Add all the A tasks

Task/Animation/0DESCRIPTION

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+Animation is the foundation of a great many parts of graphical user interfaces, including both the fancy effects when things change used in window managers, and of course games. The core of any animation system is a scheme for periodically changing the display while still remaining responsive to the user. This task demonstrates this.
+
+Create a window containing the string "<code>Hello World! </code>" (the trailing space is significant). Make the text appear to be rotating right by periodically removing one letter from the end of the string and attaching it to the front. When the user clicks on the text, it should reverse its direction.

Task/Animation/1META.yaml

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+---
+category:
+- GUI
+note: Temporal media
+requires:
+- Graphics

Task/Animation/ActionScript/animation.as

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+//create the text box
+var textBox:TextField = new TextField();
+addChild(textBox);
+
+var text = "Hello, World! ";
+var goingRight = true;
+
+//modify the string and update it in the text box
+function animate(e:Event)
+{
+	if(goingRight)
+		text = text.slice(text.length-1,text.length) + text.slice(0, text.length - 1);
+	else
+		text = text.slice(1) + text.slice(0,1);
+	textBox.text = text;
+}
+
+//event handler to perform the animation
+textBox.addEventListener(Event.ENTER_FRAME, animate);
+//event handler to register clicks
+textBox.addEventListener(MouseEvent.MOUSE_DOWN, function(){goingRight = !goingRight;});

Task/Animation/Ada/animation.ada

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+with Gtk.Main;
+with Gtk.Handlers;
+with Gtk.Label;
+with Gtk.Button;
+with Gtk.Window;
+with Glib.Main;
+
+procedure Animation is
+   Scroll_Forwards : Boolean := True;
+
+   package Button_Callbacks is new Gtk.Handlers.Callback
+     (Gtk.Button.Gtk_Button_Record);
+
+   package Label_Timeout is new Glib.Main.Generic_Sources
+     (Gtk.Label.Gtk_Label);
+
+   package Window_Callbacks is new Gtk.Handlers.Return_Callback
+     (Gtk.Window.Gtk_Window_Record, Boolean);
+
+   --  Callback for click event
+   procedure On_Button_Click
+     (Object : access Gtk.Button.Gtk_Button_Record'Class);
+
+   --  Callback for delete event
+   function On_Main_Window_Delete
+     (Object : access Gtk.Window.Gtk_Window_Record'Class)
+      return   Boolean;
+
+   function Scroll_Text (Data : Gtk.Label.Gtk_Label) return Boolean;
+
+   procedure On_Button_Click
+     (Object : access Gtk.Button.Gtk_Button_Record'Class)
+   is
+      pragma Unreferenced (Object);
+   begin
+      Scroll_Forwards := not Scroll_Forwards;
+   end On_Button_Click;
+
+   function On_Main_Window_Delete
+     (Object : access Gtk.Window.Gtk_Window_Record'Class)
+      return   Boolean
+   is
+      pragma Unreferenced (Object);
+   begin
+      Gtk.Main.Main_Quit;
+      return True;
+   end On_Main_Window_Delete;
+
+   function Scroll_Text (Data : Gtk.Label.Gtk_Label) return Boolean is
+      Text : constant String := Gtk.Label.Get_Text (Data);
+   begin
+      if Scroll_Forwards then
+         Gtk.Label.Set_Text
+           (Label => Data,
+            Str   => Text (Text'First + 1 .. Text'Last) & Text (Text'First));
+      else
+         Gtk.Label.Set_Text
+           (Label => Data,
+            Str   => Text (Text'Last) & Text (Text'First .. Text'Last - 1));
+      end if;
+      return True;
+   end Scroll_Text;
+
+   Main_Window     : Gtk.Window.Gtk_Window;
+   Text_Button     : Gtk.Button.Gtk_Button;
+   Scrolling_Text  : Gtk.Label.Gtk_Label;
+   Timeout_ID      : Glib.Main.G_Source_Id;
+   pragma Unreferenced (Timeout_ID);
+
+begin
+   Gtk.Main.Init;
+   Gtk.Window.Gtk_New (Window => Main_Window);
+   Gtk.Label.Gtk_New (Label => Scrolling_Text, Str => "Hello World! ");
+   Gtk.Button.Gtk_New (Button => Text_Button);
+   Gtk.Button.Add (Container => Text_Button, Widget => Scrolling_Text);
+   Button_Callbacks.Connect
+     (Widget => Text_Button,
+      Name   => "clicked",
+      Marsh  => Button_Callbacks.To_Marshaller (On_Button_Click'Access));
+   Timeout_ID :=
+     Label_Timeout.Timeout_Add
+       (Interval => 125,
+        Func     => Scroll_Text'Access,
+        Data     => Scrolling_Text);
+   Gtk.Window.Add (Container => Main_Window, Widget => Text_Button);
+   Window_Callbacks.Connect
+     (Widget => Main_Window,
+      Name   => "delete_event",
+      Marsh  => Window_Callbacks.To_Marshaller (On_Main_Window_Delete'Access));
+   Gtk.Window.Show_All (Widget => Main_Window);
+   Gtk.Main.Main;
+end Animation;

