# Tcl Programming/Tk

### Introduction

The Tk (Tool Kit) is the most popular Tcl extension for designing
graphical user interfaces (GUI) on Macintosh, Unix/Linux, or Windows
operating systems.

With little effort, it allows to put together useful

-   windows (forms, as some call them) consisting of
-   *widgets*, which are managed by
-   *geometry managers*. Also, you can easily define
-   bindings of mouse or keyboard events to trigger the actions you
    want.

#### Example: calculator

Here is a very simple, complete Tcl/Tk script that implements a
calculator:

`package require Tk`\
`pack [entry .e -textvar e -width 50]`\
`bind .e ``<Return>`{=html}` {`\
`   set e  [regsub { *=.*} $e ""] ;# remove evaluation (Chris)`\
`   catch {expr [string map {/ *1./} $e]} res`\
`   append e " = $res"`\
`} `

It creates an *entry* widget named *.e*, into which you can type from
the keyboard, with an associated variable *e* (which will mirror the
entry\'s content), and manages it with *pack*.

One binding is defined: if with keyboard focus on .e, the
`<Return>`{=html} key is hit, then

-   all division operators (/) in the variable *e* are mapped to
    \"\*1./\" (this forces floating point division),
-   the resulting string is fed to *expr* to evaluate it as an
    arithmetic/logic expression
-   as there may be errors in the user input, the *expr* call is wrapped
    into a *catch* which assigns either the result of *expr*, or the
    error message if one occurred, into the variable *res*
-   the result of the last evaluation is cleared by deleting everything
    after *=*
-   finally, an equal sign and the value of the *res* variable are
    *append*ed to *e*, making input and result immediately visible in
    the entry.

#### Example: a tiny IRC client

As before in the Tcl section, here\'s a working little script again: a
client for IRC (Internet Relay Chat) in 38 lines of code, that features
a **text** and an **entry** widget:

![](Picoirc.gif "Picoirc.gif")

`package require Tk`\
`set ::server irc.freenode.org`\
`set ::chan   #tcl`\
`set ::me     $tcl_platform(user)`\
`text .t -height 30 -wrap word -font {Arial 9}`\
`.t tag config bold   -font [linsert [.t cget -font] end bold]`\
`.t tag config italic -font [linsert [.t cget -font] end italic]`\
`.t tag config blue   -foreground blue`\
`entry .cmd`\
`pack .cmd -side bottom -fill x`\
`pack .t -fill both -expand 1`\
`bind .cmd ``<Return>`{=html}` post`\
`proc recv {} {`\
`    gets $::fd line`\
`    if {[regexp {:([^!]*)![^ ].* +PRIVMSG ([^ :]+) +:(.*)} $line -> \`\
`        nick target msg]} {`\
`        set tag ""`\
`        if [regexp {\001ACTION(.+)\001} $msg -> msg] {set tag italic}`\
`        if [in {azbridge ijchain} $nick] {regexp {<([^>]+)>(.+)} $msg -> nick msg}`\
`       .t insert end $nick\t bold $msg\n $tag`\
`    } else {.t insert end $line\n italic}`\
`    .t yview end`\
`}`\
`proc in {list element} {expr {[lsearch -exact $list $element]>=0}}`\
`proc post {} {`\
`    set msg [.cmd get]`\
`    if [regexp {^/me (.+)} $msg -> action] {set msg "\001ACTION $action\001"}`\
`    foreach line [split $msg \n] {send "PRIVMSG $::chan :$line"}`\
`    .cmd delete 0 end`\
`    set tag ""`\
`    if [regexp {\001ACTION(.+)\001} $msg -> msg] {set tag italic}`\
`    .t insert end $::me\t {bold blue} $msg\n [list blue $tag]`\
`    .t yview end`\
`}`\
`proc send str {puts $::fd $str; flush $::fd}`\
`set ::fd [socket $::server 6667]`\
`send "NICK $::me"`\
`send "USER $::me 0 * :PicoIRC user"`\
`send "JOIN $::chan"`\
`fileevent $::fd readable recv`\
`bind . ``<Escape>`{=html}` {exec wish $argv0 &; exit}`

The last line is a quick debugging helper: if you modified the script in
the editor, save to disk, then hit `<Escape>`{=html} in the app to start
it anew.

### Widgets

Widgets are GUI objects that, when mapped by a geometry manager,
correspond to a rectangular area on the screen, with different
properties and capabilities.

Widgets are named with *path* names, somehow resembling file system path
names, except that the separator for widgets is a period \".\". For
example, *.foo.bar* is a child of *foo* which is a child of \".\"
Parent-child relation occurs typically with containers, e.g. *toplevel,
frame, canvas, text*. The name parts (i.e. between the dots) can be
almost any string that does not contain \".\" of course, or starts with
a Capital Letter (this is because widget class names with capital
initial have a special meaning, they denote class-wide options).

