/*

  KLayout Layout Viewer
  Copyright (C) 2006-2021 Matthias Koefferlein

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

*/


#include "layD25ViewWidget.h"
#include "layD25ViewUtils.h"
#include "layLayoutView.h"

#include "dbRecursiveShapeIterator.h"
#include "dbD25TechnologyComponent.h"
#include "dbEdgeProcessor.h"
#include "dbPolygonGenerators.h"
#include "dbPolygonTools.h"
#include "dbClip.h"

#include "tlException.h"

#include <QWheelEvent>
#include <QMouseEvent>
#include <QKeyEvent>
#include <QImage>
#include <QPainter>
#include <QOpenGLTexture>

#include "math.h"

namespace lay
{

// ------------------------------------------------------------------------------

D25InteractionMode::D25InteractionMode (D25ViewWidget *view)
  : mp_view (view)
{
  //  .. nothing yet ..
}

D25InteractionMode::~D25InteractionMode ()
{
  //  .. nothing yet ..
}


// ------------------------------------------------------------------------------

class D25PanInteractionMode
  : public D25InteractionMode
{
public:
  D25PanInteractionMode (D25ViewWidget *widget, const QPoint &pos)
    : D25InteractionMode (widget), m_start_pos (pos)
  {
    m_start_displacement = widget->displacement ();

    double px = (pos.x () - widget->width () / 2) * 2.0 / widget->width ();
    double py = -(pos.y () - widget->height () / 2) * 2.0 / widget->height ();

    //  compute vector of line of sight
    std::pair<QVector3D, QVector3D> ray = camera_normal (view ()->cam_perspective () * view ()->cam_trans (), px, py);

    //  by definition the ray goes through the camera position
    QVector3D hp = widget->hit_point_with_scene (ray.second);

    m_focus_dist = (widget->cam_position () - hp).length ();
  }

  virtual ~D25PanInteractionMode ()
  {
    //  .. nothing yet ..
  }

  virtual void mouse_move (QMouseEvent *event)
  {
    QPoint d = event->pos () - m_start_pos;
    double f = tan ((view ()->cam_fov () / 2) / 180.0 * M_PI) * m_focus_dist * 2.0 / double (view ()->height ());
    double dx = d.x () * f;
    double dy = -d.y () * f;

    QVector3D xv (cos (view ()->cam_azimuth () * M_PI / 180.0), 0.0, sin (view ()->cam_azimuth () * M_PI / 180.0));
    double re = sin (view ()->cam_elevation () * M_PI / 180.0);
    QVector3D yv (-re * xv.z (), cos (view ()->cam_elevation () * M_PI / 180.0), re * xv.x ());
    QVector3D drag = xv * dx + yv * dy;

    view ()->set_displacement (m_start_displacement + drag / view ()->scale_factors ());
  }

private:
  QPoint m_start_pos;
  double m_focus_dist;
  QVector3D m_start_displacement;
};

// ------------------------------------------------------------------------------

class D25Rotate2DInteractionMode
  : public D25InteractionMode
{
public:
  D25Rotate2DInteractionMode (D25ViewWidget *widget, const QPoint &pos)
    : D25InteractionMode (widget), m_start_pos (pos)
  {
    m_start_cam_azimuth = widget->cam_azimuth ();
    m_start_cam_elevation = widget->cam_elevation ();
  }

  virtual ~D25Rotate2DInteractionMode ()
  {
    //  .. nothing yet ..
  }

  virtual void mouse_move (QMouseEvent *event)
  {
    //  fixed focus point for rotation
    double focus_dist = 2.0;

    QPoint d = event->pos () - m_start_pos;
    double f = tan ((view ()->cam_fov () / 2) / 180.0 * M_PI) * focus_dist * 2.0 / double (view ()->height ());
    double dx = d.x () * f;
    double dy = -d.y () * f;

    double da = dx / (view ()->cam_dist () - focus_dist) * 180.0 / M_PI;
    view ()->set_cam_azimuth (m_start_cam_azimuth + da);

    double de = dy / (view ()->cam_dist () - focus_dist) * 180.0 / M_PI;
    view ()->set_cam_elevation (m_start_cam_elevation + de);
  }

private:
  QPoint m_start_pos;
  double m_start_cam_azimuth, m_start_cam_elevation;
};

// ------------------------------------------------------------------------------

class D25RotateAzimuthInteractionMode
  : public D25InteractionMode
{
public:
  D25RotateAzimuthInteractionMode (D25ViewWidget *widget, const QPoint &pos)
    : D25InteractionMode (widget), m_start_pos (pos)
  {
    //  .. nothing yet ..
  }

  virtual ~D25RotateAzimuthInteractionMode ()
  {
    //  .. nothing yet ..
  }

  virtual void mouse_move (QMouseEvent *event)
  {
    //  simple change of azimuth only - with center in the middle

    QPoint m = event->pos () - m_start_pos;
    QVector3D p (m_start_pos.x () - view ()->width () / 2, -m_start_pos.y () + view ()->height () / 2, 0);
    QVector3D d (m.x (), -m.y (), 0);

    double cp = QVector3D::crossProduct (p, p + d).z () / p.length () / (p + d).length ();
    cp = std::max (-1.0, std::min (1.0, cp));
    double da = asin (cp) * 180.0 / M_PI;

    view ()->set_cam_azimuth (view ()->cam_azimuth () + da);
    m_start_pos = event->pos ();
  }

private:
  QPoint m_start_pos;
};

// ------------------------------------------------------------------------------

D25ViewWidget::D25ViewWidget (QWidget *parent)
  : QOpenGLWidget (parent),
    m_shapes_program (0), m_gridplane_program (0)
{
  QSurfaceFormat format;
  format.setDepthBufferSize (24);
  format.setSamples (4); //  more -> widget extends beyond boundary!
  format.setStencilBufferSize (8);
  setFormat (format);

  m_zmin = m_zmax = 0.0;
  mp_view = 0;

  reset_viewport ();
}

D25ViewWidget::~D25ViewWidget ()
{
  // Make sure the context is current and then explicitly
  // destroy all underlying OpenGL resources.
  makeCurrent ();

  delete m_shapes_program;

  doneCurrent ();
}

void
D25ViewWidget::reset_viewport ()
{
  m_scale_factor = 1.0;
  m_vscale_factor = 1.0;
  mp_mode.reset (0);

  camera_init ();
}

void
D25ViewWidget::reset ()
{
  reset_viewport ();
  emit scale_factor_changed (m_scale_factor);
  emit vscale_factor_changed (m_vscale_factor);
  refresh ();
}

void
D25ViewWidget::wheelEvent (QWheelEvent *event)
{
  if (event->angleDelta ().y () == 0) {
    return;
  }

  double px = (event->pos ().x () - width () / 2) * 2.0 / width ();
  double py = -(event->pos ().y () - height () / 2) * 2.0 / height ();

  if (top_view ()) {

    //  Plain zoom

    QVector3D hp (px, py, 0.0);

    double f = exp (event->angleDelta ().y () * (1.0 / (90 * 8)));

    m_scale_factor *= f;
    m_displacement += hp * (1.0 - f) / m_scale_factor;

    emit scale_factor_changed (m_scale_factor);

  } else {

    double d = event->angleDelta ().y () * (1.0 / (90 * 16));

    if (! (event->modifiers () & Qt::ControlModifier)) {

      //  No Ctrl is "move horizontally along the azimuth axis"

      QMatrix4x4 t;
      t.rotate (cam_azimuth (), 0.0, 1.0, 0.0);
      QVector3D cd = t.inverted ().map (QVector3D (0, 0, cam_dist ()));

      m_displacement += d * cd / m_scale_factor;

    } else {

      //  "Ctrl" is zoom

      m_scale_factor *= exp (d);

      emit scale_factor_changed (m_scale_factor);

    }

  }

  refresh ();
}

void
D25ViewWidget::keyPressEvent (QKeyEvent *event)
{
  if (event->key () == Qt::Key_Shift) {

    mp_mode.reset (0);
    set_top_view (true);

  } else if (event->key () == Qt::Key_Up || event->key () == Qt::Key_Down) {

    if (! top_view () && (event->modifiers () & Qt::ControlModifier) != 0) {

      //  Ctrl + up/down changes elevation

      double d = (event->key () == Qt::Key_Up ? 2 : -2);

      set_cam_elevation (std::max (-90.0, std::min (90.0, cam_elevation () + d)));

    } else {

      //  Move "into" or "out"

      double d = (event->key () == Qt::Key_Up ? 0.1 : -0.1);

      QMatrix4x4 t;
      t.rotate (cam_azimuth (), 0.0, 1.0, 0.0);
      QVector3D cd = t.inverted ().map (QVector3D (0, 0, cam_dist ()));

      set_displacement (displacement () + d * cd);

    }

  } else if (event->key () == Qt::Key_Left || event->key () == Qt::Key_Right) {

    if (! top_view () && (event->modifiers () & Qt::ControlModifier) != 0) {

      //  Ctrl + left/right changes azimuths

      double d = (event->key () == Qt::Key_Right ? 2 : -2);

      double a = cam_azimuth () + d;
      if (a < -180.0) {
        a += 360.0;
      } else if (a > 180.0) {
        a -= 360.0;
      }

      set_cam_azimuth (a);

    } else {

      //  Move "left" and "right"

      double d = (event->key () == Qt::Key_Left ? 0.1 : -0.1);

      QMatrix4x4 t;
      t.rotate (cam_azimuth (), 0.0, 1.0, 0.0);
      QVector3D cd = t.inverted ().map (QVector3D (cam_dist (), 0, 0));

      set_displacement (displacement () + d * cd);

    }

  }
}

void
D25ViewWidget::keyReleaseEvent (QKeyEvent *event)
{
  if (event->key () == Qt::Key_Shift) {
    mp_mode.reset (0);
    set_top_view (false);
  }
}

QVector3D
D25ViewWidget::hit_point_with_scene (const QVector3D &line_dir)
{
  double min_focus_dist = 0.5;

