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.

plugins/SSH.koplugin/main.lua

@@ -21,7 +21,7 @@ if not util.pathExists("dropbear") then
     return { disabled = true, }
 end
 
-local SSH = WidgetContainer:new{
+local SSH = WidgetContainer:extend{
     name = "SSH",
     is_doc_only = false,
 }

plugins/autodim.koplugin/main.lua

@@ -23,7 +23,9 @@ local DEFAULT_AUTODIM_DURATION_S = 5
 local DEFAULT_AUTODIM_FRACTION = 20
 local AUTODIM_EVENT_FREQUENCY = 2 -- in Hz; Frequenzy for FrontlightChangedEvent on E-Ink devices
 
-local AutoDim = WidgetContainer:new{ name = "autodim" }
+local AutoDim = WidgetContainer:extend{
+    name = "autodim",
+}
 
 function AutoDim:init()
     self.autodim_starttime_m = G_reader_settings:readSetting("autodim_starttime_minutes", -1)

plugins/autofrontlight.koplugin/main.lua

@@ -92,7 +92,7 @@ end
 
 AutoFrontlight:init()
 
-local AutoFrontlightWidget = WidgetContainer:new{
+local AutoFrontlightWidget = WidgetContainer:extend{
     name = "autofrontlight",
 }
 

plugins/autostandby.koplugin/main.lua

@@ -13,7 +13,7 @@ local SpinWidget = require("ui/widget/spinwidget")
 local logger = require("logger")
 local _ = require("gettext")
 
-local AutoStandby = WidgetContainer:new{
+local AutoStandby = WidgetContainer:extend{
     is_doc_only = false,
     name = "autostandby",
 

plugins/autosuspend.koplugin/main.lua

@@ -21,7 +21,7 @@ local default_autoshutdown_timeout_seconds = 3*24*60*60 -- three days
 local default_auto_suspend_timeout_seconds = 15*60 -- 15 minutes
 local default_auto_standby_timeout_seconds = 4 -- 4 seconds; should be safe on Kobo/Sage
 
-local AutoSuspend = WidgetContainer:new{
+local AutoSuspend = WidgetContainer:extend{
     name = "autosuspend",
     is_doc_only = false,
     autoshutdown_timeout_seconds = default_autoshutdown_timeout_seconds,

plugins/autoturn.koplugin/main.lua

@@ -9,7 +9,7 @@ local util = require("util")
 local _ = require("gettext")
 local T = require("ffi/util").template
 
-local AutoTurn = WidgetContainer:new{
+local AutoTurn = WidgetContainer:extend{
     name = "autoturn",
     is_doc_only = true,
     autoturn_sec = 0,

plugins/autowarmth.koplugin/main.lua

@@ -43,10 +43,10 @@ local function frac(x)
     return x - math.floor(x)
 end
 
-local AutoWarmth = WidgetContainer:new{
+local AutoWarmth = WidgetContainer:extend{
     name = "autowarmth",
-    sched_times_s = {},
-    sched_warmths = {},
+    sched_times_s = nil, -- array
+    sched_warmths = nil, -- array
     fl_turned_off = nil -- true/false if autowarmth has toggled the frontlight
 }
 

plugins/backgroundrunner.koplugin/commandrunner.lua

@@ -33,7 +33,6 @@ function CommandRunner:createEnvironment()
 end
 
 function CommandRunner:start(job)
-    assert(self ~= nil)
     assert(self.pio == nil)
     assert(self.job == nil)
     self.job = job
@@ -51,7 +50,6 @@ end
 -- @return a table contains the result from luawrapper.sh. Returns nil if the
 --         command has not been finished.
 function CommandRunner:poll()
-    assert(self ~= nil)
     assert(self.pio ~= nil)
     assert(self.job ~= nil)
     local line = self.pio:read()
@@ -87,7 +85,6 @@ end
 --- Whether this is a running job.
 -- @treturn boolean
 function CommandRunner:pending()
-    assert(self ~= nil)
     return self.pio ~= nil
 end
 

plugins/backgroundrunner.koplugin/main.lua

@@ -115,7 +115,6 @@ function BackgroundRunner:_shouldRepeat(job)
 end
 
 function BackgroundRunner:_finishJob(job)
-    assert(self ~= nil)
     if type(job.executable) == "function" then
         local time_diff = job.end_time - job.start_time
         local threshold = time.s(1)
@@ -159,7 +158,6 @@ end
 