If you have a proc that takes a parent widget *w* and adds children, it
may be important to distinguish whether *w* is \".\" or another -
because you can\'t concatenate a child widget name directly to \".\" -
\$w.kid will make an invalid name if \$w == \".\". Here\'s how to avoid
this:

`set w2 [expr {$w eq "."? "": $w}]`\
`button $w2.$kid ...`

Widgets are created by a command named after their class, which then
takes the path name (requiring that parent widgets have to exist by that
time) and any number of *-key value* options that make up the original
configuration, e.g.

`button .b -text "Hello!" -command {do something}`

After creation, communication with the widget goes via a created command
that corresponds to its name. For instance, the configuration options
can be queried

`set text [.b cget -text]`

or changed

`.b configure -text Goodbye! -background red`

Some \"methods\" like *cget, configure* are generic to all widget
classes, others are specific to one or a few. For instance, both
\'text*and*entry*accept the*insert\'\' method. See the manual pages for
all the details.

Widgets appear on screen only after they have been given to a **geometry
manager** (see more below). Example:

`text .t -wrap word`\
`pack .t -fill both -expand 1`

As widget creation commands return the pathname, these two steps can
also be nested like

`pack [text .t -wrap word] -fill both -expand 1`

The **destroy** command deletes a widget and all of its child widgets,
if present:

`destroy .b`

The following sub-chapters describe the widgets available in Tk.

------------------------------------------------------------------------

#### button

With text and/or image, calls a configurable command when clicked.
Example:

`button .b -text Hello! -command {puts "hello, world"}`

#### canvas

Scrollable graphic surface for line, rectangle, polygon, oval, and text
items, as well as bitmaps and photo images and whole embedded windows.
See for example \"A tiny drawing program\" below. Example:

`pack [canvas .c -background white]`\
`.c create line 50 50 100 100 150 50 -fill red -width 3`\
`.c create text 100 50 -text Example`

**Pan a canvas** (scroll it inside its window with middle mouse-button
held down) by inheriting the text widget bindings:

` bind .c <2> [bind Text <2>]`\
` bind .c ``<B2-Motion>`{=html}` [bind Text ``<B2-Motion>`{=html}`]`

#### entry

One-line editable text field, horizontally scrollable (see example
above). You can specify a validation function to constrain what is
entered. Example:

`entry .e -width 20 -textvariable myVar`\
`set myVar "this text appears in the entry"`

#### frame

Container for several widgets, often used with *pack*, or for wrapping
\"megawidgets\"

#### label

One- or multiline field for text display, can be tied to a text variable
to update when that variable changes. Linebreaks are specified by \\n in
the text to be displayed.

#### labelframe

A container similar to a **frame**, decorated with a thin rectangle
around, and a label at top-left position. Example (a tiny radio band
selector):

`pack [labelframe .lf -text Band]`\
`pack [radiobutton .lf.am -text AM -variable band -value AM]`\
`pack [radiobutton .lf.fm -text FM -variable band -value FM]`\
`set band AM`

![](Labelframe_radiobuttons.jpg "Labelframe_radiobuttons.jpg")

#### listbox

Multiline display of a list, scrollable. Single or multiple items can be
selected with the mouse.

#### menu

To add a menu to a GUI application, take steps of three kinds:

-   Create the toplevel horizontal menu (needed only once):

`. configure -menu [menu .m]`

-   For each item in the top menu, create a cascaded submenu, e.g.

`.m add cascade -label File -menu [menu .m.mFile]`

-   For each entry in a submenu, add it like this:

`.m.mFile add command -label Open -command {openFile ...}`\
`.m.mFile add separator`

As these commands are a bit verbose, one can wrap them into a little
helper:

`proc m+ {head name {cmd ""}} {`\
`   if {![winfo exists .m.m$head]} {`\
`        .m add cascade -label $head -menu [menu .m.m$head -tearoff 0]`\
`   }`\
`   if [regexp ^-+$ $name] {`\
`           .m.m$head add separator`\
`   } else {.m.m$head add command -label $name -comm $cmd}`\
`}`

Demo example - now menu items can be created in a much clearer way:

`. configure -menu [menu .m]`\
`m+ File Open {.t insert end "opened\n"}`\
`m+ File Save {.t insert end "saved\n"}`\
`m+ File -----`\
`m+ File Exit exit`\
`m+ Edit Cut ...`\
`pack [text .t -wrap word] -fill both -expand 1`

#### radiobutton

A button with a selector field which can be on or off, and a label.
Clicking the selector field with the mouse changes the value of an
associated global variable. Typically, multiple radiobuttons are tied to
the same variable. For examples, see **labelframe** above.

