=head1 NAME

GvaScript.ChoiceList - Dropdown list of choices with navigation

=head1 SYNOPSIS

  var choiceList = new GvaScript.ChoiceList(["foo", "bar", "buz"]);
  choiceList.fillContainer($('myChoiceDiv'));

=head1 DESCRIPTION

Displays a list of "choices", handles navigation in those
choices, and generates events when a choice is highlighted, then selected,
or when the list display is cancelled.

At any moment the choiceList is bound to maximum one "container",
and highlights exactly one choice in the list.

=head1 BEHAVIOUR

Once a choice list is displayed, the user can move the mouse over the
list, thus highlighting various choices; then click on the highlighted
choice to select it. Alternatively, the user can navigate the list
with keys C<DOWN>, C<UP>, C<HOME>, C<END>, and then use either
C<RETURN> (for selecting) or C<ESCAPE> (for cancelling).




=head1 CONSTRUCTOR

  var choiceList = new GvaScript.ChoiceList(choices, options);

=head2 Choices

The choice list must be an array. Each item in the list is either

=over

=item a plain string

this string will be displayed in the choice list

=item an inline object

this object is supposed to have a C<label> property, which 
will be displayed in the choice list. Actually, this is the default name
for the property; it can be changed in the constructor options.

The C<label> property may contain rich HTML, i.e. including
formatting tags.

=back



=head2 Options

The options to construct an choiceList object are :

=over

=item labelField

Name of the field that contains the HTML to display
(default is C<label>).

=item idForChoices

Prefix that will be used to generate ids for choice elements in
the generated HTML. The default is C<CL_choice>, so choice elements
will have ids C<CL_choice.0>, C<CL_choice.1>, etc.

=item keymap

If defined, the choiceList will add rules to the supplied keymap,
instead of creating a new one.

=item scrollCount

How many items to skip when hitting the 
C<PAGE_UP> or C<PAGE_DOWN> keys. 
Default is 5


=item classes

Classes that will be assigned to choice elements in the generated
HTML. Possible classes are C<choiceItem> (default value C<CL_choiceItem>) and
C<choiceHighlight> (default value C<CL_highlight>).


=item htmlWrapper

Callback function for generating HTML for the choiceList.
This function is called with some pre-built HTML containing
all current choices; the wrapper has a chance to modify 
that HTML for example for adding classes, borders or 
table headers. Default is the identity function.


=item choiceItemTagName

HTML tag name for generating a choice entry in the choice list.
Default is "div". Set it to "tr" if you want the choice list
to be displayed as a table (but then you also have to 
open and close the table within the C<htmlWrapper> callback).


=back

=head1 METHODS

=head2 fillContainer

  choiceList.fillContainer(someDiv);

This method generates HTML from the choice list, and inserts
it in the C<innerHTML> of the supplied container; furthermore,
it registers a keymap on that container in order to manage navigation
from keyboard (C<DOWN>, C<UP>, etc.).


=head1 EVENTS

=head2 onHighlight

This event is triggered when a choice in the list is highlighted.
The event handler may use C<event.index> to know the index of the
highlighted choice.

=head2 onPing

This event is triggered when a choice in the list is "ping-ed", i.e.
either by clicking or by pressing the C<RETURN> key.
Usually this means "select", but it is up to the event handler to decide
how to interpret the event.
The event handler may use C<event.index> to know the index of the
ping-ed choice.


=head2 onCancel

This event is triggered when the user presses the C<ESCAPE> key.
