A strip of live coin prices sits on top of every app, windowed and borderless games included. Press F7 to hide it or bring it back. Press F8 for a menu where you can refresh, open a coin, and set an alert that pops up when its price crosses a line.

Prices come from CoinGecko, with each coin's change over the last 24 hours in green or red.

Needs Rebind 3.11.1 or newer on Windows or macOS. It requests network access to api.coingecko.com only, and it never reads the screen.

Set up

Put the coins you want in Coins, separated by commas. Each name is the CoinGecko id: the last part of the coin's address on coingecko.com, such as bitcoin for coingecko.com/en/coins/bitcoin. A name CoinGecko does not know, or one with characters other than letters, digits, and hyphens, shows up in the strip after unknown:.

Use

F7 hides the strip or shows it again.
F8 opens the menu. Press a number, or move with Up and Down and press Enter. Escape closes it. While the menu is open, those keys go to the menu only.

In the menu, pick a coin to set an alert 1 or 5 percent above or below its current price, or to remove one you set. When the price crosses an alert, a notice shows the new price for 10 seconds and Rebind beeps. The alert is then gone. Alerts are kept when the script restarts, and each one belongs to the currency it was set in.

The menu can also hide or show the strip, refresh the prices right away, and clear every alert at once.

Settings

Open the menu and Show or hide the ticker: the two hotkeys.
Coins: the CoinGecko ids to show, in order.
Currency: USD, EUR, GBP, JPY, CAD, AUD, or CHF.
Refresh every: 30 seconds to 10 minutes, 60 seconds by default.
Position: top or bottom of the screen, centered or in a corner.
Theme: the colors of the strip, menu, and notices.
Beep on alerts: turn the sound off and keep the notice.

Limits

CoinGecko's free API limits how often one address can ask. When it does, the strip says so and the next refresh tries again. It says offline when CoinGecko does not answer.
A game in exclusive full-screen mode on Windows hides the strip, the menu, and notices. An alert that fires meanwhile still beeps, and its notice waits up to a minute to appear.
The strip shows the price from the last refresh, not every trade.
Live use remains unverified on Windows and macOS.

Stop

Stop the package from the editor toolbar, or press Left Ctrl + Left Alt + K to stop all scripts.

Version 0.1.0 (current)

main.luau

-- Crypto Ticker: a strip of live CoinGecko prices over every app, a hotkey to
-- show or hide it, and a menu to refresh, pick a coin and set price alerts
-- that pop up as a notice when the price crosses them.

local CURRENCIES = { "USD", "EUR", "GBP", "JPY", "CAD", "AUD", "CHF" }
local POSITIONS = {
  "top",
  "top-left",
  "top-right",
  "bottom",
  "bottom-left",
  "bottom-right",
}
local THEMES =
  { "rebind", "rebind-light", "catppuccin", "tokyo-night", "contrast" }

local cfg = rb.ui.schema({
  menu_key = rb.ui.keybind("F8", { label = "Open the menu" }),
  toggle_key = rb.ui.keybind("F7", { label = "Show or hide the ticker" }),
  coins = rb.ui.text("bitcoin, ethereum, solana", {
    label = "Coins",
    tooltip = "CoinGecko ids, separated by commas: the end of a coin's page address on coingecko.com",
  }),
  currency = rb.ui.select("USD", CURRENCIES, { label = "Currency" }),
  refresh = rb.ui.slider(60, {
    label = "Refresh every",
    min = 30,
    max = 600,
    step = 30,
    suffix = " s",
  }),
  position = rb.ui.select("top", POSITIONS, { label = "Position" }),
  theme = rb.ui.select("rebind", THEMES, { label = "Theme" }),
  beep = rb.ui.toggle(true, { label = "Beep on alerts" }),
})

local API =
  "https://api.coingecko.com/api/v3/coins/markets?vs_currency=%s&ids=%s"
-- CoinGecko refuses a request without a User-Agent with 403
local REQUEST = {
  headers = { ["User-Agent"] = "Rebind Crypto Ticker" },
  timeout = 10000,
}
-- hidden, so a packed copy of the package never carries someone's alerts
local ALERTS_FILE = ".alerts.json"
local SYMBOLS = { USD = "$", EUR = "€", GBP = "£", JPY = "¥" }

