画质设置：画质档位的切换与预览

-- 错误：两档一刀切，高低配两头挨投诉
function setQuality(high)
    setFx(high and 2 or 0)
end

local QUALITY = {
    low  = {fx = 0, shadow = false, scale = 0.8},
    mid  = {fx = 1, shadow = false, scale = 1},
    high = {fx = 2, shadow = true,  scale = 1},
}
local function applyQuality(name)
    local q = QUALITY[name]
    if q == nil then return end
    setFxLevel(q.fx)
    setShadow(q.shadow)
    setRenderScale(q.scale)
    saveSetting("quality", name)
end