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- Committer: Josh C
- Date: 2013-04-23 15:22:15 UTC
- Revision ID: josh@9ix.org-20130423152215-hacpxl91eiiq2ras
zoetrope 1.4
- files added:
- zoetrope
- zoetrope/core
- zoetrope/input
- zoetrope/sprites
- zoetrope/ui
- zoetrope/utils
added
removed
zoetrope/core/tween.lua
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-- Class: Tween
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-- A tween transitions a property from one state to another
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-- in in-game time. A tween instance is designed to manage
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-- many of these transitions at once, in fact. In order for it
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-- to work properly, it must receive update events, so it must
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-- be added somewhere in the current view or app. If you are using
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-- the <View> class, this is already done for you.
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Tween = Sprite:extend{
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tweens = {},
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visible = false,
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active = false,
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solid = false,
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-- Property: easers
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-- These are different methods of easing a tween, and
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-- can be set via the ease property of an individual tween.
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-- They should be referred to by their key name, not the property
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-- (e.g. 'linear', no Tweener.easers.linear).
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-- See http://www.gizma.com/easing/ for details.
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easers =
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{
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linear = function (elapsed, start, change, duration)
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return change * elapsed / duration + start
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end,
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quadIn = function (elapsed, start, change, duration)
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elapsed = elapsed / duration
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return change * elapsed * elapsed + start
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end,
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quadOut = function (elapsed, start, change, duration)
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elapsed = elapsed / duration
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return - change * elapsed * (elapsed - 2) + start
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end,
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quadInOut = function (elapsed, start, change, duration)
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elapsed = elapsed / (duration / 2)
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if (elapsed < 1) then
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return change / 2 * elapsed * elapsed + start
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else
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elapsed = elapsed - 1
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return - change / 2 * (elapsed * (elapsed - 2) - 1) + start
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end
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end
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},
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-- Method: reverseForever
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-- A utility function; if set via <Promise.andAfter()> for an individual
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-- tween, it reverses the tween that just happened. Use this to get a tween
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-- to repeat back and forth indefinitely (e.g. to have something glow).
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reverseForever = function (tween, tweener)
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tween.to = tween.from
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tweener:start(tween.target, tween.property, tween.to, tween.duration, tween.ease):andThen(Tween.reverseForever)
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end,
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-- Method: reverseOnce
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-- A utility function; if set via <Promise.andAfter()> for an individual
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-- tween, it reverses the tween that just happened-- then stops the tween after that.
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reverseOnce = function (tween, tweener)
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tween.to = tween.from
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tweener:start(tween.target, tween.property, tween.to, tween.duration, tween.ease)
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end,
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-- Method: start
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-- Begins a tweened transition, overriding any existing tween.
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--
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-- Arguments:
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-- target - target object
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-- property - Usually, this is a string name of a property of the target object.
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-- You may also specify a table of getter and setter methods instead,
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-- i.e. { myGetter, mySetter }. In either case, the property or functions
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-- must work with either number values, or tables of numbers.
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-- to - destination value, either number or color table
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-- duration - how long the tween should last in seconds, default 1
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-- ease - function name (in Tween.easers) to use to control how the value changes, default 'linear'
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--
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-- Returns:
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-- A <Promise> that is fulfilled when the tween completes. If the object is already
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-- in the state requested, the promise resolves immediately. The tween object returns two
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-- things to the promise: a table of properties about the tween that match the arguments initially
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-- passed, and a reference to the Tween that completing the tween.