#### scrollbar

Horizontal or vertical scrollbars (vertical being the default, for
horizontal specify: -orientation horizontal, or -ori hori if you like it
short) can be tied to canvas, entry, listbox or text widgets. The
interaction between a scrollbar and its scrolled widget goes with
callbacks, in which one notifies the other:

-   scrollbar to widget: *xview* or *yview* method
-   widget to scrollbar: *set* method

Arguments to these methods will be automatically added when the
callbacks are invoked.

For example, here\'s how to connect a text widget with a vertical
scrollbar:

`pack [scrollbar .y -command ".t yview"] -side right -fill y`\
`pack [text .t -wrap word -yscrollc ".y set"] \`\
`     -side right -fill both -expand 1`

With most widgets, scrollbars adjust automatically to the widget\'s
contents. For canvas widgets, you need to update the scrollregion after
adding new items. most simply like this:

`$canvas configure -scrollregion [$canvas bbox all]`

#### text

Scrollable editable multiline text with many formatting options. Can
also contain images and embedded widgets. The default wrapping setting
is \"none\", so you might need a horizontal scrollbar to see all of long
lines. In many cases it\'s more user-friendly to configure a text widget
as *-wrap word* - then you only need a vertical scrollbar at most.

Positions in a text widget are specified as *line.column*, where line
starts from 1, and column from 0, so 1.0 is the very first character in
a text widget. Example how to delete all contents:

`$t delete 1.0 end`

For highlighting part of the contents, you can define *tags* and assign
them to subsequences:

`$t tag configure ul -underline 1`\
`$t insert end "The next word is " {} underlined ul ", the rest is not."`

#### toplevel

Standalone frame window, mostly with decorations (title bar, buttons)
from the window manager. When you start Tk, you receive an initially
empty toplevel named \".\" (one dot). If you want more toplevels, create
them like this:

`toplevel .mySecondWindow`

Such toplevels are logically children of \".\". To assign a nice title
to a toplevel, use

`wm title $toplevel "This is the title"`

You can also control the geometry (size and position) of a toplevel with

`wm geometry $toplevel ${width}x$height+$x+$y`

------------------------------------------------------------------------

### Geometry managers

------------------------------------------------------------------------

The purpose of geometry managers is to compute the required height,
width, and location of widgets, and map them on screen. Besides *grid*,
*pack* and *place*, the *canvas* and *text* widgets can also manage
embedded widgets.

Calls to geometry managers always start with the manager\'s name, then
(mostly) one or more widget names, then any number of *-name value*
options

#### grid

This geometry manager is best suited for tabular window layout
consisting of rows and columns. Example, to put three widgets in a
horizontal row:

`grid .1 .2 .3 -sticky news`

The *-sticky* option indicates what side of its box the widget should
stick to, in compass direction; \"news\" is north-east-west-south\",
i.e. all four sides.

Here\'s a minimal solution to display a table (list of lists) in a grid
of labels:

![](grid_table.jpg "grid_table.jpg")

`package require Tk`\
`proc table {w content args} {`\
`    frame $w -bg black`\
`    set r 0`\
`    foreach row $content {`\
`        set fields {}`\
`        set c 0`\
`        foreach col $row {`\
`            lappend fields [label $w.$r/$c -text $col]`\
`            incr c`\
`        }`\
`        eval grid $fields -sticky news -padx 1 -pady 1`\
`        incr r`\
`    }`\
`    set w`\
`}`

`#--- Test:`\
`table .t {`\
`   {Row Head1 Head2}`\
`   {1   foo   42}`\
`   {2   bar   1234}`\
`   {3   grill testing}`\
`}`\
`pack .t`

`#--- Changing the contents, given row and column number:`\
`after 2000 .t.3/2 config -text Coucou`

#### pack

This used to be the workhorse manager, but in recent years has been less
popular than **grid**. Anyway, it is still good for cases where you have
widgets aligned in only one direction (horizontally or vertically). For
more complex layouts, one used to insert intermediate frames, but grid
makes such jobs just easier. Example:

`pack .x -fill both -expand 1 -side left`

#### place

This geometry manager is not often used, mostly for special
applications, like when you want to highlight the current tab of a tab
notebook. It allows pixel-precise placement of widgets, but is less
dynamic in reaction to resizing of the toplevel or inner widgets.

### Dialogs

Dialogs are toplevels that are to tell a message, or answer a question.
You don\'t have to assign a widget path name to them. Just call them as
functions and evaluate the result (often \"\" if the dialog was
canceled).