  QVector3D corner = (QVector3D (m_bbox.left (), m_zmin, -(m_bbox.bottom () + m_bbox.height ())) + m_displacement) * scale_factors ();
  QVector3D dim = QVector3D (m_bbox.width (), m_zmax - m_zmin, m_bbox.height ()) * scale_factors ();
  QVector3D line = cam_position ();

  std::pair<bool, QVector3D> hp = lay::hit_point_with_cuboid (line, line_dir, corner, dim);
  if (! hp.first) {
    return line + line_dir * min_focus_dist;
  } else if (QVector3D::dotProduct (line_dir, hp.second - line) < min_focus_dist) {
    //  limit to min focus distance (not behind)
    return line + line_dir * min_focus_dist;
  } else {
    return hp.second;
  }
}

void
D25ViewWidget::mousePressEvent (QMouseEvent *event)
{
  mp_mode.reset (0);

  if (event->button () == Qt::MidButton) {
    mp_mode.reset (new D25PanInteractionMode (this, event->pos ()));
  } else if (event->button () == Qt::LeftButton) {
    if (! top_view ()) {
      mp_mode.reset (new D25Rotate2DInteractionMode (this, event->pos ()));
    } else {
      mp_mode.reset (new D25RotateAzimuthInteractionMode (this, event->pos ()));
    }
  }
}

void
D25ViewWidget::mouseReleaseEvent (QMouseEvent * /*event*/)
{
  mp_mode.reset (0);
}

void
D25ViewWidget::mouseMoveEvent (QMouseEvent *event)
{
  if (mp_mode.get ()) {
    mp_mode->mouse_move (event);
  }
}

inline double square (double x) { return x * x; }

void
D25ViewWidget::fit ()
{
  //  we pick a scale factor to adjust the z dimension roughly to 1/4 of the screen height at a focus distance of 2
  double norm_height = 0.5;
  double in_focus = 2.0;
  m_scale_factor = (tan (cam_fov () * M_PI / 180.0 / 2.0) * 2.0) * in_focus * norm_height / std::max (0.001, (m_zmax - m_zmin));

  QVector3D dim = QVector3D (m_bbox.width (), m_zmax - m_zmin, m_bbox.height ()) * m_scale_factor;
  QVector3D bll = QVector3D (m_bbox.left (), m_zmin, -(m_bbox.bottom () + m_bbox.height ()));

  //  now we pick a displacement which moves the center to y = 0 and x, y in a way that the dimension covers the field of
  //  view and is centered.
  //  (we use the elliptic approximation which works exactly for azimuth angles which are a multiple of 90 degree)

  double dh = sqrt (square (cos (cam_azimuth () * M_PI / 180.0) * dim.x ()) + square (sin (cam_azimuth () * M_PI / 180.0) * dim.z ()));
  double dv = sqrt (square (cos (cam_azimuth () * M_PI / 180.0) * dim.z ()) + square (sin (cam_azimuth () * M_PI / 180.0) * dim.x ()));

  double d = std::max (dh, fabs (sin (cam_elevation ()) * dv));

  QVector3D new_center (0.0, 0.0, -dv / 2.0 + std::max (0.0, -d / (2.0 * tan (cam_fov () * M_PI / 180.0 / 2.0)) + cam_dist ()));
  QVector3D new_center_in_scene = cam_trans ().inverted ().map (new_center);

  m_displacement = (new_center_in_scene - dim * 0.5) / m_scale_factor - bll;
  m_displacement.setY (0.0);

  refresh ();

  emit scale_factor_changed (m_scale_factor);
}

void
D25ViewWidget::refresh ()
{
  update ();
}

void
D25ViewWidget::showEvent (QShowEvent *)
{
  //  NOTE: This should happen automatically, but apparently the OpenGL widget doesn't do an automatic refresh:
  update ();
}

void
D25ViewWidget::camera_changed ()
{
  refresh ();
}

double
D25ViewWidget::aspect_ratio () const
{
  return double (width ()) / double (height ());
}

bool
D25ViewWidget::attach_view (LayoutView *view)
{
  bool any = false;

  if (mp_view != view) {

    mp_view = view;

    any = prepare_view ();
    reset ();

  }

  return any;
}

namespace {

  class ZDataCache
  {
  public:
    ZDataCache () { }

    std::vector<db::D25LayerInfo> operator() (lay::LayoutView *view, int cv_index, int layer_index)
    {
      std::map<int, std::map<int, std::vector<db::D25LayerInfo> > >::const_iterator c = m_cache.find (cv_index);
      if (c != m_cache.end ()) {
        std::map<int, std::vector<db::D25LayerInfo> >::const_iterator l = c->second.find (layer_index);
        if (l != c->second.end ()) {
          return l->second;
        } else {
          return std::vector<db::D25LayerInfo> ();
        }
      }

      std::map<int, std::vector<db::D25LayerInfo> > &lcache = m_cache [cv_index];

      const db::D25TechnologyComponent *comp = 0;

      const lay::CellView &cv = view->cellview (cv_index);
      if (cv.is_valid () && cv->technology ()) {
        const db::Technology *tech = cv->technology ();
        comp = dynamic_cast<const db::D25TechnologyComponent *> (tech->component_by_name ("d25"));
      }

      if (comp) {

        std::multimap<db::LayerProperties, db::D25LayerInfo, db::LPLogicalLessFunc> zi_by_lp;

        db::D25TechnologyComponent::layers_type layers = comp->compile_from_source ();
        for (db::D25TechnologyComponent::layers_type::const_iterator i = layers.begin (); i != layers.end (); ++i) {
          zi_by_lp.insert (std::make_pair (i->layer (), *i));
        }

