koreader/frontend/device/input.lua

--[[--
An interface to get input events.
--]]

local DataStorage = require("datastorage")
local DEBUG = require("dbg")
local Event = require("ui/event")
local GestureDetector = require("device/gesturedetector")
local Key = require("device/key")
local framebuffer = require("ffi/framebuffer")
local input = require("ffi/input")
local logger = require("logger")
local time = require("ui/time")
local _ = require("gettext")

-- We're going to need a few <linux/input.h> constants...
local ffi = require("ffi")
local C = ffi.C
require("ffi/posix_h")
require("ffi/linux_input_h")

-- luacheck: push
-- luacheck: ignore
-- key press event values (KEY.value)
local EVENT_VALUE_KEY_PRESS   = 1
local EVENT_VALUE_KEY_REPEAT  = 2
local EVENT_VALUE_KEY_RELEASE = 0

-- For Kindle Oasis orientation events (ABS.code)
-- the ABS code of orientation event will be adjusted to -24 from 24 (C.ABS_PRESSURE)
-- as C.ABS_PRESSURE is also used to detect touch input in KOBO devices.
local ABS_OASIS_ORIENTATION                     = -24
local DEVICE_ORIENTATION_PORTRAIT_LEFT          = 15
local DEVICE_ORIENTATION_PORTRAIT_RIGHT         = 17
local DEVICE_ORIENTATION_PORTRAIT               = 19
local DEVICE_ORIENTATION_PORTRAIT_ROTATED_LEFT  = 16
local DEVICE_ORIENTATION_PORTRAIT_ROTATED_RIGHT = 18
local DEVICE_ORIENTATION_PORTRAIT_ROTATED       = 20
local DEVICE_ORIENTATION_LANDSCAPE              = 21
local DEVICE_ORIENTATION_LANDSCAPE_ROTATED      = 22

-- Kindle Oasis 2 & 3 variant
-- c.f., drivers/input/misc/accel/bma2x2.c
local UPWARD_PORTRAIT_UP_INTERRUPT_HAPPENED     = 15
local UPWARD_PORTRAIT_DOWN_INTERRUPT_HAPPENED   = 16
local UPWARD_LANDSCAPE_LEFT_INTERRUPT_HAPPENED  = 17
local UPWARD_LANDSCAPE_RIGHT_INTERRUPT_HAPPENED = 18

-- For the events of the Forma & Libra accelerometers (MSC.value)
-- c.f., drivers/hwmon/mma8x5x.c
local MSC_RAW_GSENSOR_PORTRAIT_DOWN             = 0x17
local MSC_RAW_GSENSOR_PORTRAIT_UP               = 0x18
local MSC_RAW_GSENSOR_LANDSCAPE_RIGHT           = 0x19
local MSC_RAW_GSENSOR_LANDSCAPE_LEFT            = 0x1a
-- Not that we care about those, but they are reported, and accurate ;).
local MSC_RAW_GSENSOR_BACK                      = 0x1b
local MSC_RAW_GSENSOR_FRONT                     = 0x1c

-- Based on ABS_MT_TOOL_TYPE values on Elan panels
local TOOL_TYPE_FINGER = 0
local TOOL_TYPE_PEN    = 1

-- For debug logging of ev.type
local linux_evdev_type_map = {
    [C.EV_SYN] = "EV_SYN",
    [C.EV_KEY] = "EV_KEY",
    [C.EV_REL] = "EV_REL",
    [C.EV_ABS] = "EV_ABS",
    [C.EV_MSC] = "EV_MSC",
    [C.EV_SW] = "EV_SW",
    [C.EV_LED] = "EV_LED",
    [C.EV_SND] = "EV_SND",
    [C.EV_REP] = "EV_REP",
    [C.EV_FF] = "EV_FF",
    [C.EV_PWR] = "EV_PWR",
    [C.EV_FF_STATUS] = "EV_FF_STATUS",
    [C.EV_MAX] = "EV_MAX",
    [C.EV_SDL] = "EV_SDL",
}

-- For debug logging of ev.code
local linux_evdev_syn_code_map = {
    [C.SYN_REPORT] = "SYN_REPORT",
    [C.SYN_CONFIG] = "SYN_CONFIG",
    [C.SYN_MT_REPORT] = "SYN_MT_REPORT",
    [C.SYN_DROPPED] = "SYN_DROPPED",
}

local linux_evdev_key_code_map = {
    [C.KEY_BATTERY] = "KEY_BATTERY",
    [C.BTN_TOOL_PEN] = "BTN_TOOL_PEN",
    [C.BTN_TOOL_FINGER] = "BTN_TOOL_FINGER",
    [C.BTN_TOOL_RUBBER] = "BTN_TOOL_RUBBER",
    [C.BTN_TOUCH] = "BTN_TOUCH",
    [C.BTN_STYLUS] = "BTN_STYLUS",
    [C.BTN_STYLUS2] = "BTN_STYLUS2",
}

local linux_evdev_abs_code_map = {
    [C.ABS_X] = "ABS_X",
    [C.ABS_Y] = "ABS_Y",
    [C.ABS_PRESSURE] = "ABS_PRESSURE",
    [C.ABS_DISTANCE] = "ABS_DISTANCE",
    [C.ABS_MT_SLOT] = "ABS_MT_SLOT",
    [C.ABS_MT_TOUCH_MAJOR] = "ABS_MT_TOUCH_MAJOR",
    [C.ABS_MT_TOUCH_MINOR] = "ABS_MT_TOUCH_MINOR",
    [C.ABS_MT_WIDTH_MAJOR] = "ABS_MT_WIDTH_MAJOR",
    [C.ABS_MT_WIDTH_MINOR] = "ABS_MT_WIDTH_MINOR",
    [C.ABS_MT_ORIENTATION] = "ABS_MT_ORIENTATION",
    [C.ABS_MT_POSITION_X] = "ABS_MT_POSITION_X",
    [C.ABS_MT_POSITION_Y] = "ABS_MT_POSITION_Y",
    [C.ABS_MT_TOOL_TYPE] = "ABS_MT_TOOL_TYPE",
    [C.ABS_MT_BLOB_ID] = "ABS_MT_BLOB_ID",
    [C.ABS_MT_TRACKING_ID] = "ABS_MT_TRACKING_ID",
    [C.ABS_MT_PRESSURE] = "ABS_MT_PRESSURE",
    [C.ABS_TILT_X] = "ABS_TILT_X",
    [C.ABS_TILT_Y] = "ABS_TILT_Y",
    [C.ABS_MT_DISTANCE] = "ABS_MT_DISTANCE",
    [C.ABS_MT_TOOL_X] = "ABS_MT_TOOL_X",
    [C.ABS_MT_TOOL_Y] = "ABS_MT_TOOL_Y",
}

local linux_evdev_msc_code_map = {
    [C.MSC_RAW] = "MSC_RAW",
}

local linux_evdev_rep_code_map = {
    [C.REP_DELAY] = "REP_DELAY",
    [C.REP_PERIOD] = "REP_PERIOD",
}
-- luacheck: pop

local _internal_clipboard_text = nil -- holds the last copied text

local Input = {
    -- must point to the device implementation when instantiating
    device = nil,
    -- this depends on keyboard layout and should be overridden:
    event_map = {},
    -- adapters are post processing functions that transform a given event to another event
    event_map_adapter = {},
    -- EV_ABS event to honor for pressure event (if any)
    pressure_event = nil,

    group = {
        Cursor = { "Up", "Down", "Left", "Right" },
        PgFwd = { "RPgFwd", "LPgFwd" },
        PgBack = { "RPgBack", "LPgBack" },
        Back = { "Back" },
        Alphabet = {
            "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
            "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        },
        AlphaNumeric = {
            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
            "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
            "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        },
        Numeric = {
            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"
        },
        Text = {
            " ", ".", "/",
            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
            "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
            "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        },
        Any = {
            " ", ".", "/",
            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
            "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
            "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
            "Up", "Down", "Left", "Right", "Press", "Backspace", "End",
            "Back", "Sym", "AA", "Menu", "Home", "Del",
            "LPgBack", "RPgBack", "LPgFwd", "RPgFwd"
        },
    },

    fake_event_set = {
        IntoSS = true, OutOfSS = true,
        UsbPlugIn = true, UsbPlugOut = true,
        Charging = true, NotCharging = true,
        WakeupFromSuspend = true, ReadyToSuspend = true,
        UsbDevicePlugIn = true, UsbDevicePlugOut = true,
    },

    -- NOTE: When looking at the device in Portrait mode, that's assuming PgBack is on TOP, and PgFwd on the BOTTOM
    rotation_map = {
        [framebuffer.ORIENTATION_PORTRAIT] = {},
        [framebuffer.ORIENTATION_LANDSCAPE] = { Up = "Right", Right = "Down", Down = "Left", Left = "Up", LPgBack = "LPgFwd", LPgFwd = "LPgBack", RPgBack = "RPgFwd", RPgFwd = "RPgBack" },
        [framebuffer.ORIENTATION_PORTRAIT_ROTATED] = { Up = "Down", Right = "Left", Down = "Up", Left = "Right", LPgFwd = "LPgBack", LPgBack = "LPgFwd", RPgFwd = "RPgBack", RPgBack = "RPgFwd" },
        [framebuffer.ORIENTATION_LANDSCAPE_ROTATED] = { Up = "Left", Right = "Up", Down = "Right", Left = "Down" }
    },

    timer_callbacks = nil, -- instance-specific table, because the object may get destroyed & recreated at runtime
    disable_double_tap = true,
    tap_interval_override = nil,

    -- keyboard state:
    modifiers = {
        Alt = false,
        Ctrl = false,
        Shift = false,
        Sym = false,
        Meta = false,
    },

    -- repeat state:
    repeat_count = 0,

    -- touch state:
    main_finger_slot = 0,
    cur_slot = 0,
    MTSlots = nil, -- table, object may be replaced at runtime
    active_slots = nil, -- ditto
    ev_slots = nil, -- table
    gesture_detector = nil,

    -- simple internal clipboard implementation, can be overidden to use system clipboard
    hasClipboardText = function()
        return _internal_clipboard_text ~= nil and _internal_clipboard_text ~= ""
    end,
    getClipboardText = function()
        return _internal_clipboard_text
    end,
    setClipboardText = function(text)
        _internal_clipboard_text = text
    end,
}

function Input:new(o)
    o = o or {}
    setmetatable(o, self)
    self.__index = self
    if o.init then o:init() end
    return o
end

function Input:init()
    -- Initialize instance-specific tables
    -- NOTE: All of these arrays may be destroyed & recreated at runtime, so we don't want a parent/class object for those.
    self.timer_callbacks = {}
    self.MTSlots = {}
    self.active_slots = {}

    -- Handle default finger slot
    self.cur_slot = self.main_finger_slot
    self.ev_slots = {
        [self.main_finger_slot] = {
            slot = self.main_finger_slot,
        },
    }

    self.gesture_detector = GestureDetector:new{
        screen = self.device.screen,
        input = self,
    }

    -- set up fake event map
    self.event_map[10000] = "IntoSS" -- go into screen saver
    self.event_map[10001] = "OutOfSS" -- go out of screen saver
    self.event_map[10010] = "UsbPlugIn"
    self.event_map[10011] = "UsbPlugOut"
    self.event_map[10020] = "Charging"
    self.event_map[10021] = "NotCharging"
    self.event_map[10030] = "WakeupFromSuspend"
    self.event_map[10031] = "ReadyToSuspend"
    self.event_map[10040] = "UsbDevicePlugIn"
    self.event_map[10041] = "UsbDevicePlugOut"

    -- user custom event map
    local custom_event_map_location = string.format(
        "%s/%s", DataStorage:getSettingsDir(), "event_map.lua")
    local ok, custom_event_map = pcall(dofile, custom_event_map_location)
    if ok then
        for key, value in pairs(custom_event_map) do
            self.event_map[key] = value
        end
        logger.info("loaded custom event map", custom_event_map)
    end

    if G_reader_settings:isTrue("backspace_as_back") then
        table.insert(self.group.Back, "Backspace")
    end

    -- setup inhibitInputUntil scheduling function
    self._inhibitInputUntil_func = function() self:inhibitInputUntil() end
end

--[[--
Wrapper for FFI input open.

Note that we adhere to the "." syntax here for compatibility.

@todo Clean up separation FFI/this.
--]]
function Input.open(device, is_emu_events)
    return input.open(device, is_emu_events and 1 or 0)
end

--[[--
Different device models can implement their own hooks
and register them.
--]]
function Input:registerEventAdjustHook(hook, hook_params)
    local old = self.eventAdjustHook
    self.eventAdjustHook = function(this, ev)
        old(this, ev)
        hook(this, ev, hook_params)
    end
end

function Input:registerGestureAdjustHook(hook, hook_params)
    local old = self.gestureAdjustHook
    self.gestureAdjustHook = function(this, ges)
        old(this, ges)
        hook(this, ges, hook_params)
    end
end

function Input:eventAdjustHook(ev)
    -- do nothing by default
end

function Input:gestureAdjustHook(ges)
    -- do nothing by default
end

--- Catalog of predefined hooks.
function Input:adjustTouchSwitchXY(ev)
    if ev.type == C.EV_ABS then
        if ev.code == C.ABS_X then
            ev.code = C.ABS_Y
        elseif ev.code == C.ABS_Y then
            ev.code = C.ABS_X
        elseif ev.code == C.ABS_MT_POSITION_X then
            ev.code = C.ABS_MT_POSITION_Y
        elseif ev.code == C.ABS_MT_POSITION_Y then
            ev.code = C.ABS_MT_POSITION_X
        end
    end
end

function Input:adjustTouchScale(ev, by)
    if ev.type == C.EV_ABS then
        if ev.code == C.ABS_X or ev.code == C.ABS_MT_POSITION_X then
            ev.value = by.x * ev.value
        end
        if ev.code == C.ABS_Y or ev.code == C.ABS_MT_POSITION_Y then
            ev.value = by.y * ev.value
        end
    end
end

function Input:adjustTouchMirrorX(ev, max_x)
    if ev.type == C.EV_ABS
    and (ev.code == C.ABS_X or ev.code == C.ABS_MT_POSITION_X) then
        ev.value = max_x - ev.value
    end
end

function Input:adjustTouchMirrorY(ev, max_y)
    if ev.type == C.EV_ABS
    and (ev.code == C.ABS_Y or ev.code == C.ABS_MT_POSITION_Y) then
        ev.value = max_y - ev.value
    end
end

function Input:adjustTouchTranslate(ev, by)
    if ev.type == C.EV_ABS then
        if ev.code == C.ABS_X or ev.code == C.ABS_MT_POSITION_X then
            ev.value = by.x + ev.value
        end
        if ev.code == C.ABS_Y or ev.code == C.ABS_MT_POSITION_Y then
            ev.value = by.y + ev.value
        end
    end
end

function Input:adjustKindleOasisOrientation(ev)
    if ev.type == C.EV_ABS and ev.code == C.ABS_PRESSURE then
        ev.code = ABS_OASIS_ORIENTATION
    end
end

function Input:setTimeout(slot, ges, cb, origin, delay)
    local item = {
        slot     = slot,
        gesture  = ges,
        callback = cb,
    }

