Ubuntu Manpage: Tk::Listbox - Create and manipulate Listbox widgets

Provided by: perl-tk_804.036+dfsg1-1ubuntu3_amd64

NAME

       Tk::Listbox - Create and manipulate Listbox widgets

SYNOPSIS

       $listbox = $parent->Listbox(?options?);

STANDARD OPTIONS

       -background -borderwidth -cursor -disabledforeground -exportselection -font -foreground -height
       -highlightbackground -highlightcolor -highlightthickness -offset -relief -selectbackground
       -selectborderwidth -selectforeground -setgrid -state -takefocus -tile -width -xscrollcommand
       -yscrollcommand

       See Tk::options for details of the standard options.

WIDGET-SPECIFIC OPTIONS

Name: activeStyle
Class: ActiveStyle
Switch: -activestyle
Specifies the style in which to draw the active element. This must be one of dotbox (show a focus
ring around the active element), none (no special indication of active element) or underline
(underline the active element). The default is underline.

Name: height
Class: Height
Switch: -height
Specifies the desired height for the window, in lines. If zero or less, then the desired height for
the window is made just large enough to hold all the elements in the listbox.

Name: listVariable
Class: Variable
Switch: -listvariable
The following is only partially implemented in Perl/Tk:

Specifies the reference of a variable. The value of the variable is an array to be displayed inside
the widget; if the variable value changes then the widget will automatically update itself to reflect
the new value. Attempts to assign a variable with an invalid list value to -listvariable will cause
an error. Attempts to unset a variable in use as a -listvariable will fail but will not generate an
error.

Name: selectMode
Class: SelectMode
Switch: -selectmode
Specifies one of several styles for manipulating the selection. The value of the option may be
arbitrary, but the default bindings expect it to be either single, browse, multiple, or extended;
the default value is browse.

Name: state
Class: State
Switch: -state
Specifies one of two states for the listbox: normal or disabled. If the listbox is disabled then
items may not be inserted or deleted, items are drawn in the -disabledforeground color, and selection
cannot be modified and is not shown (though selection information is retained).

Name: width
Class: Width
Switch: -width
Specifies the desired width for the window in characters. If the font doesn't have a uniform width
then the width of the character ``0'' is used in translating from character units to screen units.
If zero or less, then the desired width for the window is made just large enough to hold all the
elements in the listbox.

DESCRIPTION

The Listbox method creates a new window (given by the $widget argument) and makes it into a listbox
widget. Additional options, described above, may be specified on the command line or in the option
database to configure aspects of the listbox such as its colors, font, text, and relief. The listbox
command returns its $widget argument. At the time this command is invoked, there must not exist a window
named $widget, but $widget's parent must exist.

A listbox is a widget that displays a list of strings, one per line. When first created, a new listbox
has no elements. Elements may be added or deleted using methods described below. In addition, one or
more elements may be selected as described below. If a listbox is exporting its selection (see
exportSelection option), then it will observe the standard X11 protocols for handling the selection.
Listbox selections are available as type STRING; the value of the selection will be the text of the
selected elements, with newlines separating the elements.

It is not necessary for all the elements to be displayed in the listbox window at once; commands
described below may be used to change the view in the window. Listboxes allow scrolling in both
directions using the standard xScrollCommand and yScrollCommand options. They also support scanning, as
described below.

INDICES

       Many of the methods for listboxes take one or more indices as arguments.  An index specifies a particular
       element of the listbox, in any of the following ways:

       number
           Specifies the element as a numerical index, where 0 corresponds to the first element in the listbox.

       active
           Indicates the element that has the location cursor.  This element will be displayed with an underline
           when the listbox has the keyboard focus, and it is specified with the activate method.

       anchor
           Indicates the anchor point for the selection, which is set with the selection anchor method.

       end Indicates the end of the listbox.  For most commands this refers to the last element in the  listbox,
           but for a few commands such as index and insert it refers to the element just after the last one.

       @x,y
           Indicates  the  element  that  covers  the point in the listbox window specified by x and y (in pixel
           coordinates).  If no element covers that point, then the closest element to that point is used.

