local glBeginEnd = gl.BeginEnd
local glColor = gl.Color
local glLineWidth = gl.LineWidth
local glVertex = gl.Vertex
local glRect = gl.Rect
local GL_LINES = GL.LINES
-- remember to repositionate everything using gl.Translate where you want before calling this code!
local horizontalDivisions = 10 -- 10 main divisions
local verticalDivisions = 8 -- 8 main divisions
local cellSideSize = 10 -- division size, in pixel ( you should use a number divisible by 5, for subdivisions! )
local horizontalSize = horizontalDivisions * cellSideSize
local verticalSize = verticalDivisions * cellSideSize
local oscopeBackground = glCreateList( function()
   glColor(0.5, 1.0, 0.5, 0.3)
   glLineWidth(1.0)
   glRect( 0, 0, horizontalSize, verticalSize ) -- draw faint green background
   glColor(0.0, 0.5, 0.0, 0.5) --darker grid
   glLineWidth(0.8)
   local horCount = 0
   while( horCount < (horizontalDivisions+1) ) do -- draw vertical lines
      glBeginEnd(GL_LINES, function()
         glVertex( horCount*cellSideSize, 0)
         glVertex( horCount*cellSideSize, verticalSize)
      end)
      horCount = horCount +1
   end
   local verCount = 0
   while( verCount < (verticalDivisions +1) ) do -- draw horizontal lines
      glBeginEnd(GL_LINES, function()
         glVertex( 0, verCount*cellSideSize)
         glVertex( horizontalSize, verCount*cellSideSize)
      end)
      verCount = verCount +1
   end
end)
local horizontalScale = 1
local verticalScale = 1
local centerPosition = verticalDivisions/2 * cellSideSize
local verticalGain = verticalScale*cellSideSize*verticalDivisions/2
local wavestream = { 0.1, 0.5, -0.3, 0.33  } -- index = sample index, content = value normalized between +-1
local kplogo = glCreateList( function()
   glColor(0.9, 1.0, 0.9, 1.0) -- bright line marks
   glLineWidth(1.5)
   --glSmoothing() --perhaps enable smoothing?
   local previousValue = 0
   for x,y in ipairs(wavestream) do
      local currentPos = (x*horizontalScale) % (horizontalSize)
      local previousPos = ((x-1)*horizontalScale) % (horizontalSize)
      if previousPos ~= (horizontalSize-1) then -- don't draw the line connecting end to begin
         glBeginEnd(GL_LINES, function()
            glVertex(previousPos, centerPosition + previousValue*verticalGain) -- draw a segment connecting to the previous sample
            glVertex(currentPos, centerPosition + y*verticalGain)
         end)
      end
      previousValue = y
   end
end)