package Slic3r::GUI::PreviewCanvas;
use strict;
use warnings;

use Wx::Event qw(EVT_PAINT EVT_SIZE EVT_ERASE_BACKGROUND EVT_IDLE EVT_MOUSEWHEEL EVT_MOUSE_EVENTS);
# must load OpenGL *before* Wx::GLCanvas
use OpenGL qw(:glconstants :glfunctions :glufunctions :gluconstants);
use base qw(Wx::GLCanvas Class::Accessor);
use Math::Trig qw(asin);
use List::Util qw(reduce min max first);
use Slic3r::Geometry qw(X Y Z MIN MAX triangle_normal normalize deg2rad tan scale unscale);
use Slic3r::Geometry::Clipper qw(offset_ex intersection_pl);
use Wx::GLCanvas qw(:all);
 
__PACKAGE__->mk_accessors( qw(_quat _dirty init
                              enable_picking
                              enable_moving
                              on_hover
                              on_select
                              on_double_click
                              on_right_click
                              on_move
                              volumes
                              print
                              _sphi _stheta
                              cutting_plane_z
                              cut_lines_vertices
                              bed_shape
                              bed_triangles
                              bed_grid_lines
                              origin
                              _mouse_pos
                              _hover_volume_idx
                              _drag_volume_idx
                              _drag_start_pos
                              _drag_start_xy
                              _dragged
                              _camera_target
                              _zoom
                              ) );

use constant TRACKBALLSIZE => 0.8;
use constant TURNTABLE_MODE => 1;
use constant GROUND_Z       => 0.02;
use constant SELECTED_COLOR => [0,1,0,1];
use constant HOVER_COLOR    => [0.8,0.8,0,1];
use constant COLORS => [ [1,1,0], [1,0.5,0.5], [0.5,1,0.5], [0.5,0.5,1] ];

# make OpenGL::Array thread-safe
{
    no warnings 'redefine';
    *OpenGL::Array::CLONE_SKIP = sub { 1 };
}

sub new {
    my ($class, $parent) = @_;
    
    # we request a depth buffer explicitely because it looks like it's not created by 
    # default on Linux, causing transparency issues
    my $self = $class->SUPER::new($parent, -1, Wx::wxDefaultPosition, Wx::wxDefaultSize, 0, "",
        [WX_GL_RGBA, WX_GL_DOUBLEBUFFER, WX_GL_DEPTH_SIZE, 16, 0]);
   
    $self->_quat((0, 0, 0, 1));
    $self->_stheta(45);
    $self->_sphi(45);
    $self->_zoom(1);
    
    # 3D point in model space
    $self->_camera_target(Slic3r::Pointf3->new(0,0,0));
    
    $self->reset_objects;
    
    EVT_PAINT($self, sub {
        my $dc = Wx::PaintDC->new($self);
        $self->Render($dc);
    });
    EVT_SIZE($self, sub { $self->_dirty(1) });
    EVT_IDLE($self, sub {
        return unless $self->_dirty;
        return if !$self->IsShownOnScreen;
        $self->Resize( $self->GetSizeWH );
        $self->Refresh;
    });
    EVT_MOUSEWHEEL($self, sub {
        my ($self, $e) = @_;
        
        # Calculate the zoom delta and apply it to the current zoom factor
        my $zoom = $e->GetWheelRotation() / $e->GetWheelDelta();
        $zoom = max(min($zoom, 4), -4);
        $zoom /= 10;
        $self->_zoom($self->_zoom * (1-$zoom));
        
        # In order to zoom around the mouse point we need to translate
        # the camera target
        my $size = Slic3r::Pointf->new($self->GetSizeWH);
        my $pos = Slic3r::Pointf->new($e->GetX, $size->y - $e->GetY); #-
        $self->_camera_target->translate(
            # ($pos - $size/2) represents the vector from the viewport center
            # to the mouse point. By multiplying it by $zoom we get the new,
            # transformed, length of such vector.
            # Since we want that point to stay fixed, we move our camera target
            # in the opposite direction by the delta of the length of such vector
            # ($zoom - 1). We then scale everything by 1/$self->_zoom since 
            # $self->_camera_target is expressed in terms of model units.
            -($pos->x - $size->x/2) * ($zoom) / $self->_zoom,
            -($pos->y - $size->y/2) * ($zoom) / $self->_zoom,
            0,
        ) if 0;
        $self->_dirty(1);
        $self->Refresh;
    });
    EVT_MOUSE_EVENTS($self, \&mouse_event);
    
    return $self;
}

sub mouse_event {
    my ($self, $e) = @_;
    
    my $pos = Slic3r::Pointf->new($e->GetPositionXY);
    if ($e->Entering && &Wx::wxMSW) {
        # wxMSW needs focus in order to catch mouse wheel events
        $self->SetFocus;
    } elsif ($e->LeftDClick) {
        $self->on_double_click->()
            if $self->on_double_click;
    } elsif ($e->LeftDown || $e->RightDown) {
        # If user pressed left or right button we first check whether this happened
        # on a volume or not.
        my $volume_idx = $self->_hover_volume_idx // -1;
        
        # select volume in this 3D canvas
        if ($self->enable_picking) {
            $self->deselect_volumes;
            $self->select_volume($volume_idx);
            $self->Refresh;
        }
        
        # propagate event through callback
        $self->on_select->($volume_idx)
            if $self->on_select;
        
        if ($volume_idx != -1) {
            if ($e->LeftDown && $self->enable_moving) {
                $self->_drag_volume_idx($volume_idx);
                $self->_drag_start_pos($self->mouse_to_3d(@$pos));
            } elsif ($e->RightDown) {
                # if right clicking on volume, propagate event through callback
                $self->on_right_click->($e->GetPosition)
                    if $self->on_right_click;
            }
        }
    } elsif ($e->Dragging && $e->LeftIsDown && defined($self->_drag_volume_idx)) {
        # get volume being dragged
        my $volume = $self->volumes->[$self->_drag_volume_idx];
        
        # get new position at the same Z of the initial click point
        my $mouse_ray = $self->mouse_ray($e->GetX, $e->GetY);
        my $cur_pos = $mouse_ray->intersect_plane($self->_drag_start_pos->z);
        
        # calculate the translation vector
        my $vector = $self->_drag_start_pos->vector_to($cur_pos);
        
        # apply new temporary volume origin and ignore Z
        $volume->origin->translate($vector->x, $vector->y, 0); #,,
        $self->_drag_start_pos($cur_pos);
        $self->_dragged(1);
        $self->Refresh;
    } elsif ($e->Dragging && !defined $self->_hover_volume_idx) {
        if ($e->LeftIsDown) {
            # if dragging over blank area with left button, rotate
            if (defined $self->_drag_start_pos) {
                my $orig = $self->_drag_start_pos;
                if (TURNTABLE_MODE) {
                    $self->_sphi($self->_sphi + ($pos->x - $orig->x) * TRACKBALLSIZE);
                    $self->_stheta($self->_stheta - ($pos->y - $orig->y) * TRACKBALLSIZE);        #-
                    $self->_stheta(150) if $self->_stheta > 150;
                    $self->_stheta(0) if $self->_stheta < 0;
                } else {
                    my $size = $self->GetClientSize;
                    my @quat = trackball(
                        $orig->x / ($size->width / 2) - 1,
                        1 - $orig->y / ($size->height / 2),       #/
                        $pos->x / ($size->width / 2) - 1,
                        1 - $pos->y / ($size->height / 2),        #/
                    );
                    $self->_quat(mulquats($self->_quat, \@quat));
                }
                $self->Refresh;
            }
            $self->_drag_start_pos($pos);
        } elsif ($e->RightIsDown) {
            # if dragging over blank area with right button, translate
            
            if (defined $self->_drag_start_xy) {
                # get point in model space at Z = 0
                my $cur_pos = $self->mouse_ray($e->GetX, $e->GetY)->intersect_plane(0);
                my $orig    = $self->mouse_ray(@{$self->_drag_start_xy})->intersect_plane(0);
                $self->_camera_target->translate(
                    @{$orig->vector_to($cur_pos)->negative},
                );
                $self->Refresh;
            }
            $self->_drag_start_xy($pos);
        }
    } elsif ($e->LeftUp || $e->RightUp) {
        if ($self->on_move && defined $self->_drag_volume_idx) {
            $self->on_move->($self->_drag_volume_idx) if $self->_dragged;
        }
        $self->_drag_volume_idx(undef);
        $self->_drag_start_pos(undef);
        $self->_drag_start_xy(undef);
        $self->_dragged(undef);
    } elsif ($e->Moving) {
        $self->_mouse_pos($pos);
        $self->Refresh;
    } else {
        $e->Skip();
    }
}

sub reset_objects {
    my ($self) = @_;
    
    $self->volumes([]);
    $self->_dirty(1);
}

sub zoom_to_bounding_box {
    my ($self, $bb) = @_;
    
    # calculate the zoom factor needed to adjust viewport to
    # bounding box
    my $max_size = max(@{$bb->size}) * 2;
    my $min_viewport_size = min($self->GetSizeWH);
    $self->_zoom($min_viewport_size / $max_size);
    
    # center view around bounding box center
    $self->_camera_target($bb->center);
}

sub zoom_to_bed {
    my ($self) = @_;
    
    if ($self->bed_shape) {
        $self->zoom_to_bounding_box($self->bed_bounding_box);
    }
}

sub zoom_to_volume {
    my ($self, $volume_idx) = @_;
    
    my $volume = $self->volumes->[$volume_idx];
    my $bb = $volume->bounding_box;
    $self->zoom_to_bounding_box($bb);
}

sub zoom_to_volumes {
    my ($self) = @_;
    $self->zoom_to_bounding_box($self->volumes_bounding_box);
}

sub volumes_bounding_box {
    my ($self) = @_;
    
    my $bb = Slic3r::Geometry::BoundingBoxf3->new;
    $bb->merge($_->bounding_box) for @{$self->volumes};
    return $bb;
}

sub bed_bounding_box {
    my ($self) = @_;
    
    my $bb = Slic3r::Geometry::BoundingBoxf3->new;
    $bb->merge_point(Slic3r::Pointf3->new(@$_, 0)) for @{$self->bed_shape};
    return $bb;
}

sub max_bounding_box {
    my ($self) = @_;
    
    my $bb = $self->bed_bounding_box;
    $bb->merge($self->volumes_bounding_box);
    return $bb;
}

sub set_auto_bed_shape {
    my ($self, $bed_shape) = @_;
    
    # draw a default square bed around object center
    my $max_size = max(@{ $self->volumes_bounding_box->size });
    my $center = $self->volumes_bounding_box->center;
    $self->set_bed_shape([
        [ $center->x - $max_size, $center->y - $max_size ],  #--
        [ $center->x + $max_size, $center->y - $max_size ],  #--
        [ $center->x + $max_size, $center->y + $max_size ],  #++
        [ $center->x - $max_size, $center->y + $max_size ],  #++
    ]);
    $self->origin(Slic3r::Pointf->new(@$center[X,Y]));
}

sub set_bed_shape {
    my ($self, $bed_shape) = @_;
    
    $self->bed_shape($bed_shape);
    
    # triangulate bed
    my $expolygon = Slic3r::ExPolygon->new([ map [map scale($_), @$_], @$bed_shape ]);
    my $bed_bb = $expolygon->bounding_box;
    
    {
        my @points = ();
        foreach my $triangle (@{ $expolygon->triangulate }) {
            push @points, map {+ unscale($_->x), unscale($_->y), GROUND_Z } @$triangle;  #))
        }
        $self->bed_triangles(OpenGL::Array->new_list(GL_FLOAT, @points));
    }
    
    {
        my @lines = ();
        for (my $x = $bed_bb->x_min; $x <= $bed_bb->x_max; $x += scale 10) {
            push @lines, Slic3r::Polyline->new([$x,$bed_bb->y_min], [$x,$bed_bb->y_max]);
        }
        for (my $y = $bed_bb->y_min; $y <= $bed_bb->y_max; $y += scale 10) {
            push @lines, Slic3r::Polyline->new([$bed_bb->x_min,$y], [$bed_bb->x_max,$y]);
        }
        @lines = @{intersection_pl(\@lines, [ @$expolygon ])};
        my @points = ();
        foreach my $polyline (@lines) {
            push @points, map {+ unscale($_->x), unscale($_->y), GROUND_Z } @$polyline;  #))
        }
        $self->bed_grid_lines(OpenGL::Array->new_list(GL_FLOAT, @points));
    }
    
    $self->origin(Slic3r::Pointf->new(0,0));
}

sub load_object {
    my ($self, $object, $all_instances) = @_;
    
    my $z_min = $object->raw_bounding_box->z_min;
    