 --- Polls the status of the pending CommandRunner.
 function BackgroundRunner:_poll()
-    assert(self ~= nil)
     assert(CommandRunner:pending())
     local result = CommandRunner:poll()
     if result == nil then return end
@@ -169,7 +167,6 @@ end
 
 function BackgroundRunner:_execute()
     logger.dbg("BackgroundRunner: _execute() @ ", os.time())
-    assert(self ~= nil)
     if CommandRunner:pending() then
         self:_poll()
     else
@@ -236,7 +233,6 @@ function BackgroundRunner:_execute()
 end
 
 function BackgroundRunner:_schedule()
-    assert(self ~= nil)
     if self.running == false then
         if #self.jobs == 0 and not CommandRunner:pending() then
             logger.dbg("BackgroundRunnerWidget: no job, not running @ ", os.time())
@@ -252,14 +248,13 @@ function BackgroundRunner:_schedule()
 end
 
 function BackgroundRunner:_insert(job)
-    assert(self ~= nil)
     job.insert_time = UIManager:getTime()
     table.insert(self.jobs, job)
 end
 
 BackgroundRunner:_schedule()
 
-local BackgroundRunnerWidget = WidgetContainer:new{
+local BackgroundRunnerWidget = WidgetContainer:extend{
     name = "backgroundrunner",
     runner = BackgroundRunner,
 }

plugins/batterystat.koplugin/main.lua

@@ -263,7 +263,7 @@ end
 
 BatteryStat:init()
 
-local BatteryStatWidget = WidgetContainer:new{
+local BatteryStatWidget = WidgetContainer:extend{
     name = "batterystat",
 }
 

plugins/bookshortcuts.koplugin/main.lua

@@ -12,7 +12,7 @@ local util = require("util")
 local _ = require("gettext")
 local T = FFIUtil.template
 
-local BookShortcuts = WidgetContainer:new{
+local BookShortcuts = WidgetContainer:extend{
     name = "bookshortcuts",
     shortcuts = LuaSettings:open(DataStorage:getSettingsDir() .. "/bookshortcuts.lua"),
     updated = false,

plugins/calibre.koplugin/main.lua

@@ -20,7 +20,7 @@ local _ = require("gettext")
 local C_ = _.pgettext
 local T = require("ffi/util").template
 
-local Calibre = WidgetContainer:new{
+local Calibre = WidgetContainer:extend{
     name = "calibre",
     is_doc_only = false,
 }

plugins/calibre.koplugin/search.lua

@@ -9,11 +9,11 @@ local Device = require("device")
 local DocumentRegistry = require("document/documentregistry")
 local InputDialog = require("ui/widget/inputdialog")
 local InfoMessage = require("ui/widget/infomessage")
-local InputContainer = require("ui/widget/container/inputcontainer")
 local Menu = require("ui/widget/menu")
 local Persist = require("persist")
 local Screen = require("device").screen
 local UIManager = require("ui/uimanager")
+local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local lfs = require("libs/libkoreader-lfs")
 local logger = require("logger")
 local rapidjson = require("rapidjson")
@@ -155,7 +155,8 @@ local function getBookInfo(book)
         size)
 end
 
-local CalibreSearch = InputContainer:new{
+-- This is a singleton
+local CalibreSearch = WidgetContainer:extend{
     books = {},
     libraries = {},
     last_scan = {},

plugins/calibre.koplugin/wireless.lua

@@ -10,11 +10,11 @@ local CalibreSearch = require("search")
 local ConfirmBox = require("ui/widget/confirmbox")
 local Device = require("device")
 local FFIUtil = require("ffi/util")
-local InputContainer = require("ui/widget/container/inputcontainer")
 local InputDialog = require("ui/widget/inputdialog")
 local InfoMessage = require("ui/widget/infomessage")
 local NetworkMgr = require("ui/network/manager")
 local UIManager = require("ui/uimanager")
+local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local lfs = require("libs/libkoreader-lfs")
 local logger = require("logger")
 local rapidjson = require("rapidjson")
@@ -55,7 +55,7 @@ local function updateDir(dir)
     end
 end
 
