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package Graphics::Grid::Viewport;
# ABSTRACT: Viewport
use Graphics::Grid::Class;
our $VERSION = '0.001'; # VERSION
use Types::Standard qw(Int InstanceOf Num Str ArrayRef HashRef);
use Graphics::Grid::Types qw(:all);
use Graphics::Grid::Unit;
has clip => (is => 'ro', isa => Clip, default => 'inherit' );
my $Scale = ( ArrayRef [Num] )->where( sub { @$_ == 2 } );
has [ "xscale", "yscale" ] => (
    is      => 'ro',
    isa     => $Scale,
    default => sub { [ 0, 1 ] },
);
has angle => (
    is      => 'ro',
    isa     => Num,
    default => 0
);
has layout => (
    is  => 'ro',
    isa => InstanceOf ["Graphics::Grid::Layout"],
    writer => '_set_layout',
);
has [qw(layout_pos_row layout_pos_col)] => (
    is  => 'ro',
    isa => ( ArrayRef [Int] )->plus_coercions(ArrayRefFromAny),
    coerce => 1,
);
with qw(
  Graphics::Grid::ViewportLike
  Graphics::Grid::Positional
  Graphics::Grid::Dimensional
  Graphics::Grid::HasJust
);
sub _build_name { $_[0]->_uid; }
__PACKAGE__->meta->make_immutable;
1;
__END__
HideShow 159 lines of Pod
=pod
=encoding UTF-8
=head1 NAME
Graphics::Grid::Viewport - Viewport
=head1 VERSION
version 0.001
=head1 SYNOPSIS
    use Graphics::Grid::Viewport;
    use Graphics::Grid::GPar;
     
    my $vp = Graphics::Grid::Viewport->new(
            x => 0.6, y => 0.6,
            width => 1, height => 1,
            angle => 45,
            gp => Graphics::Grid::GPar->new(col => "red") );
=head1 DESCRIPTION
Viewports describe rectangular regions on a graphics device and define a
number of coordinate systems within those regions.
=head1 ATTRIBUTES
=head2 x
A Grahpics::Grid::Unit object specifying x-location.
Default to C<unit(0.5, "npc")>.
=head2 y
A Grahpics::Grid::Unit object specifying y-location.
Default to C<unit(0.5, "npc")>.
The reference point is the left-bottom of parent viewport.
=head2 width
A Grahpics::Grid::Unit object specifying width.
Default to C<unit(1, "npc")>.
=head2 height
Similar to the C<width> attribute except that it is for height. 
=head2 just
The justification of the object, which consumes this role, relative to
its (x, y) location.
The value is an arrayref in the form of C<[$hjust, $vjust]>, where $hjust
and $vjust are two numbers for horizontal and vertical justification
respectively. Each number is usually from 0 to 1, but can also beyond 
hat range. 0 means left alignment and 1 means right alighment.
Default is C<[0.5, 0.5]>, which means the object's center is aligned to
its (x, y) position.
For example, for a rectangle which has $width and $height, and positioned
at ($x, $y), the position of its left-bottom corner can be calculated in
this way,
    $left   = $x - $hjust * $width;
    $bottom = $y - $vjust * $height;
This attribute also supports some string values. They map to numeric values
like below.
    string                          numeric
    ---------------------------     ------------
    left                            [ 0,   0.5 ]
    top                             [ 0.5, 1   ]
    right                           [ 1,   0.5 ]
    bottom                          [ 0.5, 0   ]
    center | centre                 [ 0.5, 0.5 ]
    bottom_left | left_bottom       [ 0,   0   ]
    top_left | left_top             [ 0,   1   ]
    bottom_right | right_bottom     [ 1,   0   ]
    top_right | right_top           [ 1,   1   ]
=head2 hjust
A reader accessor for the horizontal justification.
=head2 vjust
A reader accessor for vertical justification.
=head2 gp
An object of L<Graphics::Grid::GPar>. Default is an empty gpar object.
=head2 clip
=head2 xscale
A numeric array ref of length two indicating the minimum and maximum on
the x-scale. The limits may not be identical.
Default is C<[0, 1]>.
=head2 yscale
A numeric array ref of length two indicating the minimum and maximum on
the y-scale. The limits may not be identical.
Default is C<[0, 1]>.
=head2 angle
A numeric value indicating the angle of rotation of the viewport. Positive
values indicate the amount of rotation, in degrees, anticlockwise from the
positive x-axis. Default is 0.
=head2 layout
A L<Graphics::Grid::Layout> object which splits the viewport into subregions.
=head2 layout_pos_row
Indices of rows occupied by this viewport in its parent's layout.
=head2 layout_pos_col
Indices of columns occupied by this viewport in its parent's layout.
=head2 name
A string to uniquely identify the viewport once it has been pushed onto the
viewport tree. If not specified, it would be assigned automatically.
=head1 SEE ALSO
L<Graphics::Grid>
L<Graphics::Grid::ViewportLike>
=head1 AUTHOR
Stephan Loyd <sloyd@cpan.org>
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2018-2023 by Stephan Loyd.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut