【界面UI】进度条动画：经验条的增长缓动

---经验条的缓动推进
ExpBar = { cur = 0, target = 0, bar = nil }

function ExpBar.bind(node)
    ExpBar.bar = GUI:LoadingBar_Create(node, "exp", 0, 0)
    GUI:LoadingBar_setType(ExpBar.bar, 0)
    GUI:LoadingBar_setPercent(ExpBar.bar, 0)
    SL:Schedule(0.033, function() ExpBar.tick() end)
end

---目标值更新：只记终点，动画追赶
function ExpBar.setTarget(pct)
    ExpBar.target = pct
end

---每帧缓动：cubic 出减速入
function ExpBar.tick()
    local diff = ExpBar.target - ExpBar.cur
    if math.abs(diff) < 0.1 then
        ExpBar.cur = ExpBar.target
    else
        ExpBar.cur = ExpBar.cur + diff * 0.12
    end
    GUI:LoadingBar_setPercent(ExpBar.bar, ExpBar.cur)
end

---升级瞬间的满条闪烁
function ExpBar.onLevelUp()
    GUI:LoadingBar_setPercent(ExpBar.bar, 100)
    SL:PlayAudio(1030)
    SL:ShowSystemTips("等级提升！")
    ExpBar.cur = 0
    ExpBar.target = 0
end

---经验加成的浮动提示
function ExpBar.showGain(amount)
    local txt = GUI:Text_Create(ExpBar.node, "gain",
        ExpBar.barW / 2, -16, 12, "#7CFC00",
        "+" .. amount)
    SL:Schedule(1.0, function()
        GUI:removeNode(txt)
    end)
end