-- { id, symbol, name, price, change }, in the order of cfg.coins
local coins = {}
-- shown after the prices while something is wrong
local note = "loading"
local updated = nil
local shown = true
local wake = false
local strip, strip_key = nil, nil
-- { id, symbol, currency, above, price }
local alerts = {}

local function money(price)
  local sign = SYMBOLS[cfg.currency] or (cfg.currency .. " ")
  if price >= 1000 then
    local reversed = string.reverse(tostring(math.floor(price + 0.5)))
    local grouped = string.reverse((string.gsub(reversed, "(%d%d%d)", "%1,")))
    return sign .. (string.gsub(grouped, "^,", ""))
  elseif price >= 1 then
    return sign .. string.format("%.2f", price)
  elseif price <= 0 then
    return sign .. "0"
  end
  -- four significant digits (0.5123, 0.00000488), trailing zeros dropped
  -- past the second decimal
  local decimals = math.min(3 - math.floor(math.log10(price)), 12)
  local text = string.format("%." .. decimals .. "f", price)
  return sign .. (string.gsub(text, "(%.%d%d%d-)0+$", "%1"))
end

local function percent(change)
  if type(change) ~= "number" then
    return { "", "faint" }
  end
  local arrow = if change >= 0 then "▲" else "▼"
  local role = if change >= 0 then "positive" else "danger"
  return { string.format("%s%.1f%%", arrow, math.abs(change)), role }
end

-- the CoinGecko ids in cfg.coins, and the entries that cannot be one
local function ids()
  local list, bad = {}, {}
  for _, part in string.split(cfg.coins, ",") do
    local id = string.lower((string.gsub(part, "%s", "")))
    if string.match(id, "^[%w%-]+$") then
      table.insert(list, id)
    elseif id ~= "" then
      table.insert(bad, id)
    end
  end
  return list, bad
end

-- strip ------------------------------------------------------------------

local function draw()
  if not shown then
    if strip then
      strip.remove()
      strip = nil
    end
    return
  end
  local spans = {}
  for i, c in coins do
    if i > 1 then
      table.insert(spans, { "   " })
    end
    table.insert(spans, { string.upper(c.symbol) .. " ", "dim" })
    table.insert(spans, { money(c.price) .. " ", "text", true })
    table.insert(spans, percent(c.change))
  end
  if note then
    local gap = if #coins > 0 then "   " else ""
    table.insert(spans, { gap .. note, "faint" })
  end
  -- position and theme are fixed when a strip is made: a change needs a new one
  local key = cfg.position .. "/" .. cfg.theme
  if strip and strip_key ~= key then
    strip.remove()
    strip = nil
  end
  -- a strip too wide for an overlay keeps its last state instead of
  -- stopping the price loop
  local ok, err = pcall(function()
    if strip then
      strip.set(spans)
    else
      strip =
        rb.overlay.status(spans, { anchor = cfg.position, theme = cfg.theme })
      strip_key = key
    end
  end)
  if not ok then
    rb.log.warn("could not draw the ticker: " .. tostring(err))
  end
end

-- notices go top-right, below the strip when it sits there too
local function notice(text, options)
  options.theme = cfg.theme
  if cfg.position == "top-right" then
    options.offset_y = 56
  end
  local ok, err = pcall(rb.overlay.toast, text, options)
  if not ok then
    rb.log.warn("could not show a notice: " .. tostring(err))
  end
end

-- alerts -----------------------------------------------------------------

local function save_alerts()
  local ok, err = pcall(rb.file.write_json, ALERTS_FILE, alerts)
  if not ok then
    rb.log.warn("could not save alerts: " .. tostring(err))
  end
end

local function load_alerts()
  if not rb.file.exists(ALERTS_FILE) then
    return
  end
  local ok, saved = pcall(rb.file.read_json, ALERTS_FILE)
  if not ok or type(saved) ~= "table" then
    return
  end
  -- an edited or damaged file keeps only the entries that are whole
  for _, a in saved do
    if
      type(a) == "table"
      and type(a.id) == "string"
      and type(a.symbol) == "string"
      and type(a.currency) == "string"
      and type(a.above) == "boolean"
      and type(a.price) == "number"
    then
      table.insert(alerts, a)
    end
  end
end

local function remove_alert(a)
  local i = table.find(alerts, a)
  if i then
    table.remove(alerts, i)
    save_alerts()
  end
end

-- alerts for coin `id` in the current currency
local function alerts_for(id)
  local list = {}
  for _, a in alerts do
    if a.id == id and a.currency == cfg.currency then
      table.insert(list, a)
    end
  end
  return list
end

local function crossed(a, price)
  if a.above then
    return price >= a.price
  end
  return price <= a.price
end

local function check_alerts()
  local by_id = {}
  for _, c in coins do
    by_id[c.id] = c
  end
  local fired = {}
  for i = #alerts, 1, -1 do
    local a = alerts[i]
    local c = by_id[a.id]
    if c and a.currency == cfg.currency and crossed(a, c.price) then
      table.remove(alerts, i)
      table.insert(fired, { alert = a, coin = c })
    end
  end
  if #fired == 0 then
    return
  end
  -- saved first, so an alert never fires twice
  save_alerts()
  for _, f in fired do
    local role = if f.alert.above then "positive" else "danger"
    local text = {
      { string.upper(f.alert.symbol) .. " ", "text", true },
      { money(f.coin.price), role, true },
    }
    local verb = if f.alert.above then "rose above " else "fell below "
    notice(text, {
      title = "Price alert",
      meta = verb .. money(f.alert.price),
      duration = 10000,
    })
  end
  if cfg.beep then
    rb.audio.beep()
  end
end

