#include "GLCanvas3D.hpp"

#include "../../slic3r/GUI/3DScene.hpp"
#include "../../libslic3r/ClipperUtils.hpp"

#include <wx/glcanvas.h>

#include <iostream>

static const bool TURNTABLE_MODE = true;
static const float GIMBALL_LOCK_THETA_MAX = 180.0f;
static const float GROUND_Z = -0.02f;

// phi / theta angles to orient the camera.
static const float VIEW_DEFAULT[2] = { 45.0f, 45.0f };
static const float VIEW_LEFT[2] = { 90.0f, 90.0f };
static const float VIEW_RIGHT[2] = { -90.0f, 90.0f };
static const float VIEW_TOP[2] = { 0.0f, 0.0f };
static const float VIEW_BOTTOM[2] = { 0.0f, 180.0f };
static const float VIEW_FRONT[2] = { 0.0f, 90.0f };
static const float VIEW_REAR[2] = { 180.0f, 90.0f };

namespace Slic3r {
namespace GUI {

bool GeometryBuffer::set_from_triangles(const Polygons& triangles, float z)
{
    m_data.clear();

    unsigned int size = 9 * (unsigned int)triangles.size();
    if (size == 0)
        return false;

    m_data = std::vector<float>(size, 0.0f);

    unsigned int coord = 0;
    for (const Polygon& t : triangles)
    {
        for (unsigned int v = 0; v < 3; ++v)
        {
            const Point& p = t.points[v];
            m_data[coord++] = (float)unscale(p.x);
            m_data[coord++] = (float)unscale(p.y);
            m_data[coord++] = z;
        }
    }

    return true;
}

bool GeometryBuffer::set_from_lines(const Lines& lines, float z)
{
    m_data.clear();

    unsigned int size = 6 * (unsigned int)lines.size();
    if (size == 0)
        return false;

    m_data = std::vector<float>(size, 0.0f);

    unsigned int coord = 0;
    for (const Line& l : lines)
    {
        m_data[coord++] = (float)unscale(l.a.x);
        m_data[coord++] = (float)unscale(l.a.y);
        m_data[coord++] = z;
        m_data[coord++] = (float)unscale(l.b.x);
        m_data[coord++] = (float)unscale(l.b.y);
        m_data[coord++] = z;
    }

    return true;
}

const float* GeometryBuffer::get_data() const
{
    return m_data.data();
}

unsigned int GeometryBuffer::get_data_size() const
{
    return (unsigned int)m_data.size();
}

GLCanvas3D::Camera::Camera()
    : m_type(CT_Ortho)
    , m_zoom(1.0f)
    , m_phi(45.0f)
    , m_theta(45.0f)
    , m_distance(0.0f)
    , m_target(0.0, 0.0, 0.0)
{
}

GLCanvas3D::Camera::EType GLCanvas3D::Camera::get_type() const
{
    return m_type;
}

void GLCanvas3D::Camera::set_type(GLCanvas3D::Camera::EType type)
{
    m_type = type;
}

std::string GLCanvas3D::Camera::get_type_as_string() const
{
    switch (m_type)
    {
    default:
    case CT_Unknown:
        return "unknown";
    case CT_Perspective:
        return "perspective";
    case CT_Ortho:
        return "ortho";
    };
}

float GLCanvas3D::Camera::get_zoom() const
{
    return m_zoom;
}

void GLCanvas3D::Camera::set_zoom(float zoom)
{
    m_zoom = zoom;
}

float GLCanvas3D::Camera::get_phi() const
{
    return m_phi;
}

void GLCanvas3D::Camera::set_phi(float phi)
{
    m_phi = phi;
}

float GLCanvas3D::Camera::get_theta() const
{
    return m_theta;
}

void GLCanvas3D::Camera::set_theta(float theta)
{
    m_theta = theta;

    // clamp angle
    if (m_theta > GIMBALL_LOCK_THETA_MAX)
        m_theta = GIMBALL_LOCK_THETA_MAX;

    if (m_theta < 0.0f)
        m_theta = 0.0f;
}

float GLCanvas3D::Camera::get_distance() const
{
    return m_distance;
}

void GLCanvas3D::Camera::set_distance(float distance)
{
    m_distance = distance;
}

const Pointf3& GLCanvas3D::Camera::get_target() const
{
    return m_target;
}

void GLCanvas3D::Camera::set_target(const Pointf3& target)
{
    m_target = target;
}

const Pointfs& GLCanvas3D::Bed::get_shape() const
{
    return m_shape;
}

void GLCanvas3D::Bed::set_shape(const Pointfs& shape)
{
    m_shape = shape;