    # color mesh(es) by material
    my @materials = ();
    
    # sort volumes: non-modifiers first
    my @volumes = sort { ($a->modifier // 0) <=> ($b->modifier // 0) } @{$object->volumes};
    my @volumes_idx = ();
    foreach my $volume (@volumes) {
        my @instance_idxs = $all_instances ? (0..$#{$object->instances}) : (0);
        foreach my $instance_idx (@instance_idxs) {
            my $instance = $object->instances->[$instance_idx];
            my $mesh = $volume->mesh->clone;
            $instance->transform_mesh($mesh);
            
            my $material_id = $volume->material_id // '_';
            my $color_idx = first { $materials[$_] eq $material_id } 0..$#materials;
            if (!defined $color_idx) {
                push @materials, $material_id;
                $color_idx = $#materials;
            }
        
            my $color = [ @{COLORS->[ $color_idx % scalar(@{&COLORS}) ]} ];
            push @$color, $volume->modifier ? 0.5 : 1;
            push @{$self->volumes}, my $v = Slic3r::GUI::PreviewCanvas::Volume->new(
                instance_idx    => $instance_idx,
                mesh            => $mesh,
                color           => $color,
                origin          => Slic3r::Pointf3->new(0,0,-$z_min),
            );
            push @volumes_idx, $#{$self->volumes};
        
            {
                my $vertices = $mesh->vertices;
                my @verts = map @{ $vertices->[$_] }, map @$_, @{$mesh->facets};
                $v->verts(OpenGL::Array->new_list(GL_FLOAT, @verts));
            }
        
            {
                my @norms = map { @$_, @$_, @$_ } @{$mesh->normals};
                $v->norms(OpenGL::Array->new_list(GL_FLOAT, @norms));
            }
        }
    }
    
    return @volumes_idx;
}

sub deselect_volumes {
    my ($self) = @_;
    $_->selected(0) for @{$self->volumes};
}

sub select_volume {
    my ($self, $volume_idx) = @_;
    
    $self->volumes->[$volume_idx]->selected(1)
        if $volume_idx != -1;
}

sub SetCuttingPlane {
    my ($self, $z) = @_;
    
    $self->cutting_plane_z($z);
    
    # perform cut and cache section lines
    my @verts = ();
    foreach my $volume (@{$self->volumes}) {
        foreach my $volume (@{$self->volumes}) {
            my $expolygons = $volume->mesh->slice([ $z - $volume->origin->z ])->[0];
            $expolygons = offset_ex([ map @$_, @$expolygons ], scale 0.1);
            
            foreach my $line (map @{$_->lines}, map @$_, @$expolygons) {
                push @verts, (
                    unscale($line->a->x), unscale($line->a->y), $z,  #))
                    unscale($line->b->x), unscale($line->b->y), $z,  #))
                );
            }
        }
    }
    $self->cut_lines_vertices(OpenGL::Array->new_list(GL_FLOAT, @verts));
}

# Given an axis and angle, compute quaternion.
sub axis_to_quat {
    my ($ax, $phi) = @_;
    
    my $lena = sqrt(reduce { $a + $b } (map { $_ * $_ } @$ax));
    my @q = map { $_ * (1 / $lena) } @$ax;
    @q = map { $_ * sin($phi / 2.0) } @q;
    $q[$#q + 1] = cos($phi / 2.0);
    return @q;
}

# Project a point on the virtual trackball. 
# If it is inside the sphere, map it to the sphere, if it outside map it
# to a hyperbola.
sub project_to_sphere {
    my ($r, $x, $y) = @_;
    
    my $d = sqrt($x * $x + $y * $y);
    if ($d < $r * 0.70710678118654752440) {     # Inside sphere
        return sqrt($r * $r - $d * $d);
    } else {                                    # On hyperbola
        my $t = $r / 1.41421356237309504880;
        return $t * $t / $d;
    }
}

sub cross {
    my ($v1, $v2) = @_;
  
    return (@$v1[1] * @$v2[2] - @$v1[2] * @$v2[1],
            @$v1[2] * @$v2[0] - @$v1[0] * @$v2[2],
            @$v1[0] * @$v2[1] - @$v1[1] * @$v2[0]);
}

