--******************************************************************************
--*                                                                            *
--*  File:        Clock.lua                             Revision:  1.0         *
--*                                                                            *
--*  Contents:    a simple analog clock (just a "tkcanvas" experiment)         *
--*                                                                            *
--*  Creation:    04.03.2002                   Last Modification:  04.03.2002  *
--*                                                                            *
--*  Platform:    IBM-compatible PC running Windows 98SE                       *
--*                                                                            *
--*  Environment: Lua 4.0, TkLua 4.0                                           *
--*                                                                            *
--*  Author:      Andreas Rozek           Phone:  ++49 (711) 6770682           *
--*               Kirschblütenweg 15      Fax:    -                            *
--*             D-70569 Stuttgart         EMail:  Andreas.Rozek@T-Online.De    *
--*               Germany                                                      *
--*                                                                            *
--*  URL:         http://www.Andreas-Rozek.de/                                 *
--*                                                                            *
--*  Copyright:   the software is published under the "GNU Lesser General Pub- *
--*               lic  License" (see "http://www.fsf.org/copyleft/lesser.html" *
--*               for additional information)                                  *
--*                                                                            *
--*  Comments:    since 'tktimer' "fires" after a given interval plus the time *
--*               required to process the timer function, the display of this  *
--*               clock my sometimes skip a second...                          *
--*                                                                            *
--******************************************************************************

--**** global constants and variables ****

  ClockView = nil;                          -- contains the actual clock display

  HourHand_NodeList   = {-2,-1, -2,40, 2,40, 2,-1};
  MinuteHand_NodeList = {-1,-3, -1,50, 1,50, 1,-3};
  SecondHand_NodeList = {0,-5, 0,58};

--**** local constants and variables ****

  local Title    = "Clock";
  local Subtitle = "a simple analog clock";

  local LargeTick_NodeList = {-2,0, 2,0, 2,-10, -2,-10};
  local SmallTick_NodeList = {-1,0, 1,0, 1,-5,  -1,-5};
  local TinyTick_NodeList  = {0,0, 0,-2};

--******************************************************************************
--*                                                                            *
--* createTick                                     creates a single clock tick *
--*                                                                            *
--******************************************************************************

  function createTick (NodeList, Angle)
    local mx,my  = 64,64;                         -- coordinates of clock center
    local radius = 60;                                           -- clock radius
    local sinPhi,cosPhi = sin(Angle),cos(Angle);        -- required for rotation

    local ArgList = {ClockView};              -- arguments for Tk canvas command

    local NodeCount = getn(NodeList);        -- actually, it's twice the # nodes
    if (NodeCount == 4) then
      tinsert(ArgList, "line");
    else
      tinsert(ArgList, "polygon");
    end;

    for i = 1,NodeCount-1,2 do
      local x = NodeList[i];
      local y = NodeList[i+1] + radius;

      tinsert(ArgList, mx+(x*cosPhi+y*sinPhi));
      tinsert(ArgList, my+(x*sinPhi-y*cosPhi));
    end;

    call(ClockView.create, ArgList);         -- a method invoked like a function
  end;

--******************************************************************************
--*                                                                            *
--* newHand                                        creates a single clock hand *
--*                                                                            *
--******************************************************************************

  function newHand (NodeList, Angle)
    local mx,my  = 64,64;                         -- coordinates of clock center
    local sinPhi,cosPhi = sin(Angle),cos(Angle);        -- required for rotation

    local ArgList = {ClockView};              -- arguments for Tk canvas command

    local NodeCount = getn(NodeList);        -- actually, it's twice the # nodes
    if (NodeCount == 4) then
      tinsert(ArgList, "line");
    else
      tinsert(ArgList, "polygon");
    end;

    for i = 1,NodeCount-1,2 do
      local x = NodeList[i];
      local y = NodeList[i+1];

      tinsert(ArgList, mx+(x*cosPhi+y*sinPhi));
      tinsert(ArgList, my+(x*sinPhi-y*cosPhi));
    end;

    return call(ClockView.create, ArgList);  -- a method invoked like a function
  end;

--******************************************************************************
--*                                                                            *
--* updateDisplay                             updates the actual clock display *
--*                                                                            *
--******************************************************************************

  HourHand,   HourHand_Angle   = nil;    -- canvas ids and angles of clock hands
  MinuteHand, MinuteHand_Angle = nil;
  SecondHand, SecondHand_Angle = nil;

  function updateDisplay ()
    local a,b,hour,minute,second = strfind(date(),"(%d*)%:(%d*)%:(%d*)$");

--**** calculate the angles of each clock hand ****

    local HourAngle   = mod(hour,12)*360/12 + minute*30/60;
    local MinuteAngle = minute*360/60;
    local SecondAngle = second*360/60;

--**** then (re)create an appropriate canvas object for each hand ****

    if (HourHand == nil) or (HourHand_Angle ~= HourAngle) then
      if (HourHand ~= nil) then ClockView:delete(HourHand); end;

      HourHand = newHand(HourHand_NodeList, HourAngle);
      HourHand_Angle = HourAngle;                      -- update global variable
    end;

    if (MinuteHand == nil) or (MinuteHand_Angle ~= MinuteAngle) then
      if (MinuteHand ~= nil) then ClockView:delete(MinuteHand); end;

      MinuteHand = newHand(MinuteHand_NodeList, MinuteAngle);
      MinuteHand_Angle = MinuteAngle;                  -- update global variable
    end;

    if (SecondHand == nil) or (SecondHand_Angle ~= SecondAngle) then
      if (SecondHand ~= nil) then ClockView:delete(SecondHand); end;

      SecondHand = newHand(SecondHand_NodeList, SecondAngle);
      SecondHand_Angle = SecondAngle;                  -- update global variable
    end;
  end;

--******************************************************************************
--*                                                                            *
--*                                main program                                *
--*                                                                            *
--******************************************************************************

--**** define display components ****

  ClockView = tkcanvas{width=128, height=128};
    for Angle = 0,359,6 do
      if     (mod(Angle,90) == 0) then
        createTick(LargeTick_NodeList, Angle);
      elseif (mod(Angle,30) == 0) then
        createTick(SmallTick_NodeList, Angle);
      else
        createTick(TinyTick_NodeList,  Angle);
      end;
    end;
--updateDisplay();                            -- creates the initial clock hands

--**** construct application window ****

  local MainWindow = tkmain{ClockView, {fill="both", expand=1}};

--**** display application window ****

  MainWindow:title(Title.." - "..Subtitle);
  MainWindow:show();                            -- also triggers a window layout
  MainWindow:resizable(0,0);                     -- disables window size changes
  MainWindow:raise();                   -- brings the window into the foreground

  updateDisplay();      -- the canvas must be visible for this to work properly!

--**** start continous display ****

  tktimer(1000,function() updateDisplay(); end); -- may sometimes skip a second!

--**** provide an explicit method to terminate this program! ****

  MainWindow:protocol("WM_DELETE_WINDOW", "print('done...'); tkexit()");