    _calc_bounding_box();

    ExPolygon poly;
    for (const Pointf& p : m_shape)
    {
        poly.contour.append(Point(scale_(p.x), scale_(p.y)));
    }

    _calc_triangles(poly);

    const BoundingBox& bed_bbox = poly.contour.bounding_box();
    _calc_gridlines(poly, bed_bbox);

    m_polygon = offset_ex(poly.contour, bed_bbox.radius() * 1.7, jtRound, scale_(0.5))[0].contour;

    set_origin(Pointf(0.0, 0.0));
}

const BoundingBoxf3& GLCanvas3D::Bed::get_bounding_box() const
{
    return m_bounding_box;
}

const Pointf& GLCanvas3D::Bed::get_origin() const
{
    return m_origin;
}

void GLCanvas3D::Bed::set_origin(const Pointf& origin)
{
    m_origin = origin;
}

void GLCanvas3D::Bed::render()
{
    unsigned int triangles_vcount = m_triangles.get_data_size() / 3;
    if (triangles_vcount > 0)
    {
        ::glDisable(GL_DEPTH_TEST);

        ::glEnable(GL_BLEND);
        ::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

        ::glEnableClientState(GL_VERTEX_ARRAY);

        ::glColor4f(0.8f, 0.6f, 0.5f, 0.4f);
        ::glNormal3d(0.0f, 0.0f, 1.0f);
        ::glVertexPointer(3, GL_FLOAT, 0, (GLvoid*)m_triangles.get_data());
        ::glDrawArrays(GL_TRIANGLES, 0, (GLsizei)triangles_vcount);

        // we need depth test for grid, otherwise it would disappear when looking
        // the object from below
        glEnable(GL_DEPTH_TEST);

        // draw grid
        unsigned int gridlines_vcount = m_gridlines.get_data_size() / 3;

        ::glLineWidth(3.0f);
        ::glColor4f(0.2f, 0.2f, 0.2f, 0.4f);
        ::glVertexPointer(3, GL_FLOAT, 0, (GLvoid*)m_gridlines.get_data());
        ::glDrawArrays(GL_LINES, 0, (GLsizei)gridlines_vcount);

        ::glDisableClientState(GL_VERTEX_ARRAY);

        ::glDisable(GL_BLEND);
    }
}

void GLCanvas3D::Bed::_calc_bounding_box()
{
    m_bounding_box = BoundingBoxf3();
    for (const Pointf& p : m_shape)
    {
        m_bounding_box.merge(Pointf3(p.x, p.y, 0.0));
    }
}

void GLCanvas3D::Bed::_calc_triangles(const ExPolygon& poly)
{
    Polygons triangles;
    poly.triangulate(&triangles);

    if (!m_triangles.set_from_triangles(triangles, GROUND_Z))
        printf("Unable to create bed triangles\n");
}

void GLCanvas3D::Bed::_calc_gridlines(const ExPolygon& poly, const BoundingBox& bed_bbox)
{
    Polylines axes_lines;
    for (coord_t x = bed_bbox.min.x; x <= bed_bbox.max.x; x += scale_(10.0))
    {
        Polyline line;
        line.append(Point(x, bed_bbox.min.y));
        line.append(Point(x, bed_bbox.max.y));
        axes_lines.push_back(line);
    }
    for (coord_t y = bed_bbox.min.y; y <= bed_bbox.max.y; y += scale_(10.0))
    {
        Polyline line;
        line.append(Point(bed_bbox.min.x, y));
        line.append(Point(bed_bbox.max.x, y));
        axes_lines.push_back(line);
    }

    // clip with a slightly grown expolygon because our lines lay on the contours and may get erroneously clipped
    Lines gridlines = to_lines(intersection_pl(axes_lines, offset(poly, SCALED_EPSILON)));

