Convert to GutenPalm or to PalmDoc by Charles Vidal About the author: President of a gastronomic lug in Paris. He likes the GNU and Open Source philosophy, because they both allow people to share knowledge. He would like to find time to play Saxophone. Content: Tk the Graphical Toolkit for Tcl :WISH Hello world ! Tk graphical object creation The tree structure of the graphical object in the gui Creation of graphical objects: "hello world" Layouts: Manager of the widgets positions. Associating graphical objects and variables. Layout manager The list of the created widgets Events A little example Ressources Talkback form for this article

An introduction to Tk

Abstract:

This article introduces you to the features of the Tcl graphical toolkit: Tk. We shall see how easy it is to make a GUI (Graphical User Interface) with a few lines of code.

Tk the Graphical Toolkit for Tcl :WISH

Tk has been created to give the Tcl language a graphical toolkit. We usually call it Tcl/Tk; it is pronounced Tikel/Tikey.

It is a mutli-platform graphical toolkit with the look of the native os. It combines perfectly with the Tcl language which is also mutli-platform. The great advantage of Tcl/Tk is its simplicity. The couple allows you to rapidly create portable applications. Just as tclsh exists for tcl, there is wish for Tk.

Hello world !

pack [ label .l -text "Bonjour monde" ]

#include <gtk/gtk.h>
Int main( int   argc,
          char *argv[] )
{
   /* GtkWidget is the storage type for widgets */
    GtkWidget *window;
    GtkWidget *button;

    gtk_init(&&argc, &&argv);
   /* create a new window */
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    button = gtk_button_new_with_label ("Bonjour Monde");
    gtk_container_add (GTK_CONTAINER (window), button);
    gtk_widget_show (button);

    /* and the window */
    gtk_widget_show (window);
    gtk_main ();

    return(0);
}

/* COMPILE  cc xmhello.c -L/usr/X11R6/lib  -lXm -lXt -lX11 -lXmu -o xmhello */

#include <Xm/PushB.h>
#include <Xm/Form.h>

/* Widget */

	Widget      main_widget, pushb;

main(int argc, char **argv)
{
	Widget      form;
	Arg         args[1];
	int         ac = 0;
	XmString    label_str;

	main_widget = XtInitialize(argv[0], "test", NULL, 0, &&argc, argv);
	label_str = XmStringCreate("Bonjour Monde", XmSTRING_DEFAULT_CHARSET);
	XtSetArg(args[ac], XmNlabelString, label_str);
	ac++;
	pushb = XmCreatePushButton(main_widget, "hello", args, ac);
	XtManageChild(pushb);
	XtRealizeWidget(main_widget);
	XtMainLoop();
}

• C
• C++
• Python ( Tkinter )
• Perl
• Eiffel
• Ada
• Modula-3
• caml
• ...For more information

Tk graphical object creation

• labels : label
• buttons : button
• check buttons: checkbutton
• radio buttons  : radiobutton
• menus : menubutton
• menus items : command, radio, check, cascade
• scrollbar : scrollbar
• text : text
• entry  : entry
  
• canvas : canvas
  
• frame : frame
• listbox  : listbox
• scale  :scale
• Misc dialog box ( fileselection box, warning dialog etc. )

To watch a demo of all the available widgets, go into the directory /usr/local/lib/tk8.0/demos/ and launch widget.

The set of these graphical objects is limited (there are no tree widget, combobox ...). However people or companies made some valuable extensions, the most famous is : Tix the widgets Incr Tcl and recently the great BWidget, all of the extensions are available from the scriptics web site.

The tree structure of the graphical object in the gui

• the . for the root
• the .(name_container.)*name_of_graphical_object

Creation of graphical objects: "hello world"

As you can see, the action is carried out by giving the name of the graphical object to create, here a .label, next the name of the container, where . is the root window, and at the end you specify the properties (-text " hello Word "). We notice here that these arguments can be accessed or modified constantly after the creation of the graphical object.

• To access the properties of the graphical object, we use the command cget (for Configuring get).
  Example:

  .mylabel cget text hello world
  

• To modify the configuration, we use the command configure. This command returns the name of the created object, here .mylabel
  Example:

  .mylabel configure -text "Bonjour Monde in french :)"
  

.mylabel configure -text " This is the date [exec date ]"

Layouts: Manager of the widgets positions.

Indeed, you just have created an object of the label type, but you did not ask to display it. This is because the display of this object requires information you did not yet specify; that is in which layout (a layout is a manager which helps positioning windows) you wish to put this object.

