Listbox(3pm) User Contributed Perl Documentation Listbox(3pm)NAMETk::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
SEE ALSO
Tk::HList, Tk::TextList.
perl v5.26.0 2017-07-22 Listbox(3pm)
