#  You may distribute under the terms of either the GNU General Public License
#  or the Artistic License (the same terms as Perl itself)
#  (C) Paul Evans, 2011-2018 -- leonerd@leonerd.org.uk

package Tickit::OneLineWidget;

use strict;
use warnings;
use base qw( Tickit::Widget );
use Tickit::WidgetRole::Alignable name => 'valign', dir => 'v';

our $VERSION = '0.51';

use Carp;

=head1 NAME

C<Tickit::OneLineWidget> - a widget which occupies only one line


This subclass of L<Tickit::Widget> provides a convenient base for widgets that
only want to occupy a single line of the window. It provides the C<valign>
accessor to control alignment of the widget's content within the window, and
a C<render> method that clears all the unused lines of the window. This class
also provides the C<lines> method, returning a constant value of C<1>.


sub new
   my $class = shift;
   my %args = @_;

   foreach my $method (qw( render_line )) {
      $class->can( $method ) or
         croak "$class cannot ->$method - do you subclass and implement it?";

   my $self = $class->SUPER::new( %args );

   $self->set_valign( $args{valign} || 0 );

   return $self;



sub lines
   return 1;

=head2 valign

   $valign = $widget->valign

=head2 set_valign

   $widget->set_valign( $valign )

Accessor for vertical alignment value.

Gives a value in the range from C<0.0> to C<1.0> to align the content display
within the window. If the window is taller than one line, it will be aligned
according to this value; with C<0.0> at the top, C<1.0> at the bottom, and
other values inbetween.

See also L<Tickit::WidgetRole::Alignable>


sub render
   my $self = shift;
   my %args = @_;

   my $win = $self->window or return;
   $win->is_visible or return;
   my $rect = $args{rect};

   my ( $above ) = $self->_valign_allocation( 1, $win->lines );

   my $cols = $win->cols;

   $win->goto( $_, 0 ), $win->erasech( $cols ) for $rect->top .. $above - 1;

   $win->goto( $above, 0 );

   $win->goto( $_, 0 ), $win->erasech( $cols ) for $above + 1 .. $rect->bottom - 1;


Because this is an abstract class, the constructor must be called on a
subclass which implements the following methods.

=head2 render_line


Called to redraw the widget's content to its window. When invoked, the window
cursor will already be in column C<0> of the required line of the window, as
determined by the C<valign> value.


=head1 AUTHOR

Paul Evans <leonerd@leonerd.org.uk>