        const db::Layout &ly = cv->layout ();
        for (int l = 0; l < int (ly.layers ()); ++l) {
          if (ly.is_valid_layer (l)) {
            db::LayerProperties lp = ly.get_properties (l);
            std::multimap<db::LayerProperties, db::D25LayerInfo, db::LPLogicalLessFunc>::const_iterator z = zi_by_lp.find (lp);
            if ((z == zi_by_lp.end () || ! z->first.log_equal (lp)) && ! lp.name.empty ()) {
              //  If possible, try by name only
              lp = db::LayerProperties (lp.name);
              z = zi_by_lp.find (lp);
            }
            while (z != zi_by_lp.end () && z->first.log_equal (lp)) {
              lcache[l].push_back (z->second);
              ++z;
            }
          }
        }

      }

      std::map<int, std::vector<db::D25LayerInfo> >::const_iterator l = lcache.find (layer_index);
      if (l != lcache.end ()) {
        return l->second;
      } else {
        return std::vector<db::D25LayerInfo> ();
      }
    }

  private:
    std::map<int, std::map<int, std::vector<db::D25LayerInfo> > > m_cache;
  };

}

bool
D25ViewWidget::prepare_view ()
{
  m_layers.clear ();
  m_vertex_chunks.clear ();

  bool zset = false;
  m_zmin = m_zmax = 0.0;

  if (! mp_view) {
    m_bbox = db::DBox (-1.0, -1.0, 1.0, 1.0);
    return false;
  }

  m_bbox = mp_view->viewport ().box ();

  ZDataCache zdata;
  bool any = false;

  for (lay::LayerPropertiesConstIterator lp = mp_view->begin_layers (); ! lp.at_end (); ++lp) {

    std::vector<db::D25LayerInfo> zinfo;
    if (! lp->has_children () && lp->visible (true)) {
      zinfo = zdata (mp_view, lp->cellview_index (), lp->layer_index ());
    }

    for (std::vector<db::D25LayerInfo>::const_iterator zi = zinfo.begin (); zi != zinfo.end (); ++zi) {

      any = true;

      double z0 = zi->zstart ();
      double z1 = zi->zstop ();

      lay::color_t color = lp->fill_color (true);

      m_vertex_chunks.push_back (chunks_type ());

      LayerInfo info;
      info.color[0] = ((color >> 16) & 0xff) / 255.0f;
      info.color[1] = ((color >> 8) & 0xff) / 255.0f;
      info.color[2] = (color & 0xff) / 255.0f;
      info.vertex_chunk = &m_vertex_chunks.back ();

      m_layers.push_back (info);

      const lay::CellView &cv = mp_view->cellview ((unsigned int) lp->cellview_index ());
      render_layout (m_vertex_chunks.back (), cv->layout (), *cv.cell (), db::CplxTrans (cv->layout ().dbu ()).inverted () * m_bbox, (unsigned int) lp->layer_index (), z0, z1);

      if (! zset) {
        m_zmin = z0;
        m_zmax = z1;
        zset = true;
      } else {
        m_zmin = std::min (z0, m_zmin);
        m_zmax = std::max (z1, m_zmax);
      }

    }

  }

  return any;
}

void
D25ViewWidget::render_polygon (D25ViewWidget::chunks_type &chunks, const db::Polygon &poly, double dbu, double zstart, double zstop)
{
  if (poly.holes () > 0) {

    std::vector<db::Polygon> poly_heap;

    db::EdgeProcessor ep;
    ep.insert_sequence (poly.begin_edge ());
    db::PolygonContainer pc (poly_heap);
    db::PolygonGenerator out (pc, true /*resolve holes*/, true /*min coherence*/);
    db::SimpleMerge op;
    ep.process (out, op);

    for (std::vector<db::Polygon>::const_iterator p = poly_heap.begin (); p != poly_heap.end (); ++p) {
      render_polygon (chunks, *p, dbu, zstart, zstop);
    }

  } else if (poly.hull ().size () > 4) {

    std::vector<db::Polygon> poly_heap;

    db::split_polygon (poly, poly_heap);
    for (std::vector<db::Polygon>::const_iterator p = poly_heap.begin (); p != poly_heap.end (); ++p) {
      render_polygon (chunks, *p, dbu, zstart, zstop);
    }

  } else if (poly.hull ().size () >= 3) {

    db::Point pts [4];
    std::copy (poly.hull ().begin (), poly.hull ().end (), &pts [0]);

    //  triangle bottom

    chunks.add (pts[0].x () * dbu, zstart, pts[0].y () * dbu);
    chunks.add (pts[2].x () * dbu, zstart, pts[2].y () * dbu);
    chunks.add (pts[1].x () * dbu, zstart, pts[1].y () * dbu);

    //  triangle top
    chunks.add (pts[0].x () * dbu, zstop, pts[0].y () * dbu);
    chunks.add (pts[1].x () * dbu, zstop, pts[1].y () * dbu);
    chunks.add (pts[2].x () * dbu, zstop, pts[2].y () * dbu);

    if (poly.hull ().size () == 4) {

      //  triangle bottom
      chunks.add (pts[0].x () * dbu, zstart, pts[0].y () * dbu);
      chunks.add (pts[3].x () * dbu, zstart, pts[3].y () * dbu);
      chunks.add (pts[2].x () * dbu, zstart, pts[2].y () * dbu);

