=head1 NAME 

Tk::MListbox - Multicolumn Listbox.

=head1 SYNOPSIS

  use Tk::MListbox;
  $ml = $parent->MListbox (<options>);

=head1 DESCRIPTION

Tk::MListbox is a multicolumn Listbox widget with builtin capabilites for
sorting, resizing and repositioning of the columns.

Sorting is done by clicking on one of the column headings in the 
widget. The first click will sort the data with the selected column
as key, a new click will reverse the sort order.

The columns may be resized by dragging a separator line which
is drawn between each column.

A column's position in the widget might be changed by dragging 
it's heading left or right.

Tk::MListbox is used in a way similar to the standard Listbox, but in 
stead of scalar values MListbox operates on lists of data. In addition
to methods for accessing the data in the MListbox, the widget offer 
methods for manipulation of the individual columns.


=head1 AUTHOR

Hans Jorgen Helgesen, hans_helgesen@hotmail.com (from March 2000: hans.helgesen@novit.no)

=head1 SEE ALSO

L<Tk::Listbox>

=head1 STANDARD OPTIONS

B<-background> B<-foreground> B<-relief> B<-takefocus>
B<-borderwidth>	B<-heigh> B<-selectbackground>	B<-cursor>
B<-highlightbackground> B<-selectborderwidth> B<-xscrollcommand>
B<-exportselection> B<-highlightcolor> B<-selectforeground>
B<-yscrollcommand> B<-font> B<-highlightthickness> B<-setgrid>

See L<Tk::options> for details of the standard options.

=head1 REQUIREMENTS

Tk::MListbox requires Tk::Pane.
(and basic Perl/Tk of course....)

=head1 WIDGET SPECIFIC OPTIONS

=over 4

=item -columns => I<list>

Defines the columns in the widget. Each element in the list 
describes a column. See the B<COLUMNS> section below.

=item -configurecommand => I<callback>

The -configurecommand callback will be called whenever the layout of the
widget has changed due to user interaction. That is, the user changes the
width of a column by dragging the separator, or moves a column by dragging
the column header. 

This option is useful if the application wants to store the widget layout 
for later retrieval. The widget layout can be obtained by the callback
by calling the method columnPackInfo().

=item -moveable => I<boolean>

A value of B<1> indicates that it is okay for the user to move
the columns by dragging the column headers. B<0> disables this
function.

Default: B<1>

=item -resizeable => I<boolean>

A value of B<1> indicates that it is okay for the user to resize
the columns by dragging the column separators. B<0> disables 
this function.

Default: B<1>

Note that you can also specify -resizeable on a column
by column basis. See the B<COLUMNS> section below.

=item -selectmode => I<string>

Should be "single", "browse", "multiple", or "extended".

Default is "browse". See L<Tk::Listbox>.

=item -separatorcolor => I<string>

Specifies the color of the separator lines 
(the vertical lines that separates the columns). 

Default: B<black>

Note that you can also specify -separatorcolor on a column
by column basis. See the B<COLUMNS> section below.

=item -separatorwidth => I<integer>

Specifies the width in pixels of the separator lines 
(the vertical lines that separates the columns). 

Default: B<1>

Note that you can also specify -separatorwidth on a column
by column basis. See the B<COLUMNS> section below.

=item -sortable => I<boolean>

A value of B<1> indicates that it is okay for the user to sort
the data by clicking column headings. B<0> disables this function.

Default: B<1>

Note that you can also specify -sortable on a column
by column basis. See I<COLUMNS> below.

=head1 COLUMNS

The MListbox widget is a collection of I<MLColumn> widgets. 
Each MLColumn contains a Listbox, a heading and the separator bar.
The columns are created and maintained through the -columns 
option or the column methods of the widget. The columns are indexed
from 0 and up. Initially, column 0 is the leftmost column of the
widget. The column indices B<are not changed> when the columns
are moved or hidden. The only ways to change the column indices 
are to call columnInsert(), columnDelete() or configure(-column).

Each column has its own set of options which might be passed to 
MListbox::configure(-columns), MListbox::insert(),
MListbox::columnConfigure() or MLColumn::configure().

The following code snippets are all equal:

1.  $ml=$mw->MListbox(-columns=>[[-text=>'Heading1',
                                  -sortable=>0],
                                 [-text=>'Heading2']]);

2.  $ml=$mw->MListbox;
    $ml->columnInsert(0,-text=>'Heading1', -sortable=>0);
    $ml->columnInsert(0,-text=>'Heading2');

3.  $ml=$mw->MListbox;
    $c=$ml->columnInsert(0,-text=>'Heading1');
    $ml->columnInsert(0,-text=>'Heading2');
    $c->configure(-sortable=>0);

4.  $ml=$mw->MListbox;
    $ml->columnInsert(0,-text=>'Heading1');
    $ml->columnInsert(0,-text=>'Heading2');
    $ml->columnConfigure(0,-sortable=>0);

(See the columnConfigure() method below for details on column options).