# Simulate a track-ball. Project the points onto the virtual trackball, 
# then figure out the axis of rotation, which is the cross product of 
# P1 P2 and O P1 (O is the center of the ball, 0,0,0) Note: This is a 
# deformed trackball-- is a trackball in the center, but is deformed 
# into a hyperbolic sheet of rotation away from the center. 
# It is assumed that the arguments to this routine are in the range 
# (-1.0 ... 1.0).
sub trackball {
    my ($p1x, $p1y, $p2x, $p2y) = @_;
    
    if ($p1x == $p2x && $p1y == $p2y) {
        # zero rotation
        return (0.0, 0.0, 0.0, 1.0);
    }
    
    # First, figure out z-coordinates for projection of P1 and P2 to
    # deformed sphere
    my @p1 = ($p1x, $p1y, project_to_sphere(TRACKBALLSIZE, $p1x, $p1y));
    my @p2 = ($p2x, $p2y, project_to_sphere(TRACKBALLSIZE, $p2x, $p2y));
    
    # axis of rotation (cross product of P1 and P2)
    my @a = cross(\@p2, \@p1);

    # Figure out how much to rotate around that axis.
    my @d = map { $_ * $_ } (map { $p1[$_] - $p2[$_] } 0 .. $#p1);
    my $t = sqrt(reduce { $a + $b } @d) / (2.0 * TRACKBALLSIZE);
    
    # Avoid problems with out-of-control values...
    $t = 1.0 if ($t > 1.0);
    $t = -1.0 if ($t < -1.0);
    my $phi = 2.0 * asin($t);

    return axis_to_quat(\@a, $phi);
}

# Build a rotation matrix, given a quaternion rotation.
sub quat_to_rotmatrix {
    my ($q) = @_;
  
    my @m = ();
  
    $m[0] = 1.0 - 2.0 * (@$q[1] * @$q[1] + @$q[2] * @$q[2]);
    $m[1] = 2.0 * (@$q[0] * @$q[1] - @$q[2] * @$q[3]);
    $m[2] = 2.0 * (@$q[2] * @$q[0] + @$q[1] * @$q[3]);
    $m[3] = 0.0;

    $m[4] = 2.0 * (@$q[0] * @$q[1] + @$q[2] * @$q[3]);
    $m[5] = 1.0 - 2.0 * (@$q[2] * @$q[2] + @$q[0] * @$q[0]);
    $m[6] = 2.0 * (@$q[1] * @$q[2] - @$q[0] * @$q[3]);
    $m[7] = 0.0;

    $m[8] = 2.0 * (@$q[2] * @$q[0] - @$q[1] * @$q[3]);
    $m[9] = 2.0 * (@$q[1] * @$q[2] + @$q[0] * @$q[3]);
    $m[10] = 1.0 - 2.0 * (@$q[1] * @$q[1] + @$q[0] * @$q[0]);
    $m[11] = 0.0;

    $m[12] = 0.0;
    $m[13] = 0.0;
    $m[14] = 0.0;
    $m[15] = 1.0;
  
    return @m;
}

sub mulquats {
    my ($q1, $rq) = @_;
  
    return (@$q1[3] * @$rq[0] + @$q1[0] * @$rq[3] + @$q1[1] * @$rq[2] - @$q1[2] * @$rq[1],
            @$q1[3] * @$rq[1] + @$q1[1] * @$rq[3] + @$q1[2] * @$rq[0] - @$q1[0] * @$rq[2],
            @$q1[3] * @$rq[2] + @$q1[2] * @$rq[3] + @$q1[0] * @$rq[1] - @$q1[1] * @$rq[0],
            @$q1[3] * @$rq[3] - @$q1[0] * @$rq[0] - @$q1[1] * @$rq[1] - @$q1[2] * @$rq[2])
}

sub mouse_to_3d {
    my ($self, $x, $y, $z) = @_;

    my @viewport    = glGetIntegerv_p(GL_VIEWPORT);             # 4 items
    my @mview       = glGetDoublev_p(GL_MODELVIEW_MATRIX);      # 16 items
    my @proj        = glGetDoublev_p(GL_PROJECTION_MATRIX);     # 16 items
    