       In the method descriptions below, arguments named index, first, and last always contain text  indices  in
       one of the above forms.

WIDGET METHODS

The Listbox method creates a widget object. This object supports the configure and cget methods
described in Tk::options which can be used to enquire and modify the options described above. The widget
also inherits all the methods provided by the generic Tk::Widget class.

The following additional methods are available for listbox widgets:

$listbox->activate(index)
Sets the active element to the one indicated by index. If index is outside the range of elements in
the listbox then the closest element is activated. The active element is drawn with an underline
when the widget has the input focus, and its index may be retrieved with the index active.

$listbox->bbox(index)
Returns a list of four numbers describing the bounding box of the text in the element given by index.
The first two elements of the list give the x and y coordinates of the upper-left corner of the
screen area covered by the text (specified in pixels relative to the widget) and the last two
elements give the width and height of the area, in pixels. If no part of the element given by index
is visible on the screen, or if index refers to a non-existent element, then the result is an empty
string; if the element is partially visible, the result gives the full area of the element,
including any parts that are not visible.

$listbox->curselection
Returns a list containing the numerical indices of all of the elements in the listbox that are
currently selected. If there are no elements selected in the listbox then an empty string is
returned.

$listbox->delete(first, ?last?)
Deletes one or more elements of the listbox. First and last are indices specifying the first and
last elements in the range to delete. If last isn't specified it defaults to first, i.e. a single
element is deleted.

$listbox->get(first, ?last?)
If last is omitted, returns the contents of the listbox element indicated by first, or an empty
string if first refers to a non-existent element. If last is specified, the command returns a list
whose elements are all of the listbox elements between first and last, inclusive. Both first and
last may have any of the standard forms for indices.

$listbox->index(index)
Returns the integer index value that corresponds to index. If index is end the return value is a
count of the number of elements in the listbox (not the index of the last element).

$listbox->insert(index, ?element, element, ...?)
Inserts zero or more new elements in the list just before the element given by index. If index is
specified as end then the new elements are added to the end of the list. Returns an empty string.

$listbox->itemcget(index, option)
Returns the current value of the item configuration option given by option. Option may have any of
the values accepted by the listbox itemconfigure command.

$listbox->itemconfigure(index, ?option, value, option, value, ...?)
Query or modify the configuration options of an item in the listbox. If no option is specified,
returns a list describing all of the available options for the item (see Tk_ConfigureInfo for
information on the format of this list). If option is specified with no value, then the command
returns a list describing the one named option (this list will be identical to the corresponding
sublist of the value returned if no option is specified). If one or more option-value pairs are
specified, then the command modifies the given widget option(s) to have the given value(s); in this
case the command returns an empty string. The following options are currently supported for items:

-background => color
Color specifies the background color to use when displaying the item. It may have any of the
forms accepted by Tk_GetColor.

-foreground => color
Color specifies the foreground color to use when displaying the item. It may have any of the
forms accepted by Tk_GetColor.

-selectbackground => color
Color specifies the background color to use when displaying the item while it is selected. It may
have any of the forms accepted by Tk_GetColor.

-selectforeground => color
Color specifies the foreground color to use when displaying the item while it is selected. It may
have any of the forms accepted by Tk_GetColor.

$listbox->nearest(y)
Given a y-coordinate within the listbox window, this command returns the index of the (visible)
listbox element nearest to that y-coordinate.

$listbox->scan(option, args)
This command is used to implement scanning on listboxes. It has two forms, depending on option:

$listbox->scanMark(x, y)
Records x and y and the current view in the listbox window; used in conjunction with later
scan dragto commands. Typically this command is associated with a mouse button press in the
widget. It returns an empty string.

$listbox->scanDragto(x, y.)
This command computes the difference between its x and y arguments and the x and y arguments
to the last scan mark command for the widget. It then adjusts the view by 10 times the
difference in coordinates. This command is typically associated with mouse motion events in
the widget, to produce the effect of dragging the list at high speed through the window. The
return value is an empty string.