      //  triangle top
      chunks.add (pts[0].x () * dbu, zstop, pts[0].y () * dbu);
      chunks.add (pts[2].x () * dbu, zstop, pts[2].y () * dbu);
      chunks.add (pts[3].x () * dbu, zstop, pts[3].y () * dbu);

    }

  }
}

void
D25ViewWidget::render_wall (D25ViewWidget::chunks_type &chunks, const db::Edge &edge, double dbu, double zstart, double zstop)
{
  chunks.add (edge.p1 ().x () * dbu, zstart, edge.p1 ().y () * dbu);
  chunks.add (edge.p2 ().x () * dbu, zstop, edge.p2 ().y () * dbu);
  chunks.add (edge.p1 ().x () * dbu, zstop, edge.p1 ().y () * dbu);
  chunks.add (edge.p1 ().x () * dbu, zstart, edge.p1 ().y () * dbu);
  chunks.add (edge.p2 ().x () * dbu, zstart, edge.p2 ().y () * dbu);
  chunks.add (edge.p2 ().x () * dbu, zstop, edge.p2 ().y () * dbu);
}

void
D25ViewWidget::render_layout (D25ViewWidget::chunks_type &chunks, const db::Layout &layout, const db::Cell &cell, const db::Box &clip_box, unsigned int layer, double zstart, double zstop)
{
  std::vector<db::Polygon> poly_heap;

  //  TODO: hidden cells, hierarchy depth ...

  db::RecursiveShapeIterator s (layout, cell, layer, clip_box);
  s.shape_flags (db::ShapeIterator::Polygons | db::ShapeIterator::Paths | db::ShapeIterator::Boxes);
  for ( ; ! s.at_end (); ++s) {

    db::Polygon polygon;
    s->polygon (polygon);
    polygon.transform (s.trans ());

    poly_heap.clear ();
    db::clip_poly (polygon, clip_box, poly_heap, false /*keep holes*/);

    for (std::vector<db::Polygon>::const_iterator p = poly_heap.begin (); p != poly_heap.end (); ++p) {

      render_polygon (chunks, *p, layout.dbu (), zstart, zstop);

      for (db::Polygon::polygon_edge_iterator e = p->begin_edge (); ! e.at_end (); ++e) {
        render_wall (chunks, *e, layout.dbu (), zstart, zstop);
      }

    }

  }
}

static std::pair<double, double> find_grid (double v)
{
  for (int p = -12; p < 12; ++p) {
    double g10 = pow (10, double (p));
    if (v > 100 * g10) {
      continue;
    } else if (v < 10 * g10) {
      return std::make_pair (g10, g10);
    } else if (v < 20 * g10) {
      return std::make_pair (g10, g10 * 0.1);
    } else if (v < 50 * g10) {
      return std::make_pair (2.0 * g10, g10);
    } else {
      return std::make_pair (5.0 * g10, g10);
    }
  }

  return std::make_pair (v, v);
}

void
D25ViewWidget::initializeGL ()
{
  tl_assert (m_shapes_program == 0);
  tl_assert (m_gridplane_program == 0);

  bool error = false;

  try {
    do_initialize_gl ();
  } catch (tl::Exception &ex) {
    m_error = ex.msg ();
    error = true;
  } catch (std::exception &ex) {
    m_error = ex.what ();
    error = true;
  } catch (...) {
    m_error = "(unspecific error)";
    error = true;
  }

  if (error) {

    delete m_shapes_program;
    m_shapes_program = 0;
    delete m_gridplane_program;
    m_gridplane_program = 0;

    emit init_failed ();

  }
}

void
D25ViewWidget::do_initialize_gl ()
{
  QOpenGLFunctions::initializeOpenGLFunctions();

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

  static const char *shapes_vertex_shader_source =
      "#version 150\n"
      "\n"
      "in vec4 posAttr;\n"
      "\n"
      "void main() {\n"
      "   gl_Position = posAttr;\n"
      "}\n";

  static const char *shapes_geometry_shader_source =
      "#version 150\n"
      "\n"
      "uniform vec4 color;\n"
      "uniform vec4 ambient;\n"
      "uniform vec3 illum;\n"
      "out lowp vec4 vertexColor;\n"
      "uniform mat4 matrix;\n"
      "layout (triangles) in;\n"
      "layout (triangle_strip, max_vertices = 3) out;\n"
      "\n"
      "void main() {\n"
      "   vec4 p0 = gl_in[0].gl_Position;\n"
      "   vec4 p1 = gl_in[1].gl_Position;\n"
      "   vec4 p2 = gl_in[2].gl_Position;\n"
      "   vec3 n = cross(p2.xyz - p0.xyz, p1.xyz - p0.xyz);\n"
      "   float dp = dot(normalize(n), illum);\n"
      "   vertexColor = color * (dp * 0.5 + 0.5) - (min(0.0, dp) * ambient);\n"
      "   vertexColor.a = 1.0;\n"
      "   gl_Position = matrix * p0;\n"
      "   EmitVertex();\n"
      "   gl_Position = matrix * p1;\n"
      "   EmitVertex();\n"
      "   gl_Position = matrix * p2;\n"
      "   EmitVertex();\n"
      "   EndPrimitive();\n"
      "}\n";

