Computercraft: Multitasking Windows API

local width, height = term.getSize()
local programs = {}
local userEvents = {"mouse_click", "mouse_up", "mouse_drag", "char", "key", "monitor_touch", "key_up", "paste", "terminate"}

programs.new = function(func, x, y, w, h)
  local x = x or 1
  local y = y or 1
  local w = w or widht
  local h = h or height
  local program = {
    x = x, y = y, w = w, h = h,
    term = window.create(
      term.current(), x, y, w, h
    ),
    selected = false,
    coroutine = coroutine.create(func),
    reposition = function(self, x, y)
      self.x, self.y = x, y
      self.term.reposition(x, y)
    end,
    resize = function(self, w, h)
      oldX, oldY = self.term.getPosition()
      self.term.reposition(oldX, oldY, w, h)
      os.queueEvent("term_resize")
    end,
    reset = function(self, x, y, w, h)
      self.x, self.y, self.w, self.h = x, y, w, h
      self.term.reposition(x, y, w, h)
      os.queueEvent("term_resize")
    end
  }
  return program
end

local updateProgram = function(programs, programNum, event, var1, var2, var3, isUserEvent)
  local program = programs[programNum]
  local event, var1, var2, var3 = event, var1, var2, var3

  -- redirect to programs terminal
  local oldTerm = term.redirect(program.term)

  -- give the mouse click as seen from the program window
  if string.sub(event, 1, #"mouse") == "mouse" then
    var2 = var2-program.x+1
    var3 = var3-program.y+1
  end

  -- find out if the program window is clicked
  if event == "mouse_click" and var2>=0 and var3>=0 and var2<=program.w and var3<=program.h then
    -- select this program and deselect every other one
    for programNum = 1, #programs do
      programs[programNum].selected = false
    end
    program.selected = true
    if var3 == 0 then
      program.barSelected = true
      program.barSelectedX = var2
      if var2 == 1 then
        program.resizeIconSelected = true
      end
      if var2 == program.w then
        table.remove(programs, programNum)
        term.redirect(oldTerm)
        return
      end
    end

    -- resort program table

    local selectedProgram
    for i = 1, #programs do
      if programs[i].selected then
        selectedProgram = programs[i]
        table.remove(programs, i)
        break
      end
    end
    table.insert(programs, selectedProgram)
  end

  -- move window when mouse is dragged
  if event == "mouse_drag" and program.barSelected then
    if program.resizeIconSelected then
      program:reset(program.x + var2-program.barSelectedX, program.y+var3, program.w-var2+1, program.h-var3)
    else
      program:reposition(program.x + var2-program.barSelectedX, program.y+var3)
    end
  end

  -- deselect bar if mouse is released
  if event == "mouse_up" then
    program.barSelected = false
    program.resizeIconSelected = false
  end

  -- only give program user events if selected
  if isUserEvent and not program.selected then
    event, var1, var2, var3 = ""
  end

  -- resume program
  coroutine.resume(program.coroutine, event, var1, var2, var3)

  -- delete program if it is finished
  if coroutine.status(program.coroutine) == "dead" then
    table.remove(programs, programNum)
    term.redirect(oldTerm)
    return true
  end

  program.term.redraw()
  term.redirect(oldTerm)

  -- draw line above program
  if program.selected then
    term.setBackgroundColor(colors.lightGray)
    term.setTextColor(colors.gray)
  else
    term.setBackgroundColor(colors.gray)
    term.setTextColor(colors.lightGray)
  end
  paintutils.drawLine(program.x, program.y-1, program.x+program.w-1, program.y-1)

  -- draw resize icon
  term.setCursorPos(program.x, program.y-1)
  term.write("/")

  -- draw close icon
  term.setCursorPos(program.x+program.w-1, program.y-1)
  term.setTextColor(colors.orange)
  term.write("x")
end

programs.update = function(programs, event, var1, var2, var3)
  -- check if event is made from the user
  local isUserEvent = false
  for userEventNum = 1, #userEvents do
    local userEvent = userEvents[userEventNum]
    if event == userEvent then
      isUserEvent = true
      break
    end
  end

  -- update every program
  for programNum = 1, #programs do
    if updateProgram(programs, programNum, event, var1, var2, var3, isUserEvent) then break end
  end
end

return programs