gistfile1.lua

local filters = {
    {"No Filter", ""},
    {"Bilinear Filter", "bilinear_filter"},
    {"Trilinear Filter", "trilinear_filter"},
}

<snip>

function getFilterSettingIndex()
     for i in ipairs(filters) do
         print("I==" .. i)
         if i > 1 then -- no filter is default
             print("checking for: " .. filters[i][2])
             if core.setting_getbool(filters[i][2]) then
                 print(" returning index: " .. i)
                 return i
             end
         end
     end
     print("no setting found, defaulting to 1")
     return 1
end

<snip>

  tab_string = tab_string ..            
            "dropdown[3.86,0.2;3.75;dd_filters;" .. filters[1][1] .. "," .. filters[2][1] .. "," .. filters[3][1]
              .. ";" .. getFilterSettingIndex() .. "]"