【界面UI】图标系统：道具图标的合图与加载

---图标合图：散图打进图集
function IconAtlas.build(sourceDir, outputFile)
    local icons = IconAtlas.scan(sourceDir)
    local atlas = AtlasPacker.new(1024, 1024)
    for _, icon in ipairs(icons) do
        atlas:add(icon.name, icon.path)
    end
    atlas:pack()
    atlas:save(outputFile)
    Ops.log('合图完成: ' .. #icons .. ' 个图标')
end

---图标加载：从合图裁切显示
function IconAtlas.get(iconName)
    local info = IconAtlas.mapping[iconName]
    if not info then
        return IconAtlas.fallback()
    end
    local sprite = AtlasSprite.new(IconAtlas.texture,
        info.x, info.y, info.w, info.h)
    return sprite
end

---缺省图标的兜底
function IconAtlas.fallback()
    return AtlasSprite.new(IconAtlas.texture,
        IconAtlas.defaultX, IconAtlas.defaultY, 32, 32)
end