1. The packer
2. The placer
3. The grid

Fully featured Hello Word
label .mylabel -text "hello world"
pack .mylabel
Or in one line
pack [label .mylabel -text "hello world"]

The button Let us study the case of a button:

button .myboutton -text "hello world" -command "exit"
pack .myboutton
We notice that the button has a "command" property as an argument (only one). It is the tcl command to execute when the user clicks the button. In this example, the command to execute is exit , this causes the program to quit.

Associating graphical objects and variables.

Example

The checkbuttons and radiobuttons.

1. A checkbutton is a button reflecting a state.
   This button shows a boolean state (set or not). We can associate a variable to it which takes the value 0 (defaut) or 1 according to the state of the checkbutton. But we can also define the value the variable takes according to the state of the checkbutton.
   Example:
   
checkbutton $w.b1 -text "Wipers OK" -variable wipers -relief flat -onvalue "Ok" -offvalue "not Ok"

   
2. A radiobutton is a button reflecting the state of a set of buttons.
   The radiobuttons are often grouped, this allows to choose one among others. In order to group them together, you have to assign them the same variable name and give it the value this variable takes when the radiobutton is selected.
   Exemple:
   
   
   
radiobutton .b1 -text "Premier " -variable size -value 1
radiobutton .b2 -text "Second " -variable size -value 2


Layout manager

1. The packer: It positions the graphical objet according to an orientation:
   1. top
   2. bottom
   3. right
   4. left

   Example:

   pack [ button .b1 -text top ] -side top pack [ button .b2 -text bottom ] -side bottom pack [ button .b3 -text right ] -side right pack [ button .b4 -text right ] -side left

   We can also configure the expansion of the widget inside: option -expand (yes|no) -fill ( x|y| both)
   

2. The placer: We can place a graphical objet at the x y position.

   Example: place [ label .l -text "With Place"] -x 100 -y 100 .l configure -bg red

   
3. The grid places widgets on a virtual grid made of rows and columns. It is the ideal layout for listboxes or multiple line editboxes. The syntax is: First create widgets, for instance .e_name then display them using:
   
label .mainlbl2 -text "Label 2" -bd 2 -relief sunken
grid .mainlbl2 -row 0 -column 1 -sticky news
label .mainlbl1 -text "Label 1" -bd 2 -relief raised
grid .mainlbl1 -row 0 -column 0 -sticky news
label .mainlbl3 -text "Label 3" -bd 2 -relief solid
grid .mainlbl3 -row 1 -column 0
label .mainlbl4 -text "Label 4" -bd 2 -relief groove
grid .mainlbl4 -row 1 -column 1

   

The list of the created widgets

We can get the list the graphical objects created with the command winfo.

 winfo exists name_object

winfo children .

Events

Tk treats the event and executes a command when -command was given to it. But there are cases where one wishes to manage events more precisely or manage several events for one widget. The canvas is such a widget.

A little example

1. We build the gui (proc makegui).
2. We insert all the paths of the widget in a hashtable tabgui.
3. We scan the number of arguments; if it's equal to zero the application exits.
4. We open the handle from a pipe with the program tar -tzvf name_file_tar.
5. We insert each line read from the pipe into the list.

bind all <Control-c> {destroy .}

#!/bin/sh
# the next line restarts using wish \
exec wish8.0 "$0" "$@"

global tabgui

proc makegui { } {
global tabgui
#
# Creation of the  scrollbars for the list
# then the horizontal scrollbar is placed right, filling up horizontally the window
# and the vertical scrollbaris placed below, filling up vertically the window
#
set tabgui(scrollv) [scrollbar .scrollv -command ".list yview"]
pack $tabgui(scrollv) -side right -fill y
set tabgui(scrollh) [scrollbar .scrollh -command ".list xview" -orient horizontal ]
pack $tabgui(scrollh) -side bottom -fill x
#
# Creation of the list associating it to the scrollbar
#
#
set tabgui(list) [listbox .list  \
                -yscroll "$tabgui(scrollv) set" \
                -xscroll "$tabgui(scrollh) set" \
                -relief sunken -width 20 -height 20 \
        -setgrid yes ]
pack $tabgui(list) -side left -fill both -expand yes
wm minsize . 1 1
}

#
# Creation of the GUI
#
makegui

if $argc>0 {set tarfile [lindex $argv 0]} else {puts stderr "tar file missing" ; exit}
set command "tar -tzvf $tarfile"
set tube [ open |$command r]
 while {![eof $tube]} {
    set tarresult  [ gets $tube ]
    $tabgui(list)  insert end $tarresult
}

bind all <Control-c> {destroy .}

Ressources

• A good tutorial (in french)
• Unifix online and the B Widget
• Scriptics

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