#### tk_getOpenFile

A file selector dialog (limited to existing files). Returns the selected
file with path name, or \"\" if canceled.

#### tk_getSaveFile

A file selector dialog, which also allows specification of a not
existing file. Returns the selected file with path name, or \"\" if
canceled.

#### tk_messageBox

A simple dialog that displays a string and can be closed with an \"OK\"
button. Example:

`tk_messageBox -message "hello, world!"`

#### tk_chooseColor

Displays a dialog for color selection. The returned value is the
selected color in one of the representations conformant to Tcl\'s
comprehension of such information; on Microsoft Windows systems this
might constitute a hexadecimal string in the format "#RRGGBB". Upon
abortion of the process, the empty string is instead delivered. The
dialog may be configured to preselect a certain default color via the
"-initialcolor" option, a subordination into a parent widget with
"-parent", and a title caption through "-title".

` tk_chooseColor -initialcolor #FF0000 -parent . -title "What tincture do you wish?"`

#### Custom dialogs

Besides the prefabricated dialogs that come with Tk, it\'s also not too
hard to build custom ones. As a very simple example, here\'s a \"value
dialog\" that prompts the user for to type in a value:

![](ValueDialog.jpg "ValueDialog.jpg")

`proc value_dialog {string} {`\
`   set w [toplevel .[clock seconds]]`\
`   wm resizable $w 0 0`\
`   wm title $w "Value request"`\
`   label  $w.l -text $string`\
`   entry  $w.e -textvar $w -bg white`\
`   bind $w.e ``<Return>`{=html}` {set done 1}`\
`   button $w.ok     -text OK     -command {set done 1}`\
`   button $w.c      -text Clear  -command "set $w {}"`\
`   button $w.cancel -text Cancel -command "set $w {}; set done 1"`\
`   grid $w.l  -    -        -sticky news`\
`   grid $w.e  -    -        -sticky news`\
`   grid $w.ok $w.c $w.cancel`\
`   vwait done`\
`   destroy $w`\
`   set ::$w`\
`}`

Test:

`set test [value_dialog "Give me a value please:"]`\
`puts test:$test`\
`pack [ label .l -text "Value: '$test' " ]`

For a more elaborate example, here is a record editor dialog (multiple
fields, each with a label and entry (or text for multi-line input)):

`proc editRecord {title headers fields} {`\
`    set oldfocus [focus]`\
`    set w [toplevel .[clock clicks]]`\
`    wm resizable $w 1 0`\
`    wm title $w $title`\
`    set n 0`\
`    foreach h $headers f $fields {`\
`        if ![regexp {(.+)([=+])} $h -> hdr type] {set hdr $h; set type ""}`\
`        label $w.h$n -text $hdr -anchor ne`\
`        switch -- $type {`\
`            = {label $w.e$n -width [string length $f] -text $f -anchor w -bg white}`\
`            + {[text $w.e$n -width 20 -height 6] insert end $f}`\
`            default {[entry $w.e$n -width [string length $f]] insert end $f}`\
`        }`\
`        grid $w.h$n $w.e$n -sticky news`\
`        incr n`\
`    }`\
`    button $w.ok -text OK -width 5 -command [list set $w 1]`\
`    button $w.cancel -text Cancel -command [list set $w 0]`\
`    grid $w.ok $w.cancel -pady 5`\
`    grid columnconfigure $w 1 -weight 1`\
`    vwait ::$w`\
`    if [set ::$w] { #-- collect the current entry contents`\
`        set n 0`\
`        foreach h $headers f $fields {`\
`            regexp {([^=+].+)([=+]?)} $h -> hdr type`\
`            switch -- $type {`\
`                "" {lappend res [$w.e$n get]}`\
`                =  {lappend res [$w.e$n cget -text]}`\
`                +  {lappend res [$w.e$n get 1.0 end]}`\
`            }`\
`            incr n`\
`        }`\
`    } else {set res {}}`\
`    destroy $w`\
`    unset ::$w ;#-- clean up the vwait variable`\
`    focus $oldfocus`\
`    return $res`\
`}`

Quick test:

`editRecord Test {foo= bar grill+} {one two three}`

### Megawidgets made easy

The term \"megawidgets\" is popular for compound widgets that in
themselves contain other widgets, even though they will hardly number a
million (what the prefix *Mega-* suggests), more often the child
widgets\' number will not exceed ten.

To create a megawidget, one needs one proc with the same signature as Tk
widget creation commands. This proc will, when called, create another
proc named after the widget, and dispatch methods either to specific
handlers, or the generic widget command created by Tk.

