h")
 
 local function yes() return true end
 local function no() return false end
+local function NOP() return end
 
 local function koboEnableWifi(toggle)
     if toggle == true then
@@ -131,7 +132,7 @@ local function getRTCName()
     end
 end
 
-local Kobo = Generic:new{
+local Kobo = Generic:extend{
     model = "Kobo",
     isKobo = yes,
     isTouchDevice = yes, -- all of them are
@@ -192,21 +193,21 @@ local Kobo = Generic:new{
 }
 
 -- Kobo Touch A/B:
-local KoboTrilogyAB = Kobo:new{
+local KoboTrilogyAB = Kobo:extend{
     model = "Kobo_trilogy_AB",
     touch_kobo_mk3_protocol = true,
     hasKeys = yes,
     hasMultitouch = no,
 }
 -- Kobo Touch C:
-local KoboTrilogyC = Kobo:new{
+local KoboTrilogyC = Kobo:extend{
     model = "Kobo_trilogy_C",
     hasKeys = yes,
     hasMultitouch = no,
 }
 
 -- Kobo Mini:
-local KoboPixie = Kobo:new{
+local KoboPixie = Kobo:extend{
     model = "Kobo_pixie",
     display_dpi = 200,
     hasMultitouch = no,
@@ -215,7 +216,7 @@ local KoboPixie = Kobo:new{
 }
 
 -- Kobo Aura One:
-local KoboDaylight = Kobo:new{
+local KoboDaylight = Kobo:extend{
     model = "Kobo_daylight",
     hasFrontlight = yes,
     touch_phoenix_protocol = true,
@@ -229,8 +230,10 @@ local KoboDaylight = Kobo:new{
 }
 
 -- Kobo Aura H2O:
-local KoboDahlia = Kobo:new{
+local KoboDahlia = Kobo:extend{
     model = "Kobo_dahlia",
+    canToggleChargingLED = no,  -- Possibly weird interactions with Nickel
+    led_uses_channel_3 = true,
     hasFrontlight = yes,
     touch_phoenix_protocol = true,
     -- There's no slot 0, the first finger gets assigned slot 1, and the second slot 2.
@@ -243,7 +246,7 @@ local KoboDahlia = Kobo:new{
 }
 
 -- Kobo Aura HD:
-local KoboDragon = Kobo:new{
+local KoboDragon = Kobo:extend{
     model = "Kobo_dragon",
     hasFrontlight = yes,
     hasMultitouch = no,
@@ -251,7 +254,7 @@ local KoboDragon = Kobo:new{
 }
 
 -- Kobo Glo:
-local KoboKraken = Kobo:new{
+local KoboKraken = Kobo:extend{
     model = "Kobo_kraken",
     hasFrontlight = yes,
     hasMultitouch = no,
@@ -259,7 +262,7 @@ local KoboKraken = Kobo:new{
 }
 
 -- Kobo Aura:
-local KoboPhoenix = Kobo:new{
+local KoboPhoenix = Kobo:extend{
     model = "Kobo_phoenix",
     hasFrontlight = yes,
     touch_phoenix_protocol = true,
@@ -273,7 +276,7 @@ local KoboPhoenix = Kobo:new{
 }
 
 -- Kobo Aura H2O2:
-local KoboSnow = Kobo:new{
+local KoboSnow = Kobo:extend{
     model = "Kobo_snow",
     hasFrontlight = yes,
     touch_snow_protocol = true,
@@ -289,7 +292,7 @@ local KoboSnow = Kobo:new{
 
 -- Kobo Aura H2O2, Rev2:
 --- @fixme Check if the Clara fix actually helps here... (#4015)
-local KoboSnowRev2 = Kobo:new{
+local KoboSnowRev2 = Kobo:extend{
     model = "Kobo_snow_r2",
     isMk7 = yes,
     hasFrontlight = yes,
@@ -303,7 +306,7 @@ local KoboSnowRev2 = Kobo:new{
 }
 