-local CalibreWireless = InputContainer:new{
+local CalibreWireless = WidgetContainer:extend{
     id = "KOReader",
     model = require("device").model,
     version = require("version"):getCurrentRevision(),
@@ -85,10 +85,11 @@ local CalibreWireless = InputContainer:new{
         SET_CALIBRE_DEVICE_NAME   = 2,
         TOTAL_SPACE               = 4,
     },
-    calibre = {},
+    calibre = nil, -- hash
 }
 
 function CalibreWireless:init()
+    self.calibre = {}
     -- reversed operator codes and names dictionary
     self.opnames = {}
     for name, code in pairs(self.opcodes) do

plugins/coverbrowser.koplugin/listmenu.lua

@@ -51,7 +51,7 @@ local scale_by_size = Screen:scaleBySize(1000000) / 1000000
 
 -- ItemShortCutIcon (for keyboard navigation) is private to menu.lua and can't be accessed,
 -- so we need to redefine it
-local ItemShortCutIcon = WidgetContainer:new{
+local ItemShortCutIcon = WidgetContainer:extend{
     dimen = Geom:new{ w = Screen:scaleBySize(22), h = Screen:scaleBySize(22) },
     key = nil,
     bordersize = Size.border.default,
@@ -94,8 +94,8 @@ end
 
 
 -- Based on menu.lua's MenuItem
-local ListMenuItem = InputContainer:new{
-    entry = {},
+local ListMenuItem = InputContainer:extend{
+    entry = nil, -- hash, mandatory
     text = nil,
     show_parent = nil,
     detail = nil,

plugins/coverbrowser.koplugin/main.lua

@@ -1,5 +1,5 @@
-local InputContainer = require("ui/widget/container/inputcontainer")
 local UIManager = require("ui/uimanager")
+local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local logger = require("logger")
 local _ = require("gettext")
 local BookInfoManager = require("bookinfomanager")
@@ -45,7 +45,7 @@ local history_display_mode = false -- not initialized yet
 local collection_display_mode = false -- not initialized yet
 local series_mode = nil -- defaults to not display series
 
-local CoverBrowser = InputContainer:new{
+local CoverBrowser = WidgetContainer:extend{
     name = "coverbrowser",
 }
 

plugins/coverbrowser.koplugin/mosaicmenu.lua

@@ -48,7 +48,7 @@ local progress_widget
 
 -- ItemShortCutIcon (for keyboard navigation) is private to menu.lua and can't be accessed,
 -- so we need to redefine it
-local ItemShortCutIcon = WidgetContainer:new{
+local ItemShortCutIcon = WidgetContainer:extend{
     dimen = Geom:new{ w = Screen:scaleBySize(22), h = Screen:scaleBySize(22) },
     key = nil,
     bordersize = Size.border.default,
@@ -95,7 +95,7 @@ end
 -- The rendering of the TextBoxWidget we're doing below
 -- with decreasing font sizes till it fits is quite expensive.
 
-local FakeCover = FrameContainer:new{
+local FakeCover = FrameContainer:extend{
     width = nil,
     height = nil,
     margin = 0,
@@ -343,8 +343,8 @@ end
 
 
 -- Based on menu.lua's MenuItem
-local MosaicMenuItem = InputContainer:new{
-    entry = {},
+local MosaicMenuItem = InputContainer:extend{
+    entry = nil, -- table, mandatory
     text = nil,
     show_parent = nil,
     detail = nil,

plugins/coverimage.koplugin/main.lua

@@ -62,7 +62,7 @@ local function getExtension(filename)
     return util.getFileNameSuffix(name):lower()
 end
 
-local CoverImage = WidgetContainer:new{
+local CoverImage = WidgetContainer:extend{
     name = "coverimage",
     is_doc_only = true,
 }

plugins/docsettingtweak.koplugin/main.lua

@@ -17,7 +17,7 @@ local filemanagerutil = require("apps/filemanager/filemanagerutil")
 local lfs = require("libs/libkoreader-lfs")
 local util = require("util")
 