    -- We're going to need the clock source id for these events from GestureDetector
    local clock_id = self.gesture_detector:getClockSource()
    local deadline

    -- If we're on a platform with the timerfd backend, handle that
    local timerfd
    if input.setTimer then
        -- If GestureDetector's clock source probing was inconclusive, do this on the UI timescale instead.
        if clock_id == -1 then
            deadline = time.now() + delay
            clock_id = C.CLOCK_MONOTONIC
        else
            deadline = origin + delay
        end
        -- What this does is essentially to ask the kernel to wake us up when the timer expires,
        -- instead of ensuring that ourselves via a polling timeout.
        -- This ensures perfect accuracy, and allows it to be computed in the event's own timescale.
        local sec, usec = time.split_s_us(deadline)
        timerfd = input.setTimer(clock_id, sec, usec)
    end
    if timerfd then
            -- It worked, tweak the table a bit to make it clear the deadline will be handled by the kernel
            item.timerfd = timerfd
            -- We basically only need this for the sorting ;).
            item.deadline = deadline
    else
        -- No timerfd, we'll compute a poll timeout ourselves.
        if clock_id == C.CLOCK_MONOTONIC then
            -- If the event's clocksource is monotonic, we can use it directly.
            deadline = origin + delay
        else
            -- Otherwise, fudge it by using a current timestamp in the UI's timescale (MONOTONIC).
            -- This isn't the end of the world in practice (c.f., #7415).
            deadline = time.now() + delay
        end
        item.deadline = deadline
    end
    table.insert(self.timer_callbacks, item)

    -- NOTE: While the timescale is monotonic, we may interleave timers based on different delays, so we still need to sort...
    table.sort(self.timer_callbacks, function(v1, v2)
        return v1.deadline < v2.deadline
    end)
end

-- Clear all timeouts for a specific slot (and a specific gesture, if ges is set)
function Input:clearTimeout(slot, ges)
    for i = #self.timer_callbacks, 1, -1 do
        local item = self.timer_callbacks[i]
        if item.slot == slot and (not ges or item.gesture == ges) then
            -- If the timerfd backend is in use, close the fd and free the list's node, too.
            if item.timerfd then
                input.clearTimer(item.timerfd)
            end
            table.remove(self.timer_callbacks, i)
        end
    end
end

function Input:clearTimeouts()
    -- If the timerfd backend is in use, close the fds, too
    if input.setTimer then
        for _, item in ipairs(self.timer_callbacks) do
            if item.timerfd then
                input.clearTimer(item.timerfd)
            end
        end
    end

    self.timer_callbacks = {}
end

-- Reset the gesture parsing state to a blank slate
function Input:resetState()
    if self.gesture_detector then
        self.gesture_detector:dropContacts()
        -- Resets the clock source probe
        self.gesture_detector:resetClockSource()
    end
    self:clearTimeouts()
end

function Input:handleKeyBoardEv(ev)
    -- Detect loss of contact for the "snow" protocol...
    -- NOTE: Some ST devices may also behave similarly, but we handle those via ABS_PRESSURE
    if self.snow_protocol then
        if ev.code == C.BTN_TOUCH and ev.value == 0 then
            -- Kernel sends it after loss of contact for *all* slots,
            -- only once the final contact point has been lifted.
            if #self.MTSlots == 0 then
                -- Likely, since this is usually in its own event stream,
                -- meaning self.MTSlots has *just* been cleared by our last EV_SYN:SYN_REPORT handler...
                -- So, poke at the actual data to find the slots that are currently active (i.e., in the down state),
                -- and re-populate a minimal self.MTSlots array that simply switches them to the up state ;).
                for _, slot in pairs(self.ev_slots) do
                    if slot.id ~= -1 then
                        table.insert(self.MTSlots, slot)
                        slot.id = -1
                    end
                end
            else
                -- Unlikely, given what we mentioned above...
                -- Note that, funnily enough, its EV_KEY:BTN_TOUCH:1 counterpart
                -- *can* be in the same initial event stream as the EV_ABS batch...
                for _, MTSlot in ipairs(self.MTSlots) do
                    self:setMtSlot(MTSlot.slot, "id", -1)
                end
            end

            return
        end
    elseif self.wacom_protocol then
        if ev.code == C.BTN_TOOL_PEN then
            -- Always send pen data to slot 0
            self:setupSlotData(0)
            if ev.value == 1 then
                self:setCurrentMtSlot("tool", TOOL_TYPE_PEN)
            else
                self:setCurrentMtSlot("tool", TOOL_TYPE_FINGER)
            end
        elseif ev.code == C.BTN_TOUCH then
            -- Much like on snow, use this to detect contact down & lift,
            -- as ABS_PRESSURE may be entirely omitted from hover events,
            -- and ABS_DISTANCE is not very clear cut...
            self:setupSlotData(0)
            if ev.value == 1 then
                self:setCurrentMtSlot("id", 0)
            else
                self:setCurrentMtSlot("id", -1)
            end
        end
    end

    local keycode = self.event_map[ev.code]
    if not keycode then
        -- do not handle keypress for keys we don't know
        return
    end

    if self.event_map_adapter[keycode] then
        return self.event_map_adapter[keycode](ev)
    end

    -- take device rotation into account
    if self.rotation_map[self.device.screen:getRotationMode()][keycode] then
        keycode = self.rotation_map[self.device.screen:getRotationMode()][keycode]
    end

    if self.fake_event_set[keycode] then
        return keycode
    end

    -- The hardware camera button is used in Android to toggle the touchscreen
    if keycode == "Camera" and ev.value == EVENT_VALUE_KEY_RELEASE
        and G_reader_settings:isTrue("camera_key_toggles_touchscreen") then
        local isAndroid, android = pcall(require, "android")
        if isAndroid then
            -- toggle touchscreen behaviour
            android.toggleTouchscreenIgnored()

            -- show a toast with the new behaviour
            if android.isTouchscreenIgnored() then
                android.notification(_("Touchscreen disabled"))
            else
                android.notification(_("Touchscreen enabled"))
            end
        end
        return
    end

    if keycode == "Power" then
        -- Kobo generates Power keycode only, we need to decide whether it's
        -- power-on or power-off ourselves.
        if ev.value == EVENT_VALUE_KEY_PRESS then
            return "PowerPress"
        elseif ev.value == EVENT_VALUE_KEY_RELEASE then
            return "PowerRelease"
        end
    end

