Logo api v0.3.2 (computercraft lua)

--[[

LOGO Turtle graphics API v0.3.2
code by GopherAtl.
Do anything you want with this code except claim credit for it.
If you distribute a program that uses it, please link users to the
official thread on the cc forums here:
http://www.computercraft.info/forums2/index.php?/topic/4006-logo-interpreter/
If you distribute a modified version with fixes or enhancements, please link to
it in the official thread as well.

--]]

--character aspect ratio - constant
local charAspect=6.0/9.0

--current turtle location info
local curX,curY=0,0
local curAngle=0

--the view scale - how many units from center to the nearest edge (usually top/bottom)
local curScale=100

--pen state
local isPenDown=true
local curPenChar="X"

--list of display objects being used
local displays={}

--unused at present, will remember line data so it can be redrawn
local lineData={
    { pos={0, 0, 0}, angle=0 }
}


--Bresenham's line algo, adapted to lua by me
function line(device,x1,y1,x2,y2,ch)
  local steep = math.abs(y2-y1)>math.abs(x2-x1)
  local setPos
  if steep then
    y1,x1=x1,y1
    y2,x2=x2,y2
    setPos=function(y,x) device.setCursorPos(x,y) end
  else
    setPos=function(x,y) device.setCursorPos(x,y) end
  end
  if x1>x2 then
    x1,x2=x2,x1
    y1,y2=y2,y1
  end
  local dx=x2-x1
  local dy=math.abs(y2-y1)
  local err=dx/2
  local ys= y1<y2 and 1 or -1
  local y=y1

  for x=x1,x2 do
    setPos(x,y)
    device.write(ch)
    err=err-dy
    if err<0 then
      y=y+ys
      err=err+dx
    end
  end
end



--reset the state of all api variables.
function reset()
  home()
  curPenChar="x"
  isPenDown=true
  curScale=100
  displays={}
  lineData={
      { pos={0, 0, 0}, angle=0 }
    }
end

function penUp()
  isPenDown=false
end

function penDown()
  isPenDown=true
end

function penChar(ch)
  curPenChar=string.sub(ch,1,1)
end

function moveTo(x,y)
  if isPenDown then
    for k,v in pairs(displays) do
      local x1,y1=posToScreen(curX,curY,k)
      local x2,y2=posToScreen(x,y,k)
      line(displays[k].wrapper,x1,y1,x2,y2,curPenChar)
    end
  end
  curX=x
  curY=y
end

function turn(angle)
  curAngle=(curAngle+angle)%360
end

function turnTo(angle)
  curAngle=angle%360
end

function forward(dist)
  local angleRad=curAngle*math.pi/180.0
  local newX=curX+dist*math.sin(angleRad)
  local newY=curY+dist*math.cos(angleRad)
  moveTo(newX,newY)
end


--[[
generates values needed for saling lines to a given display
device based on it's dimensions and defined bounds and the
current scale.
--]]
local function scaleDisplay(name)
  if displays[name].width*6>displays[name].height*9 then
    --height is smaller
    displays[name].scaleY=displays[name].centerY/curScale
    displays[name].scaleX=displays[name].scaleY/charAspect

  else
    displays[name].scaleX=displays[name].centerX/curScale
    displays[name].scaleY=displays[name].scaleX*charAspect
  end
end

--[[
set the scale for all devices to render; the smaller of the
two axes, width or height, as determined by both the dimensions
in characters of the screen and the dimensions of a single
character in the font, will range from -newScale to scale, the
other axis will be larger proportional to trueAspect.
--]]
function scale(newScale)
  curScale=newScale
  --smaller dimension of monitor will be scale
  for k,v in pairs(displays) do
    scaleDisplay(k)
  end
end

--convert a coordinate to a position on a given display with
--the current scale
function posToScreen(x,y,display)
  return x*displays[display].scaleX+displays[display].centerX+1, y*displays[display].scaleY+displays[display].centerY+1
end


--erases the draw area and clears the draw history
function clean()
  for k,v in pairs(displays) do
    for y=v.minY, v.maxY do
      v.wrapper.setCursorPos(v.minX,y)
      v.wrapper.write(string.rep(" ",v.width))
    end
  end

  lineData={
      { pos={0, 0, 0}, angle=0 }
  }
end

--restores the turtle to it's initial state
function home()
  curX=0
  curY=0
  curAngle=0
end

--[[
add a display to the devices it's drawing to.
wrapper is the interface, term for terminal or result of
  peripheral.wrap() for monitors.
min/max values specify a region of the screen to draw in;
  default to full screen
--]]
function addDisplay(name,wrapper,minX,minY,maxX,maxY)
  --set default params
  if minX==nil then
    minX=1
  end
  if minY==nil then
    minY=1
  end
  if maxX==nil then
    local t
    maxX, t=wrapper.getSize()
  end
  if maxY==nil then
    local t
    t, maxY=wrapper.getSize()
  end
  local width, height=maxX-minX+1, maxY-minY+1

  displays[name]={
    minX=minX,
    minY=minY,
    maxX=maxX,
    maxY=maxY,
    wrapper=wrapper,
    width=width,
    height=height,
    centerX=width/2,
    centerY=height/2,
    aspect=width/height,
    trueAspect=charAspect*width/height,
  }

  scaleDisplay(name)
end