Task/Animation/AutoHotkey/animation.ahk

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+SetTimer, Animate ; Timer runs every 250 ms.
+String := "Hello World "
+Gui, Add, Text, vS gRev, %String%
+Gui, +AlwaysOnTop -SysMenu
+Gui, Show
+Return
+
+Animate:
+	String := (!Reverse) ? (SubStr(String, 0) . Substr(String, 1, StrLen(String)-1)) : (SubStr(String, 2) . SubStr(String, 1, 1))
+	GuiControl,,S, %String%
+return
+
+Rev: ; Runs whenever user clicks on the text control
+	Reverse := !Reverse
+return

Task/Animation/C/animation.c

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+#include <stdlib.h>
+#include <string.h>
+#include <gtk/gtk.h>
+
+const gchar *hello = "Hello World! ";
+gint direction = -1;
+gint cx=0;
+gint slen=0;
+
+GtkLabel *label;
+
+void change_dir(GtkLayout *o, gpointer d)
+{
+  direction = -direction;
+}
+
+gchar *rotateby(const gchar *t, gint q, gint l)
+{
+  gint i, cl = l, j;
+  gchar *r = malloc(l+1);
+  for(i=q, j=0; cl > 0; cl--, i = (i + 1)%l, j++)
+    r[j] = t[i];
+  r[l] = 0;
+  return r;
+}
+
+gboolean scroll_it(gpointer data)
+{
+  if ( direction > 0 )
+    cx = (cx + 1) % slen;
+  else
+    cx = (cx + slen - 1 ) % slen;
+  gchar *scrolled = rotateby(hello, cx, slen);
+  gtk_label_set_text(label, scrolled);
+  free(scrolled);
+  return TRUE;
+}
+
+
+int main(int argc, char **argv)
+{
+  GtkWidget *win;
+  GtkButton *button;
+  PangoFontDescription *pd;
+
+  gtk_init(&argc, &argv);
+  win = gtk_window_new(GTK_WINDOW_TOPLEVEL);
+  gtk_window_set_title(GTK_WINDOW(win), "Basic Animation");
+  g_signal_connect(G_OBJECT(win), "delete-event", gtk_main_quit, NULL);
+
+  label = (GtkLabel *)gtk_label_new(hello);
+
+  // since we shift a whole character per time, it's better to use
+  // a monospace font, so that the shifting seems done at the same pace
+  pd = pango_font_description_new();
+  pango_font_description_set_family(pd, "monospace");
+  gtk_widget_modify_font(GTK_WIDGET(label), pd);
+
+  button = (GtkButton *)gtk_button_new();
+  gtk_container_add(GTK_CONTAINER(button), GTK_WIDGET(label));
+
+  gtk_container_add(GTK_CONTAINER(win), GTK_WIDGET(button));
+  g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(change_dir), NULL);
+
+  slen = strlen(hello);
+
+  g_timeout_add(125, scroll_it, NULL);
+
+  gtk_widget_show_all(GTK_WIDGET(win));
+  gtk_main();
+  return 0;
+}