$listbox->see(index)
Adjust the view in the listbox so that the element given by index is visible. If the element is
already visible then the command has no effect; if the element is near one edge of the window then
the listbox scrolls to bring the element into view at the edge; otherwise the listbox scrolls to
center the element.

$listbox->selection(option, arg)
This command is used to adjust the selection within a listbox. It has several forms, depending on
option:

$listbox->selectionAnchor(index)
Sets the selection anchor to the element given by index. If index refers to a non-existent
element, then the closest element is used. The selection anchor is the end of the selection
that is fixed while dragging out a selection with the mouse. The index anchor may be used to
refer to the anchor element.

$listbox->selectionClear(first, ?last?)
If any of the elements between first and last (inclusive) are selected, they are deselected.
The selection state is not changed for elements outside this range.

$listbox->selectionIncludes(index)
Returns 1 if the element indicated by index is currently selected, 0 if it isn't.

$listbox->selectionSet(first, ?last?)
Selects all of the elements in the range between first and last, inclusive, without affecting
the selection state of elements outside that range.

$listbox->size
Returns a decimal string indicating the total number of elements in the listbox.

$listbox->xview(args)
This command is used to query and change the horizontal position of the information in the widget's
window. It can take any of the following forms:

$listbox->xview
Returns a list containing two elements. Each element is a real fraction between 0 and 1;
together they describe the horizontal span that is visible in the window. For example, if
the first element is .2 and the second element is .6, 20% of the listbox's text is off-screen
to the left, the middle 40% is visible in the window, and 40% of the text is off-screen to
the right. These are the same values passed to scrollbars via the -xscrollcommand option.

$listbox->xview(index)
Adjusts the view in the window so that the character position given by index is displayed at
the left edge of the window. Character positions are defined by the width of the character
0.

$listbox->xviewMoveto( fraction );
Adjusts the view in the window so that fraction of the total width of the listbox text is
off-screen to the left. fraction must be a fraction between 0 and 1.

$listbox->xviewScroll( number, what );
This command shifts the view in the window left or right according to number and what.
Number must be an integer. What must be either units or pages or an abbreviation of one of
these. If what is units, the view adjusts left or right by number character units (the width
of the 0 character) on the display; if it is pages then the view adjusts by number
screenfuls. If number is negative then characters farther to the left become visible; if it
is positive then characters farther to the right become visible.

$listbox->yview(?args?)
This command is used to query and change the vertical position of the text in the widget's window.
It can take any of the following forms:

$listbox->yview
Returns a list containing two elements, both of which are real fractions between 0 and 1.
The first element gives the position of the listbox element at the top of the window,
relative to the listbox as a whole (0.5 means it is halfway through the listbox, for
example). The second element gives the position of the listbox element just after the last
one in the window, relative to the listbox as a whole. These are the same values passed to
scrollbars via the -yscrollcommand option.

$listbox->yview(index)
Adjusts the view in the window so that the element given by index is displayed at the top of
the window.

$listbox->yviewMoveto( fraction );
Adjusts the view in the window so that the element given by fraction appears at the top of
the window. Fraction is a fraction between 0 and 1; 0 indicates the first element in the
listbox, 0.33 indicates the element one-third the way through the listbox, and so on.

$listbox->yviewScroll( number, what );
This command adjusts the view in the window up or down according to number and what. Number
must be an integer. What must be either units or pages. If what is units, the view adjusts
up or down by number lines; if it is pages then the view adjusts by number screenfuls. If
number is negative then earlier elements become visible; if it is positive then later
elements become visible.

DEFAULT BINDINGS

Tk automatically creates class bindings for listboxes that give them Motif-like behavior. Much of the
behavior of a listbox is determined by its selectMode option, which selects one of four ways of dealing
with the selection.

If the selection mode is single or browse, at most one element can be selected in the listbox at once.
In both modes, clicking button 1 on an element selects it and deselects any other selected item. In
browse mode it is also possible to drag the selection with button 1.

