X-Plane 12: progressive single button brake (lua script)

progressive_brakes.lua

-- progressive_brakes.lua
-- XP12 + FlyWithLua
-- Progressive both-brakes command for whitelisted aircraft only
-- Includes double-tap brake hold

local SCRIPT_NAME = "progressive_brakes"

------------------------------------------------------------
-- User configuration
------------------------------------------------------------

local SECONDS_TO_FULL_BRAKE = 3.0
local SECONDS_TO_RELEASE    = 1.5
local DOUBLE_TAP_WINDOW     = 0.5

local aircraft_config = {
    ["A330.acf"] = {
        override_toe_brakes = false,
    },

    -- ["Some_Other_Aircraft.acf"] = {
    --     override_toe_brakes = true,
    -- },
}

------------------------------------------------------------
-- Datarefs
------------------------------------------------------------

dataref("total_running_time_sec", "sim/time/total_running_time_sec")

dataref("left_brake_ratio_dref",  "sim/cockpit2/controls/left_brake_ratio",  "writable")
dataref("right_brake_ratio_dref", "sim/cockpit2/controls/right_brake_ratio", "writable")

------------------------------------------------------------
-- Internal state
------------------------------------------------------------

local enabled = false
local current_aircraft_config = nil

local brake_ratio = 0.0
local brake_start_time = 0.0
local brake_release_time = 0.0

local brake_ratio_at_press = 0.0
local brake_ratio_at_release = 0.0

local last_release_time = -999.0
local brake_hold_active = false

------------------------------------------------------------
-- Aircraft whitelist
------------------------------------------------------------

local function get_aircraft_config()
    local current_acf = tostring(AIRCRAFT_FILENAME or "")
    return aircraft_config[current_acf]
end

current_aircraft_config = get_aircraft_config()

local function is_whitelisted_aircraft()
    local current_acf = tostring(AIRCRAFT_FILENAME or "")

    for _, acf in ipairs(whitelisted_acf) do
        if current_acf == acf then
            return true
        end
    end

    return false
end

if current_aircraft_config ~= nil then
    enabled = true

    if current_aircraft_config.override_toe_brakes == true then
        set("sim/operation/override/override_toe_brakes", 1)
        logMsg(SCRIPT_NAME .. ": override_toe_brakes enabled")
    end

    logMsg(SCRIPT_NAME .. ": enabled for " .. tostring(AIRCRAFT_FILENAME))
else
    enabled = false
    logMsg(SCRIPT_NAME .. ": disabled for " .. tostring(AIRCRAFT_FILENAME))
end

------------------------------------------------------------
-- Helpers
------------------------------------------------------------

local function clamp(value, min_value, max_value)
    return math.max(min_value, math.min(max_value, value))
end

local function set_both_brakes(ratio)
    brake_ratio = clamp(ratio, 0.0, 1.0)

    left_brake_ratio_dref = brake_ratio
    right_brake_ratio_dref = brake_ratio
end

------------------------------------------------------------
-- Command callbacks
------------------------------------------------------------

function progressive_brakes_start()
    if not enabled then return end

    local now = total_running_time_sec
    local is_double_tap = (now - last_release_time) <= DOUBLE_TAP_WINDOW

    if is_double_tap then
        -- Second press within the double-tap window:
        -- hold the current brake pressure while the button remains pressed.
        brake_hold_active = true
        brake_start_time = 0.0
        brake_release_time = 0.0
        brake_ratio_at_press = brake_ratio
        brake_ratio_at_release = 0.0

        set_both_brakes(brake_ratio)
        return
    end

    -- Normal press:
    -- start progressive braking from the current brake ratio.
    brake_hold_active = false
    brake_start_time = now
    brake_release_time = 0.0
    brake_ratio_at_press = brake_ratio
end

function progressive_brakes_held()
    if not enabled then return end
    if brake_hold_active then return end
    if brake_start_time == 0.0 then return end

    local elapsed = total_running_time_sec - brake_start_time
    local ratio = brake_ratio_at_press + elapsed / SECONDS_TO_FULL_BRAKE

    set_both_brakes(ratio)
end

function progressive_brakes_released()
    if not enabled then return end

    local now = total_running_time_sec
    last_release_time = now

    -- If the second press was holding the brakes,
    -- releasing the button releases the brakes normally.
    if brake_hold_active then
        brake_hold_active = false
    end

    brake_start_time = 0.0
    brake_release_time = now
    brake_ratio_at_release = brake_ratio
end

------------------------------------------------------------
-- Per-frame update
------------------------------------------------------------

function progressive_brakes_update()
    if not enabled then return end
    if brake_hold_active then return end
    if brake_release_time == 0.0 then return end

    local elapsed = total_running_time_sec - brake_release_time
    local ratio = brake_ratio_at_release - elapsed / SECONDS_TO_RELEASE

    set_both_brakes(ratio)

    if ratio <= 0.0 then
        brake_release_time = 0.0
        brake_ratio_at_release = 0.0
    end
end

------------------------------------------------------------
-- FlyWithLua command
------------------------------------------------------------

create_command(
    "neucoas/single_button_brake",
    "Single button brake",
    "progressive_brakes_start()",
    "progressive_brakes_held()",
    "progressive_brakes_released()"
)

do_every_frame("progressive_brakes_update()")