Task/Animation/Clojure/animation.clj

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+(import '[javax.swing JFrame JLabel])
+(import '[java.awt.event MouseAdapter])
+
+(def text "Hello World! ")
+(def text-ct (count text))
+(def rotations
+  (vec
+    (take text-ct
+      (map #(apply str %)
+        (partition text-ct 1 (cycle text))))))
+
+(def pos (atom 0))  ;position in rotations vector being displayed
+(def dir (atom 1))  ;direction of next position (-1 or 1)
+
+(def label (JLabel. text))
+
+(.addMouseListener label
+  (proxy [MouseAdapter] []
+    (mouseClicked [evt] (swap! dir -))))
+
+(defn animator []
+  (while true
+    (Thread/sleep 100)
+    (swap! pos #(-> % (+ @dir) (mod text-ct)))
+    (.setText label (rotations @pos))))
+
+(doto (JFrame.)
+  (.add label)
+  (.pack)
+  (.setDefaultCloseOperation JFrame/EXIT_ON_CLOSE)
+  (.setVisible true))
+
+(future-call animator)  ;simple way to run animator on a separate thread

Task/Animation/Haskell/animation-1.hs

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+import Graphics.HGL.Units (Time, Point, Size, )
+import Graphics.HGL.Draw.Monad (Graphic, )
+import Graphics.HGL.Draw.Text
+import Graphics.HGL.Draw.Font
+import Graphics.HGL.Window
+import Graphics.HGL.Run
+import Graphics.HGL.Utils
+
+import Control.Exception (bracket, )
+
+runAnim = runGraphics $
+ bracket
+  (openWindowEx "Basic animation task" Nothing (250,50) DoubleBuffered (Just 110))
+  closeWindow
+  (\w -> do
+    f <- createFont (64,28) 0 False False "courier"
+    let loop t dir = do
+	  e <- maybeGetWindowEvent w
+	  let d = case e of
+		  Just (Button _ True False)  -> -dir
+		  _ -> dir
+	      t' = if d == 1 then last t : init t else tail t ++ [head t]
+	  setGraphic w (withFont f $ text (5,10) t') >> getWindowTick w
+	  loop  t' d
+	
+    loop "Hello world ! " 1  )

Task/Animation/Haskell/animation-2.hs

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+*Main> runAnim

Task/Animation/Java/animation.java

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+import java.awt.event.MouseAdapter;
+import java.awt.event.MouseEvent;
+import java.util.Timer;
+import java.util.TimerTask;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+
+public class Rotate extends JFrame {
+  String text = "Hello World! ";
+  JLabel label = new JLabel(text);
+  boolean rotRight = true;
+  int startIdx = 0;
+
+  public Rotate() {
+    label.addMouseListener(new MouseAdapter() {
+      @Override
+      public void mouseClicked(MouseEvent evt) {
+        rotRight = !rotRight;
+      }
+    });
+    add(label);
+    pack();
+    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+    setVisible(true);
+  }
+
+  public static void main(String[] args) {
+    final Rotate rot = new Rotate();
+    TimerTask task = new TimerTask() {
+      public void run() {
+        if (rot.rotRight) {
+          rot.startIdx++;
+          if (rot.startIdx >= rot.text.length()) {
+            rot.startIdx -= rot.text.length();
+          }
+        } else {
+          rot.startIdx--;
+          if (rot.startIdx < 0) {
+            rot.startIdx += rot.text.length();
+          }
+        }
+        rot.label.setText(getRotatedText(rot.text, rot.startIdx));
+      }
+    };
+    Timer timer = new Timer(false);
+    timer.schedule(task, 0, 500);
+  }
+
+  public static String getRotatedText(String text, int startIdx) {
+    String ret = "";
+    int i = startIdx;
+    do {
+      ret += text.charAt(i) + "";
+      i++;
+      i = i % text.length();
+    } while (i != startIdx);
+    return ret;
+  }
+}

Task/Animation/JavaScript/animation.js

@@ -0,0 +1,23 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="100" height="40">
+    <script type="text/javascript">
+        function animate(element) {
+            var textNode = element.childNodes[0]; // assuming no other children
+            var text = textNode.data;
+            var reverse = false;
+
+            element.onclick = function () { reverse = !reverse; };
+
+            setInterval(function () {
+                if (reverse)
+                    text = text.substring(1) + text[0];
+                else
+                    text = text[text.length - 1] + text.substring(0, text.length - 1);
+                textNode.data = text;
+            }, 100);
+        }
+    </script>
+
+    <rect width="100" height="40" fill="yellow"/>
+    <text x="2" y="20" onload="animate(this);">Hello World! </text>
+</svg>

