【界面UI】列表虚拟化：千条聊天记录的流畅滚动实现

local rows = {}
local ITEM_H = 24
local VISIBLE = 15
local function initList(parent)
    for i = 1, VISIBLE do
        rows[i] = GUI:RichText_Create(parent, "Row" .. i, 0, (i - 1) * ITEM_H, "", 340, 12, "#E8E8E8", 2, nil, "")
    end
end
local function updateVisible(scrollOffset)
    local startIdx = math.floor(scrollOffset / ITEM_H) + 1
    for i = 1, VISIBLE do
        local dataIdx = startIdx + i - 1
        local item = mailData[dataIdx]
        if item then
            GUI:setText(rows[i].label, item.title)
        else
            GUI:setText(rows[i].label, "")
        end
    end
end

local lastOffset = -1
local function onScroll(offset)
    if math.abs(offset - lastOffset) < ITEM_H / 2 then return end
    lastOffset = offset
    updateVisible(offset)
end