    $y = $viewport[3] - $y;
    $z //= glReadPixels_p($x, $y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT);
    my @projected = gluUnProject_p($x, $y, $z, @mview, @proj, @viewport);
    return Slic3r::Pointf3->new(@projected);
}

sub mouse_ray {
    my ($self, $x, $y) = @_;
    
    return Slic3r::Linef3->new(
        $self->mouse_to_3d($x, $y, 0),
        $self->mouse_to_3d($x, $y, 1),
    );
}

sub GetContext {
    my ($self) = @_;
    
    if (Wx::wxVERSION >= 2.009) {
        return $self->{context} ||= Wx::GLContext->new($self);
    } else {
        return $self->SUPER::GetContext;
    }
}
 
sub SetCurrent {
    my ($self, $context) = @_;
    
    if (Wx::wxVERSION >= 2.009) {
        return $self->SUPER::SetCurrent($context);
    } else {
        return $self->SUPER::SetCurrent;
    }
}

sub Resize {
    my ($self, $x, $y) = @_;
 
    return unless $self->GetContext;
    $self->_dirty(0);
 
    $self->SetCurrent($self->GetContext);
    glViewport(0, 0, $x, $y);
 
    $x /= $self->_zoom;
    $y /= $self->_zoom;
    
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(
        -$x/2, $x/2, -$y/2, $y/2,
        -200, 10 * max(@{ $self->max_bounding_box->size }),
    );
 
    glMatrixMode(GL_MODELVIEW);
}
 
sub InitGL {
    my $self = shift;
 
    return if $self->init;
    return unless $self->GetContext;
    $self->init(1);
    
    glClearColor(0, 0, 0, 1);
    glColor3f(1, 0, 0);
    glEnable(GL_DEPTH_TEST);
    glClearDepth(1.0);
    glDepthFunc(GL_LEQUAL);
    glEnable(GL_CULL_FACE);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    
    # Set antialiasing/multisampling
    glDisable(GL_LINE_SMOOTH);
    glDisable(GL_POLYGON_SMOOTH);
    glEnable(GL_MULTISAMPLE);
    
    # ambient lighting
    glLightModelfv_p(GL_LIGHT_MODEL_AMBIENT, 0.1, 0.1, 0.1, 1);
    
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHT1);
    glLightfv_p(GL_LIGHT0, GL_POSITION, 0.5, 0.5, 1, 0);
    glLightfv_p(GL_LIGHT0, GL_SPECULAR, 0.5, 0.5, 0.5, 1);
    glLightfv_p(GL_LIGHT0, GL_DIFFUSE,  0.8, 0.8, 0.8, 1);
    glLightfv_p(GL_LIGHT1, GL_POSITION, 1, 0, 0.5, 0);
    glLightfv_p(GL_LIGHT1, GL_SPECULAR, 0.5, 0.5, 0.5, 1);
    glLightfv_p(GL_LIGHT1, GL_DIFFUSE,  1, 1, 1, 1);
    
    # Enables Smooth Color Shading; try GL_FLAT for (lack of) fun.
    glShadeModel(GL_SMOOTH);
    
    glMaterialfv_p(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, 0.5, 0.3, 0.3, 1);
    glMaterialfv_p(GL_FRONT_AND_BACK, GL_SPECULAR, 1, 1, 1, 1);
    glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 50);
    glMaterialfv_p(GL_FRONT_AND_BACK, GL_EMISSION, 0.1, 0, 0, 0.9);
    
    # A handy trick -- have surface material mirror the color.
    glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);
    glEnable(GL_COLOR_MATERIAL);
    glEnable(GL_MULTISAMPLE);
}
 
sub Render {
    my ($self, $dc) = @_;
    
    # prevent calling SetCurrent() when window is not shown yet
    return unless $self->IsShownOnScreen;
    return unless my $context = $self->GetContext;
    $self->SetCurrent($context);
    $self->InitGL;
    
    glClearColor(1, 1, 1, 1);
    glClearDepth(1);
    glDepthFunc(GL_LESS);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    
    if (TURNTABLE_MODE) {
        glRotatef(-$self->_stheta, 1, 0, 0); # pitch
        glRotatef($self->_sphi, 0, 0, 1);    # yaw
    } else {
        my @rotmat = quat_to_rotmatrix($self->quat);
        glMultMatrixd_p(@rotmat[0..15]);
    }
    glTranslatef(@{ $self->_camera_target->negative });
    
    if ($self->enable_picking) {
        glDisable(GL_LIGHTING);
        $self->draw_volumes(1);
        glFlush();
        glFinish();
        
        if (my $pos = $self->_mouse_pos) {
            my $col = [ glReadPixels_p($pos->x, $self->GetSize->GetHeight - $pos->y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE) ];
            my $volume_idx = $col->[0] + $col->[1]*256 + $col->[2]*256*256;
            $self->_hover_volume_idx(undef);
            $_->hover(0) for @{$self->volumes};
            if ($volume_idx <= $#{$self->volumes}) {
                $self->_hover_volume_idx($volume_idx);
                $self->volumes->[$volume_idx]->hover(1);
                $self->on_hover->($volume_idx) if $self->on_hover;
            }
        }
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glFlush();
        glFinish();
        glEnable(GL_LIGHTING);
    }
    # draw objects
    $self->draw_volumes;
    