    -- toggle fullscreen on F11
    if self:isEvKeyPress(ev) and keycode == "F11" and not self.device:isAlwaysFullscreen() then
        local UIManager = require("ui/uimanager")
        UIManager:broadcastEvent(Event:new("ToggleFullscreen"))
    end

    -- quit on Alt + F4
    -- this is also emitted by the close event in SDL
    if self:isEvKeyPress(ev) and self.modifiers["Alt"] and keycode == "F4" then
        local UIManager = require("ui/uimanager")
        UIManager:broadcastEvent(Event:new("Close")) -- Tell all widgets to close.
        UIManager:nextTick(function() UIManager:quit() end) -- Ensure the program closes in case of some lingering dialog.
    end

    -- handle modifier keys
    if self.modifiers[keycode] ~= nil then
        if ev.value == EVENT_VALUE_KEY_PRESS then
            self.modifiers[keycode] = true
        elseif ev.value == EVENT_VALUE_KEY_RELEASE then
            self.modifiers[keycode] = false
        end
        return
    end

    local key = Key:new(keycode, self.modifiers)

    if ev.value == EVENT_VALUE_KEY_PRESS then
        return Event:new("KeyPress", key)
    elseif ev.value == EVENT_VALUE_KEY_REPEAT then
        -- NOTE: We only care about repeat events from the pageturn buttons...
        --       And we *definitely* don't want to flood the Event queue with useless SleepCover repeats!
        if keycode == "LPgBack"
        or keycode == "RPgBack"
        or keycode == "LPgFwd"
        or keycode == "RPgFwd" then
            --- @fixme Crappy event staggering!
            --
            -- The Forma & co repeats every 80ms after a 400ms delay, and 500ms roughly corresponds to a flashing update,
            -- so stuff is usually in sync when you release the key.
            -- Obvious downside is that this ends up slower than just mashing the key.
            --
            -- A better approach would be an onKeyRelease handler that flushes the Event queue...
            self.repeat_count = self.repeat_count + 1
            if self.repeat_count == 1 then
                return Event:new("KeyRepeat", key)
            elseif self.repeat_count >= 6 then
                self.repeat_count = 0
            end
        end
    elseif ev.value == EVENT_VALUE_KEY_RELEASE then
        self.repeat_count = 0
        return Event:new("KeyRelease", key)
    end
end

-- Mangled variant of handleKeyBoardEv that will only handle power management related keys.
-- (Used when blocking input during suspend via sleep cover).
function Input:handlePowerManagementOnlyEv(ev)
    local keycode = self.event_map[ev.code]
    if not keycode then
        -- Do not handle keypress for keys we don't know
        return
    end

    -- We'll need to parse the synthetic event map, because SleepCover* events are synthetic.
    if self.event_map_adapter[keycode] then
        keycode = self.event_map_adapter[keycode](ev)
    end

    -- Power management synthetic events
    if keycode == "SleepCoverClosed" or keycode == "SleepCoverOpened"
    or keycode == "Suspend" or keycode == "Resume" then
        return keycode
    end

    if self.fake_event_set[keycode] then
        return keycode
    end

    if keycode == "Power" then
        -- Kobo generates Power keycode only, we need to decide whether it's
        -- power-on or power-off ourselves.
        if ev.value == EVENT_VALUE_KEY_PRESS then
            return "PowerPress"
        elseif ev.value == EVENT_VALUE_KEY_RELEASE then
            return "PowerRelease"
        end
    end

    -- Nothing to see, move along!
    return
end

-- Empty event handler used to send input to the void
function Input:voidEv(ev)
    return
end

-- Generic event handler for unhandled input events
function Input:handleGenericEv(ev)
    return Event:new("GenericInput", ev)
end

function Input:handleMiscEv(ev)
    -- should be handled by a misc event protocol plugin
end

function Input:handleSdlEv(ev)
    -- overwritten by device implementation
end

--[[--
Parse each touch ev from kernel and build up tev.
tev will be sent to GestureDetector:feedEvent

Events for a single tap motion from Linux kernel (MT protocol B):

    MT_TRACK_ID: 0
    MT_X: 222
    MT_Y: 207
    SYN REPORT
    MT_TRACK_ID: -1
    SYN REPORT

Notice that each line is a single event.

From kernel document:
For type B devices, the kernel driver should associate a slot with each
identified contact, and use that slot to propagate changes for the contact.
Creation, replacement and destruction of contacts is achieved by modifying
the C.ABS_MT_TRACKING_ID of the associated slot.  A non-negative tracking id
is interpreted as a contact, and the value -1 denotes an unused slot.  A
tracking id not previously present is considered new, and a tracking id no
longer present is considered removed.  Since only changes are propagated,
the full state of each initiated contact has to reside in the receiving
end.  Upon receiving an MT event, one simply updates the appropriate
attribute of the current slot.
--]]
function Input:handleTouchEv(ev)
    if ev.type == C.EV_ABS then
        -- NOTE: Ideally, an input frame starts with either ABS_MT_SLOT or ABS_MT_TRACKING_ID,
        --       but they *both* may be omitted if the last contact point just moved without lift.
        --       The use of setCurrentMtSlotChecked instead of setCurrentMtSlot ensures
        --       we actually setup the slot data storage and/or reference for the current slot in this case,
        --       as the reference list is empty at the beginning of an input frame (c.f., Input:newFrame).
        --       The most common platforms where you'll see this happen are:
        --       * PocketBook, because of our InkView EVT_POINTERMOVE translation
        --         (c.f., translateEvent @ ffi/input_pocketbook.lua).
        --       * SDL, because of our SDL_MOUSEMOTION/SDL_FINGERMOTION translation
        --         (c.f., waitForEvent @ ffi/SDL2_0.lua).
        if ev.code == C.ABS_MT_SLOT then
            self:setupSlotData(ev.value)
        elseif ev.code == C.ABS_MT_TRACKING_ID then
            if self.snow_protocol then
                -- NOTE: We'll never get an ABS_MT_SLOT event, instead we have a slot-like ABS_MT_TRACKING_ID value...
                --       This also means this may never be set to -1 on contact lift,
                --       which is why we instead rely on EV_KEY:BTN_TOUCH:0 for that (c.f., handleKeyBoardEv).
                self:setupSlotData(ev.value)
            else
                -- The Elan driver needlessly repeats unchanged ABS_MT_TRACKING_ID values,
                -- which allows us to do this here instead of relying more aggressively on setCurrentMtSlotChecked.
                if #self.MTSlots == 0 then
                    self:addSlot(self.cur_slot)
                end
            end
            self:setCurrentMtSlot("id", ev.value)
        elseif ev.code == C.ABS_MT_TOOL_TYPE then
            -- NOTE: On the Elipsa: Finger == 0; Pen == 1
            self:setCurrentMtSlot("tool", ev.value)
        elseif ev.code == C.ABS_MT_POSITION_X or ev.code == C.ABS_X then
            self:setCurrentMtSlotChecked("x", ev.value)
        elseif ev.code == C.ABS_MT_POSITION_Y or ev.code == C.ABS_Y then
            self:setCurrentMtSlotChecked("y", ev.value)
        elseif self.pressure_event and ev.code == self.pressure_event and ev.value == 0 then
            -- Drop hovering *pen* events
            local tool = self:getCurrentMtSlotData("tool")
            if tool and tool == TOOL_TYPE_PEN then
                self:setCurrentMtSlot("id", -1)
            end
        end
    elseif ev.type == C.EV_SYN then
        if ev.code == C.SYN_REPORT then
            for _, MTSlot in ipairs(self.MTSlots) do
                self:setMtSlot(MTSlot.slot, "timev", time.timeval(ev.time))
            end
            -- feed ev in all slots to state machine
            local touch_gestures = self.gesture_detector:feedEvent(self.MTSlots)
            self:newFrame()
            local ges_evs = {}
            for _, touch_ges in ipairs(touch_gestures) do
                self:gestureAdjustHook(touch_ges)
                table.insert(ges_evs, Event:new("Gesture", self.gesture_detector:adjustGesCoordinate(touch_ges)))
            end
            return ges_evs
        end
    end
end

function Input:handleTouchEvPhoenix(ev)
    -- Hack on handleTouchEV for the Kobo Aura
    -- It seems to be using a custom protocol:
    --        finger 0 down:
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TRACKING_ID, 0);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TOUCH_MAJOR, 1);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_WIDTH_MAJOR, 1);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_X, x1);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_Y, y1);
    --            input_mt_sync (elan_touch_data.input);
    --        finger 1 down:
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TRACKING_ID, 1);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TOUCH_MAJOR, 1);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_WIDTH_MAJOR, 1);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_X, x2);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_Y, y2);
    --            input_mt_sync (elan_touch_data.input);
    --        finger 0 up:
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TRACKING_ID, 0);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TOUCH_MAJOR, 0);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_WIDTH_MAJOR, 0);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_X, last_x);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_Y, last_y);
    --            input_mt_sync (elan_touch_data.input);
    --        finger 1 up:
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TRACKING_ID, 1);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_TOUCH_MAJOR, 0);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_WIDTH_MAJOR, 0);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_X, last_x2);
    --            input_report_abs(elan_touch_data.input, C.ABS_MT_POSITION_Y, last_y2);
    --            input_mt_sync (elan_touch_data.input);
    if ev.type == C.EV_ABS then
        if ev.code == C.ABS_MT_TRACKING_ID then
            self:setupSlotData(ev.value)
            self:setCurrentMtSlot("id", ev.value)
        elseif ev.code == C.ABS_MT_TOUCH_MAJOR and ev.value == 0 then
            self:setCurrentMtSlot("id", -1)
        elseif ev.code == C.ABS_MT_POSITION_X then
            self:setCurrentMtSlot("x", ev.value)
        elseif ev.code == C.ABS_MT_POSITION_Y then
            self:setCurrentMtSlot("y", ev.value)
        end
    elseif ev.type == C.EV_SYN then
        if ev.code == C.SYN_REPORT then
            for _, MTSlot in ipairs(self.MTSlots) do
                self:setMtSlot(MTSlot.slot, "timev", time.timeval(ev.time))
            end
            -- feed ev in all slots to state machine
            local touch_gestures = self.gesture_detector:feedEvent(self.MTSlots)
            self:newFrame()
            local ges_evs = {}
            for _, touch_ges in ipairs(touch_gestures) do
                self:gestureAdjustHook(touch_ges)
                table.insert(ges_evs, Event:new("Gesture", self.gesture_detector:adjustGesCoordinate(touch_ges)))
            end
            return ges_evs
        end
    end
end

function Input:handleTouchEvLegacy(ev)
    -- Single Touch Protocol.
    -- Some devices emit both singletouch and multitouch events,
    -- on those devices, the 'handleTouchEv' function may not behave as expected. Use this one instead.
    if ev.type == C.EV_ABS then
        if ev.code == C.ABS_X then
            self:setCurrentMtSlotChecked("x", ev.value)
        elseif ev.code == C.ABS_Y then
            self:setCurrentMtSlotChecked("y", ev.value)
        elseif ev.code == C.ABS_PRESSURE then
            if ev.value ~= 0 then
                self:setCurrentMtSlotChecked("id", 1)
            else
                self:setCurrentMtSlotChecked("id", -1)

                -- On Kobo Mk. 3 devices, the frame that reports a contact lift *actually* does the coordinates transform for us...
                -- Unfortunately, our own transforms are not stateful, so, just revert 'em here,
                -- since we can't simply avoid not doing 'em for that frame...
                -- c.f., https://github.com/koreader/koreader/issues/2128#issuecomment-1236289909 for logs on a Touch B
                -- NOTE: We can afford to do this here instead of on SYN_REPORT because the kernel *always*
                --       reports ABS_PRESSURE after ABS_X/ABS_Y.
                if self.touch_kobo_mk3_protocol then
                    local y = 599 - self:getCurrentMtSlotData("x") -- Mk. 3 devices are all 600x800, so just hard-code it here.
                    local x = self:getCurrentMtSlotData("y")
                    self:setCurrentMtSlot("x", x)
                    self:setCurrentMtSlot("y", y)
                end
            end
        end
    elseif ev.type == C.EV_SYN then
        if ev.code == C.SYN_REPORT then
            for _, MTSlot in ipairs(self.MTSlots) do
                self:setMtSlot(MTSlot.slot, "timev", time.timeval(ev.time))
            end

            -- feed ev in all slots to state machine
            local touch_gestures = self.gesture_detector:feedEvent(self.MTSlots)
            self:newFrame()
            local ges_evs = {}
            for _, touch_ges in ipairs(touch_gestures) do
                self:gestureAdjustHook(touch_ges)
                table.insert(ges_evs, Event:new("Gesture", self.gesture_detector:adjustGesCoordinate(touch_ges)))
            end
            return ges_evs
        end
    end
end

function Input:handleOasisOrientationEv(ev)
    local rotation_mode, screen_mode
    if self.device:isZelda() then
        if ev.value == UPWARD_PORTRAIT_UP_INTERRUPT_HAPPENED then
            -- i.e., UR
            rotation_mode = framebuffer.ORIENTATION_PORTRAIT
            screen_mode = 'portrait'
        elseif ev.value == UPWARD_LANDSCAPE_LEFT_INTERRUPT_HAPPENED then
            -- i.e., CW
            rotation_mode = framebuffer.ORIENTATION_LANDSCAPE
            screen_mode = 'landscape'
        elseif ev.value == UPWARD_PORTRAIT_DOWN_INTERRUPT_HAPPENED then
            -- i.e., UD
            rotation_mode = framebuffer.ORIENTATION_PORTRAIT_ROTATED
            screen_mode = 'portrait'
        elseif ev.value == UPWARD_LANDSCAPE_RIGHT_INTERRUPT_HAPPENED then
            -- i.e., CCW
            rotation_mode = framebuffer.ORIENTATION_LANDSCAPE_ROTATED
            screen_mode = 'landscape'
        end
    else
        if ev.value == DEVICE_ORIENTATION_PORTRAIT
            or ev.value == DEVICE_ORIENTATION_PORTRAIT_LEFT
            or ev.value == DEVICE_ORIENTATION_PORTRAIT_RIGHT then
            -- i.e., UR
            rotation_mode = framebuffer.ORIENTATION_PORTRAIT
            screen_mode = 'portrait'
        elseif ev.value == DEVICE_ORIENTATION_LANDSCAPE then
            -- i.e., CW
            rotation_mode = framebuffer.ORIENTATION_LANDSCAPE
            screen_mode = 'landscape'
        elseif ev.value == DEVICE_ORIENTATION_PORTRAIT_ROTATED
            or ev.value == DEVICE_ORIENTATION_PORTRAIT_ROTATED_LEFT
            or ev.value == DEVICE_ORIENTATION_PORTRAIT_ROTATED_RIGHT then
            -- i.e., UD
            rotation_mode = framebuffer.ORIENTATION_PORTRAIT_ROTATED
            screen_mode = 'portrait'
        elseif ev.value == DEVICE_ORIENTATION_LANDSCAPE_ROTATED then
            -- i.e., CCW
            rotation_mode = framebuffer.ORIENTATION_LANDSCAPE_ROTATED
            screen_mode = 'landscape'
        end
    end

