Lua坐标换算：世界坐标与屏幕坐标的三次变换

flowchart LR
    A["格子坐标 gx, gy"] -- "gx*格宽 gy*格高" --> B["世界坐标 wx, wy"]
    B -- "wx*缩放 - 相机X" --> C["屏幕坐标 sx, sy"]
    C -- "绘制节点 setPosition" --> D["屏幕上的像素"]
    D -- "点击命中" --> E["屏幕坐标 click"]
    E -- "+相机偏移 ÷缩放" --> F["世界坐标"]
    F -- "÷格宽格高 取整" --> G["格子坐标"]
    G -.-> A

-- 世界坐标 → 屏幕坐标
function World2Screen(srcPos)
    local camera = global.Director:getRunningScene():getCamera()
    local zoom   = CalcCameraZoom(camera)          -- 当前相机缩放
    local visible = global.Director:getVisibleSize()
    local camX = camera:getPositionX() - visible.width  * 0.5 * zoom
    local camY = camera:getPositionY() - visible.height * 0.5 * zoom
    local pt = cc.p(srcPos.x * zoom - camX, srcPos.y * zoom - camY)
    return pt
end

-- 屏幕坐标 → 世界坐标(逆运算)
function Screen2World(srcPos)
    local camera = global.Director:getRunningScene():getCamera()
    local zoom   = CalcCameraZoom(camera)
    local visible = global.Director:getVisibleSize()
    local camX = camera:getPositionX() - visible.width  * 0.5 * zoom
    local camY = camera:getPositionY() - visible.height * 0.5 * zoom
    return cc.p((srcPos.x + camX) / zoom, (srcPos.y + camY) / zoom)
end

-- 格子 ⇄ 世界
function MapPos2WorldPos(gx, gy)
    return cc.p(gx * global.MMO.MAP_CELL_W, gy * global.MMO.MAP_CELL_H)
end