 -- Kobo Aura second edition:
-local KoboStar = Kobo:new{
+local KoboStar = Kobo:extend{
     model = "Kobo_star",
     hasFrontlight = yes,
     touch_phoenix_protocol = true,
@@ -311,7 +314,7 @@ local KoboStar = Kobo:new{
 }
 
 -- Kobo Aura second edition, Rev 2:
-local KoboStarRev2 = Kobo:new{
+local KoboStarRev2 = Kobo:extend{
     model = "Kobo_star_r2",
     isMk7 = yes,
     hasFrontlight = yes,
@@ -320,7 +323,7 @@ local KoboStarRev2 = Kobo:new{
 }
 
 -- Kobo Glo HD:
-local KoboAlyssum = Kobo:new{
+local KoboAlyssum = Kobo:extend{
     model = "Kobo_alyssum",
     hasFrontlight = yes,
     touch_phoenix_protocol = true,
@@ -329,14 +332,14 @@ local KoboAlyssum = Kobo:new{
 }
 
 -- Kobo Touch 2.0:
-local KoboPika = Kobo:new{
+local KoboPika = Kobo:extend{
     model = "Kobo_pika",
     touch_phoenix_protocol = true,
     main_finger_slot = 1,
 }
 
 -- Kobo Clara HD:
-local KoboNova = Kobo:new{
+local KoboNova = Kobo:extend{
     model = "Kobo_nova",
     isMk7 = yes,
     canToggleChargingLED = yes,
@@ -362,7 +365,7 @@ local KoboNova = Kobo:new{
 --       i.e., this will affect KSM users.
 --       c.f., https://github.com/koreader/koreader/pull/4414#issuecomment-449652335
 --       There's also a CM_ROTARY_ENABLE command, but which seems to do as much nothing as the STATUS one...
-local KoboFrost = Kobo:new{
+local KoboFrost = Kobo:extend{
     model = "Kobo_frost",
     isMk7 = yes,
     canToggleChargingLED = yes,
@@ -387,7 +390,7 @@ local KoboFrost = Kobo:new{
 
 -- Kobo Libra:
 -- NOTE: Assume the same quirks as the Forma apply.
-local KoboStorm = Kobo:new{
+local KoboStorm = Kobo:extend{
     model = "Kobo_storm",
     isMk7 = yes,
     canToggleChargingLED = yes,
@@ -418,7 +421,7 @@ local KoboStorm = Kobo:new{
 
 -- Kobo Nia:
 --- @fixme: Mostly untested, assume it's Clara-ish for now.
-local KoboLuna = Kobo:new{
+local KoboLuna = Kobo:extend{
     model = "Kobo_luna",
     isMk7 = yes,
     canToggleChargingLED = yes,
@@ -428,7 +431,7 @@ local KoboLuna = Kobo:new{
 }
 
 -- Kobo Elipsa
-local KoboEuropa = Kobo:new{
+local KoboEuropa = Kobo:extend{
     model = "Kobo_europa",
     isSunxi = yes,
     hasEclipseWfm = yes,
@@ -448,7 +451,7 @@ local KoboEuropa = Kobo:new{
 }
 
 -- Kobo Sage
-local KoboCadmus = Kobo:new{
+local KoboCadmus = Kobo:extend{
     model = "Kobo_cadmus",
     isSunxi = yes,
     hasEclipseWfm = yes,
@@ -481,7 +484,7 @@ local KoboCadmus = Kobo:new{
 }
 
 -- Kobo Libra 2:
-local KoboIo = Kobo:new{
+local KoboIo = Kobo:extend{
     model = "Kobo_io",
     isMk7 = yes,
     hasEclipseWfm = yes,
@@ -513,7 +516,7 @@ local KoboIo = Kobo:new{
 }
 
 -- Kobo Clara 2E:
-local KoboGoldfinch = Kobo:new{
+local KoboGoldfinch = Kobo:extend{
     model = "Kobo_goldfinch",
     isMk7 = yes,
     hasEclipseWfm = yes,
@@ -682,15 +685,15 @@ function Kobo:init()
     self.default_cpu_governor = getCPUGovernor(self.cpu_governor_knob)
     -- NOP unsupported methods
     if not self.default_cpu_governor then
-        self.performanceCPUGovernor = function() end
-        self.defaultCPUGovernor = function() end
+        self.performanceCPUGovernor = NOP
+        self.defaultCPUGovernor = NOP
     end
 