    local old_rotation_mode = self.device.screen:getRotationMode()
    if self.device:isGSensorLocked() then
        local old_screen_mode = self.device.screen:getScreenMode()
        if rotation_mode ~= old_rotation_mode and screen_mode == old_screen_mode then
            -- Cheaper than a full SetRotationMode event, as we don't need to re-layout anything.
            self.device.screen:setRotationMode(rotation_mode)
            local UIManager = require("ui/uimanager")
            UIManager:onRotation()
        end
    else
        if rotation_mode ~= old_rotation_mode then
            return Event:new("SetRotationMode", rotation_mode)
        end
    end
end

--- Accelerometer on the Forma/Libra
function Input:handleMiscEvNTX(ev)
    local rotation_mode, screen_mode
    if ev.code == C.MSC_RAW then
        if ev.value == MSC_RAW_GSENSOR_PORTRAIT_UP then
            -- i.e., UR
            rotation_mode = framebuffer.ORIENTATION_PORTRAIT
            screen_mode = 'portrait'
        elseif ev.value == MSC_RAW_GSENSOR_LANDSCAPE_RIGHT then
            -- i.e., CW
            rotation_mode = framebuffer.ORIENTATION_LANDSCAPE
            screen_mode = 'landscape'
        elseif ev.value == MSC_RAW_GSENSOR_PORTRAIT_DOWN then
            -- i.e., UD
            rotation_mode = framebuffer.ORIENTATION_PORTRAIT_ROTATED
            screen_mode = 'portrait'
        elseif ev.value == MSC_RAW_GSENSOR_LANDSCAPE_LEFT then
            -- i.e., CCW
            rotation_mode = framebuffer.ORIENTATION_LANDSCAPE_ROTATED
            screen_mode = 'landscape'
        else
            -- Discard FRONT/BACK
            return
        end
    else
        -- Discard unhandled event codes, just to future-proof this ;).
        return
    end

    local old_rotation_mode = self.device.screen:getRotationMode()
    if self.device:isGSensorLocked() then
        local old_screen_mode = self.device.screen:getScreenMode()
        if rotation_mode and rotation_mode ~= old_rotation_mode and screen_mode == old_screen_mode then
            -- Cheaper than a full SetRotationMode event, as we don't need to re-layout anything.
            self.device.screen:setRotationMode(rotation_mode)
            local UIManager = require("ui/uimanager")
            UIManager:onRotation()
        end
    else
        if rotation_mode and rotation_mode ~= old_rotation_mode then
            return Event:new("SetRotationMode", rotation_mode)
        end
    end
end

--- Allow toggling the accelerometer at runtime.
function Input:toggleMiscEvNTX(toggle)
    if toggle == true then
        -- Honor Gyro events
        if not self.isNTXAccelHooked then
            self.handleMiscEv = self.handleMiscEvNTX
            self.isNTXAccelHooked = true
        end
    elseif toggle == false then
        -- Ignore Gyro events
        if self.isNTXAccelHooked then
            self.handleMiscEv = self.voidEv
            self.isNTXAccelHooked = false
        end
    else
        -- Toggle it
        if self.isNTXAccelHooked then
            self.handleMiscEv = self.voidEv
        else
            self.handleMiscEv = self.handleMiscEvNTX
        end

        self.isNTXAccelHooked = not self.isNTXAccelHooked
    end
end

-- helpers for touch event data management:

function Input:initMtSlot(slot)
    if not self.ev_slots[slot] then
        self.ev_slots[slot] = {
            slot = slot
        }
    end
end

function Input:setMtSlot(slot, key, val)
    self.ev_slots[slot][key] = val
end

function Input:setCurrentMtSlot(key, val)
    self:setMtSlot(self.cur_slot, key, val)
end

-- Same as above, but ensures the current slot actually has a live ref first
function Input:setCurrentMtSlotChecked(key, val)
    if #self.MTSlots == 0 then
        self:addSlot(self.cur_slot)
    end

    self:setMtSlot(self.cur_slot, key, val)
end

function Input:getMtSlot(slot)
    return self.ev_slots[slot]
end

function Input:getCurrentMtSlot()
    return self:getMtSlot(self.cur_slot)
end

function Input:getCurrentMtSlotData(key)
    local slot = self:getCurrentMtSlot()
    if slot then
        return slot[key]
    end

    return nil
end

function Input:newFrame()
    -- Array of references to the data for each slot seen in this input frame
    -- (Points to self.ev_slots, c.f., getMtSlot)
    self.MTSlots = {}
    -- Simple hash to keep track of which references we've inserted into self.MTSlots (keys are slot numbers)
    self.active_slots = {}
end

function Input:addSlot(value)
    self:initMtSlot(value)
    table.insert(self.MTSlots, self:getMtSlot(value))
    self.active_slots[value] = true
    self.cur_slot = value
end

function Input:addSlotIfChanged(value)
    if self.cur_slot ~= value then
        -- We've already seen that slot in this frame, don't insert a duplicate reference!
        if self.active_slots[value] then
            self.cur_slot = value
        else
            self:addSlot(value)
        end
    end
end

function Input:setupSlotData(value)
    if #self.MTSlots == 0 then
        self:addSlot(value)
    else
        self:addSlotIfChanged(value)
    end
end

function Input:isEvKeyPress(ev)
    return ev.value == EVENT_VALUE_KEY_PRESS
end

function Input:isEvKeyRepeat(ev)
    return ev.value == EVENT_VALUE_KEY_REPEAT
end

function Input:isEvKeyRelease(ev)
    return ev.value == EVENT_VALUE_KEY_RELEASE
end


