/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the examples of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** You may use this file under the terms of the BSD license as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
**     of its contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
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** $QT_END_LICENSE$
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****************************************************************************/

#include <QtWidgets>
#include <QtOpenGL>

#include "glwidget.h"

GLWidget::GLWidget(QWidget *parent, QGLWidget *shareWidget)
    : QGLWidget(parent, shareWidget)
{
    clearColor = Qt::black;
    xRot = 0;
    yRot = 0;
    zRot = 0;
    program = 0;
}

GLWidget::~GLWidget()
{
}

QSize GLWidget::minimumSizeHint() const
{
    return QSize(50, 50);
}

QSize GLWidget::sizeHint() const
{
    return QSize(200, 200);
}

void GLWidget::rotateBy(int xAngle, int yAngle, int zAngle)
{
    xRot += xAngle;
    yRot += yAngle;
    zRot += zAngle;
    updateGL();
}

void GLWidget::setClearColor(const QColor &color)
{
    clearColor = color;
    updateGL();
}

void GLWidget::initializeGL()
{
    initializeOpenGLFunctions();

    makeObject();

    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
#ifdef GL_TEXTURE_2D
    glEnable(GL_TEXTURE_2D);
#endif

#define PROGRAM_VERTEX_ATTRIBUTE 0
#define PROGRAM_TEXCOORD_ATTRIBUTE 1

    QGLShader *vshader = new QGLShader(QGLShader::Vertex, this);
    const char *vsrc =
        "attribute highp vec4 vertex;\n"
        "attribute mediump vec4 texCoord;\n"
        "varying mediump vec4 texc;\n"
        "uniform mediump mat4 matrix;\n"
        "void main(void)\n"
        "{\n"
        "    gl_Position = matrix * vertex;\n"
        "    texc = texCoord;\n"
        "}\n";
    vshader->compileSourceCode(vsrc);

    QGLShader *fshader = new QGLShader(QGLShader::Fragment, this);
    const char *fsrc =
        "uniform sampler2D texture;\n"
        "varying mediump vec4 texc;\n"
        "void main(void)\n"
        "{\n"
        "    gl_FragColor = texture2D(texture, texc.st);\n"
        "}\n";
    fshader->compileSourceCode(fsrc);

    program = new QGLShaderProgram(this);
    program->addShader(vshader);
    program->addShader(fshader);
    program->bindAttributeLocation("vertex", PROGRAM_VERTEX_ATTRIBUTE);
    program->bindAttributeLocation("texCoord", PROGRAM_TEXCOORD_ATTRIBUTE);
    program->link();

    program->bind();
    program->setUniformValue("texture", 0);
}

void GLWidget::paintGL()
{
    qglClearColor(clearColor);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    QMatrix4x4 m;
    m.ortho(-0.5f, +0.5f, +0.5f, -0.5f, 4.0f, 15.0f);
    m.translate(0.0f, 0.0f, -10.0f);
    m.rotate(xRot / 16.0f, 1.0f, 0.0f, 0.0f);
    m.rotate(yRot / 16.0f, 0.0f, 1.0f, 0.0f);
    m.rotate(zRot / 16.0f, 0.0f, 0.0f, 1.0f);

    program->setUniformValue("matrix", m);
    program->enableAttributeArray(PROGRAM_VERTEX_ATTRIBUTE);
    program->enableAttributeArray(PROGRAM_TEXCOORD_ATTRIBUTE);
    program->setAttributeArray
        (PROGRAM_VERTEX_ATTRIBUTE, vertices.constData());
    program->setAttributeArray
        (PROGRAM_TEXCOORD_ATTRIBUTE, texCoords.constData());

    for (int i = 0; i < 6; ++i) {
        glBindTexture(GL_TEXTURE_2D, textures[i]);
        glDrawArrays(GL_TRIANGLE_FAN, i * 4, 4);
    }
}

void GLWidget::resizeGL(int width, int height)
{
    int side = qMin(width, height);
    glViewport((width - side) / 2, (height - side) / 2, side, side);
}

void GLWidget::mousePressEvent(QMouseEvent *event)
{
    lastPos = event->pos();
}

void GLWidget::mouseMoveEvent(QMouseEvent *event)
{
    int dx = event->x() - lastPos.x();
    int dy = event->y() - lastPos.y();

    if (event->buttons() & Qt::LeftButton) {
        rotateBy(8 * dy, 8 * dx, 0);
    } else if (event->buttons() & Qt::RightButton) {
        rotateBy(8 * dy, 0, 8 * dx);
    }
    lastPos = event->pos();
}

void GLWidget::mouseReleaseEvent(QMouseEvent * /* event */)
{
    emit clicked();
}

void GLWidget::makeObject()
{
    static const int coords[6][4][3] = {
        { { +1, -1, -1 }, { -1, -1, -1 }, { -1, +1, -1 }, { +1, +1, -1 } },
        { { +1, +1, -1 }, { -1, +1, -1 }, { -1, +1, +1 }, { +1, +1, +1 } },
        { { +1, -1, +1 }, { +1, -1, -1 }, { +1, +1, -1 }, { +1, +1, +1 } },
        { { -1, -1, -1 }, { -1, -1, +1 }, { -1, +1, +1 }, { -1, +1, -1 } },
        { { +1, -1, +1 }, { -1, -1, +1 }, { -1, -1, -1 }, { +1, -1, -1 } },
        { { -1, -1, +1 }, { +1, -1, +1 }, { +1, +1, +1 }, { -1, +1, +1 } }
    };

    for (int j=0; j < 6; ++j) {
        textures[j] = bindTexture
            (QPixmap(QString(":/images/side%1.png").arg(j + 1)), GL_TEXTURE_2D);
    }

    for (int i = 0; i < 6; ++i) {
        for (int j = 0; j < 4; ++j) {
            texCoords.append
                (QVector2D(j == 0 || j == 3, j == 0 || j == 1));
            vertices.append
                (QVector3D(0.2 * coords[i][j][0], 0.2 * coords[i][j][1],
                           0.2 * coords[i][j][2]));
        }
    }
}