All column methods expects one or two column indices as arguments.
The column indices might be an integer (between 0 and the number
of columns minus one), 'end' for the last column, or a reference
to the MLColumn widget (obtained by calling MListbox->columnGet() 
or by storing the return value from MListbox->columnInsert()).

=head1 WIDGET METHODS

=over 4

=item $ml->bindColumns(I<sequence>,I<callback>)

Adds the binding to all column headers in the widget. See the section
BINDING EVENTS TO MLISTBOX below.

=item $ml->bindRows(I<sequence>,I<callback>)

Adds the binding to all listboxes in the widget. See the section
BINDING EVENTS TO MLISTBOX below.

=item $ml->bindSeparators(I<sequence>,I<callback>)

Adds the binding to all separators in the widget. See the section
BINDING EVENTS TO MLISTBOX below.

=back

=head2 COLUMN METHODS

(Methods for accessing and manipulating individual columns
in the MListbox widget)

=item $ml->columnConfigure(I<index>,I<option>=>I<value>...)

Set option values for a specific column.
Equal to $ml->columnGet(I<index>)->configure(...).

The following column options are supported:

=over 4

=item

-comparecommand => I<callback>

Specifies a callback to use when sorting the MListbox with this
column as key. The callback will be called with two scalar arguments,
each a value from this particular column. The callback should 
return an integer less than, equal to, or greater than 0, depending
on how the tow arguments are ordered. If for example the column
should be sorted by numerical value:

    -comparecommand => sub { $_[0] <=> $_[1]}

The default is to sort the columns alphabetically.

=item

-text => I<string>

Specifies the text to be used in the heading button of the column.

=item

-resizeable => I<boolean>

A value of B<1> indicates that it is okay for the user to resize
this column by dragging the separator. B<0> disables this function.

Default: B<1>

=item

-separatorcolor => I<string>

Specifies the color of the separator line, default is B<black>.

=item

-separatorwidth => I<integer>

Specifies the width of the separator line in pixels. Default is B<1>.

=item

-sortable => I<boolean>

A value of B<1> indicates that it is okay for the user to sort
the data by clicking this column's heading. B<0> disables this 
function.

Default: B<1>

=back

=item $ml->columnDelete(I<first>,I<last>)

If I<last> is omitted, deletes column I<first>. If I<last> is
specified, deletes all columns from I<first> to I<last>, inclusive.

All previous column indices greater than I<last> (or I<first> if
I<last> is omitted) are decremented by the number of columns 
deleted.

=item $ml->columnGet(I<first>,I<last>)

If I<last> is not specified, returns the MLColumn widget specified by I<first>.
If both I<first> and I<last> are specified, returns an array containing all
columns from I<first> to I<last>.

=item $ml->columnHide(I<first>,I<last>)

If I<last> is omitted, hides column I<first>. If I<last> is
specified, hides all columns from I<first> to I<last>, inclusive.

Hiding a column is equal to calling $ml->columnGet(I<index>)->packForget. 
The column is B<not> deleted, all data are still available, 
and the column indices remain the same.

See also the columnShow() method below.

=item $ml->columnIndex(I<index>)

Returns an integer index for the column specifed by I<index>.

=item $ml->columnInsert(I<index>,I<option>=>I<value>...)

Creates a new column in the MListbox widget. The column will 
get the index specified by I<index>. If I<index> is 'end', the
new column's index will be one more than the previous highest
column index.

If column I<index> exists, the new column will be placed
to the B<left> of this column. All previous column indices 
equal to or greater than I<index> will be incremented by one.

Returns the newly created MLColumn widget.

(See the columnConfigure() method above for details on column options).

=item $ml->columnPack(I<array>)

Repacks all columns in the MListbox widget according to the 
specification in I<array>. Each element in I<array> is a string
on the format B<index:width>. I<index> is a column index, I<width> 
defines the columns width in pixels (may be omitted). The columns 
are packed left to right in the order specified by by I<array>.
Columns not specified in I<array> will be hidden.

This method is most useful if used together with the 
columnPackInfo() method.

=item $ml->columnPackInfo

Returns an array describing the current layout of the MListbox
widget. Each element of the array is a string on the format
B<index:width> (see columnPack() above). Only indices of columns that 
are currently shown (not hidden) will be returned. The first element
in the returned array represents the leftmost column.

This method may be used in conjunction with columnPack() to save
and restore the column configuration. 

=item $ml->columnShow(I<index>,I<option>=>I<value>)

Shows a hidden column (see the columnHide() method above). 
The column to show is specified by I<index>.

By default, the column is pack'ed at the rigthmost end of the
MListbox widget. This might be overridden by specifying one of
the following options:

=over 4

=item 

-after => I<index>

Place the column B<after> (to the right of) the column specified
by I<index>.

=item 

-before => I<index>

Place the column B<before> (to the left of) the column specified
by I<index>.

