[HELP] Why not working this code with isElementOnScreen() argument?

[Turbesz]

local startTime = getTickCount() 
function ColorMarker() 
    for _,v in pairs(getElementsByType("marker", root, true)) do 
        if getElementData(v,"rgb") == true and isElementOnScreen(v) then 
            local progress = math.fmod(getTickCount() - startTime, 10000) / 10000 
            local length = interpolateBetween(400, 0, 0, 700, 0, 0, progress, "Linear") 
            local r, g, b = wavelengthToRGBA(length) 
            setMarkerColor(v, r, g, b, 100) 
        end 
    end 
end 
addEventHandler("onClientPreRender", getRootElement(), ColorMarker) 

if i remove that argument, the script works fine. but i think without that can cause lag with many players.

there is no errors and warnings in debugscript, then what wrong?  

Edited December 8, 2020 by Turbesz

[Patrick]

Hi. I think this function still not works with markers.