  static const char *shapes_fragment_shader_source =
      "#version 150\n"
      "\n"
      "in lowp vec4 vertexColor;\n"
      "out lowp vec4 fragColor;\n"
      "uniform highp float mist_factor;\n"
      "uniform highp float mist_add;\n"
      "\n"
      "lowp vec4 color_by_z(lowp vec4 c, highp float z) {\n"
      "  highp float mist_rgb = c.g * mist_factor + mist_add;\n"
      "  lowp vec4 mist_color = vec4(mist_rgb, mist_rgb, mist_rgb, 1.0);\n"
      "  highp float d = 0.12;\n" //  d + dd/2 = 0.15 = 1/?
      "  highp float dd = 0.06;\n"
      "  highp float f = 1.0;\n"
      "  if (z < d - dd) {\n"
      "    f = 0.0;\n"
      "  } else if (z < d + dd) {\n"
      "    f = (z - (d - dd)) / (2.0 * dd);\n"
      "  }\n"
      "  return (1.0 - f) * mist_color + f * c;\n"
      "};\n"
      "\n"
      "void main() {\n"
      "   fragColor = color_by_z(vertexColor, gl_FragCoord.w);\n"
      "}\n";

  m_shapes_program = new QOpenGLShaderProgram (this);
  if (! m_shapes_program->addShaderFromSourceCode (QOpenGLShader::Vertex, shapes_vertex_shader_source)) {
    throw tl::Exception (std::string ("Shapes vertex shader compilation failed:\n") + tl::to_string (m_shapes_program->log ()));
  }
  if (! m_shapes_program->addShaderFromSourceCode (QOpenGLShader::Geometry, shapes_geometry_shader_source)) {
    throw tl::Exception (std::string ("Shapes geometry shader compilation failed:\n") + tl::to_string (m_shapes_program->log ()));
  }
  if (! m_shapes_program->addShaderFromSourceCode (QOpenGLShader::Fragment, shapes_fragment_shader_source)) {
    throw tl::Exception (std::string ("Shapes fragment shader compilation failed:\n") + tl::to_string (m_shapes_program->log ()));
  }
  if (! m_shapes_program->link ()) {
    throw tl::Exception (std::string ("Shapes shader program linking failed failed:\n") + tl::to_string (m_shapes_program->log ()));
  }

  //  grid plane shader source

  static const char *gridplan_vertex_shader_source =
      "#version 150\n"
      "\n"
      "in vec4 posAttr;\n"
      "uniform mat4 matrix;\n"
      "\n"
      "void main() {\n"
      "   gl_Position = matrix * posAttr;\n"
      "}\n";

  static const char *gridplan_fragment_shader_source =
      "#version 150\n"
      "\n"
      "uniform lowp vec4 color;\n"
      "out lowp vec4 fragColor;\n"
      "void main() {\n"
      "   fragColor = color;\n"
      "}\n";

  m_gridplane_program = new QOpenGLShaderProgram (this);
  if (! m_gridplane_program->addShaderFromSourceCode (QOpenGLShader::Vertex, gridplan_vertex_shader_source)) {
    throw tl::Exception (std::string ("Grid plane vertex shader compilation failed:\n") + tl::to_string (m_gridplane_program->log ()));
  }
  if (! m_gridplane_program->addShaderFromSourceCode (QOpenGLShader::Fragment, gridplan_fragment_shader_source)) {
    throw tl::Exception (std::string ("Grid plane fragment shader compilation failed:\n") + tl::to_string (m_gridplane_program->log ()));
  }
  if (! m_gridplane_program->link ()) {
    throw tl::Exception (std::string ("Grid plane shader program linking failed:\n") + tl::to_string (m_gridplane_program->log ()));
  }
}

void
D25ViewWidget::paintGL ()
{
  const qreal retina_scale = devicePixelRatio ();
  glViewport (0, 0, width () * retina_scale, height () * retina_scale);

  QColor c = mp_view->background_color ();
  float foreground_rgb = (c.green () > 128 ? 0.0f : 1.0f);
  float ambient = (c.green () > 128 ? 0.8f : 0.25f);
  float mist_factor = (c.green () > 128 ? 0.2f : 0.4f);
  float mist_add = (c.green () > 128 ? 0.8f : 0.2f);
  glClearColor (float (c.red ()) / 255.0f, float (c.green ()) / 255.0f, float (c.blue ()) / 255.0f, 1.0);
  glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  if (! m_shapes_program || ! m_gridplane_program) {
    return;
  }

  int positions = m_shapes_program->attributeLocation ("posAttr");

  QMatrix4x4 scene_trans, scene_trans_wo_y;

  //  provide the displacement and scaling (in this order!)
  scene_trans.scale (m_scale_factor, m_scale_factor * m_vscale_factor, m_scale_factor);
  scene_trans.translate (m_displacement);
  //  this way we can use y as z coordinate when drawing
  scene_trans.scale (1.0, 1.0, -1.0);

  scene_trans_wo_y = scene_trans;
  scene_trans_wo_y.translate (QVector3D (0.0, -m_displacement.y (), 0.0));

  m_shapes_program->bind ();