=back

=head2 ROW METHODS

(Methods for accessing and manipulating rows of data)

Many of the methods for MListbox take one or more indices as 
arguments. See L<Tk::Listbox> for a description of row indices.

=item $ml->delete(I<first>,I<last>)

Deletes one or more row elements of the MListbox. I<First> and I<last>
are indices specifying the first and last elements in the range to 
delete. If I<last> isn't specified it defaults to I<first>, 
i.e. a single element is deleted. 

=item $ml->get(I<first>,I<last>)

If I<last> is omitted, returns the content of the MListbox row
indicated by I<first>. If I<last> is specified, the command returns
a list whose elements are all of the listbox rows between 
I<first> and I<last>.

The returned elements are all array references. The referenced
arrays contains one element for each column of the MListbox.

=item $ml->getRow(I<index>)

In scalar context, returns the value of column 0 in the MListbox
row specified by I<index>. In list context, returns the content
of all columns in the row as an array.

This method is provided for convenience, since retrieving a single
row with the get() method might produce some ugly code.

The following two code snippets are equal:

   1. @row=$ml->getRow(0);

   2. @row=@{($ml->get(0))[0]};


=item $ml->sort(I<descending>, I<columnindex>...)

Sorts the content of the MListbox. If I<descending> is a B<true> 
value, the sort order will be descending. The default is ascending
sort.

If I<columnindex> is specified, the sort will be done with the 
specified column as key. You can specify as many I<columnindex>
arguments as you wish. Sorting is done on the first column, then
on the second, etc...

The default is to sort the data on all columns of the listbox, 
with column 0 as the first sort key, column 1 as the second, etc.

=head1 OTHER LISTBOX METHODS

Most other Tk::Listbox methods works for the MListbox widget.
This includes the methods activate, cget, curselection, index,
nearest, see, selectionXXX, size, xview, yview.

See L<Tk::Listbox>.

=head1 ADVERTISED SUBWIDGETS

=item pane

All MListbox columns are packed inside a Tk::Pane (this is done
to enable horizontal scrolling).

=back 

Apart from "pane", the MListbox widget has no subwidgets, 
except for the variable number of MLColumns, which obviously 
cannot be advertised. The MLColumn widgets might be obtained 
by calling the columnGet() or columnInsert() methods.

The MLColumn widget (which represents a single column in the
MListbox) advertises the following subwidgets:

=over 4

=item listbox

The individual Listbox. Note that this is B<not> the standard
Tk::Listbox, but a derived version (CListbox). Several of the
widget's methods will not work as expected.

=item separator

The column separator line. This is a Canvas.

=item heading

The column heading. This is a "HButton" (a Button with an additional
-pixelwidth option).

=item frame

A Frame which contains the "listbox" and the "heading"
subwidgets (but not the "separator").

=back

Example: If you want to change the background color of the
heading of column 4:

    $ml->columnGet(4)->Subwidget("heading")
        ->configure(-background=>'blue');

=head1 BINDING EVENTS TO MLISTBOX

Calling $ml->bind(...) probably makes little sense, since the call does not
specify whether the binding should apply to the listbox, the header button 
or the separator line between each column.

In stead of the ordinary bind, the following methods should be used:

=over 4

=item $ml->bind(I<sequence>,I<callback>)

Synonym for $ml->bindRows(I<sequence>,I<callback>).

=item $ml->bindRows(I<sequence>,I<callback>)

Synonym for $ml->bindSubwidgets('listbox',I<sequence>,I<callback>)

=item $ml->bindColumns(I<sequence>,I<callback>)

Synonym for $ml->bindSubwidgets('heading',I<sequence>,I<callback>)

=item $ml->bindSeparators(I<sequence>,I<callback>)

Synonym for $ml->bindSubwidgets('separator',I<sequence>,I<callback>)

=item $ml->bindSubwidgets(I<subwidget>,I<sequence>,I<callback>)

Adds the binding specified by I<sequence> and I<callback> to all subwidgets
of the given type (should be 'listbox', 'heading' or 'separator'). 

The binding is stored in the widget, and if you create a new column 
by calling $ml->columnInsert(), all bindings created by $ml->bindSubwidgets()
are automatically copied to the new column.

The callback is called with the MListbox widget as first argument, and
the index of the column where the event occured as the second argument.

NOTE that $ml->bindSubwidgets() does not support all of Tk's callback formats.
The following are supported:

     \&subname
     sub { code }
     [ \&subname, arguments...]
     [ sub { code }, arguments...]

If I<sequence> is undefined, then the return value is a list whose elements 
are all the sequences for which there exist bindings for I<subwidget>.

If I<sequence> is specified without I<callback>, then the callback currently 
bound to sequence is returned, or an empty string is returned if there is no
binding for sequence.

If I<sequence> is specified, and I<callback> is an empty string, then the
current binding for sequence is destroyed, leaving sequence unbound. 
An empty string is returned.

An empty string is returned in all other cases.

=back

=cut