Task/Animation/Perl/animation.pl

@@ -0,0 +1,11 @@
+use XUL::Gui;
+
+my $dir = '(.+)(.)';
+interval {
+    ID(lbl)->value =~ s/$dir/$2$1/;
+} 75;
+
+display Label
+    id    => 'lbl',
+    value => "Hello World! ",
+    onclick => sub {toggle $dir => '(.+)(.)', '(.)(.+)'};

Task/Animation/PicoLisp/animation-1.l

@@ -0,0 +1,14 @@
+#!/usr/bin/picolisp /usr/lib/picolisp/lib.l
+
+(prin "^[[?9h")  # Mouse reporting on
+
+(setq Dir 1  Text (chop "Hello World! "))
+
+(loop
+   (prin (do Dir (rot Text)))
+   (when (= "^[" (key 200))
+      (key) (key)
+      (when (= " " (key))  # Left button
+         (setq Dir (if (= 1 Dir) 12 1)) )
+      (key) (key) )
+   (do (length Text) (prin "^H")) )

Task/Animation/PicoLisp/animation-2.l

@@ -0,0 +1,18 @@
+#!/usr/bin/picolisp /usr/lib/picolisp/lib.l
+
+(load "@ext.l" "@lib/http.l" "@lib/xhtml.l" "@lib/form.l")
+
+(one *Dir)
+
+(de start ()
+   (app)
+   (action
+      (html 0 "Animation" "@lib.css" NIL
+         (form NIL
+            (gui '(+Button)
+               '(pack (do *Dir (rot '`(chop "Hello World! "))))
+               '(setq *Dir (if (= 1 *Dir) 12 1)) )
+            (gui '(+Click +Auto +Button) 400 'This 1000 "Start") ) ) ) )
+
+(server 8080 "!start")
+(wait)

Task/Animation/PicoLisp/animation-3.l

@@ -0,0 +1,22 @@
+#!ersatz/pil
+
+(setq
+   Dir 1
+   Text (chop "Hello World! ")
+   Frame (java "javax.swing.JFrame" T "Animation")
+   Label (java "javax.swing.JLabel" T (pack Text)) )
+
+(java Label 'addMouseListener
+   (interface "java.awt.event.MouseListener"
+      'mouseClicked '((Ev) (setq Dir (if (= 1 Dir) 12 1)))
+      'mouseEntered nil
+      'mouseExited nil
+      'mousePressed nil
+      'mouseReleased nil ) )
+
+(java Frame 'add Label)
+(java Frame 'pack)
+(java Frame 'setVisible T)
+(loop
+   (wait 200)
+   (java Label 'setText (pack (do Dir (rot Text)))) )

Task/Animation/Prolog/animation.pro

@@ -0,0 +1,74 @@
+:- use_module(library(pce)).
+
+animation :-
+    new(D, window('Animation')),
+    new(Label, label(hello, 'Hello world ! ')),
+    send(D, display, Label, point(1,10)),
+    new(@animation, animation(Label)),
+    send(D, recogniser,
+         new(_G, my_click_gesture(left, ''))),
+
+    send(D, done_message, and(message(@animation, free),
+                  message(@receiver, destroy))),
+    send(D, open),
+    send(@animation?mytimer, start).
+
+
+:- pce_begin_class(animation(label), object).
+variable(label, object,  both, "Display window").
+variable(delta,    object, both,  "increment of the angle").
+variable(mytimer, timer, both, "timer of the animation").
+
+initialise(P, W:object) :->
+        "Creation of the object"::
+        send(P, label, W),
+        send(P, delta, to_left),
+    send(P, mytimer, new(_, timer(0.5,message(P, anim_message)))).
+
+% method called when the object is destroyed
+% first the timer is stopped
+% then all the resources are freed
+unlink(P) :->
+    send(P?mytimer, stop),
+    send(P, send_super, unlink).
+
+
+% message processed by the timer
+anim_message(P) :->
+    get(P, label, L),
+    get(L, selection, S),
+    get(P, delta, Delta),
+    compute(Delta, S, S1),
+    new(A, name(S1)),
+    send(L, selection, A).
+
+
+:- pce_end_class.
+
+:- pce_begin_class(my_click_gesture, click_gesture,
+           "Click in a window").
+
+class_variable(button, button_name, left,
+           "By default click with left button").
+
+terminate(G, Ev:event) :->
+    send(G, send_super, terminate, Ev),
+    get(@animation, delta, D),
+    (   D = to_left -> D1 = to_right; D1 = to_left),
+    send(@animation, delta, D1).
+
+:- pce_end_class.
+
+
+% compute next text to be dispalyed
+compute(to_right, S, S1) :-
+    get(S, size, Len),
+    Len1 is Len - 1,
+    get(S, sub, Len1, Str),
+    get(S, delete_suffix, Str, V),
+    get(Str, append, V, S1).
+
+compute(to_left, S, S1) :-
+    get(S, sub, 0, 1, Str),
+    get(S, delete_prefix, Str, V),
+    get(V, append, Str, S1).

Task/Animation/Python/animation-1.py

@@ -0,0 +1,55 @@
+import pygame, sys
+from pygame.locals import *
+pygame.init()
+
+YSIZE = 40
+XSIZE = 150
+
+TEXT = "Hello World! "
+FONTSIZE = 32
+
+LEFT = False
+RIGHT = True
+
+DIR = RIGHT
+
+TIMETICK = 180
+TICK = USEREVENT + 2
+
+TEXTBOX = pygame.Rect(10,10,XSIZE,YSIZE)
+
+pygame.time.set_timer(TICK, TIMETICK)
+
+window = pygame.display.set_mode((XSIZE, YSIZE))
+pygame.display.set_caption("Animation")
+
+font = pygame.font.SysFont(None, FONTSIZE)
+screen = pygame.display.get_surface()
+
+def rotate():
+    index = DIR and -1 or 1
+    global TEXT
+    TEXT = TEXT[index:]+TEXT[:index]
+
+def click(position):
+    if TEXTBOX.collidepoint(position):
+        global DIR
+        DIR = not DIR
+
+def draw():
+    surface = font.render(TEXT, True, (255,255,255), (0,0,0))
+    global TEXTBOX
+    TEXTBOX = screen.blit(surface, TEXTBOX)
+
+def input(event):
+    if event.type == QUIT:
+        sys.exit(0)
+    elif event.type == MOUSEBUTTONDOWN:
+        click(event.pos)
+    elif event.type == TICK:
+        draw()
+        rotate()
+
+while True:
+    input(pygame.event.wait())
+    pygame.display.flip()

Task/Animation/Python/animation-2.py

@@ -0,0 +1,23 @@
+import Tkinter as tki
+
+def scroll_text(s, how_many):
+    return s[how_many:] + s[:how_many]
+
+direction = 1
+tk = tki.Tk()
+var = tki.Variable(tk)
+
+def mouse_handler(point):
+    global direction
+    direction *= -1
+
+def timer_handler():
+    var.set(scroll_text(var.get(),direction))
+    tk.after(125, timer_handler)
+
+var.set('Hello, World! ')
+tki.Label(tk, textvariable=var).pack()
+tk.bind("<Button-1>", mouse_handler)
+tk.after(125, timer_handler)
+tk.title('Python Animation')
+tki.mainloop()

Task/Animation/R/animation.r

@@ -0,0 +1,39 @@
+rotate_string <- function(x, forwards)
+{
+   nchx <- nchar(x)
+   if(forwards)
+   {                                  
+      paste(substr(x, nchx, nchx), substr(x, 1, nchx - 1), sep = "")
+   } else
+   {                                                          
+      paste(substr(x, 2, nchx), substr(x, 1, 1), sep = "")
+   }
+}
+
+handle_rotate_label <- function(obj, interval = 100)
+{
+  addHandlerIdle(obj,
+    handler = function(h, ...)
+    {
+       svalue(obj) <- rotate_string(svalue(obj), tag(obj, "forwards"))
+    },
+    interval = interval
+  )
+}
+
+handle_change_direction_on_click <- function(obj)
+{
+  addHandlerClicked(obj,
+    handler = function(h, ...)
+    {
+      tag(h$obj, "forwards") <- !tag(h$obj, "forwards")
+    }
+  )
+}
+
+library(gWidgets)
+library(gWidgetstcltk) #or library(gWidgetsRGtk2) or library(gWidgetsrJava)             
+lab <- glabel("Hello World! ", container = gwindow())  
+tag(lab, "forwards") <- TRUE
+handle_rotate_label(lab)
+handle_change_direction_on_click(lab)