  //  draw the actual layout

  m_shapes_program->setUniformValue ("matrix", cam_perspective () * cam_trans () * scene_trans);

  //  NOTE: z axis of illum points towards the scene because we include the z inversion in the scene transformation matrix
  m_shapes_program->setUniformValue ("illum", QVector3D (-3.0, -4.0, 2.0).normalized ());

  m_shapes_program->setUniformValue ("ambient", QVector4D (ambient, ambient, ambient, 1.0));
  m_shapes_program->setUniformValue ("mist_factor", mist_factor);
  m_shapes_program->setUniformValue ("mist_add", mist_add);

  glEnable (GL_DEPTH_TEST);
  glEnableVertexAttribArray (positions);

  for (std::list<LayerInfo>::const_iterator l = m_layers.begin (); l != m_layers.end (); ++l) {
    m_shapes_program->setUniformValue ("color", l->color [0], l->color [1], l->color [2], l->color [3]);
    l->vertex_chunk->draw_to (this, positions, GL_TRIANGLES);
  }

  glDisableVertexAttribArray (positions);

  m_shapes_program->release ();


  //  decoration

  positions = m_gridplane_program->attributeLocation ("posAttr");

  //  a vertex buffer for the decoration
  lay::mem_chunks<float, 1024 * 18> vertexes;

  m_gridplane_program->bind ();

  glEnable (GL_DEPTH_TEST);
  glEnableVertexAttribArray (positions);

  //  draw pivot compass

  m_gridplane_program->setUniformValue ("matrix", cam_perspective () * cam_trans ());

  double compass_rad = 0.3;
  double compass_bars = 0.4;

  vertexes.add (-compass_bars, 0.0, 0.0);
  vertexes.add (compass_bars, 0.0, 0.0);

  vertexes.add (0.0, 0.0, -compass_bars);
  vertexes.add (0.0, 0.0, compass_bars);

  int ncircle = 64;
  double x = compass_rad, z = 0.0;
  double da = 1.0 / double (ncircle) * M_PI * 2.0;

  for (int i = 0; i < ncircle; ++i) {

    double a = double (i + 1) * da;
    double xx = compass_rad * cos (a);
    double zz = compass_rad * sin (a);

    vertexes.add (x, 0.0, z);
    vertexes.add (xx, 0.0, zz);

    x = xx;
    z = zz;

  }

  m_gridplane_program->setUniformValue ("color", foreground_rgb, foreground_rgb, foreground_rgb, 0.25f);

  glLineWidth (2.0);
  vertexes.draw_to (this, positions, GL_LINES);

  //  arrow

  vertexes.clear ();

  vertexes.add (-0.25 * compass_rad, 0.0, 0.6 * compass_rad);
  vertexes.add (0.0, 0.0, -0.8 * compass_rad);
  vertexes.add (0.0, 0.0, -0.8 * compass_rad);
  vertexes.add (0.25 * compass_rad, 0.0, 0.6 * compass_rad);
  vertexes.add (0.25 * compass_rad, 0.0, 0.6 * compass_rad);
  vertexes.add (-0.25 * compass_rad, 0.0, 0.6 * compass_rad);

  vertexes.draw_to (this, positions, GL_LINES);

  //  draw base plane

  m_gridplane_program->setUniformValue ("matrix", cam_perspective () * cam_trans () * scene_trans_wo_y);

  std::pair<double, double> gg = find_grid (std::max (m_bbox.width (), m_bbox.height ()));
  double gminor = gg.second, gmajor = gg.first;

  double margin = std::max (m_bbox.width (), m_bbox.height ()) * 0.02;

  double l = m_bbox.left ();
  double r = m_bbox.right ();
  double b = m_bbox.bottom ();
  double t = m_bbox.top ();

  //  major and minor grid lines

  vertexes.clear ();

  const double epsilon = 1e-6;

  for (int major = 0; major < 2; ++major) {

    m_gridplane_program->setUniformValue ("color", foreground_rgb, foreground_rgb, foreground_rgb, major ? 0.25f : 0.15f);

    double x, y;
    double step = (major ? gmajor : gminor);

    x = ceil (l / step) * step;
    for ( ; x < r - step * epsilon; x += step) {
      if ((fabs (floor (x / gmajor + 0.5) * gmajor - x) < epsilon) == (major != 0)) {
        vertexes.add (x, 0.0, b - margin);
        vertexes.add (x, 0.0, t + margin);
      }
    }

    y = ceil (b / step) * step;
    for ( ; y < t - step * epsilon; y += step) {
      if ((fabs (floor (y / gmajor + 0.5) * gmajor - y) < epsilon) == (major != 0)) {
        vertexes.add (l - margin, 0.0, y);
        vertexes.add (r + margin, 0.0, y);
      }
    }

    glLineWidth (2.0);
    vertexes.draw_to (this, positions, GL_LINES);

  }

  //  the plane itself

  vertexes.clear ();

  vertexes.add (l, 0.0, b);
  vertexes.add (l, 0.0, t);
  vertexes.add (r, 0.0, t);

  vertexes.add (l, 0.0, b);
  vertexes.add (r, 0.0, b);
  vertexes.add (r, 0.0, t);

  m_gridplane_program->setUniformValue ("color", foreground_rgb, foreground_rgb, foreground_rgb, 0.1f);

  vertexes.draw_to (this, positions, GL_TRIANGLES);