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start = function (self, target, property, to, duration, ease)
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duration = duration or 1
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ease = ease or 'linear'
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local propType = type(property)
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if STRICT then
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assert(type(target) == 'table' or type(target) == 'userdata', 'target must be a table or userdata')
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assert(propType == 'string' or propType == 'number' or propType == 'table', 'property must be a key or table of getter/setter methods')
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if propType == 'string' or propType == 'number' then
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assert(target[property], 'no such property ' .. tostring(property) .. ' on target')
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end
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assert(type(duration) == 'number', 'duration must be a number')
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assert(self.easers[ease], 'easer ' .. ease .. ' is not defined')
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end
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-- check for an existing tween for this target and property
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for i, existing in ipairs(self.tweens) do
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if target == existing.target and property == existing.property then
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if to == existing.to then
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return existing.promise
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else
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table.remove(self.tweens, i)
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end
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end
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end
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-- add it
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tween = { target = target, property = property, propType = propType, to = to, duration = duration, ease = ease }
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tween.from = self:getTweenValue(tween)
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tween.type = type(tween.from)
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-- calculate change; if it's trivial, skip the tween
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if tween.type == 'number' then
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tween.change = tween.to - tween.from
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if math.abs(tween.change) < NEARLY_ZERO then
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return Promise:new{ state = 'fulfilled', _resolvedWith = { tween, self } }
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end
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elseif tween.type == 'table' then
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tween.change = {}
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local skip = true
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for i, value in ipairs(tween.from) do
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tween.change[i] = tween.to[i] - tween.from[i]
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if math.abs(tween.change[i]) > NEARLY_ZERO then
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skip = false
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end
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end
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if skip then
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return Promise:new{ state = 'fulfilled', _resolvedWith = { tween, self } }
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end
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else
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error('tweened property must either be a number or a table of numbers, is ' .. tween.type)
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end
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tween.elapsed = 0
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tween.promise = Promise:new()
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table.insert(self.tweens, tween)
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self.active = true
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return tween.promise
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end,
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-- Method: status
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-- Returns how much time is left for a particular tween to run.
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--
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-- Arguments:
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-- target - target object
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-- property - name of the property being tweened, or getter
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-- (as set in the orignal <start()> call)
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--
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-- Returns:
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-- Either the time left in the tween, or nil if there is
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-- no tween matching the arguments passed.
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status = function (self, target, property)
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for _, t in pairs(self.tweens) do
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if t.target == target then
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if t.property == property or (type(t.property) == 'table' and t.property[1] == property) then
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return t.duration - t.elapsed
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end
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end
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end
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return nil
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end,
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-- Method: stop
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-- Stops a tween. The promise associated with it will be failed.
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--
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-- Arguments:
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-- target - tween target
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-- property - name of property being tweened, or getter (as set in the original <start()> call);
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-- if omitted, stops all tweens on the target
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--
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-- Returns:
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-- nothing
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stop = function (self, target, property)
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local found = false
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for i, tween in ipairs(self.tweens) do
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if tween.target == target and (tween.property == property or
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(type(tween.property) == 'table' and tween.property[1] == property) or
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not property) then
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found = true
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tween.promise:fail('Tween stopped')
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table.remove(self.tweens, i)
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end
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end
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if STRICT and not found then
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local info = debug.getinfo(2, 'Sl')
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print('Warning: asked to stop a tween, but no active tweens match it (' ..
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info.short_src .. ', line ' .. info.currentline .. ')')
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end
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end,
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update = function (self, elapsed)
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for i, tween in ipairs(self.tweens) do
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self.active = true
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tween.elapsed = tween.elapsed + elapsed
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if tween.elapsed >= tween.duration then
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-- tween is completed
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self:setTweenValue(tween, tween.to)
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table.remove(self.tweens, i)
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tween.promise:fulfill(tween, self)
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else
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-- move tween towards finished state
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if tween.type == 'number' then
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self:setTweenValue(tween, self.easers[tween.ease](tween.elapsed,
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tween.from, tween.change, tween.duration))
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elseif tween.type == 'table' then
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local now = {}
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for i, value in ipairs(tween.from) do
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now[i] = self.easers[tween.ease](tween.elapsed, tween.from[i],
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tween.change[i], tween.duration)
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end
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self:setTweenValue(tween, now)
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end
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end
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end
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self.active = (#self.tweens > 0)
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end,
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getTweenValue = function (self, tween)
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if tween.propType == 'string' or tween.propType == 'number' then
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return tween.target[tween.property]
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else
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return tween.property[1](tween.target)
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end
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end,
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setTweenValue = function (self, tween, value)
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if tween.propType == 'string' or tween.propType == 'number' then
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tween.target[tween.property] = value
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else
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tween.property[2](tween.target, value)
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end
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end,
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__tostring = function (self)
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local result = 'Tween ('
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if self.active then
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result = result .. 'active, '
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result = result .. #self.tweens .. ' tweens running'
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else
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result = result .. 'inactive'
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end
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return result .. ')'
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end
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}
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