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.
- 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.
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" arguement 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.