    // append bed contours
    Lines contour_lines = to_lines(poly);
    std::copy(contour_lines.begin(), contour_lines.end(), std::back_inserter(gridlines));

    if (!m_gridlines.set_from_lines(gridlines, GROUND_Z))
        printf("Unable to create bed grid lines\n");
}

GLCanvas3D::CuttingPlane::CuttingPlane()
    : m_z(-1.0f)
{
}

bool GLCanvas3D::CuttingPlane::set(float z, const ExPolygons& polygons)
{
    m_z = z;

    // grow slices in order to display them better
    ExPolygons expolygons = offset_ex(polygons, scale_(0.1));
    Lines lines = to_lines(expolygons);
    return m_lines.set_from_lines(lines, m_z);
}

void GLCanvas3D::CuttingPlane::render_plane(const BoundingBoxf3& bb)
{
    if (m_z >= 0.0f)
    {
        ::glDisable(GL_CULL_FACE);
        ::glDisable(GL_LIGHTING);
        ::glEnable(GL_BLEND);
        ::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

        float margin = 20.0f;
        float min_x = bb.min.x - margin;
        float max_x = bb.max.x + margin;
        float min_y = bb.min.y - margin;
        float max_y = bb.max.y + margin;

        ::glBegin(GL_QUADS);
        ::glColor4f(0.8f, 0.8f, 0.8f, 0.5f);
        ::glVertex3f(min_x, min_y, m_z);
        ::glVertex3f(max_x, min_y, m_z);
        ::glVertex3f(max_x, max_y, m_z);
        ::glVertex3f(min_x, max_y, m_z);
        ::glEnd();

        ::glEnable(GL_CULL_FACE);
        ::glDisable(GL_BLEND);
    }
}

void GLCanvas3D::CuttingPlane::render_contour()
{
    ::glEnableClientState(GL_VERTEX_ARRAY);

    if (m_z >= 0.0f)
    {
        unsigned int lines_vcount = m_lines.get_data_size() / 3;

        ::glLineWidth(2.0f);
        ::glColor3f(0.0f, 0.0f, 0.0f);
        ::glVertexPointer(3, GL_FLOAT, 0, (GLvoid*)m_lines.get_data());
        ::glDrawArrays(GL_LINES, 0, (GLsizei)lines_vcount);
    }

    ::glDisableClientState(GL_VERTEX_ARRAY);
}

GLCanvas3D::GLCanvas3D(wxGLCanvas* canvas, wxGLContext* context)
    : m_canvas(canvas)
    , m_context(context)
    , m_volumes(nullptr)
    , m_dirty(true)
    , m_apply_zoom_to_volumes_filter(false)
{
}

GLCanvas3D::~GLCanvas3D()
{
    _deregister_callbacks();
}

void GLCanvas3D::set_current()
{
    if ((m_canvas != nullptr) && (m_context != nullptr))
        m_canvas->SetCurrent(*m_context);
}

bool GLCanvas3D::is_dirty() const
{
    return m_dirty;
}

void GLCanvas3D::set_dirty(bool dirty)
{
    m_dirty = dirty;
}

bool GLCanvas3D::is_shown_on_screen() const
{
    return (m_canvas != nullptr) ? m_canvas->IsShownOnScreen() : false;
}

void GLCanvas3D::resize(unsigned int w, unsigned int h)
{
    if (m_context == nullptr)
        return;
    
    set_current();
    ::glViewport(0, 0, w, h);

    ::glMatrixMode(GL_PROJECTION);
    ::glLoadIdentity();

    BoundingBoxf3 bbox = max_bounding_box();

    switch (get_camera_type())
    {
    case Camera::CT_Ortho:
        {
            float w2 = w;
            float h2 = h;
            float two_zoom = 2.0f * get_camera_zoom();
            if (two_zoom != 0.0f)
            {
                float inv_two_zoom = 1.0f / two_zoom;
                w2 *= inv_two_zoom;
                h2 *= inv_two_zoom;
            }

