The Text Widget (Perl in a Nutshell, 2nd Edition)

21.11.1. Text Indexes and Modifiers

In a Text widget, several indexes are defined to identify positions in the text. These are used by the methods that retrieve and manipulate text.

n.m: 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: The character after the last character in the word

21.11.2. Text Methods

In addition to configure and cget, the following methods are defined for the Text widget:

bbox

Returns the location and dimensions of the bounding box surrounding the character at the specified index. 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.

compare

Performs a comparison on two indexes. For example:

if ($text->compare('insert', '==', 'end') { 
        # we're at the end of the text
}

The valid operators are <, <=, ==, >=, and !=.

debug

Given a Boolean, turns debugging on or off.

delete

Deletes text from the text widget. To delete everything:

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

dlineinfo

Returns the location and dimensions of the bounding box surrounding the line at the specified index. The returned list contains five 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, the height of the text in pixels, and the baseline position of the line.

get

Returns the text located in the given index range.

index

Given a named index, returns its numeric equivalent in the format line.char.

insert

Inserts text into the widget at the specified location. The second argument is the text to insert, and the third argument is either a single tag or a list reference containing the names of multiple tags to apply to the text. Subsequent arguments alternate between text and tags. For example:

$text->insert('end', 'You want to do ', 'normal', 
                     'what?!', ['bold','red']);

search

Returns the index containing a particular string in the Text widget. For example, to search backwards for a case-insensitive hostname starting from the end of the text:

$hostindex = $text->search(-nocase, -backwards, $hostname, 'end');

The search method takes several switches to modify the search, each starting with -. The first argument that does not start with - is taken to be the search string. The switches are:

-forwards: Searches forwards starting at the specified index.
-backwards: Searches backwards starting at the specified index.
-exact: Matches the string exactly (default).
-regexp: Treat the pattern as a regular expression.
-nocase: Ignores case.
-count => $variable: Stores the number of matches into the specified variable.
--: Interprets the next argument as the pattern. (Useful when the pattern starts with a -.)

see

Scrolls the text so that the portion of the text containing the specified index is visible.

window

Embeds widgets within the Text widget. The first argument can be any of: create, names, cget, and configure.

create

Inserts an embedded widget at a specified index. Each widget occupies one character in the Text widget. The widget must have already been created as a child of the Text widget. For example:

$button = $text->Label(-text => "How ya doing?");
$text->window('create','end', -window => $button);

Here, the -window option is used to identify the widget to embed. The list of options to window ('create') is:

-align

Determines the positioning within the line of text. Values are baseline, bottom, top, or center (default).

-padx

Adds padding in the x direction.

-pady

Adds padding in the y direction.

-window

Identifies the widget to embed.

names

Returns a list of widget types embedded into the Text widget.

cget

Returns information on the widget at the specified index:

$text->window('cget',0);

configure

Configures widget at the specified index:

$text->window('configure',0,-background => "green");

xview

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

21.11.3. Tags

You can associate a distinct set of format properties to a portion of the text using tags. A tag is defined with the tagConfigure method, and text is associated with a tag via an option to the insert or tagAdd method. For example:

$text->Text->pack;
$text->tagConfigure('bold', -font =>
     '-*-Courier-Medium-B-Normal-*-120-*-*-*-*-*-*');
$text->insert('end', "Normal text\n");
$text->insert('end', "Bold text\n", 'bold');

There are several methods defined for manipulating text tags:

tagAdd

Adds a tag to the text within the specified index range. For example, to assign the bold tag defined above to the current selection:

$text->tagAdd('bold','sel.first','sel.last');

You can supply multiple ranges as arguments to tagAdd.

tagBind

Executes a callback when a specified event happens on the tagged text. For example:

$text->tagBind('goto_end', "<Button-1>", sub {shift->see('end');} );

tagConfigure

Creates or changes settings for a text tag. For example:

$text->tagConfigure('link', -foreground => 'red');

Options for configuring text tags are:

-background => color: The color to use behind the text.
-bgstipple => bitmap: A pattern to draw behind the text.
-borderwidth => amount: The width of the edge drawn around the text.
-fgstipple => bitmap: A pattern used to draw the text.
-font => fontname: The font used for the text.
-foreground => color: The color of the text.
-justify => position: The justification of the text (any of left, right, and center). The default is left.
-lmargin1 => amount: The indentation for the first line of a paragraph.
-lmargin2 => amount: The indentation for subsequent lines of a paragraph (for hanging indents).
-offset => amount: The amount the text is raised or lowered from the baseline (for subscripts and superscripts).
-overstrike => boolean: Draws the text with a line through it.
-relief => type: The types of edges drawn around the text. Values for type can be flat, groove, raised, ridge, and sunken. Default is flat.
-rmargin => amount: The right margin.
-spacing1 => amount: The amount of space left on the top of a line of text that starts on its own line.
-spacing2 => amount: The amount of space left on the top of a line of text after it has been automatically wrapped by the Text widget.
-spacing3 => amount: The amount of space left after a line of text ended by \n.
-tabs => list: A list of tab stops to use in the Text widget.
-underline => boolean: Whether to underline the text.
-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).

tagCget

Returns configuration settings for a tag.

tagDelete

Deletes the specified tag(s).

tagRemove

Removes the tags from the text in the specified index range. (The tag itself remains defined, but is no longer applied to that text.)

tagRaise

Increases priority for a specified tag. With only one argument, the tag takes highest priority over all others; with a second argument of another tag, the tag's priority is just higher than the second tag. For example:

$text->tagRaise('bold','italic');

tagLower

Decreases priority for a specified tag. With only one argument, the tag takes lowest priority to all others; with a second argument of another tag, the tag's priority is just lower than the second tag. For example:

$text->tagLower('italic','bold');

tagNames

Returns the names of all tags applying to the specified index. With no index specified, returns all tags defined for the Text widget, regardless of whether they have been applied. For example:

@defined_tags = $text->tagNames;

tagRanges

Returns a list of index ranges to which the specified tag is defined. The returned list contains pairs of starting and ending indexes for the ranges. For example:

@bold_indexes = $text->tagRanges('bold');

tagNextrange

Given a tag name and an index, returns the next index range to which the specified tag is defined. For example:

@next_bold = $text->tagRanges('bold', 'insert');

21.11.4. Marks

A mark is a particular position between characters in a Text widget. Once you create a mark, you can use it as an index. The gravity of the mark affects to which side the text is inserted. Right gravity is the default, in which case the text is inserted to the right of the mark.

The two marks that are automatically set are insert and current. The insert mark refers to the position of the insert cursor. The current mark is the position closest to the mouse cursor.

The following methods are defined for marking:

markGravity

Sets the gravity of a mark. For example: