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.
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();
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, $length, @list
The delete function is implemented slightly differently from the standard
array implementation. Instead of setting the element at that index to undef
it instead physically removes it from the Listbox. This has the effect of
changing the array indices, so for instance if you had a list on non-continuous
indices you wish to remove from the Listbox you should reverse sort the list
and then apply the delete function, e.g.
would safely remove indices 20, 12, 4, 2 and 1 from the Listbox without
problems. It should also be noted that a similar warning applies to the
splice function (which would normally be used in this context to perform
the same job).
Tied Scalars
Unlike tied arrays, if you tie a scalar to the Listbox you can retrieve the
currently selected elements in the box as an array referenced by the scalar,
for instance
inserts @list as elements in an already existing listbox and selects the
element at index 1, which is ``b''. If we then
print @$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.
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.