            // FIXME: calculate a tighter value for depth will improve z-fighting
            float depth = 5.0f * (float)bbox.max_size();
            ::glOrtho(-w2, w2, -h2, h2, -depth, depth);

            break;
        }
    case Camera::CT_Perspective:
        {
            float bbox_r = (float)bbox.radius();
            float fov = PI * 45.0f / 180.0f;
            float fov_tan = tan(0.5f * fov);
            float cam_distance = 0.5f * bbox_r / fov_tan;
            set_camera_distance(cam_distance);

            float nr = cam_distance - bbox_r * 1.1f;
            float fr = cam_distance + bbox_r * 1.1f;
            if (nr < 1.0f)
                nr = 1.0f;

            if (fr < nr + 1.0f)
                fr = nr + 1.0f;

            float h2 = fov_tan * nr;
            float w2 = h2 * w / h;
            ::glFrustum(-w2, w2, -h2, h2, nr, fr);

            break;
        }
    default:
        {
            throw std::runtime_error("Invalid camera type.");
            break;
        }
    }

    ::glMatrixMode(GL_MODELVIEW);

    set_dirty(false);
}

GLVolumeCollection* GLCanvas3D::get_volumes()
{
    return m_volumes;
}

void GLCanvas3D::set_volumes(GLVolumeCollection* volumes)
{
    m_volumes = volumes;
}

void GLCanvas3D::set_bed_shape(const Pointfs& shape)
{
    m_bed.set_shape(shape);
}

void GLCanvas3D::set_auto_bed_shape()
{
    // draw a default square bed around object center
    const BoundingBoxf3& bbox = volumes_bounding_box();
    coordf_t max_size = bbox.max_size();
    const Pointf3& center = bbox.center();

    Pointfs bed_shape;
    bed_shape.reserve(4);
    bed_shape.emplace_back(center.x - max_size, center.y - max_size);
    bed_shape.emplace_back(center.x + max_size, center.y - max_size);
    bed_shape.emplace_back(center.x + max_size, center.y + max_size);
    bed_shape.emplace_back(center.x - max_size, center.y + max_size);

    set_bed_shape(bed_shape);

    // Set the origin for painting of the coordinate system axes.
    set_bed_origin(Pointf(center.x, center.y));
}

const Pointf& GLCanvas3D::get_bed_origin() const
{
    return m_bed.get_origin();
}

void GLCanvas3D::set_bed_origin(const Pointf& origin)
{
    m_bed.set_origin(origin);
}

void GLCanvas3D::set_cutting_plane(float z, const ExPolygons& polygons)
{
    m_cutting_plane.set(z, polygons);
}

GLCanvas3D::Camera::EType GLCanvas3D::get_camera_type() const
{
    return m_camera.get_type();
}

void GLCanvas3D::set_camera_type(GLCanvas3D::Camera::EType type)
{
    m_camera.set_type(type);
}

std::string GLCanvas3D::get_camera_type_as_string() const
{
    return m_camera.get_type_as_string();
}

float GLCanvas3D::get_camera_zoom() const
{
    return m_camera.get_zoom();
}

void GLCanvas3D::set_camera_zoom(float zoom)
{
    m_camera.set_zoom(zoom);
}

float GLCanvas3D::get_camera_phi() const
{
    return m_camera.get_phi();
}

void GLCanvas3D::set_camera_phi(float phi)
{
    m_camera.set_phi(phi);
}

float GLCanvas3D::get_camera_theta() const
{
    return m_camera.get_theta();
}

void GLCanvas3D::set_camera_theta(float theta)
{
    m_camera.set_theta(theta);
}

float GLCanvas3D::get_camera_distance() const
{
    return m_camera.get_distance();
}

void GLCanvas3D::set_camera_distance(float distance)
{
    m_camera.set_distance(distance);
}

const Pointf3& GLCanvas3D::get_camera_target() const
{
    return m_camera.get_target();
}

void GLCanvas3D::set_camera_target(const Pointf3& target)
{
    m_camera.set_target(target);
}

BoundingBoxf3 GLCanvas3D::bed_bounding_box() const
{
    return m_bed.get_bounding_box();
}

BoundingBoxf3 GLCanvas3D::volumes_bounding_box() const
{
    BoundingBoxf3 bb;
    if (m_volumes != nullptr)
    {
        for (const GLVolume* volume : m_volumes->volumes)
        {
            if (!m_apply_zoom_to_volumes_filter || ((volume != nullptr) && volume->zoom_to_volumes))
                bb.merge(volume->transformed_bounding_box());
        }
    }
    return bb;
}