If the selection mode is multiple or extended, any number of elements may be selected at once, including
discontiguous ranges. In multiple mode, clicking button 1 on an element toggles its selection state
without affecting any other elements. In extended mode, pressing button 1 on an element selects it,
deselects everything else, and sets the anchor to the element under the mouse; dragging the mouse with
button 1 down extends the selection to include all the elements between the anchor and the element under
the mouse, inclusive.

Most people will probably want to use browse mode for single selections and extended mode for multiple
selections; the other modes appear to be useful only in special situations.

Any time the selection changes in the listbox, the virtual event <<ListboxSelect>> will be generated. It
is easiest to bind to this event to be made aware of any changes to listbox selection.

In addition to the above behavior, the following additional behavior is defined by the default bindings:

[1] In extended mode, the selected range can be adjusted by pressing button 1 with the Shift key down:
this modifies the selection to consist of the elements between the anchor and the element under the
mouse, inclusive. The un-anchored end of this new selection can also be dragged with the button
down.

[2] In extended mode, pressing button 1 with the Control key down starts a toggle operation: the anchor
is set to the element under the mouse, and its selection state is reversed. The selection state of
other elements isn't changed. If the mouse is dragged with button 1 down, then the selection state
of all elements between the anchor and the element under the mouse is set to match that of the anchor
element; the selection state of all other elements remains what it was before the toggle operation
began.

[3] If the mouse leaves the listbox window with button 1 down, the window scrolls away from the mouse,
making information visible that used to be off-screen on the side of the mouse. The scrolling
continues until the mouse re-enters the window, the button is released, or the end of the listbox is
reached.

[4] Mouse button 2 may be used for scanning. If it is pressed and dragged over the listbox, the contents
of the listbox drag at high speed in the direction the mouse moves.

[5] If the Up or Down key is pressed, the location cursor (active element) moves up or down one element.
If the selection mode is browse or extended then the new active element is also selected and all
other elements are deselected. In extended mode the new active element becomes the selection anchor.

[6] In extended mode, Shift-Up and Shift-Down move the location cursor (active element) up or down one
element and also extend the selection to that element in a fashion similar to dragging with mouse
button 1.

[7] The Left and Right keys scroll the listbox view left and right by the width of the character 0.
Control-Left and Control-Right scroll the listbox view left and right by the width of the window.
Control-Prior and Control-Next also scroll left and right by the width of the window.

[8] The Prior and Next keys scroll the listbox view up and down by one page (the height of the window).

[9] The Home and End keys scroll the listbox horizontally to the left and right edges, respectively.

[10]
Control-Home sets the location cursor to the the first element in the listbox, selects that element,
and deselects everything else in the listbox.

[11]
Control-End sets the location cursor to the the last element in the listbox, selects that element,
and deselects everything else in the listbox.

[12]
In extended mode, Control-Shift-Home extends the selection to the first element in the listbox and
Control-Shift-End extends the selection to the last element.

[13]
In multiple mode, Control-Shift-Home moves the location cursor to the first element in the listbox
and Control-Shift-End moves the location cursor to the last element.

[14]
The space and Select keys make a selection at the location cursor (active element) just as if mouse
button 1 had been pressed over this element.

[15]
In extended mode, Control-Shift-space and Shift-Select extend the selection to the active element
just as if button 1 had been pressed with the Shift key down.

[16]
In extended mode, the Escape key cancels the most recent selection and restores all the elements in
the selected range to their previous selection state.

[17]
Control-slash selects everything in the widget, except in single and browse modes, in which case it
selects the active element and deselects everything else.

[18]
Control-backslash deselects everything in the widget, except in browse mode where it has no effect.

[19]
The F16 key (labelled Copy on many Sun workstations) or Meta-w copies the selection in the widget to
the clipboard, if there is a selection.

The behavior of listboxes can be changed by defining new bindings for individual widgets or by
redefining the class bindings.