#### A little notebook

Plain Tk does not contain a \"notebook\" widget, with labeled tabs on
top that raise one of the \"pages\", but it\'s easy to make one. This
example demonstrates how the tabs are implemented as buttons in a frame,
and how the original Tk command named like the frame is \"overloaded\"
to accept the additional *add* and *raise* methods:

`proc notebook {w args} {`\
`   frame $w`\
`   pack [frame $w.top] -side top -fill x -anchor w`\
`   rename $w _$w`\
`   proc $w {cmd args} { #-- overloaded frame command`\
`       set w [lindex [info level 0] 0]`\
`       switch -- $cmd {`\
`           add     {notebook'add   $w $args}`\
`           raise   {notebook'raise $w $args}`\
`           default {eval [linsert $args 0 _$w $cmd]}`\
`       }`\
`   }`\
`   return $w`\
`}`

`proc notebook'add {w title} {`\
`   set btn [button $w.top.b$title -text $title -command [list $w raise $title]]`\
`   pack $btn -side left -ipadx 5`\
`   set f [frame $w.f$title -relief raised -borderwidth 2]`\
`   pack $f -fill both -expand 1`\
`   $btn invoke`\
`   bind $btn <3> "destroy {$btn}; destroy {$f}" ;# (1)`\
`   return $f`\
`}`

`proc notebook'raise {w title} {`\
`   foreach i [winfo children $w.top] {$i config -borderwidth 0}`\
`   $w.top.b$title config -borderwidth 1`\
`   set frame $w.f$title`\
`   foreach i [winfo children $w] {`\
`       if {![string match *top $i] && $i ne $frame} {pack forget $i}`\
`   }`\
`   pack $frame -fill both -expand 1`\
`}`

Test and demo code:

`package require Tk`\
`pack [notebook .n] -fill both -expand 1`\
`set p1 [.n add Text]`\
`pack   [text $p1.t -wrap word] -fill both -expand 1`\
`set p2 [.n add Canvas]`\
`pack   [canvas $p2.c -bg yellow] -fill both -expand 1`\
`set p3 [.n add Options]`\
`pack   [button $p3.1 -text Console -command {console show}]`\
`.n raise Text`\
`wm geometry . 400x300`

### Binding events

Events within Tcl/Tk include actions performed by the user, such as
pressing a key or clicking the mouse. To react to mouse and keyboard
activity, the bind command is used. As shown in the calculator example:

``` tcl
 pack [entry .e -textvar e -width 50]
 bind .e <Return> {
```

The `bind` keyword operates on `.e` and associates the event related to
the `<return>` event. The following bracket indicates a start of a set
of procedures which are executed when the event is performed.

### BWidget

BWidget is an extension to Tk written in pure Tcl (therefore it can even
run on Windows Mobile-driven cell phones). It offers mega-widgets (all
class names starting with Uppercase) like

-   ComboBox
-   NoteBook
-   Tree

!`ifile01.jpg`

*Screenshot of a NoteBook and a Tree, on a PocketPC under Windows/CE*

#### Tree examples

Here is a \"hello world\" example of a Tree widget (this is a complete
script). The root node is constantly called *root*, for the others you
have to make up names:

`package require BWidget`\
`pack [Tree .t]`\
`.t insert end root n1  -text hello`\
`.t insert end root n2  -text world`\
`.t insert end n2   n21 -text (fr:monde)`\
`.t insert end n2   n22 -text (de:Welt)`

The famous typewriter test sentence represented as a syntax tree:

`package require BWidget`\
`pack [Tree .t -height 16] -fill both -expand 1`\
`foreach {from to text} {`\
`   root S S`\
`   S   np1  NP`\
`   S   vp   VP`\
`   np1 det1 Det:The`\
`   np1 ap1  AP`\
`   ap1 adj1 Adj:quick`\
`   ap1 adj2 Adj:brown`\
`   ap1 n1   N:fox`\
`   vp  v    V:jumps`\
`   vp  pp   PP`\
`   pp  prep Prep:over`\
`   pp  np2  NP`\
`   np2 det2 Det:the`\
`   np2 ap2  AP`\
`   ap2 adj3 Adj:lazy`\
`   ap2 n2   N:dog`\
`   `\
`} {.t insert end $from $to -text $text}`\
`.t opentree S`

### Tk resources

#### Colors

Colors in Tk can be specified in three ways:

-   a symbolic name, like: red green blue yellow magenta cyan
-   a hex string preceded by a #: #RGB, #RRGGBB, #RRRRGGGGBBBB
-   a list of three non-negative integers

The last form is only returned by commands. To specify a color to a
command, you\'ll have to hex-format it. For instance, white could be
described as #FFFFFF.