  //  the orientation cube

  if (! top_view ()) {

    glDisable (GL_DEPTH_TEST);

    int cube_size = 32;
    int cube_margin = 40;

    QMatrix4x4 into_top_right_corner;
    into_top_right_corner.translate (1.0 - 2.0 / width () * (cube_margin + cube_size / 2), 1.0 - 2.0 / height () * (cube_margin + cube_size / 2));
    // into_top_right_corner.translate (0.5, 0.5, 0.0);
    into_top_right_corner.scale (2.0 * cube_size / double (height ()), 2.0 * cube_size / double (height ()), 1.0);

    m_gridplane_program->setUniformValue ("matrix", into_top_right_corner * cam_perspective () * cam_trans ());

    vertexes.clear ();

    vertexes.add (-1.0, -1.0, 1.0);
    vertexes.add (-1.0, -1.0, -1.0);

    vertexes.add (-1.0, 1.0, 1.0);
    vertexes.add (-1.0, 1.0, -1.0);

    vertexes.add (1.0, -1.0, 1.0);
    vertexes.add (1.0, -1.0, -1.0);

    vertexes.add (1.0, 1.0, 1.0);
    vertexes.add (1.0, 1.0, -1.0);

    vertexes.add (-1.0, -1.0, 1.0);
    vertexes.add (-1.0, 1.0, 1.0);

    vertexes.add (1.0, -1.0, 1.0);
    vertexes.add (1.0, 1.0, 1.0);

    vertexes.add (-1.0, -1.0, 1.0);
    vertexes.add (1.0, -1.0, 1.0);

    vertexes.add (-1.0, 1.0, 1.0);
    vertexes.add (1.0, 1.0, 1.0);

    vertexes.add (-1.0, -1.0, -1.0);
    vertexes.add (-1.0, 1.0, -1.0);

    vertexes.add (1.0, -1.0, -1.0);
    vertexes.add (1.0, 1.0, -1.0);

    vertexes.add (-1.0, -1.0, -1.0);
    vertexes.add (1.0, -1.0, -1.0);

    vertexes.add (-1.0, 1.0, -1.0);
    vertexes.add (1.0, 1.0, -1.0);

    m_gridplane_program->setUniformValue ("color", foreground_rgb, foreground_rgb, foreground_rgb, 0.2f);

    vertexes.draw_to (this, positions, GL_LINES);

    vertexes.clear ();

    //  A "K" at the front
    vertexes.add (-0.8f, -0.8f, 1.0f);
    vertexes.add (-0.8f, 0.8f, 1.0f);
    vertexes.add (-0.2f, 0.8f, 1.0f);

    vertexes.add (-0.8f, -0.8f, 1.0f);
    vertexes.add (-0.2f, -0.8f, 1.0f);
    vertexes.add (-0.2f, 0.8f, 1.0f);

    vertexes.add (0.2f, 0.8f, 1.0f);
    vertexes.add (0.8f, 0.8f, 1.0f);
    vertexes.add (0.8f, 0.6f, 1.0f);

    vertexes.add (0.2f, 0.8f, 1.0f);
    vertexes.add (0.8f, 0.6f, 1.0f);
    vertexes.add (0.6f, 0.4f, 1.0f);

    vertexes.add (-0.2f, 0.4f, 1.0f);
    vertexes.add (0.2f, 0.8f, 1.0f);
    vertexes.add (0.6f, 0.4f, 1.0f);

    vertexes.add (-0.2f, 0.4f, 1.0f);
    vertexes.add (0.6f, 0.4f, 1.0f);
    vertexes.add (0.2f, 0.0f, 1.0f);

    vertexes.add (-0.2f, 0.4f, 1.0f);
    vertexes.add (0.2f, 0.0f, 1.0f);
    vertexes.add (-0.2f, -0.4f, 1.0f);

    vertexes.add (-0.2f, -0.4f, 1.0f);
    vertexes.add (0.6f, -0.4f, 1.0f);
    vertexes.add (0.2f, -0.0f, 1.0f);

    vertexes.add (-0.2f, -0.4f, 1.0f);
    vertexes.add (0.2f, -0.8f, 1.0f);
    vertexes.add (0.6f, -0.4f, 1.0f);

    vertexes.add (0.2f, -0.8f, 1.0f);
    vertexes.add (0.8f, -0.6f, 1.0f);
    vertexes.add (0.6f, -0.4f, 1.0f);

    vertexes.add (0.2f, -0.8f, 1.0f);
    vertexes.add (0.8f, -0.8f, 1.0f);
    vertexes.add (0.8f, -0.6f, 1.0f);

    m_gridplane_program->setUniformValue ("color", foreground_rgb, foreground_rgb, foreground_rgb, 0.3f);

    vertexes.draw_to (this, positions, GL_TRIANGLES);

  }

  glDisableVertexAttribArray (positions);

  m_shapes_program->release ();
}

void
D25ViewWidget::resizeGL (int /*w*/, int /*h*/)
{
  refresh ();
}

}