gear/timer.lua

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--- Timer utilities.
--
-- This is a reworked implementation of the original timer module
-- from the hump library (https://github.com/vrld/hump).
-- See README.ACKNOWLEDGEMENT for detailed information.
--
-- It offers functionality to schedule tasks for delayed or periodic
-- execution, as well as tweening.
--
-- @module gear.timer
-- @copyright 2010-2013 Matthias Richter
-- @copyright 2022 The DoubleFourteen Code Forge
-- @author Matthias Richter, Lorenzo Cogotti
local Timer = {}
Timer.__index = Timer
local function _nothing_() end
local function updateTimerHandle(handle, dt)
-- handle: {
-- time = <number>,
-- after = <function>,
-- during = <function>,
-- limit = <number>,
-- count = <number>,
-- }
handle.time = handle.time + dt
handle.during(dt, math.max(handle.limit - handle.time, 0))
while handle.time >= handle.limit and handle.count > 0 do
if handle.after(handle.after) == false then
handle.count = 0
break
end
handle.time = handle.time - handle.limit
handle.count = handle.count - 1
end
end
function Timer:update(dt)
-- timers may create new timers, which leads to undefined behavior
-- in pairs() - so we need to put them in a different table first
local to_update = {}
for handle in pairs(self.functions) do
to_update[handle] = handle
end
for handle in pairs(to_update) do
if self.functions[handle] then
updateTimerHandle(handle, dt)
if handle.count == 0 then
self.functions[handle] = nil
end
end
end
end
function Timer:during(delay, during, after)
local handle = {
time = 0,
during = during,
after = after or _nothing_,
limit = delay,
count = 1
}
self.functions[handle] = true
return handle
end
function Timer:after(delay, func)
return self:during(delay, _nothing_, func)
end
function Timer:every(delay, after, count)
local count = count or math.huge -- exploit below: math.huge - 1 = math.huge
local handle = {
time = 0,
during = _nothing_,
after = after,
limit = delay,
count = count
}
self.functions[handle] = true
return handle
end
function Timer:cancel(handle)
self.functions[handle] = nil
end
function Timer:clear()
self.functions = {}
end
function Timer:script(f)
local co = coroutine.wrap(f)
co(function(t)
self:after(t, co)
coroutine.yield()
end)
end
Timer.tween = setmetatable({
-- helper functions
out = function(f) -- 'rotates' a function
return function(s, ...) return 1 - f(1-s, ...) end
end,
chain = function(f1, f2) -- concatenates two functions
return function(s, ...) return (s < .5 and f1(2*s, ...) or 1 + f2(2*s-1, ...)) * .5 end
end,
-- useful tweening functions
linear = function(s) return s end,
quad = function(s) return s*s end,
cubic = function(s) return s*s*s end,
quart = function(s) return s*s*s*s end,
quint = function(s) return s*s*s*s*s end,
sine = function(s) return 1-math.cos(s*math.pi/2) end,
expo = function(s) return 2^(10*(s-1)) end,
circ = function(s) return 1 - math.sqrt(1-s*s) end,
back = function(s,bounciness)
bounciness = bounciness or 1.70158
return s*s*((bounciness+1)*s - bounciness)
end,
bounce = function(s) -- magic numbers ahead
local a,b = 7.5625, 1/2.75
return math.min(a*s^2, a*(s-1.5*b)^2 + .75, a*(s-2.25*b)^2 + .9375, a*(s-2.625*b)^2 + .984375)
end,
elastic = function(s, amp, period)
amp, period = amp and math.max(1, amp) or 1, period or .3
return (-amp * math.sin(2*math.pi/period * (s-1) - math.asin(1/amp))) * 2^(10*(s-1))
end,
}, {
-- register new tween
__call = function(tween, self, len, subject, target, method, after, ...)
-- recursively collects fields that are defined in both subject and target into a flat list
local function tween_collect_payload(subject, target, out)
for k,v in pairs(target) do
local ref = subject[k]
assert(type(v) == type(ref), 'Type mismatch in field "'..k..'".')
if type(v) == 'table' then
tween_collect_payload(ref, v, out)
else
local ok, delta = pcall(function() return (v-ref)*1 end)
assert(ok, 'Field "'..k..'" does not support arithmetic operations')
out[#out+1] = {subject, k, delta}
end
end
return out
end
method = tween[method or 'linear'] -- see __index
local payload, t, args = tween_collect_payload(subject, target, {}), 0, {...}
local last_s = 0
return self:during(len, function(dt)
t = t + dt
local s = method(math.min(1, t/len), unpack(args))
local ds = s - last_s
last_s = s
for _, info in ipairs(payload) do
local ref, key, delta = unpack(info)
ref[key] = ref[key] + delta * ds
end
end, after)
end,
-- fetches function and generated compositions for method `key`
__index = function(tweens, key)
if type(key) == 'function' then return key end
assert(type(key) == 'string', 'Method must be function or string.')
if rawget(tweens, key) then return rawget(tweens, key) end
local function construct(pattern, f)
local method = rawget(tweens, key:match(pattern))
if method then return f(method) end
return nil
end
local out, chain = rawget(tweens,'out'), rawget(tweens,'chain')
return construct('^in%-([^-]+)$', function(...) return ... end)
or construct('^out%-([^-]+)$', out)
or construct('^in%-out%-([^-]+)$', function(f) return chain(f, out(f)) end)
or construct('^out%-in%-([^-]+)$', function(f) return chain(out(f), f) end)
or error('Unknown interpolation method: ' .. key)
end})
-- Timer instancing
function Timer.new()
return setmetatable({functions = {}, tween = Timer.tween}, Timer)
end
return Timer