To turn a symbolic name into its RGB components:

`winfo rgb . $colorname`

Here is the list of defined color names (as from X11\'s rgb.txt):

`set COLORS { snow {ghost white} {white smoke} gainsboro {floral white}`\
`   {old lace} linen {antique white} {papaya whip} {blanched almond}`\
`   bisque {peach puff} {navajo white} moccasin cornsilk ivory {lemon`\
`   chiffon} seashell honeydew {mint cream} azure {alice blue}`\
`   lavender {lavender blush} {misty rose} white black {dark slate`\
`   gray} {dim gray} {slate gray} {light slate gray} gray {light grey}`\
`   {midnight blue} navy {cornflower blue} {dark slate blue} {slate`\
`   blue} {medium slate blue} {light slate blue} {medium blue} {royal`\
`   blue} blue {dodger blue} {deep sky blue} {sky blue} {light sky`\
`   blue} {steel blue} {light steel blue} {light blue} {powder blue}`\
`   {pale turquoise} {dark turquoise} {medium turquoise} turquoise`\
`   cyan {light cyan} {cadet blue} {medium aquamarine} aquamarine`\
`   {dark green} {dark olive green} {dark sea green} {sea green}`\
`   {medium sea green} {light sea green} {pale green} {spring green}`\
`   {lawn green} green chartreuse {medium spring green} {green yellow}`\
`   {lime green} {yellow green} {forest green} {olive drab} {dark`\
`   khaki} khaki {pale goldenrod} {light goldenrod yellow} {light`\
`   yellow} yellow gold {light goldenrod} goldenrod {dark goldenrod}`\
`   {rosy brown} {indian red} {saddle brown} sienna peru burlywood`\
`   beige wheat {sandy brown} tan chocolate firebrick brown {dark`\
`   salmon} salmon {light salmon} orange {dark orange} coral {light`\
`   coral} tomato {orange red} red {hot pink} {deep pink} pink {light`\
`   pink} {pale violet red} maroon {medium violet red} {violet red}`\
`   magenta violet plum orchid {medium orchid} {dark orchid} {dark`\
`   violet} {blue violet} purple {medium purple} thistle snow2 snow3`\
`   snow4 seashell2 seashell3 seashell4 AntiqueWhite1 AntiqueWhite2`\
`   AntiqueWhite3 AntiqueWhite4 bisque2 bisque3 bisque4 PeachPuff2`\
`   PeachPuff3 PeachPuff4 NavajoWhite2 NavajoWhite3 NavajoWhite4`\
`   LemonChiffon2 LemonChiffon3 LemonChiffon4 cornsilk2 cornsilk3`\
`   cornsilk4 ivory2 ivory3 ivory4 honeydew2 honeydew3 honeydew4`\
`   LavenderBlush2 LavenderBlush3 LavenderBlush4 MistyRose2 MistyRose3`\
`   MistyRose4 azure2 azure3 azure4 SlateBlue1 SlateBlue2 SlateBlue3`\
`   SlateBlue4 RoyalBlue1 RoyalBlue2 RoyalBlue3 RoyalBlue4 blue2 blue4`\
`   DodgerBlue2 DodgerBlue3 DodgerBlue4 SteelBlue1 SteelBlue2`\
`   SteelBlue3 SteelBlue4 DeepSkyBlue2 DeepSkyBlue3 DeepSkyBlue4`\
`   SkyBlue1 SkyBlue2 SkyBlue3 SkyBlue4 LightSkyBlue1 LightSkyBlue2`\
`   LightSkyBlue3 LightSkyBlue4 SlateGray1 SlateGray2 SlateGray3`\
`   SlateGray4 LightSteelBlue1 LightSteelBlue2 LightSteelBlue3`\
`   LightSteelBlue4 LightBlue1 LightBlue2 LightBlue3 LightBlue4`\
`   LightCyan2 LightCyan3 LightCyan4 PaleTurquoise1 PaleTurquoise2`\
`   PaleTurquoise3 PaleTurquoise4 CadetBlue1 CadetBlue2 CadetBlue3`\
`   CadetBlue4 turquoise1 turquoise2 turquoise3 turquoise4 cyan2 cyan3`\
`   cyan4 DarkSlateGray1 DarkSlateGray2 DarkSlateGray3 DarkSlateGray4`\
`   aquamarine2 aquamarine4 DarkSeaGreen1 DarkSeaGreen2 DarkSeaGreen3`\
`   DarkSeaGreen4 SeaGreen1 SeaGreen2 SeaGreen3 PaleGreen1 PaleGreen2`\
`   PaleGreen3 PaleGreen4 SpringGreen2 SpringGreen3 SpringGreen4`\
`   green2 green3 green4 chartreuse2 chartreuse3 chartreuse4`\
`   OliveDrab1 OliveDrab2 OliveDrab4 DarkOliveGreen1 DarkOliveGreen2`\
`   DarkOliveGreen3 DarkOliveGreen4 khaki1 khaki2 khaki3 khaki4`\
`   LightGoldenrod1 LightGoldenrod2 LightGoldenrod3 LightGoldenrod4`\
`   LightYellow2 LightYellow3 LightYellow4 yellow2 yellow3 yellow4`\
`   gold2 gold3 gold4 goldenrod1 goldenrod2 goldenrod3 goldenrod4`\
`   DarkGoldenrod1 DarkGoldenrod2 DarkGoldenrod3 DarkGoldenrod4`\
`   RosyBrown1 RosyBrown2 RosyBrown3 RosyBrown4 IndianRed1 IndianRed2`\
`   IndianRed3 IndianRed4 sienna1 sienna2 sienna3 sienna4 burlywood1`\
`   burlywood2 burlywood3 burlywood4 wheat1 wheat2 wheat3 wheat4 tan1`\
`   tan2 tan4 chocolate1 chocolate2 chocolate3 firebrick1 firebrick2`\
`   firebrick3 firebrick4 brown1 brown2 brown3 brown4 salmon1 salmon2`\
`   salmon3 salmon4 LightSalmon2 LightSalmon3 LightSalmon4 orange2`\
`   orange3 orange4 DarkOrange1 DarkOrange2 DarkOrange3 DarkOrange4`\
`   coral1 coral2 coral3 coral4 tomato2 tomato3 tomato4 OrangeRed2`\
`   OrangeRed3 OrangeRed4 red2 red3 red4 DeepPink2 DeepPink3 DeepPink4`\
`   HotPink1 HotPink2 HotPink3 HotPink4 pink1 pink2 pink3 pink4`\
`   LightPink1 LightPink2 LightPink3 LightPink4 PaleVioletRed1`\
`   PaleVioletRed2 PaleVioletRed3 PaleVioletRed4 maroon1 maroon2`\
`   maroon3 maroon4 VioletRed1 VioletRed2 VioletRed3 VioletRed4`\
`   magenta2 magenta3 magenta4 orchid1 orchid2 orchid3 orchid4 plum1`\
`   plum2 plum3 plum4 MediumOrchid1 MediumOrchid2 MediumOrchid3`\
`   MediumOrchid4 DarkOrchid1 DarkOrchid2 DarkOrchid3 DarkOrchid4`\
`   purple1 purple2 purple3 purple4 MediumPurple1 MediumPurple2`\
`   MediumPurple3 MediumPurple4 thistle1 thistle2 thistle3 thistle4`\
`   gray1 gray2 gray3 gray4 gray5 gray6 gray7 gray8 gray9 gray10`\
`   gray11 gray12 gray13 gray14 gray15 gray16 gray17 gray18 gray19`\
`   gray20 gray21 gray22 gray23 gray24 gray25 gray26 gray27 gray28`\
`   gray29 gray30 gray31 gray32 gray33 gray34 gray35 gray36 gray37`\
`   gray38 gray39 gray40 gray42 gray43 gray44 gray45 gray46 gray47`\
`   gray48 gray49 gray50 gray51 gray52 gray53 gray54 gray55 gray56`\
`   gray57 gray58 gray59 gray60 gray61 gray62 gray63 gray64 gray65`\
`   gray66 gray67 gray68 gray69 gray70 gray71 gray72 gray73 gray74`\
`   gray75 gray76 gray77 gray78 gray79 gray80 gray81 gray82 gray83`\
`   gray84 gray85 gray86 gray87 gray88 gray89 gray90 gray91 gray92`\
`   gray93 gray94 gray95 gray97 gray98 gray99`\
`}`