BoundingBoxf3 GLCanvas3D::max_bounding_box() const
{
    BoundingBoxf3 bb = bed_bounding_box();
    bb.merge(volumes_bounding_box());
    return bb;
}

void GLCanvas3D::zoom_to_bed()
{
    _zoom_to_bounding_box(bed_bounding_box());
}

void GLCanvas3D::zoom_to_volumes()
{
    m_apply_zoom_to_volumes_filter = true;
    _zoom_to_bounding_box(volumes_bounding_box());
    m_apply_zoom_to_volumes_filter = false;
}

void GLCanvas3D::select_view(const std::string& direction)
{
    const float* dir_vec = nullptr;

    if (direction == "iso")
        dir_vec = VIEW_DEFAULT;
    else if (direction == "left")
        dir_vec = VIEW_LEFT;
    else if (direction == "right")
        dir_vec = VIEW_RIGHT;
    else if (direction == "top")
        dir_vec = VIEW_TOP;
    else if (direction == "bottom")
        dir_vec = VIEW_BOTTOM;
    else if (direction == "front")
        dir_vec = VIEW_FRONT;
    else if (direction == "rear")
        dir_vec = VIEW_REAR;

    if ((dir_vec != nullptr) && !empty(volumes_bounding_box()))
    {
        m_camera.set_phi(dir_vec[0]);
        m_camera.set_theta(dir_vec[1]);

        m_on_viewport_changed_callback.call();
        
        if (m_canvas != nullptr)
            m_canvas->Refresh();
    }
}

void GLCanvas3D::render_bed()
{
    m_bed.render();
}

void GLCanvas3D::render_cutting_plane()
{
    m_cutting_plane.render_plane(volumes_bounding_box());
    m_cutting_plane.render_contour();
}

void GLCanvas3D::register_on_viewport_changed_callback(void* callback)
{
    if (callback != nullptr)
        m_on_viewport_changed_callback.register_callback(callback);
}

void GLCanvas3D::on_size(wxSizeEvent& evt)
{
    set_dirty(true);
}

void GLCanvas3D::on_idle(wxIdleEvent& evt)
{
    if (!is_dirty() || !is_shown_on_screen())
        return;

    if (m_canvas != nullptr)
    {
        std::pair<int, int> size = _get_canvas_size();
        resize((unsigned int)size.first, (unsigned int)size.second);
        m_canvas->Refresh();
    }
}

void GLCanvas3D::on_char(wxKeyEvent& evt)
{
    if (evt.HasModifiers())
        evt.Skip();
    else
    {
        int keyCode = evt.GetKeyCode();
        switch (keyCode - 48)
        {
        // numerical input
        case 0: { select_view("iso"); break; }
        case 1: { select_view("top"); break; }
        case 2: { select_view("bottom"); break; }
        case 3: { select_view("front"); break; }
        case 4: { select_view("rear"); break; }
        case 5: { select_view("left"); break; }
        case 6: { select_view("right"); break; }
        default:
            {
                // text input
                switch (keyCode)
                {
                // key B/b
                case 66:
                case 98:  { zoom_to_bed(); break; }
                // key Z/z
                case 90:
                case 122: { zoom_to_volumes(); break; }
                default: { evt.Skip(); break; }
                }
            }
        }
    }
}

void GLCanvas3D::_zoom_to_bounding_box(const BoundingBoxf3& bbox)
{
    // Calculate the zoom factor needed to adjust viewport to bounding box.
    float zoom = _get_zoom_to_bounding_box_factor(bbox);
    if (zoom > 0.0f)
    {
        set_camera_zoom(zoom);
        // center view around bounding box center
        set_camera_target(bbox.center());

        m_on_viewport_changed_callback.call();

        if (is_shown_on_screen())
        {
            std::pair<int, int> size = _get_canvas_size();
            resize((unsigned int)size.first, (unsigned int)size.second);
            if (m_canvas != nullptr)
                m_canvas->Refresh();
        }
    }
}

std::pair<int, int> GLCanvas3D::_get_canvas_size() const
{
    std::pair<int, int> ret(0, 0);

    if (m_canvas != nullptr)
        m_canvas->GetSize(&ret.first, &ret.second);

    return ret;
}

float GLCanvas3D::_get_zoom_to_bounding_box_factor(const BoundingBoxf3& bbox) const
{
    float max_bb_size = bbox.max_size();
    if (max_bb_size == 0.0f)
        return -1.0f;