--- Main event handling.
-- `now` corresponds to UIManager:getTime() (an fts time), and it's just been updated by UIManager.
-- `deadline` (an fts time) is the absolute deadline imposed by UIManager:handleInput() (a.k.a., our main event loop ^^):
-- it's either nil (meaning block forever waiting for input), or the earliest UIManager deadline (in most cases, that's the next scheduled task,
-- in much less common cases, that's the earliest of UIManager.INPUT_TIMEOUT (currently, only KOSync ever sets it) or UIManager.ZMQ_TIMEOUT if there are pending ZMQs).
function Input:waitEvent(now, deadline)
    -- On the first iteration of the loop, we don't need to update now, we're following closely (a couple ms at most) behind UIManager.
    local ok, ev
    -- Wrapper around the platform-specific input.waitForEvent (which itself is generally poll-like, and supposed to poll *once*).
    -- Speaking of input.waitForEvent, it can return:
    -- * true, ev: When a batch of input events was read.
    --             ev is an array of event tables, themselves mapped after the input_event <linux/input.h> struct.
    -- * false, errno, timerfd: When no input event was read, possibly for benign reasons.
    --                          One such common case is after a polling timeout, in which case errno is C.ETIME.
    --                          If the timerfd backend is in use, and the early return was caused by a timerfd expiring,
    --                          it returns false, C.ETIME, timerfd; where timerfd is a C pointer (i.e., light userdata)
    --                          to the timerfd node that expired (so as to be able to free it later, c.f., input/timerfd-callbacks.h).
    --                          Otherwise, errno is the actual error code from the backend (e.g., select's errno for the C backend).
    -- * nil: When something terrible happened (e.g., fatal poll/read failure). We abort in such cases.
    while true do
        if self.timer_callbacks[1] then
            -- If we have timers set, we need to honor them once we're done draining the input events.
            while self.timer_callbacks[1] do
                -- Choose the earliest deadline between the next timer deadline, and our full timeout deadline.
                local deadline_is_timer = false
                local with_timerfd = false
                local poll_deadline
                -- If the timer's deadline is handled via timerfd, that's easy
                if self.timer_callbacks[1].timerfd then
                    -- We use the ultimate deadline, as the kernel will just signal us when the timer expires during polling.
                    poll_deadline = deadline
                    with_timerfd = true
                else
                    if not deadline then
                        -- If we don't actually have a full timeout deadline, just honor the timer's.
                        poll_deadline = self.timer_callbacks[1].deadline
                        deadline_is_timer = true
                    else
                        if self.timer_callbacks[1].deadline < deadline then
                            poll_deadline = self.timer_callbacks[1].deadline
                            deadline_is_timer = true
                        else
                            poll_deadline = deadline
                        end
                    end
                end
                local poll_timeout
                -- With the timerfd backend, poll_deadline is set to deadline, which might be nil, in which case,
                -- we can happily block forever, like in the no timer_callbacks branch below ;).
                if poll_deadline then
                    -- If we haven't hit that deadline yet, poll until it expires, otherwise,
                    -- have select return immediately so that we trip a timeout.
                    now = now or time.now()
                    if poll_deadline > now then
                        -- Deadline hasn't been blown yet, honor it.
                        poll_timeout = poll_deadline - now
                    else
                        -- We've already blown the deadline: make select return immediately (most likely straight to timeout).
                        -- NOTE: With the timerfd backend, this is sometimes a tad optimistic,
                        --       as we may in fact retry for a few iterations while waiting for the timerfd to actually expire.
                        poll_timeout = 0
                    end
                end

                local timerfd
                local sec, usec = time.split_s_us(poll_timeout)
                ok, ev, timerfd = input.waitForEvent(sec, usec)
                -- We got an actual input event, go and process it
                if ok then break end

                -- If we've drained all pending input events, causing waitForEvent to time out, check our timers
                if ok == false and ev == C.ETIME then
                    -- Check whether the earliest timer to finalize a Gesture detection is up.
                    local consume_callback = false
                    if timerfd then
                        -- If we were woken up by a timerfd, that means the timerfd backend is in use, of course,
                        -- and it also means that we're guaranteed to have reached its deadline.
                        consume_callback = true
                    elseif not with_timerfd then
                        -- On systems where the timerfd backend is *NOT* in use, we have a few more cases to handle...
                        if deadline_is_timer then
                            -- We're only guaranteed to have blown the timer's deadline
                            -- when our actual select deadline *was* the timer's!
                            consume_callback = true
                        elseif time.now() >= self.timer_callbacks[1].deadline then
                            -- But if it was a task deadline instead, we to have to check the timer's against the current time,
                            -- to double-check whether we blew it or not.
                            consume_callback = true
                        end
                    end

                    if consume_callback then
                        local touch_ges
                        local timer_idx = 1
                        if timerfd then
                            -- If there's a deadline collision, make sure we call the callback that matches the timerfd returned.
                            -- We'll handle the next one on the next iteration, as an expired timerfd will ensure
                            -- that select will return immediately.
                            for i, item in ipairs(self.timer_callbacks) do
                                if item.timerfd == timerfd then
                                    -- In the vast majority of cases, we should find our match on the first entry ;).
                                    timer_idx = i
                                    touch_ges = item.callback()
                                    break
                                end
                            end
                        else
                            -- If there's a deadline collision, we'll just handle the next one on the next iteration,
                            -- because the blown deadline means we'll have asked waitForEvent to return immediately.
                            touch_ges = self.timer_callbacks[1].callback()
                        end

                        -- Cleanup after the timer callback.
                        -- GestureDetector has guards in place to avoid double frees in case the callback itself
                        -- affected the timerfd or timer_callbacks list (e.g., by dropping a contact).
                        if timerfd then
                            input.clearTimer(timerfd)
                        end
                        table.remove(self.timer_callbacks, timer_idx)

                        if touch_ges then
                            self:gestureAdjustHook(touch_ges)
                            return {
                                Event:new("Gesture", self.gesture_detector:adjustGesCoordinate(touch_ges))
                            }
                        end -- if touch_ges
                    end -- if poll_deadline reached
                else
                    -- Something went wrong, jump to error handling *now*
                    break
                end -- if poll returned ETIME

                -- Refresh now on the next iteration (e.g., when we have multiple timers to check, and we've just timed out)
                now = nil
            end -- while #timer_callbacks > 0
        else
            -- If there aren't any timers, just block for the requested amount of time.
            -- deadline may be nil, in which case waitForEvent blocks indefinitely (i.e., until the next input event ;)).
            local poll_timeout
            -- If UIManager put us on deadline, enforce it, otherwise, block forever.
            if deadline then
                -- Convert that absolute deadline to value relative to *now*, as we may loop multiple times between UI ticks.
                now = now or time.now()
                if deadline > now then
                    -- Deadline hasn't been blown yet, honor it.
                    poll_timeout = deadline - now
                else
                    -- Deadline has been blown: make select return immediately.
                    poll_timeout = 0
                end
            end

            local sec, usec = time.split_s_us(poll_timeout)
            ok, ev = input.waitForEvent(sec, usec)
        end -- if #timer_callbacks > 0

        -- Handle errors
        if ok then
            -- We're good, process the event and go back to UIManager.
            break
        elseif ok == false then
            if ev == C.ETIME then
                -- Don't report an error on ETIME, and go back to UIManager
                ev = nil
                break
            elseif ev == C.EINTR then  -- luacheck: ignore
                -- Retry on EINTR
            else
                -- Warn, report, and go back to UIManager
                logger.warn("Polling for input events returned an error:", ev, "->", ffi.string(C.strerror(ev)))
                break
            end
        elseif ok == nil then
            -- Something went horribly wrong, abort.
            logger.err("Polling for input events failed catastrophically")
            local UIManager = require("ui/uimanager")
            UIManager:abort()
            break
        end