-- prices -----------------------------------------------------------------

-- the coins CoinGecko knew, in the order asked for, and the ids it did not
local function read_rows(data, wanted)
  local by_id = {}
  for _, row in data do
    if
      type(row) == "table"
      and type(row.id) == "string"
      and type(row.current_price) == "number"
    then
      by_id[row.id] = row
    end
  end
  local found, missing = {}, {}
  for _, id in wanted do
    local row = by_id[id]
    if row then
      -- a JSON null is not nil in Luau, so test the type
      table.insert(found, {
        id = id,
        symbol = if type(row.symbol) == "string" then row.symbol else id,
        name = if type(row.name) == "string" then row.name else id,
        price = row.current_price,
        change = row.price_change_percentage_24h,
      })
    else
      table.insert(missing, id)
    end
  end
  return found, missing
end

local function refresh()
  local wanted, bad = ids()
  if #wanted == 0 then
    coins = {}
    note = if #bad > 0
      then "unknown: " .. table.concat(bad, ", ")
      else "add coins in the settings"
    draw()
    return
  end
  local currency = string.lower(cfg.currency)
  local url = string.format(API, currency, table.concat(wanted, ","))
  local ok, res = pcall(rb.net.get, url, REQUEST)
  if not ok then
    note = "offline"
    rb.log.warn("CoinGecko did not answer: " .. tostring(res))
  elseif res.status == 429 then
    note = "CoinGecko is limiting requests"
  elseif res.status ~= 200 then
    note = "CoinGecko answered " .. res.status
  else
    local parsed, data = pcall(rb.json.parse, res.body)
    if not parsed or type(data) ~= "table" then
      note = "CoinGecko sent something unreadable"
    else
      local found, missing = read_rows(data, wanted)
      for _, id in bad do
        table.insert(missing, id)
      end
      coins = found
      updated = os.date("%H:%M")
      note = nil
      if #missing > 0 then
        note = "unknown: " .. table.concat(missing, ", ")
      end
      check_alerts()
    end
  end
  draw()
end

-- menu -------------------------------------------------------------------

local open_main

local function open_coin(c)
  local items = {}
  for _, step in { 1, 5, -1, -5 } do
    local target = c.price * (1 + step / 100)
    local verb = if step > 0 then "Alert above " else "Alert below "
    table.insert(items, {
      label = verb .. money(target),
      hint = string.format("%+d%%", step),
      action = function()
        table.insert(alerts, {
          id = c.id,
          symbol = c.symbol,
          currency = cfg.currency,
          above = step > 0,
          price = target,
        })
        save_alerts()
        local text = "Alert set for "
          .. string.upper(c.symbol)
          .. " at "
          .. money(target)
        notice(text, {})
      end,
    })
  end
  for _, a in alerts_for(c.id) do
    local side = if a.above then "above " else "below "
    table.insert(items, {
      label = "Remove " .. side .. money(a.price),
      action = function()
        remove_alert(a)
      end,
    })
  end
  table.insert(items, {
    label = "Back",
    action = function()
      open_main()
    end,
  })
  local menu, why = rb.overlay.menu(items, {
    title = string.upper(c.symbol),
    subtitle = c.name .. "  " .. money(c.price),
    theme = cfg.theme,
  })
  if not menu then
    rb.log.warn("no menu: " .. why)
  end
end

open_main = function()
  local items = {}
  for _, c in coins do
    local count = #alerts_for(c.id)
    local hint = nil
    if count > 0 then
      hint = count .. (if count == 1 then " alert" else " alerts")
    end
    table.insert(items, {
      label = string.upper(c.symbol) .. "  " .. money(c.price),
      hint = hint,
      action = function()
        open_coin(c)
      end,
    })
  end
  table.insert(items, {
    label = if shown then "Hide the ticker" else "Show the ticker",
    action = function()
      shown = not shown
      draw()
    end,
  })
  table.insert(items, {
    label = "Refresh now",
    action = function()
      wake = true
    end,
  })
  if #alerts > 0 then
    table.insert(items, {
      label = "Clear every alert",
      hint = tostring(#alerts),
      action = function()
        alerts = {}
        save_alerts()
      end,
    })
  end
  local menu, why = rb.overlay.menu(items, {
    title = "Crypto Ticker",
    subtitle = note or (if updated then "updated " .. updated else ""),
    theme = cfg.theme,
  })
  if not menu then
    rb.log.warn("no menu: " .. why)
  end
end

rb.bind(cfg.menu_key, function()
  open_main()
end)

rb.bind(cfg.toggle_key, function()
  shown = not shown
  draw()
end)

rb.on("start", function()
  load_alerts()
  draw()
  rb.run(function()
    while true do
      refresh()
      local waited = 0
      while waited < cfg.refresh * 1000 and not wake do
        rb.sleep(250)
        waited += 250
      end
      wake = false
    end
  end)
end)

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