NAME
-
listbox - Create and manipulate listbox widgets
SYNOPSIS
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listbox pathName ?options?
STANDARD OPTIONS
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-background -highlightcolor -selectforeground
-borderwidth -highlightthickness -takefocus
-font -relief -width
-foreground -selectbackground -xscrollcommand
-height -selectborderwidth -yscrollcommand
WIDGET-SPECIFIC OPTIONS
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- -height dist
- Specifies the desired height for the window.
- -selectmode val
- 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 single.
- -width dist
- Specifies the desired width for the window.
DESCRIPTION
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The listbox command creates a new window (given by the
pathName argument) and makes it into a listbox widget.
Additional
options, described above, may be specified on the command line
to configure aspects of the listbox such as its colours, font,
text, and relief. The listbox command returns its
pathName argument. At the time this command is invoked,
there must not exist a window named pathName.
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 widget commands described
below. In addition, one or more elements may be selected as described
below.
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.
INDICES
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Many of the widget commands 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 a highlight rectangle when the listbox has the
keyboard focus, and it is specified with the activate
widget command.
- anchor
- Indicates the anchor point for the selection, which is set with the
selection anchor widget command.
- end
- Indicates the end of the listbox.
For some commands this means just after the last element;
for other commands it means the last element.
- @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 widget command descriptions below, arguments named index,
first, and last always contain text indices in one of
the above forms.
WIDGET COMMAND
-
The listbox command creates a new Tk command whose
name is pathName. This
command may be used to invoke various
operations on the widget. It has the following general form:
pathName option ?arg arg ...?
Option and the args
determine the exact behaviour of the command. The following
commands are possible for listbox widgets:
- pathName activate index
- Sets the active element to the one indicated by index.
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.
- pathName cget option
- Returns the current value of the configuration option given
by option.
Option may have any of the values accepted by the listbox
command.
- pathName configure ?option? ?value option value ...?
- Query or modify the configuration options of the widget.
If no option is specified, returns a list of all of
the available options for pathName. 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.
Option may have any of the values accepted by the listbox
command.
- pathName 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.
- pathName 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.
- pathName get first ?last?
- If last is omitted, returns the contents of the listbox
element indicated by first.
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.
- pathName index index
- Returns a decimal string giving the integer index value that
corresponds to index.
- pathName 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.
- pathName 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.
- pathName 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.
- pathName selection option arg
- This command is used to adjust the selection within a listbox. It
has several forms, depending on option:
- pathName selection anchor index
- Sets the selection anchor to the element given by index.
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.
- pathName selection clear 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.
- pathName selection includes index
- Returns 1 if the element indicated by index is currently
selected, 0 if it isn't.
- pathName selection set 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.
- pathName size
- Returns a decimal string indicating the total number of elements
in the listbox.
- pathName 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:
- pathName 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.
- pathName 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.
- pathName xview moveto 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.
- pathName xview scroll 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.
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.
- pathName 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:
- pathName 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.
- pathName yview index
- Adjusts the view in the window so that the element given by
index is displayed at the top of the window.
- pathName yview moveto 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.
- pathName yview scroll 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
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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.
The behaviour of listboxes can be changed by defining new bindings for
individual widgets. The default bindings do a grab set when button 1 is pressed
and a grab release when button 1 is released. Care must be taken when overriding
either or both of these defaults to ensure that grabbing is consistent.
BUGS
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At least one entry is required for the widget to indicate that it has keyboard focus.
SEE ALSO
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options(9),
types(9)