/****************************************************************************

   Copyright (C) 2002-2008 Gilles Debunne. All rights reserved.

   This file is part of the QGLViewer library version 2.3.5.

   http://www.libqglviewer.com - contact@libqglviewer.com

   This file may be used under the terms of the GNU General Public License
   versions 2.0 or 3.0 as published by the Free Software Foundation and
   appearing in the LICENSE file included in the packaging of this file.
   In addition, as a special exception, Gilles Debunne gives you certain
   additional rights, described in the file GPL_EXCEPTION in this package.

   libQGLViewer uses dual licensing. Commercial/proprietary software must
   purchase a libQGLViewer Commercial License.

   This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
   WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

 *****************************************************************************/

#include "thumbnail.h"
#include <math.h>

#if QT_VERSION >= 0x040000
#  include <QKeyEvent>
#endif

using namespace std;

void Viewer::draw() {
  drawSpiral(false);
}

// Draws a spiral. If thumb is true, the spiral is simplified and drawns in wireframe.
void Viewer::drawSpiral(bool thumb)
{
  float nbSteps;
  if(thumb) {
    nbSteps = 50.0;
    glColor3f(1.0, 1.0, 1.0);
  } else
    nbSteps = 200.0;

  glBegin(GL_QUAD_STRIP);
  for(float i = 0; i < nbSteps; ++i) {
    float ratio = i / nbSteps;
    float angle = 21.0 * ratio;
    float c = cos(angle);
    float s = sin(angle);
    float r1 = 1.0 - 0.8 * ratio;
    float r2 = 0.8 - 0.8 * ratio;
    float alt = ratio - 0.5;
    const float nor = 0.5;
    const float up = sqrt(1.0 - nor * nor);
    if(!thumb)
      glColor3f(1.0 - ratio, 0.2f, ratio);
    glNormal3f(nor * c, up, nor * s);
    glVertex3f(r1 * c, alt, r1 * s);
    glVertex3f(r2 * c, alt + 0.05, r2 * s);
  }
  glEnd();
}

// Manages the thumbnail display.
void Viewer::drawThumbnail()
{
  if(thumbnail_) {
    int viewport[4];
    int scissor[4];

    // The viewport and the scissor are changed to fit the lower left
    // corner. Original values are saved.
    glGetIntegerv(GL_VIEWPORT, viewport);
    glGetIntegerv(GL_SCISSOR_BOX, scissor);

    glViewport(0, 0, width() / 2, height() / 2);
    glScissor(0, 0, width() / 2, height() / 2);

    // The Z-buffer is cleared to make the thumbnail appear over the
    // original image.
    glClear(GL_DEPTH_BUFFER_BIT);

    // Here starts the drawing, with specific GL flags
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    glDisable(GL_LIGHTING);
    drawSpiral(true);
    glEnable(GL_LIGHTING);
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
    // Here ends the drawing. OpenGL state is restored.

    // The viewport and the scissor are restored.
    glScissor(scissor[0], scissor[1], scissor[2], scissor[3]);
    glViewport(viewport[0], viewport[1], viewport[2], viewport[3]);
  }
}

// The thumbnail has to be drawn at the very end to allow a correct
// display of the visual hints (axes, grid, etc).
void Viewer::postDraw()
{
  QGLViewer::postDraw();
  drawThumbnail();
}

void Viewer::keyPressEvent(QKeyEvent* e)
{
  switch(e->key()) {
  case Qt::Key_T:
    thumbnail_ = !thumbnail_;
    updateGL();
    break;
  default:
    QGLViewer::keyPressEvent(e);
  }
}

void Viewer::init()
{
  // Restore previous viewer state.
  restoreStateFromFile();

  help();

  thumbnail_ = true;

  setKeyDescription(Qt::Key_T, "Toggles thumbnail display");
}

QString Viewer::helpString() const
{
  QString text("<h2>T h u m b n a i l</h2>");
  text += "A thumbnailed view of the scene is displayed in the lower left corner.<br><br>";
  text += "Such display may be useful for illustration (e.g. to show the data structure) or to debug your ";
  text += "application. It uses <code>glScissor</code> and <code>glViewport</code> to restrict the display "
          "area.<br><br>";
  text += "Press <b>T</b> to toggle the thumbnail display";
  return text;
}
