bgColor = -1 -- white

fontW, fontH = 16, 16

displayCols, displayRows = 40, 10

displayW, displayH = fontW*displayCols, fontH*displayRows

width, height = displayW, displayH

cursorBlinkRate = 500

--eventRate = 50

eventRate = 20 -- high speed!

eventsPerCursorBlink = cursorBlinkRate/eventRate

needsRepaint = false

repaintTriggeringVars = {"curX", "curY", "cursorVisible", "scrollX", "scrollY"}

fatCursor = true

-- volatile data

if not inited then

  scrollX, scrollY = 0, 0

  curX, curY = 0, 0

  lines = {"hello", "world"}

  needsRepaint = true

  inited = true

end

local min, max = math.min, math.max

get("#109") -- copyRect

fontRendererEnv = newCleanEnv()

fontRenderer = get("#178", fontRendererEnv)

grab("#175") -- tableToString

function renderText(x, y, s)

  --print("renderText", x, y, s)

  fontRendererEnv.render(s)

  --print("fontWidth="..tostring(fontRendererEnv.fontWidth))

  copyRect(fontRendererEnv, _G, 0, 0, fontRendererEnv.width, fontRendererEnv.height, x, y)

  --[[for y=0, 1 do

    for x=0, 15 do

      print(fontRendererEnv.pixels[x+y*fontRendererEnv.width+1])

    end

  end]]

end

function setPixel(x, y, col)

  if x >= 0 and y >= 0 and x < displayW and y < displayH then

    pixels[x+y*width+1] = col

  end

end

function invertPixel(x, y)

  if x >= 0 and y >= 0 and x < displayW and y < displayH then

    local ofs = x+y*width+1

    pixels[ofs] = pixels[ofs] and -1-pixels[ofs] or -1

  end

end

function stepCursor()

  if lastCurX ~= curX or lastCurY ~= curY then

    cursorCount = -1

  end

  lastCurX = curX

  lastCurY = curY

  cursorCount = (cursorCount+1) % (eventsPerCursorBlink*2)

  cursorVisible = cursorCount < eventsPerCursorBlink

end

function renderCursor()

  if cursorVisible then

    for x=0, fatCursor and fontW-1 or 0 do

      for y=0, fontH-1 do

        invertPixel((curX-scrollX)*fontW+x, (curY-scrollY)*fontH+y)

      end

    end

  end

end

function cursorLeft()

  if curX > 0 then

    curX=curX-1

  elseif curY > 0 then

    curY=curY-1

  end

end

function cursorRight()

  curX=curX+1

end

function cursorUp()

  if curY > 0 then

    curY=curY-1

  end

end

function cursorDown()

  if curY < #lines-1 then

    curY=curY+1

  end

end

function saveVars()

  savedVars = {}

  for _, var in ipairs(repaintTriggeringVars) do

    savedVars[var] = _G[var]

  end

end

function compareVars()

  for _, var in ipairs(repaintTriggeringVars) do

    if savedVars[var] ~= _G[var] then

      needsRepaint = true

      return

    end

  end

end

function moveCursorToSpot(x, y)

  local col = math.floor((x+scrollX)/fontW)

  local row = math.floor((y+scrollY)/fontH)

  row = max(0, min(row, #lines-1))

  col = max(0, col)

  curX, curY = col, row

end

function processEvents()

  saveVars()

  if inputEvents then

    for _, e in ipairs(inputEvents) do

      --print("event:", tableToString(e))

      if e[1] == 'keyPressed' then

        if e.keyCode == 39 then

          cursorRight()

        elseif e.keyCode == 37 then

          cursorLeft()

        elseif e.keyCode == 40 then

          cursorDown()

        elseif e.keyCode == 38 then

          cursorUp()

        end

      elseif e[1] == 'mousePressed' then

        moveCursorToSpot(e.x, e.y)

      end

    end

  end

  stepCursor()

  compareVars()

end

function render()

  if needsRepaint then

    pixels = {}

    for i = 1, width*height do pixels[i] = bgColor end

    for l = 1, min(#lines-scrollY, displayRows) do

      renderText(0, (l-1)*fontH, lines[l+scrollY]:sub(scrollX+1, scrollX+1+displayCols))

    end

    renderCursor()

    needsRepaint = false

  end

end

function step()

  pixels = nil

  processEvents()

  render()

end

step()

animateAgainIn = {eventRate, step}