-local DocSettingTweak = WidgetContainer:new{
+local DocSettingTweak = WidgetContainer:extend{
     name = "docsettingtweak",
 }
 

plugins/exporter.koplugin/main.lua

@@ -27,10 +27,10 @@
 local DataStorage = require("datastorage")
 local Device = require("device")
 local InfoMessage = require("ui/widget/infomessage")
-local InputContainer = require("ui/widget/container/inputcontainer")
 local MyClipping = require("clip")
 local NetworkMgr = require("ui/network/manager")
 local UIManager = require("ui/uimanager")
+local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local logger = require("logger")
 local _ = require("gettext")
 
@@ -93,7 +93,7 @@ local function updateMyClippings(clippings, new_clippings)
     return clippings
 end
 
-local Exporter = InputContainer:new {
+local Exporter = WidgetContainer:extend{
     name = "exporter",
     clipping_dir = DataStorage:getDataDir() .. "/clipboard",
     targets = {

plugins/gestures.koplugin/main.lua

@@ -9,12 +9,12 @@ local Geom = require("ui/geometry")
 local GestureDetector = require("device/gesturedetector")
 local GestureRange = require("ui/gesturerange")
 local InfoMessage = require("ui/widget/infomessage")
-local InputContainer = require("ui/widget/container/inputcontainer")
 local InputDialog = require("ui/widget/inputdialog")
 local LuaSettings = require("luasettings")
 local Screen = require("device").screen
 local SpinWidget = require("ui/widget/spinwidget")
 local UIManager = require("ui/uimanager")
+local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local lfs = require("libs/libkoreader-lfs")
 local logger = require("logger")
 local util = require("util")
@@ -27,7 +27,7 @@ if not Device:isTouchDevice() then
     return { disabled = true, }
 end
 
-local Gestures = InputContainer:new{
+local Gestures = WidgetContainer:extend{
     name = "gestures",
     settings_data = nil,
     gestures = nil,

plugins/gestures.koplugin/migration.lua

@@ -4,7 +4,7 @@ local LuaData = require("luadata")
 local Migration = {}
 
 local custom_multiswipes_path = DataStorage:getSettingsDir().."/multiswipes.lua"
-local custom_multiswipes = LuaData:open(custom_multiswipes_path, { name = "MultiSwipes" })
+local custom_multiswipes = LuaData:open(custom_multiswipes_path, "MultiSwipes")
 local custom_multiswipes_table = custom_multiswipes:readSetting("multiswipes")
 
 function Migration:convertAction(location, ges, action)

plugins/hello.koplugin/main.lua

@@ -15,7 +15,7 @@ local UIManager = require("ui/uimanager")
 local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local _ = require("gettext")
 
-local Hello = WidgetContainer:new{
+local Hello = WidgetContainer:extend{
     name = "hello",
     is_doc_only = false,
 }

plugins/japanese.koplugin/main.lua

@@ -29,12 +29,12 @@ local _ = require("gettext")
 local N_ = _.ngettext
 local T = require("ffi/util").template
 
-local SingleInstanceDeinflector = Deinflector:new()
+local SingleInstanceDeinflector = Deinflector:new{}
 
-local Japanese = WidgetContainer:new({
+local Japanese = WidgetContainer:extend{
     name = "japanese",
     pretty_name = "Japanese",
-})
+}
 
