【界面UI】Tab 页切换：页签懒加载与状态保持

---页签容器：切换时才构建页面
local Panel = { tabs = {}, pages = {}, built = {} }

function Panel.init(win, defs)
    for i, d in ipairs(defs) do
        local btn = GUI:Button_Create(win, "tab_" .. d.key,
            10 + (i - 1) * 80, 10)
        GUI:Button_setTitleText(btn, d.title)
        GUI:addOnClickEvent(btn, function()
            Panel.switch(d.key)
        end)
        Panel.tabs[d.key] = btn
    end
    Panel.defs = defs
end

function Panel.switch(key)
    local page = Panel.pages[key]
    if not page and not Panel.built[key] then
        for _, d in ipairs(Panel.defs) do
            if d.key == key then
                page = d.build()      -- 首次进入才构建
                Panel.pages[key] = page
                Panel.built[key] = true
            end
        end
    end
    Panel.showOnly(key)
end

---页面隐藏而非销毁：滚动与输入状态保留
function Panel.showOnly(key)
    for k, page in pairs(Panel.pages) do
        GUI:setVisible(page, k == key)
    end
end

---数据变更的页面标记脏，回切时刷新
function Panel.dirty(key)
    Panel.dirtySet[key] = true
end

function Panel.switch(key)
    -- ... 懒加载逻辑 ...
    if Panel.dirtySet[key] then
        Panel.reloadPage(key)
        Panel.dirtySet[key] = nil
    end
    Panel.showOnly(key)
end