Task/Animation/Racket/animation.rkt

@@ -0,0 +1,40 @@
+#lang racket/gui
+
+;; One of 'left or 'right
+(define direction 'left)
+
+;; Set up the GUI
+(define animation-frame%
+  (class frame%
+    (super-new [label "Animation"])
+    ;; reverse direction on a click
+    (define/override (on-subwindow-event win evt)
+      (when (send evt button-down?)
+        (set! direction
+              (if (eq? direction 'left)
+                  'right
+                  'left))))))
+
+(define frame (new animation-frame%))
+(define msg (new message%
+                 [label "Hello World! "]
+                 [parent frame]))
+
+;; Timer callback to adjust the message
+(define (callback)
+  (define old-label (send msg get-label))
+  (define len (string-length old-label))
+  (if (eq? direction 'left)
+      (send msg set-label
+            (string-append (substring old-label 1)
+                           (substring old-label 0 1)))
+      (send msg set-label
+            (string-append (substring old-label (- len 1) len)
+                           (substring old-label 0 (- len 1))))))
+
+;; Set a timer and go
+(define timer (new timer%
+                   [notify-callback callback]
+                   [interval 500]))
+
+(send frame show #t)

Task/Animation/Ruby/animation-1.rb

@@ -0,0 +1,27 @@
+require 'tk'
+$str = TkVariable.new("Hello World! ")
+$dir = :right
+
+def animate
+  $str.value = shift_char($str.value, $dir)
+  $root.after(125) {animate}
+end
+
+def shift_char(str, dir)
+  case dir
+  when :right then str[-1,1] + str[0..-2]
+  when :left  then str[1..-1] + str[0,1]
+  end
+end
+
+$root = TkRoot.new("title" => "Basic Animation")
+
+TkLabel.new($root) do
+  textvariable $str
+  font "Courier 14"
+  pack {side 'top'}
+  bind("ButtonPress-1") {$dir = {:right=>:left,:left=>:right}[$dir]}
+end
+
+animate
+Tk.mainloop

Task/Animation/Ruby/animation-2.rb

@@ -0,0 +1,11 @@
+Shoes.app do
+  @direction = 1
+  @label = para "Hello World! ", :family => 'monospace'
+
+  click {|button, left, top| @direction *= -1 if button == 1}
+
+  animate(8) do |f|
+    t = @label.text
+    @label.text = @direction > 0 ? t[-1] + t[0..-2] : t[1..-1] + t[0]
+  end
+end

Task/Animation/Scala/animation.scala

@@ -0,0 +1,32 @@
+import scala.actors.Actor.{actor, loop, reactWithin, exit}
+import scala.actors.TIMEOUT
+import scala.swing.{SimpleSwingApplication, MainFrame, Label}
+import scala.swing.event.MouseClicked
+
+case object Revert
+
+object BasicAnimation extends SimpleSwingApplication {
+  val label = new Label("Hello World! ")
+  val rotator = actor {
+    var goingRight = true
+    loop {
+      reactWithin(250 /*ms*/) {
+        case Revert => goingRight = !goingRight
+        case TIMEOUT =>
+          if (goingRight)
+            label.text = label.text.last + label.text.init
+          else
+            label.text = label.text.tail + label.text.head
+        case unknown => println("Unknown message "+unknown); exit()
+      }
+    }
+  }
+  def top = new MainFrame {
+    title = "Basic Animation"
+    contents = label
+  }
+  listenTo(label.mouse.clicks) // use "Mouse" instead of "mouse" on Scala 2.7
+  reactions += {
+    case _ : MouseClicked => rotator ! Revert
+  }
+}

Task/Animation/Tcl/animation.tcl

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+package require Tk
+set s "Hello World! "
+set dir 0
+# Periodic animation callback
+proc animate {} {
+    global dir s
+    if {$dir} {
+        set s [string range $s 1 end][string index $s 0]
+    } else {
+        set s [string index $s end][string range $s 0 end-1]
+    }
+    # We will run this code ~8 times a second (== 125ms delay)
+    after 125 animate
+}
+# Make the label (constant width font looks better)
+pack [label .l -textvariable s -font {Courier 14}]
+# Make a mouse click reverse the direction
+bind .l <Button-1> {set dir [expr {!$dir}]}
+# Start the animation
+animate