In addition, the following are defined on Windows:

`set WINDOWSCOLORS {`\
`   SystemButtonFace SystemButtonText SystemDisabledText SystemHighlight`\
`   SystemHightlightText SystemMenu SystemMenuText SystemScrollbar`\
`   SystemWindow SystemWindowFrame SystemWindowText`\
`}`

#### Cursors

For every widget, you can specify how the mouse cursor should look when
over it. Here\'s the list of defined cursor names:

`set cursors {`\
`   X_cursor arrow based_arrow_down based_arrow_up boat bogosity`\
`   bottom_left_corner bottom_right_corner bottom_side bottom_tee`\
`   box_spiral center_ptr circle clock coffee_mug cross cross_reverse`\
`   crosshair diamond_cross dot dotbox double_arrow draft_large draft_small`\
`   draped_box exchange fleur gobbler gumby hand1 hand2 heart icon`\
`   iron_cross left_ptr left_side left_tee leftbutton ll_angle lr_angle`\
`   man middlebutton mouse pencil pirate plus question_arrow right_ptr`\
`   right_side right_tee rightbutton rtl_logo sailboat sb_down_arrow`\
`   sb_h_double_arrow sb_left_arrow sb_right_arrow sb_up_arrow`\
`   sb_v_double_arrow shuttle sizing spider spraycan star target tcross`\
`   top_left_arrow top_left_corner top_right_corner top_side top_tee `\
`   trek ul_angle umbrella ur_angle watch xterm`\
`}`