TIED INTERFACE

       The Tk::Listbox widget can also be tied to a scalar or array variable, with different behaviour depending
       on the variable type, with the following tie commands:

          use Tk;

          my ( @array, $scalar, $other );
          my %options = ( ReturnType => "index" );

          my $MW = MainWindow->new();
          my $lbox = $MW->Listbox()->pack();

          my @list = ( "a", "b", "c", "d", "e", "f" );
          $lbox->insert('end', @list );

          tie @array, "Tk::Listbox", $lbox
          tie $scalar, "Tk::Listbox", $lbox;
          tie $other, "Tk::Listbox", $lbox, %options;

       currently only one modifier is implemented, a 3 way flag for tied scalars  "ReturnType"  which  can  have
       values "element", "index" or "both". The default is "element".

       Tied Arrays
           If you tie an array to the Listbox you can manipulate the items currently contained by the box in the
           same manner as a normal array, e.g.

               print @array;
               push(@array, @list);
               my $popped = pop(@array);
               my $shifted = shift(@array);
               unshift(@array, @list);
               delete $array[$index];
               print $string if exists $array[$i];
               @array = ();
               splice @array, $offset, $length, @list

           The  delete  function  is  implemented  slightly  differently from the standard array implementation.
           Instead of setting the element at that index to undef it  instead  physically  removes  it  from  the
           Listbox. This has the effect of changing the array indices, so for instance if you had a list on non-
           continuous  indices  you  wish  to  remove from the Listbox you should reverse sort the list and then
           apply the delete function, e.g.

                my @list = ( 1, 2, 4, 12, 20 );
                my @remove = reverse sort { $a <=> $b } @list;
                delete @array[@remove];

           would safely remove indices 20, 12, 4, 2 and 1 from the Listbox without problems. It should  also  be
           noted  that  a  similar  warning applies to the splice function (which would normally be used in this
           context to perform the same job).

       Tied Scalars
           Unlike tied arrays, if you tie a scalar to the  Listbox  you  can  retrieve  the  currently  selected
           elements in the box as an array referenced by the scalar, for instance

               my @list = ( "a", "b", "c", "d", "e", "f" );
               $lbox->insert('end', sort @list );
               $lbox->selectionSet(1);

           inserts @list as elements in an already existing listbox and selects the element at index 1, which is
           "b". If we then

                print @$selected;

           this will return the currently selected elements, in this case "b".

           However,  if  the  "ReturnType"  argument  is  passed when tying the Listbox to the scalar with value
           "index" then the indices  of  the  selected  elements  will  be  returned  instead  of  the  elements
           themselves,  ie  in  this  case  "1". This can be useful when manipulating both contents and selected
           elements in the Listbox at the same time.

           Importantly, if a value "both" is given the scalar will not be tied to an array,  but  instead  to  a
           hash, with keys being the indices and values being the elements at those indices

           You  can  also  manipulate  the  selected  items  using  the  scalar. Equating the scalar to an array
           reference will select any elements that match elements in the Listbox, non-matching array  items  are
           ignored, e.g.

               my @list = ( "a", "b", "c", "d", "e", "f" );
               $lbox->insert('end', sort @list );
               $lbox->selectionSet(1);

           would insert the array @list into an already existing Listbox and select element at index 1, i.e. "b"

               @array = ( "a", "b", "f" );
               $selected = \@array;

           would select elements "a", "b" and "f" in the Listbox.

           Again, if the "index" we indicate we want to use indices in the options hash then the indices are use
           instead of elements, e.g.

               @array = ( 0, 1, 5 );
               $selected = \@array;

           would  have  the  same effect, selecting elements "a", "b" and "f" if the $selected variable was tied
           with %options = ( ReturnType => "index" ).

           If we are returning "both", i.e. the tied scalar points to a hash, both key  and  value  must  match,
           e.g.

               %hash = ( 0 => "a", 1 => "b", 5 => "f" );
               $selected = \%hash;

           would have the same effect as the previous examples.

           It should be noted that, despite being a reference to an array (or possibly a has), you still can not
           copy  the tied variable without it being untied, instead you must pass a reference to the tied scalar
           between subroutines.

KEYWORDS

       listbox, widget, tied