    // project the bbox vertices on a plane perpendicular to the camera forward axis
    // then calculates the vertices coordinate on this plane along the camera xy axes

    // we need the view matrix, we let opengl calculate it(same as done in render sub)
    ::glMatrixMode(GL_MODELVIEW);
    ::glLoadIdentity();

    if (TURNTABLE_MODE)
    {
        // Turntable mode is enabled by default.
        ::glRotatef(-get_camera_theta(), 1.0f, 0.0f, 0.0f); // pitch
        ::glRotatef(get_camera_phi(), 0.0f, 0.0f, 1.0f);    // yaw
    }
    else
    {
        // Shift the perspective camera.
        Pointf3 camera_pos(0.0, 0.0, -(coordf_t)get_camera_distance());
        ::glTranslatef((float)camera_pos.x, (float)camera_pos.y, (float)camera_pos.z);
//        my @rotmat = quat_to_rotmatrix($self->quat); <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< TEMPORARY COMMENTED OUT
//        glMultMatrixd_p(@rotmat[0..15]);             <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< TEMPORARY COMMENTED OUT
    }

    const Pointf3& target = get_camera_target();
    ::glTranslatef(-(float)target.x, -(float)target.y, -(float)target.z);

    // get the view matrix back from opengl
    GLfloat matrix[16];
    ::glGetFloatv(GL_MODELVIEW_MATRIX, matrix);

    // camera axes
    Pointf3 right((coordf_t)matrix[0], (coordf_t)matrix[4], (coordf_t)matrix[8]);
    Pointf3 up((coordf_t)matrix[1], (coordf_t)matrix[5], (coordf_t)matrix[9]);
    Pointf3 forward((coordf_t)matrix[2], (coordf_t)matrix[6], (coordf_t)matrix[10]);

    Pointf3 bb_min = bbox.min;
    Pointf3 bb_max = bbox.max;
    Pointf3 bb_center = bbox.center();

    // bbox vertices in world space
    std::vector<Pointf3> vertices;
    vertices.reserve(8);
    vertices.push_back(bb_min);
    vertices.emplace_back(bb_max.x, bb_min.y, bb_min.z);
    vertices.emplace_back(bb_max.x, bb_max.y, bb_min.z);
    vertices.emplace_back(bb_min.x, bb_max.y, bb_min.z);
    vertices.emplace_back(bb_min.x, bb_min.y, bb_max.z);
    vertices.emplace_back(bb_max.x, bb_min.y, bb_max.z);
    vertices.push_back(bb_max);
    vertices.emplace_back(bb_min.x, bb_max.y, bb_max.z);

    coordf_t max_x = 0.0;
    coordf_t max_y = 0.0;

    // margin factor to give some empty space around the bbox
    coordf_t margin_factor = 1.25;

    for (const Pointf3 v : vertices)
    {
        // project vertex on the plane perpendicular to camera forward axis
        Pointf3 pos(v.x - bb_center.x, v.y - bb_center.y, v.z - bb_center.z);
        Pointf3 proj_on_plane = pos - dot(pos, forward) * forward;

        // calculates vertex coordinate along camera xy axes
        coordf_t x_on_plane = dot(proj_on_plane, right);
        coordf_t y_on_plane = dot(proj_on_plane, up);

        max_x = std::max(max_x, margin_factor * std::abs(x_on_plane));
        max_y = std::max(max_y, margin_factor * std::abs(y_on_plane));
    }

    if ((max_x == 0.0) || (max_y == 0.0))
        return -1.0f;

    max_x *= 2.0;
    max_y *= 2.0;

    std::pair<int, int> cvs_size = _get_canvas_size();
    return (float)std::min((coordf_t)cvs_size.first / max_x, (coordf_t)cvs_size.second / max_y);
}

void GLCanvas3D::_deregister_callbacks()
{
    m_on_viewport_changed_callback.deregister_callback();
}

} // namespace GUI
} // namespace Slic3r