 -- Yomichan uses 10 characters as the default look-ahead, but crengine's
 -- getNextVisibleChar counts furigana if any are present, so use a higher

plugins/keepalive.koplugin/main.lua

@@ -59,7 +59,7 @@ menuItem.callback = function()
     showConfirmBox()
 end
 
-local KeepAlive = WidgetContainer:new{
+local KeepAlive = WidgetContainer:extend{
     name = "keepalive",
 }
 

plugins/kosync.koplugin/main.lua

@@ -1,18 +1,18 @@
-local Dispatcher = require("dispatcher")
-local InputContainer = require("ui/widget/container/inputcontainer")
-local LoginDialog = require("ui/widget/logindialog")
-local InfoMessage = require("ui/widget/infomessage")
 local ConfirmBox = require("ui/widget/confirmbox")
+local Device = require("device")
+local Dispatcher = require("dispatcher")
+local Event = require("ui/event")
+local InfoMessage = require("ui/widget/infomessage")
+local LoginDialog = require("ui/widget/logindialog")
+local Math = require("optmath")
 local NetworkMgr = require("ui/network/manager")
 local UIManager = require("ui/uimanager")
-local Device = require("device")
-local Event = require("ui/event")
-local Math = require("optmath")
-local Screen = Device.screen
+local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local logger = require("logger")
 local md5 = require("ffi/sha2").md5
 local random = require("random")
 local util = require("util")
+local Screen = Device.screen
 local T = require("ffi/util").template
 local _ = require("gettext")
 
@@ -20,7 +20,7 @@ if G_reader_settings:hasNot("device_id") then
     G_reader_settings:saveSetting("device_id", random.uuid())
 end
 
-local KOSync = InputContainer:new{
+local KOSync = WidgetContainer:extend{
     name = "kosync",
     is_doc_only = true,
     title = _("Register/login to KOReader server"),

plugins/movetoarchive.koplugin/main.lua

@@ -13,7 +13,7 @@ local util = require("frontend/util")
 local BaseUtil = require("ffi/util")
 local _ = require("gettext")
 
-local MoveToArchive = WidgetContainer:new{
+local MoveToArchive = WidgetContainer:extend{
     name = "movetoarchive",
 }
 

plugins/newsdownloader.koplugin/main.lua

@@ -22,7 +22,7 @@ local util = require("util")
 local _ = require("gettext")
 local T = FFIUtil.template
 
-local NewsDownloader = WidgetContainer:new{
+local NewsDownloader = WidgetContainer:extend{
     name = "news_downloader",
     initialized = false,
     feed_config_file = "feed_config.lua",
@@ -41,7 +41,7 @@ local NewsDownloader = WidgetContainer:new{
         enable_filter = false,
         filter_element = ""
     },
-    kv = {}
+    kv = nil, -- KeyValuePage
 }
 
 local FEED_TYPE_RSS = "rss"

plugins/opds.koplugin/main.lua

@@ -3,7 +3,7 @@ local UIManager = require("ui/uimanager")
 local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local _ = require("gettext")
 
-local OPDS = WidgetContainer:new{
+local OPDS = WidgetContainer:extend{
     name = "opds",
     is_doc_only = false,
 }

plugins/opds.koplugin/opdscatalog.lua

@@ -2,15 +2,15 @@ local BD = require("ui/bidi")
 local Blitbuffer = require("ffi/blitbuffer")
 local ConfirmBox = require("ui/widget/confirmbox")
 local FrameContainer = require("ui/widget/container/framecontainer")
-local InputContainer = require("ui/widget/container/inputcontainer")
 local OPDSBrowser = require("opdsbrowser")
 local UIManager = require("ui/uimanager")
+local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local logger = require("logger")
 local _ = require("gettext")
 local Screen = require("device").screen
 local T = require("ffi/util").template
 
-local OPDSCatalog = InputContainer:extend{
+local OPDSCatalog = WidgetContainer:extend{
     title = _("OPDS Catalog"),
 }
 

plugins/profiles.koplugin/main.lua

@@ -13,7 +13,7 @@ local util = require("util")
 
 local autostart_done = false
 
-local Profiles = WidgetContainer:new{
+local Profiles = WidgetContainer:extend{
     name = "profiles",
     profiles_file = DataStorage:getSettingsDir() .. "/profiles.lua",
     profiles = nil,

plugins/qrclipboard.koplugin/main.lua

@@ -10,7 +10,7 @@ local UIManager = require("ui/uimanager")
 local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local _ = require("gettext")
 
-local QRClipboard = WidgetContainer:new{
+local QRClipboard = WidgetContainer:extend{
     name = "qrclipboard",
     is_doc_only = false,
 }

plugins/readtimer.koplugin/main.lua

@@ -7,7 +7,7 @@ local util = require("util")
 local _ = require("gettext")
 local T = require("ffi/util").template
 