A little tool that presents the cursor names, and shows each cursor
shape when mousing over:

`set ncols 4`\
`for {set i 0} {$i<$ncols} {incr i} {`\
`   lappend cols col$i`\
`}`\
`set nmax [expr {int([llength $cursors]*1./$ncols)}]`\
`foreach col $cols {`\
`   set $col [lrange $cursors 0 $nmax]`\
`   set cursors [lrange $cursors [expr $nmax+1] end]`\
`}`\
`label .top -text "Move the cursor over a name to see how it looks" \`\
`   -relief ridge`\
`grid .top -columnspan $ncols -sticky news -ipady 2`\
`for {set i 0} {$i<[llength $col0]} {incr i} {`\
`   set row {}`\
`   foreach col $cols {`\
`       set name [lindex [set $col] $i]`\
`       if {$name eq ""} break`\
`       lappend row .l$name`\
`       label .l$name -text $name -anchor w`\
`       bind .l$name ``<Enter>`{=html}` [list %W config -cursor $name]`\
`   }`\
`   eval grid $row -sticky we`\
`}`

#### Fonts

Fonts are provided by the windowing system. Which are available depends
on the local installation. Find out which fonts are available with

`font families`

The typical description of a font is a list of up to three elements:

`family size ?style?`

Example:

`set f ``{{Bitstream Cyberbit} 10 bold}
Family is a name like Courier, Helvetica, Times, ... Best pick one of the names delivered by ''font families'', though there may be some mappings like "Helvetica" -> "Arial"

Size is point size (a typographer's point is 1/72th of an inch) if positive, or pixel size if negative. Normal display fonts often have a size of 9 or 10.

Style can be a list of zero or more of bold, italic, underlined, ...

==== Images: photos and bitmaps ====

Tk allows simple yet powerful operations on images. These come in two varieties: bitmaps and photos. Bitmaps are rather limited in functionality, they can be specified in XBM format, and rendered in configurable colors.

Photos have much more possibilities - you can load and save them in different file formats (Tk itself supports PPM and GIF - for others, use the Img extension), copy them with many options, like scaling/subsampling or mirroring, and get or set the color of single pixels.

Setting can also do rectangular regions in one go, as the following example shall demonstrate that creates a photo image of a tricolore flag (three even-spaced vertical bands - like France, Italy, Belgium, Ireland and many more). The default is France.
You can specify the width, the height will be 2/3 of that.
The procedure returns the image name - just save it in -format GIF if you want:

 proc tricolore {w {colors {blue white red}}`{=mediawiki}`} {`\
`   set im [image create photo]`\
`   set fromx 0`\
`   set dx [expr $w/3]`\
`   set tox $dx`\
`   set toy [expr $w*2/3]`\
`   foreach color $colors {`\
`       $im put $color -to $fromx 0 $tox $toy`\
`       incr fromx $dx; incr tox $dx`\
`   }`\
`   set im`\
`}`

`# Test - display flag on canvas:`\
`pack [canvas .c -width 200 -height 200 -background grey]`\
`.c create image 100 100 -image [tricolore 150]`

`# Test - save image of flag to file:`\
`[tricolore 300] write tric.gif -format gif`

### Debugging Tk programs

A Tk program under development can be very rapidly debugged by adding
such bindings:

`bind . ``<F1>`{=html}` {console show}`

This works only on Windows and Macintosh (pre-OS-X) and brings up a
console in which you can interact with the Tcl interpreter, inspect or
modify global variables, configure widgets, etc.

`bind . ``<Escape>`{=html}` {eval [list exec wish $argv0] $argv &; exit}`

This starts a new instance of the current program (assuming you edited a
source file and saved it to disk), and then terminates the current
instance.

For short debugging output, one can also use the window\'s title bar.
For example, to display the current mouse coordinates when it moves:

`bind . ``<Motion>`{=html}` {wm title . %X/%Y}`

### Other languages

Other programming languages have modules that interface and use Tcl/Tk:

-   In R (programming language), there\'s a tcltk library, invoked with
    the command **library(tcltk)**
-   In Python, there\'s a tkinter module, invoked with **import
    tkinter** or **from tkinter import \***
-   Common Lisp can communicate with Tcl/Tk via several externally
    available libraries, including **CL-TK** and **LTK**