    # draw ground and axes
    glDisable(GL_LIGHTING);
    my $z0 = 0;
    
    {
        # draw ground
        my $ground_z = GROUND_Z;
        if ($self->bed_triangles) {
            glEnable(GL_BLEND);
            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
            
            glEnableClientState(GL_VERTEX_ARRAY);
            glColor4f(0.6, 0.7, 0.5, 0.3);
            glNormal3d(0,0,1);
            glVertexPointer_p(3, $self->bed_triangles);
            glDrawArrays(GL_TRIANGLES, 0, $self->bed_triangles->elements / 3);
            glDisableClientState(GL_VERTEX_ARRAY);
            
            glDisable(GL_BLEND);
        
            # draw grid
            glTranslatef(0, 0, 0.02);
            glLineWidth(3);
            glColor3f(0.95, 0.95, 0.95);
            glEnableClientState(GL_VERTEX_ARRAY);
            glVertexPointer_p(3, $self->bed_grid_lines);
            glDrawArrays(GL_LINES, 0, $self->bed_grid_lines->elements / 3);
            glDisableClientState(GL_VERTEX_ARRAY);
        }
        
        my $volumes_bb = $self->volumes_bounding_box;
        
        {
            # draw axes
            $ground_z += 0.02;
            my $origin = $self->origin;
            my $axis_len = max(
                0.3 * max(@{ $self->bed_bounding_box->size }),
                  2 * max(@{ $volumes_bb->size }),
            );
            glLineWidth(2);
            glBegin(GL_LINES);
            # draw line for x axis
            glColor3f(1, 0, 0);
            glVertex3f(@$origin, $ground_z);
            glVertex3f($origin->x + $axis_len, $origin->y, $ground_z);  #,,
            # draw line for y axis
            glColor3f(0, 1, 0);
            glVertex3f(@$origin, $ground_z);
            glVertex3f($origin->x, $origin->y + $axis_len, $ground_z);  #++
            # draw line for Z axis
            glColor3f(0, 0, 1);
            glVertex3f(@$origin, $ground_z);
            glVertex3f(@$origin, $ground_z+$axis_len);
            glEnd();
        }
        
        # draw cutting plane
        if (defined $self->cutting_plane_z) {
            my $plane_z = $z0 + $self->cutting_plane_z;
            my $bb = $volumes_bb;
            glDisable(GL_CULL_FACE);
            glEnable(GL_BLEND);
            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
            glBegin(GL_QUADS);
            glColor4f(0.8, 0.8, 0.8, 0.5);
            glVertex3f($bb->x_min-20, $bb->y_min-20, $plane_z);
            glVertex3f($bb->x_max+20, $bb->y_min-20, $plane_z);
            glVertex3f($bb->x_max+20, $bb->y_max+20, $plane_z);
            glVertex3f($bb->x_min-20, $bb->y_max+20, $plane_z);
            glEnd();
            glEnable(GL_CULL_FACE);
            glDisable(GL_BLEND);
        }
    }
    
    glEnable(GL_LIGHTING);
    
    glFlush();
 
    $self->SwapBuffers();
}

sub draw_volumes {
    my ($self, $fakecolor) = @_;
    
