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Princeton COS 333 - Tcl example

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Graphical user interface software• examples– HTML, CSS, Javascript (XUL, ...) – Flash, Silverlight, ...– X Window system, GTk– Tcl/Tk, TkInter, ...–Java Swing, GWT– Microsoft Visual Studio: C#, VB, ...– XCode Interface builder, Android XML, ...• fundamental ideas– interface components: widgets, controls, objects, …– properties–methods– events: loops and callbacks– geometry and layout management– extensive use of hierarchy, inheritance• the GUI is the biggest chunk of code in many applications– libraries and components try to make it easier– development environments and wizards and builders try to make it easier– interfaces are still hard to get working – and even harder to make work wellProperties, methods, events (Javascript)<head><script>function setfocus() { document.srch.q.focus(); }</script></head><BODY onload='setfocus();'><H1>Basic events on forms</H1><form action="http://www.google.com/search" name=srch><input type=text size=25 name=q id=q value="" onmouseover='setfocus()'><input type=button value="Google" name=butonclick='window.location= "http://www.google.com/search?q="+srch.q.value'><input type=button value="Wikipedia" name=but onclick='window.location="http://en.wikipedia.com/wiki/"+srch.q.value'><input type=reset onclick='srch.q.value=""; ></form>X Windows (Bob Scheifler & Jim Gettys, 1984)• client-server over a network– works on single machine too, with IPC• variants:– "X terminal" (e.g., SunRay): server is only thing on server, clients are all remote– workstation: server is on same processor as clients– Exceed: server on PC, clients on (usually) Unix• window manager is just another client, but with more properties– clients have to let the window manager manage– permits multiple workspaces / virtual windows / virtual desktopsclient client WM clientserverdisplaymousekeyboardnetworkX Windows model (www.x.org)• serverruns on the local machine– accepts network (or local) client requests and acts on them– creates, maps and destroys windows– writes and draws in windows – manages keyboard, mouse and display– sends keyboard and mouse events back to proper clients– replies to information requests– reports errors• client application– written with X libraries (i.e. Xlib, Xt, GTk, ...) – uses the X protocol to send requests to the server, and receive replies, events, errors from server• protocol messages– requests: clients make requests to the servere.g., Create Window, Draw, Iconify, ... – replies: server answers queries ("how big is this?")– events: server forwards events to client typically keyboard or mouse input – errors: server reports request errors to clientX Windows programming model• Xlib provides client-server communication– initial connection of client to server, window creation, window properties, event mask, ...– sends client requests to server: draw, get size, ...– sends server responses, errors, etc., to client– send events from server, like button push, key press, window expose, ...• Xt intrinsics provide basic operations for creating and combining widgets• widgets implement user interface components– buttons, labels, dialog boxes, menus, …– widget set is a group of related widgets with common look and feel, e.g., Motif, GTk• applications and libraries can use all of these layersXlibXt intrinsicswidgetsapplicationEvents• client registers with windows system for events it cares about• events occur asynchronously• queued for each client• client has to be ready to handle events any time– mouse buttons or motion–keyboard input– window moved or reshaped or exposed– 30-40 others• information comes back to client in a giant union called XEvent, placed in a queue• "event loop" processes the queueXevent myevent;for (;;) {XNextEvent(mydisplay, &myevent);switch (myevent.type) {case ButtonPress: …...}Tcl/Tk• Tcl: tool command language– scripting language– extensible by writing C functions• Tk: (windowing) toolkit– widget set for graphical interfaces– (IMHO) the best widget set ever• created by John Ousterhout–Berkeley, ~1990– see www.tcl.tk• embeddings in other languages– TkInter in Python–Perl/Tk–Ruby– ...Tcl example• name-value additionwhile { [gets stdin line] > -1 } {scan $line "%s %s" name valif {[info exists tot($name)]} {incr tot($name) $val} else {set tot($name) $val}}foreach i [array names tot] {puts "[format {%10s %4d} $i $tot($i)]"}Tcl example 2: formatterset space ""; set line ""proc addword {w} {global line spaceif {[expr [string length $line] + [string length $w]] > 60} {printline}set line "$line$space$w"set space " "}proc printline {} {global line spaceif {[string length $line] > 0} {puts $line}set line ""; set space ""}while {[gets stdin in] >= 0} {if {[string length $in] > 0} {for {set i 0} {$i < [llength $in]} {incr i} {addword [lindex $in $i]}} else {printlineputs "\n"}}printlineHello world in TkInter & Ruby• Pythonfrom Tkinter import *root = Tk()frame = Frame(root)frame.pack()button = Button(frame, text="hello world", command=frame.quit)button.pack()root.mainloop()• Rubyrequire 'tk'root = TkRoot.new { }TkButton.new(root) dotext "hello world"command { exit }pack()endTk.mainloopHello world in Javaimport java.awt.*;import java.awt.event.*;import javax.swing.*;public class helloworld extends JFrame {public static void main(String[] args) {helloworld a = new helloworld();}helloworld() {JButton b = new JButton("hello world");b.addActionListener(new ActionListener() {public void actionPerformed(ActionEvent


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