Animation
You are encouraged to solve this task according to the task description, using any language you may know.
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 "Hello World!
" (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.
AutoHotkey
<lang AutoHotkey>message := "Hello World! " Gui, Add, Text, vmyedit , %message% Gui, +AlwaysOnTop +Disabled -SysMenu +Owner Gui, Show animate() Return
- IfWinActive animation.ahk
~LButton::
WinGetPos ,,, width, height MouseGetPos, x, y If x And y If (x < width) And (y < height) reverse := !reverse return
- IfWinActive
animate() {
Global Loop, { Sleep, 200 If reverse message := SubStr(message, 2, StrLen(message)) . SubStr(message,1, 1) Else message := SubStr(message, StrLen(message), 1) . SubStr(message, 1, StrLen(message) - 1) GuiControl,,myedit, %message% }
}</lang>
C
(NB: implicitly, through GTK, it uses also Pango library) <lang c>#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;
}</lang>
Common Lisp
The ltk package provides a lisp interface to Tk for creating graphical interfaces. Assuming ltk has been installed somewhere the following will work as per the Tcl example.
<lang lisp>(use-package ':ltk) (use-package :ext)
(defparameter *message* "Hello World! ") (defparameter *direction* :left) (defun animate (label)
(let* ((n (length *message*)) (i (if (eq *direction* :left) 0 (1- n))) (c (string (char *message* i)))) (if (eq *direction* :left) (setq *message* (string-concat (substring *message* 1 n) c)) (setq *message* (string-concat c (substring *message* 0 (1- n))))) (setf (ltk:text label) *message*) (ltk:after 125 (lambda () (animate label)))))
(defun basic-animation ()
(ltk:with-ltk () (let* ((label (make-instance 'label :font "Courier 14"))) (setf (text label) *message*) (ltk:bind label "<Button-1>" (lambda (event) (declare (ignore event)) (cond ((eq *direction* :left) (setq *direction* :right)) ((eq *direction* :right) (setq *direction* :left))))) (ltk:pack label) (animate label) (ltk:mainloop))))
(basic-animation)</lang>
Java
<lang java>import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.SwingUtilities;
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) { Rotate rot = new Rotate(); while (true) { try { Thread.sleep(500);//wait half a second } catch (InterruptedException ex) {} 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(); } } final Rotate fRot = rot; SwingUtilities.invokeLater(new Runnable() { public void run() { fRot.label.setText(getRotatedText(fRot.text, fRot.startIdx)); } }); } }
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; }
}</lang>
JavaScript + HTML
<lang javascript><html> <head>
<title>RC: Basic Animation</title> <script type="text/javascript"> function animate(id) { var element = document.getElementById(id); 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.substr(1, text.length) + text[0]; else text = text[text.length - 1] + text.substr(0, text.length - 1); textNode.data = text; }, 100); } </script> <style type="text/css"> #target { font-family: monospace; } </style>
</head> <body onload="animate('target')">
</body> </html></lang>
Mathematica
<lang Mathematica> mystring = "Hello World! "; Scroll[str_, dir_] := StringJoin @@ RotateLeft[str // Characters, dir]; GiveString[dir_] := (mystring = Scroll[mystring, dir]); CreateDialog[{
DynamicModule[{direction = -1}, EventHandler[ Dynamic[TextCell[ Refresh[GiveString[direction], UpdateInterval -> 1/8]], TrackedSymbols -> {}], {"MouseClicked" :> (direction *= -1)}]] }];
</lang>
Ruby
<lang ruby>require 'tk' $str = TkVariable.new("Hello World! ") $dir = 0
def animate
t = $str.value $str.value = if $dir == 0 t[1..-1] + t[0].chr else t[-1].chr + t[0..-2] end $root.after(125) {animate}
end
$root = TkRoot.new("title" => "Basic Animation")
TkLabel.new($root) do
textvariable $str font "Courier 14" pack {side 'top'} bind("ButtonPress-1") {$dir = ($dir + 1) % 2}
end
animate Tk.mainloop</lang>
Tcl
<lang tcl>package require Tk set s "Hello World! " set dir 0
- Periodic animation callback
proc animate {} {
global dir s if {$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</lang>