[Chapter 18] 18.10 The Listbox Widget

[Chapter 18] 18.10 The Listbox Widget



18.10.1 Listbox Indexes

In a Listbox widget, several indexes are defined to identify positions in the listbox, for use by the methods

used for retrieving or manipulating listbox entries. These indexes are:

n

An integer representing a position in the list, with 0 as the first item.

active

The item with the keyboard focus.

anchor

The anchored position.

end

The last element in the listbox.

@x,y

The listbox item containing the specified x,y coordinate.



18.10.2 Listbox Methods

In addition to configure and cget, the following methods are supported by Listbox:

insert

Adds items to a listbox at the specified index. For example, to insert items at the end of a list:

$listbox->insert('end', "Puerto Rico", "Virgin Islands", "Guam");

delete

Deletes items from a listbox. To delete all items:

$listbox->delete(0,'end');

get

Returns a list of elements within the specified range of indexes. For a list of all elements:

@items = $listbox->get(0,'end');

curselection

Returns a list of all currently selected elements in the listbox.

activate

Sets the specified item to be the active element.

bbox

Returns the location and dimensions of the bounding box surrounding the specified listbox element.

The returned list contains four numbers representing (respectively) the x coordinate of the upper-left

corner, the y coordinate of the upper-left corner, the width of the text in pixels, and the height of the

text in pixels.

index

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[Chapter 18] 18.10 The Listbox Widget



Converts a named index into a numeric one.

nearest

Gets the index of the listbox item nearest to a given y coordinate.

see

Pages the listbox up or down to display the specified item.

selection

Manipulates the selected block of list items. The first argument can be any of:

anchor

Sets the anchor index to the specified index.

clear

Clears any selected list items in the specified range. For example, to clear all selections:

$listbox->selection('clear', 0, 'end');

includes

Returns 0 or 1 depending on whether the specified item is already selected.

$listbox->selection('includes', 'end');

set

Selects a range of items in the listbox.

$listbox->selection('set', 0, 'end');

size

Returns the total number of items in the listbox.

xview

Manipulates the text in view. With no arguments, returns a list of two numbers between 0 and 1,

defining what portion of the list text is currently hidden on the left and right sides, respectively. With

arguments, the function of xview changes:

index

If the first argument is an index, that position becomes the leftmost position in view.

moveto

Moves the specified fraction of the listbox to the left of the visible portion.

scroll

Scrolls the text left or right by the specified number of units (characters, in this context) or pages.

Used primarily as a callback to a scrollbar; pressing on an arrow would move by units

(characters), and pressing on the trough would move by pages. The number is either 1 or -1, to

move forwards or backwards, respectively.

yview

Manipulates the text in view. With no arguments, returns a list of two numbers between 0 and 1,

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[Chapter 18] 18.10 The Listbox Widget



defining what portion of the list text is currently hidden on the top and bottom, respectively. With

arguments, the function of yview changes:

index

If the first argument is an index, that position becomes the topmost position in view.

moveto

Moves the specified fraction of the listbox to the top of the visible portion.

scroll

Scrolls the text up or down by the specified number of units (lines, in this context) or pages.

Used primarily as a callback to a scrollbar; pressing on an arrow would move by units (lines),

and pressing on the trough would move by pages. The number is either 1 or -1, to move forwards

or backwards, respectively.



18.9 The Scrollbar Widget



18.11 The Text Widget



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[Chapter 18] 18.11 The Text Widget



Chapter 18

Perl/Tk



18.11 The Text Widget

Create a text widget with the Text method:

$parentwidget->Text ( options)

The standard configuration options that apply to Text are: -background, -bg, -borderwidth, -bd,

-cursor, -exportselection, -font, -foreground, -fg, -height, -highlightbackground,

-highlightcolor, -highlightthickness, -insertbackground, -insertborderwidth,

-insertofftime, -insertontime, -insertwidth, -padx, -pady, -relief,

-selectbackground, -selectborderwidth, -selectforeground, -state, -takefocus,

-width, -xscrollcommand, and -yscrollcommand.

Other options are:

-setgrid => boolean

Turns on gridding for the text widget. Default is 0 (off).

-spacing1 => amount

Defines the amount of space left on the top of a line of text that starts on its own line. Default is 0.

-spacing2 => amount

Defines the amount of space left on the top of a line of text after it has been automatically wrapped by the

text widget. Default is 0.

-spacing3 => amount

Defines the amount of space left after a line of text that has been ended by "\n". Default is 0.

-tabs => list

Specifies a list of tab stops to use in the text widget. Default is undefined (no tab stops).

-wrap => mode

Sets the mode for determining automatic line wrapping. Values are "none" (no wrapping), "char" (wrap

at any character), or "word" (wrap at a word boundary). Default is "char".



18.11.1 Text Indexes and Modifiers

In a Text widget, several indexes are defined to identify positions in the text widget, for use by the methods used

for retrieving or manipulating text. These indexes are:

n.m



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Numbers representing character m on line n.

@x,y

The character closest to the x,y coordinate.

end

The end of the text.

insert

The character after the insert cursor.

current

The position closest to the mouse cursor.

mark

Other marks defined for the widget (see discussion of text marks later in this section).

sel.first

The first selected character.

sel.last

The character just after the last selected character.

tag.first

The first character in the widget of the specified tag type.

tag.last

The character just after the last character of the specified tag type.

widget

The location of an embedded widget.

There are also several modifiers to use with text indexes. They are:

+ n lines

- n lines

n lines before or after the index.

+ n chars

- n chars

n characters before or after the index.

linestart

The first character on the line.

lineend

The last character on the line (often a newline).

wordstart

The first character in the word.

wordend

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