        -- We'll need to refresh now on the next iteration, if there is one.
        now = nil
    end

    if ok and ev then
        local handled = {}
        -- We're guaranteed that ev is an array of event tables. Might be an array of *one* event, but an array nonetheless ;).
        for __, event in ipairs(ev) do
            if DEBUG.is_on then
                -- NOTE: This is rather spammy and computationally intensive,
                --       and we can't conditionally prevent evalutation of function arguments,
                --       so, just hide the whole thing behind a branch ;).
                if event.type == C.EV_KEY then
                    logger.dbg(string.format(
                        "key event => code: %d (%s), value: %s, time: %d.%06d",
                        event.code, self.event_map[event.code] or linux_evdev_key_code_map[event.code], event.value,
                        event.time.sec, event.time.usec))
                elseif event.type == C.EV_SYN then
                    logger.dbg(string.format(
                        "input event => type: %d (%s), code: %d (%s), value: %s, time: %d.%06d",
                        event.type, linux_evdev_type_map[event.type], event.code, linux_evdev_syn_code_map[event.code], event.value,
                        event.time.sec, event.time.usec))
                elseif event.type == C.EV_ABS then
                    logger.dbg(string.format(
                        "input event => type: %d (%s), code: %d (%s), value: %s, time: %d.%06d",
                        event.type, linux_evdev_type_map[event.type], event.code, linux_evdev_abs_code_map[event.code], event.value,
                        event.time.sec, event.time.usec))
                elseif event.type == C.EV_MSC then
                    logger.dbg(string.format(
                        "input event => type: %d (%s), code: %d (%s), value: %s, time: %d.%06d",
                        event.type, linux_evdev_type_map[event.type], event.code, linux_evdev_msc_code_map[event.code], event.value,
                        event.time.sec, event.time.usec))
                elseif event.type == C.EV_REP then
                    logger.dbg(string.format(
                        "input event => type: %d (%s), code: %d (%s), value: %s, time: %d.%06d",
                        event.type, linux_evdev_type_map[event.type], event.code, linux_evdev_rep_code_map[event.code], event.value,
                        event.time.sec, event.time.usec))
                else
                    logger.dbg(string.format(
                        "input event => type: %d (%s), code: %d, value: %s, time: %d.%06d",
                        event.type, linux_evdev_type_map[event.type], event.code, event.value,
                        event.time.sec, event.time.usec))
                end
            end
            self:eventAdjustHook(event)
            if event.type == C.EV_KEY then
                local handled_ev = self:handleKeyBoardEv(event)
                if handled_ev then
                    table.insert(handled, handled_ev)
                end
            elseif event.type == C.EV_ABS and event.code == ABS_OASIS_ORIENTATION then
                local handled_ev = self:handleOasisOrientationEv(event)
                if handled_ev then
                    table.insert(handled, handled_ev)
                end
            elseif event.type == C.EV_ABS or event.type == C.EV_SYN then
                local handled_evs = self:handleTouchEv(event)
                -- handleTouchEv only returns an array of Events once it gets a SYN_REPORT,
                -- so more often than not, we just get a nil here ;).
                if handled_evs then
                    for _, handled_ev in ipairs(handled_evs) do
                        table.insert(handled, handled_ev)
                    end
                end
            elseif event.type == C.EV_MSC then
                local handled_ev = self:handleMiscEv(event)
                if handled_ev then
                    table.insert(handled, handled_ev)
                end
            elseif event.type == C.EV_SDL then
                local handled_ev = self:handleSdlEv(event)
                if handled_ev then
                    table.insert(handled, handled_ev)
                end
            else
                -- Received some other kind of event that we do not know how to specifically handle yet
                local handled_ev = self:handleGenericEv(event)
                if handled_ev then
                    table.insert(handled, handled_ev)
                end
            end
        end
        return handled
    elseif ok == false and ev then
        return {
            Event:new("InputError", ev)
        }
    elseif ok == nil then
        -- No ok and no ev? Hu oh...
        return {
            Event:new("InputError", "Catastrophic")
        }
    end
end

-- Allow toggling the handling of most every kind of input, except for power management related events.
function Input:inhibitInput(toggle)
    if toggle then
        -- Only handle power management events
        if not self._key_ev_handler then
            logger.info("Inhibiting user input")
            self._key_ev_handler = self.handleKeyBoardEv
            self.handleKeyBoardEv = self.handlePowerManagementOnlyEv
        end
        -- And send everything else to the void
        if not self._oasis_ev_handler then
            self._oasis_ev_handler = self.handleOasisOrientationEv
            self.handleOasisOrientationEv = self.voidEv
        end
        if not self._abs_ev_handler then
            self._abs_ev_handler = self.handleTouchEv
            self.handleTouchEv = self.voidEv
        end
        if not self._msc_ev_handler then
            if not self.device:isPocketBook() and not self.device:isAndroid() then
                -- NOTE: PocketBook is a special snowflake, synthetic Power events are sent as EV_MSC.
                --       Thankfully, that's all that EV_MSC is used for on that platform.
                -- NOTE: Android, on the other hand, handles a *lot* of critical stuff over EV_MSC,
                --       as it's used to communicate between Android and Lua land ;).
                self._msc_ev_handler = self.handleMiscEv
                self.handleMiscEv = self.voidEv
            end
        end
        if not self._sdl_ev_handler then
            self._sdl_ev_handler = self.handleSdlEv
            self.handleSdlEv = self.voidEv
        end
        if not self._generic_ev_handler then
            self._generic_ev_handler = self.handleGenericEv
            self.handleGenericEv = self.voidEv
        end

        -- Reset gesture detection state to a blank slate, to avoid bogus gesture detection on restore.
        self:resetState()
    else
        -- Restore event handlers, if any
        if self._key_ev_handler then
            logger.info("Restoring user input handling")
            self.handleKeyBoardEv = self._key_ev_handler
            self._key_ev_handler = nil
        end
        if self._oasis_ev_handler then
            self.handleOasisOrientationEv = self._oasis_ev_handler
            self._oasis_ev_handler = nil
        end
        if self._abs_ev_handler then
            self.handleTouchEv = self._abs_ev_handler
            self._abs_ev_handler = nil
        end
        if self._msc_ev_handler then
            self.handleMiscEv = self._msc_ev_handler
            self._msc_ev_handler = nil
        end
        if self._sdl_ev_handler then
            self.handleSdlEv = self._sdl_ev_handler
            self._sdl_ev_handler = nil
        end
        if self._generic_ev_handler then
            self.handleGenericEv = self._generic_ev_handler
            self._generic_ev_handler = nil
        end
    end
end

--[[--
Request all input events to be ignored for some duration.

@param set_or_seconds either `true`, in which case a platform-specific delay is chosen, or a duration in seconds (***int***).
]]
function Input:inhibitInputUntil(set_or_seconds)
    local UIManager = require("ui/uimanager")
    UIManager:unschedule(self._inhibitInputUntil_func)
    if not set_or_seconds then -- remove any previously set
        self:inhibitInput(false)
        return
    end
    local delay_s
    if set_or_seconds == true then
        -- Use an adequate delay to account for device refresh duration
        -- so any events happening in this delay (ie. before a widget
        -- is really painted on screen) are discarded.
        if self.device:hasEinkScreen() then
            -- A screen refresh can take a few 100ms,
            -- sometimes > 500ms on some devices/temperatures.
            -- So, block for 400ms (to have it displayed) + 400ms
            -- for user reaction to it
            delay_s = 0.8
        else
            -- On non-eInk screen, display is usually instantaneous
            delay_s = 0.4
        end
    else -- we expect a number
        delay_s = set_or_seconds
    end
    UIManager:scheduleIn(delay_s, self._inhibitInputUntil_func)
    self:inhibitInput(true)
end

return Input