     -- And while we're on CPU-related endeavors...
     self.cpu_count = self:isSMP() and getCPUCount() or 1
     -- NOP unsupported methods
     if self.cpu_count == 1 then
-        self.enableCPUCores = function() end
+        self.enableCPUCores = NOP
     end
 
     -- Automagically set this so we never have to remember to do it manually ;p
@@ -742,6 +745,7 @@ function Kobo:init()
         dodgy_rtc = dodgy_rtc,
     }
 
+    -- Let generic properly setup the standard stuff
     Generic.init(self)
 
     -- Various HW Buttons, Switches & Synthetic NTX events
@@ -768,14 +772,14 @@ function Kobo:init()
     -- See if the device supports key repeat
     if not self:getKeyRepeat() then
         -- NOP unsupported methods
-        self.disableKeyRepeat = function() end
-        self.restoreKeyRepeat = function() end
+        self.disableKeyRepeat = NOP
+        self.restoreKeyRepeat = NOP
     end
 
     -- NOP unsupported methods
     if not self:canToggleChargingLED() then
-        self.toggleChargingLED = function() end
-        self.setupChargingLED = function() end
+        self.toggleChargingLED = NOP
+        self.setupChargingLED = NOP
     end
 
     -- We have no way of querying the current state of the charging LED, so, start from scratch.
@@ -1233,12 +1237,15 @@ function Kobo:toggleChargingLED(toggle)
     --       In fact, Nickel itself doesn't provide this feature on said older devices
     --       (when it does, it's an option in the Energy saving settings),
     --       which is why we also limit ourselves to "true" on devices where this was tested.
+    --       FWIW, on older devices, the knob is at "/sys/devices/platform/pmic_light.1/lit".
     -- c.f., drivers/misc/ntx_misc_light.c
     local f = io.open("/sys/devices/platform/ntx_led/lit", "we")
     if not f then
         logger.err("cannot open /sys/devices/platform/ntx_led/lit for writing!")
         return false
     end
+    -- Relying on LFs is mildly more elegant than spamming f:flush() calls ;).
+    C.setlinebuf(f)
 
     -- c.f., strace -fittTvyy -e trace=ioctl,file,signal,ipc,desc -s 256 -o /tmp/nickel.log -p $(pidof -s nickel) &
     -- This was observed on a Forma, so I'm mildly hopeful that it's safe on other Mk. 7 devices ;).
@@ -1247,38 +1254,13 @@ function Kobo:toggleChargingLED(toggle)
         -- NOTE: Technically, Nickel forces a toggle off before that, too.
         --       But since we do that on startup, it shouldn't be necessary here...
         if self.led_uses_channel_3 then
-            f:write("ch 3")
-            f:flush()
-            f:write("cur 1")
-            f:flush()
-            f:write("dc 63")
-            f:flush()
+            f:write("ch 3\n", "cur 1\n", "dc 63\n")
         end
-        f:write("ch 4")
-        f:flush()
-        f:write("cur 1")
-        f:flush()
-        f:write("dc 63")
-        f:flush()
+        f:write("ch 4\n", "cur 1\n", "dc 63\n")
     else
-        f:write("ch 3")
-        f:flush()
-        f:write("cur 1")
-        f:flush()
-        f:write("dc 0")
-        f:flush()
-        f:write("ch 4")
-        f:flush()
-        f:write("cur 1")
-        f:flush()
-        f:write("dc 0")
-        f:flush()
-        f:write("ch 5")
-        f:flush()
-        f:write("cur 1")
-        f:flush()
-        f:write("dc 0")
-        f:flush()
+        for ch = 3, 5 do
+            f:write("ch " .. tostring(ch) .. "\n", "cur 1\n", "dc 0\n")
+        end
     end
 
     f:close()