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    
    if (defined($self->print) && !$fakecolor) {
        my $tess = gluNewTess();
        gluTessCallback($tess, GLU_TESS_BEGIN,     'DEFAULT');
        gluTessCallback($tess, GLU_TESS_END,       'DEFAULT');
        gluTessCallback($tess, GLU_TESS_VERTEX,    'DEFAULT');
        gluTessCallback($tess, GLU_TESS_COMBINE,   'DEFAULT');
        gluTessCallback($tess, GLU_TESS_ERROR,     'DEFAULT');
        gluTessCallback($tess, GLU_TESS_EDGE_FLAG, 'DEFAULT');
        
        foreach my $object (@{$self->print->objects}) {
            foreach my $layer (@{$object->layers}) {
                my $gap = 0;
                my $top_z = $layer->print_z;
                my $bottom_z = $layer->print_z - $layer->height + $gap;
            
                foreach my $copy (@{ $object->_shifted_copies }) {
                    glPushMatrix();
                    glTranslatef(map unscale($_), @$copy, 0);
                    
                    foreach my $slice (@{$layer->slices}) {
                        glColor3f(@{COLORS->[0]});
                        gluTessBeginPolygon($tess);
                        glNormal3f(0,0,1);
                        foreach my $polygon (@$slice) {
                            gluTessBeginContour($tess);
                            gluTessVertex_p($tess, (map unscale($_), @$_), $layer->print_z) for @$polygon;
                            gluTessEndContour($tess);
                        }
                        gluTessEndPolygon($tess);
                        
                        foreach my $polygon (@$slice) {
                            foreach my $line (@{$polygon->lines}) {
                                if (0) {
                                    glLineWidth(1);
                                    glColor3f(0,0,0);
                                    glBegin(GL_LINES);
                                    glVertex3f((map unscale($_), @{$line->a}), $bottom_z);
                                    glVertex3f((map unscale($_), @{$line->b}), $bottom_z);
                                    glEnd();
                                }
                                
                                glLineWidth(0);
                                glColor3f(@{COLORS->[0]});
                                glBegin(GL_QUADS);
                                glNormal3f((map $_/$line->length, @{$line->normal}), 0);
                                glVertex3f((map unscale($_), @{$line->a}), $bottom_z);
                                glVertex3f((map unscale($_), @{$line->b}), $bottom_z);
                                glVertex3f((map unscale($_), @{$line->b}), $top_z);
                                glVertex3f((map unscale($_), @{$line->a}), $top_z);
                                glEnd();
                            }
                        }
                    }
                    
                    glPopMatrix();  # copy
                }
            }
        }
        
        gluDeleteTess($tess);
        return;
    }
    
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_NORMAL_ARRAY);
    
    foreach my $volume_idx (0..$#{$self->volumes}) {
        my $volume = $self->volumes->[$volume_idx];
        glPushMatrix();
        glTranslatef(@{$volume->origin});
        
        glVertexPointer_p(3, $volume->verts);
        
        glCullFace(GL_BACK);
        glNormalPointer_p($volume->norms);
        if ($fakecolor) {
            my $r = ($volume_idx & 0x000000FF) >>  0;
            my $g = ($volume_idx & 0x0000FF00) >>  8;
            my $b = ($volume_idx & 0x00FF0000) >> 16;
            glColor4f($r/255.0, $g/255.0, $b/255.0, 1);
        } elsif ($volume->selected) {
            glColor4f(@{ &SELECTED_COLOR });
        } elsif ($volume->hover) {
            glColor4f(@{ &HOVER_COLOR });
        } else {
            glColor4f(@{ $volume->color });
        }
        glDrawArrays(GL_TRIANGLES, 0, $volume->verts->elements / 3);
        
        glPopMatrix();
    }
    glDisableClientState(GL_NORMAL_ARRAY);
    glDisable(GL_BLEND);
    
    if (defined $self->cutting_plane_z) {
        glLineWidth(2);
        glColor3f(0, 0, 0);
        glVertexPointer_p(3, $self->cut_lines_vertices);
        glDrawArrays(GL_LINES, 0, $self->cut_lines_vertices->elements / 3);
    }
    glDisableClientState(GL_VERTEX_ARRAY);
}

package Slic3r::GUI::PreviewCanvas::Volume;
use Moo;

has 'mesh'          => (is => 'ro', required => 1);
has 'color'         => (is => 'ro', required => 1);
has 'instance_idx'  => (is => 'ro', default => sub { 0 });
has 'origin'        => (is => 'rw', default => sub { Slic3r::Pointf3->new(0,0,0) });
has 'verts'         => (is => 'rw');
has 'norms'         => (is => 'rw');
has 'selected'      => (is => 'rw', default => sub { 0 });
has 'hover'         => (is => 'rw', default => sub { 0 });

sub bounding_box {
    my ($self) = @_;
    
    my $bb = $self->mesh->bounding_box;
    $bb->translate(@{$self->origin});
    return $bb;
}

1;