-local ReadTimer = WidgetContainer:new{
+local ReadTimer = WidgetContainer:extend{
     name = "readtimer",
     time = 0,  -- The expected time of alarm if enabled, or 0.
 }

plugins/statistics.koplugin/calendarview.lua

@@ -28,7 +28,7 @@ local Input = Device.input
 local Screen = Device.screen
 local _ = require("gettext")
 
-local HistogramWidget = Widget:new{
+local HistogramWidget = Widget:extend{
     width = nil,
     height = nil,
     color = Blitbuffer.COLOR_BLACK,
@@ -76,7 +76,7 @@ function HistogramWidget:paintTo(bb, x, y)
 end
 
 
-local CalendarDay = InputContainer:new{
+local CalendarDay = InputContainer:extend{
     daynum = nil,
     ratio_per_hour = nil,
     filler = false,
@@ -170,7 +170,7 @@ function CalendarDay:onHold()
 end
 
 
-local CalendarWeek = InputContainer:new{
+local CalendarWeek = InputContainer:extend{
     width = nil,
     height = nil,
     day_width = 0,
@@ -367,7 +367,7 @@ end
 -- Fetched from db, cached as local as it might be expensive
 local MIN_MONTH = nil
 
-local CalendarView = FocusManager:new{
+local CalendarView = FocusManager:extend{
     reader_statistics = nil,
     monthTranslation = nil,
     shortDayOfWeekTranslation = nil,

plugins/statistics.koplugin/main.lua

@@ -70,19 +70,8 @@ local ReaderStatistics = Widget:extend{
     book_read_pages = 0,
     book_read_time = 0,
     avg_time = nil,
-    page_stat = {}, -- Dictionary, indexed by page (hash), contains a list (array) of { timestamp, duration } tuples.
-    data = {
-        title = "",
-        authors = "N/A",
-        language = "N/A",
-        series = "N/A",
-        performance_in_pages = {},
-        total_time_in_sec = 0,
-        highlights = 0,
-        notes = 0,
-        pages = 0,
-        md5 = nil,
-    },
+    page_stat = nil, -- Dictionary, indexed by page (hash), contains a list (array) of { timestamp, duration } tuples.
+    data = nil, -- table
 }
 
 local weekDays = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" } -- in Lua wday order
@@ -150,6 +139,20 @@ function ReaderStatistics:init()
         return
     end
 
+    -- Placeholder until onReaderReady
+    self.data = {
+        title = "",
+        authors = "N/A",
+        language = "N/A",
+        series = "N/A",
+        performance_in_pages = {},
+        total_time_in_sec = 0,
+        highlights = 0,
+        notes = 0,
+        pages = 0,
+        md5 = nil,
+    }
+
     self.start_current_period = os.time()
     self:resetVolatileStats()
 

plugins/statistics.koplugin/readerprogress.lua

@@ -25,7 +25,8 @@ local Screen = Device.screen
 local LINE_COLOR = Blitbuffer.COLOR_WEB_GRAY
 local BG_COLOR = Blitbuffer.COLOR_LIGHT_GRAY
 
-local ReaderProgress = InputContainer:new{
+-- Oh, hey, this one actually *is* an InputContainer!
+local ReaderProgress = InputContainer:extend{
     padding = Size.padding.fullscreen,
 }
 

plugins/systemstat.koplugin/main.lua

@@ -291,7 +291,7 @@ end
 
 SystemStat:init()
 
-local SystemStatWidget = WidgetContainer:new{
+local SystemStatWidget = WidgetContainer:extend{
     name = "systemstat",
 }
 

plugins/terminal.koplugin/main.lua

@@ -82,7 +82,7 @@ local T = require("ffi/util").template
 
 local CHUNK_SIZE = 80 * 40 -- max. nb of read bytes (reduce this, if taps are not detected)
 
-local Terminal = WidgetContainer:new{
+local Terminal = WidgetContainer:extend{
     name = "terminal",
     history = "",
     is_shell_open = false,
@@ -429,6 +429,11 @@ function Terminal:onClose()
     self:killShell()
 end
 
+-- Kill the shell on plugin teardown
+function Terminal:onCloseWidget()
+    self:killShell()
+end
+
 function Terminal:onTerminalStart(touchmenu_instance)
     self.touchmenu_instance = touchmenu_instance
 

plugins/terminal.koplugin/terminputtext.lua

@@ -52,10 +52,16 @@ local TermInputText = InputText:extend{
 
     wrap = true,
 
-    alternate_buffer = {},
-    save_buffer = {},
+    alternate_buffer = nil, -- table
+    save_buffer = nil, -- table
 }
 
+function TermInputText:init()
+    self.alternate_buffer = {}
+    self.save_buffer = {}
+    InputText.init(self)
+end
+
 -- disable positioning cursor by tap in emulator mode
 function TermInputText:onTapTextBox(arg, ges)
     return true

plugins/texteditor.koplugin/main.lua

@@ -26,7 +26,7 @@ local _ = require("gettext")
 local Screen = require("device").screen
 local T = ffiutil.template
 
-local TextEditor = WidgetContainer:new{
+local TextEditor = WidgetContainer:extend{
     name = "texteditor",
     settings_file = DataStorage:getSettingsDir() .. "/text_editor.lua",
     settings = nil, -- loaded only when needed

plugins/timesync.koplugin/main.lua

@@ -17,7 +17,7 @@ local T = require("ffi/util").template
 local _ = require("gettext")
 local NetworkMgr = require("ui/network/manager")
 
-local TimeSync = WidgetContainer:new{
+local TimeSync = WidgetContainer:extend{
     name = "timesync",
 }
 

plugins/vocabbuilder.koplugin/db.lua

@@ -99,7 +99,7 @@ end
 function VocabularyBuilder:insertLookupData(db_conn)
     local file_path = DataStorage:getSettingsDir() .. "/lookup_history.lua"
 
-    local lookup_history = LuaData:open(file_path, { name = "LookupHistory" })
+    local lookup_history = LuaData:open(file_path, "LookupHistory")
     if lookup_history:has("lookup_history") then
         local lookup_history_table = lookup_history:readSetting("lookup_history")
         local book_titles = {}

plugins/vocabbuilder.koplugin/main.lua

@@ -137,7 +137,7 @@ end
 --[[--
 Menu dialogue widget
 --]]--
-local MenuDialog = FocusManager:new{
+local MenuDialog = FocusManager:extend{
     padding = Size.padding.large,
     is_edit_mode = false,
     edit_callback = nil,
@@ -381,7 +381,7 @@ end
 --[[--
 Individual word info dialogue widget
 --]]--
-local WordInfoDialog = InputContainer:new{
+local WordInfoDialog = InputContainer:extend{
     title = nil,
     book_title = nil,
     dates = nil,
@@ -594,7 +594,7 @@ local point_widget = TextWidget:new{
 --[[--
 Individual word item widget
 --]]--
-local VocabItemWidget = InputContainer:new{
+local VocabItemWidget = InputContainer:extend{
     face = Font:getFace("smallinfofont"),
     width = nil,
     height = nil,
@@ -985,7 +985,7 @@ end
 --[[--
 Container widget. Same as sortwidget
 --]]--
-local VocabularyBuilderWidget = FocusManager:new{
+local VocabularyBuilderWidget = FocusManager:extend{
     title = "",
     width = nil,
     height = nil,
@@ -1414,7 +1414,7 @@ end
 --[[--
 Item shown in main menu
 --]]--
-local VocabBuilder = WidgetContainer:new{
+local VocabBuilder = WidgetContainer:extend{
     name = "vocabulary_builder",
     is_doc_only = false
 }

plugins/wallabag.koplugin/main.lua

@@ -37,7 +37,7 @@ local article_id_prefix = "[w-id_"
 local article_id_postfix = "] "
 local failed, skipped, downloaded = 1, 2, 3
 
-local Wallabag = WidgetContainer:new{
+local Wallabag = WidgetContainer:extend{
     name = "wallabag",
 }