/****************************************************************************
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** This file is part of the plugins of the Qt Toolkit.
**
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** General Public License version 2.1 as published by the Free Software
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** ensure the GNU Lesser General Public License version 2.1 requirements
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
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****************************************************************************/

#include "qeglfscompositor.h"
#include "qeglfswindow.h"
#include "qeglfscontext.h"

#include <QtGui/QOpenGLContext>
#include <QtGui/QOpenGLShaderProgram>
#include <QtGui/QOpenGLFramebufferObject>

QT_BEGIN_NAMESPACE

static QEglFSCompositor *compositor = 0;

QEglFSCompositor::QEglFSCompositor()
    : m_screen(0),
      m_program(0)
{
    Q_ASSERT(!compositor);
    m_updateTimer.setSingleShot(true);
    m_updateTimer.setInterval(0);
    connect(&m_updateTimer, SIGNAL(timeout()), SLOT(renderAll()));
}

QEglFSCompositor::~QEglFSCompositor()
{
    Q_ASSERT(compositor == this);
    delete m_program;
    compositor = 0;
}

void QEglFSCompositor::schedule(QEglFSScreen *screen)
{
    m_screen = screen;
    if (!m_updateTimer.isActive())
        m_updateTimer.start();
}

void QEglFSCompositor::renderAll()
{
    QEglFSWindow *rootWin = m_screen->rootWindow();
    if (!rootWin)
        return;

    Q_ASSERT(rootWin->hasNativeWindow());
    QOpenGLContext *context = m_screen->rootContext();
    Q_ASSERT(context);

    context->makeCurrent(rootWin->window());
    ensureProgram();
    m_program->bind();

    QList<QEglFSWindow *> windows = m_screen->windows();
    for (int i = 0; i < windows.size(); ++i) {
        QEglFSWindow *window = windows.at(i);
        uint texture = window->texture();
        if (texture)
            render(window, texture, window->isRaster());
    }

    m_program->release();
    context->swapBuffers(rootWin->window());
}

void QEglFSCompositor::ensureProgram()
{
    if (!m_program) {
        static const char *textureVertexProgram =
            "attribute highp vec2 vertexCoordEntry;\n"
            "attribute highp vec2 textureCoordEntry;\n"
            "varying highp vec2 textureCoord;\n"
            "void main() {\n"
            "   textureCoord = textureCoordEntry;\n"
            "   gl_Position = vec4(vertexCoordEntry, 0.0, 1.0);\n"
            "}\n";

        static const char *textureFragmentProgram =
            "uniform sampler2D texture;\n"
            "varying highp vec2 textureCoord;\n"
            "uniform bool isRaster;\n"
            "void main() {\n"
            "   lowp vec4 c = texture2D(texture, textureCoord);\n"
            "   gl_FragColor = isRaster ? c.bgra : c.rgba;\n"
            "}\n";

        m_program = new QOpenGLShaderProgram;

        m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, textureVertexProgram);
        m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, textureFragmentProgram);
        m_program->link();

        m_vertexCoordEntry = m_program->attributeLocation("vertexCoordEntry");
        m_textureCoordEntry = m_program->attributeLocation("textureCoordEntry");
        m_isRasterEntry = m_program->uniformLocation("isRaster");
    }
}

void QEglFSCompositor::render(QEglFSWindow *window, uint texture, bool raster)
{
    const GLfloat textureCoordinates[] = {
        0, 0,
        1, 0,
        1, 1,
        0, 1
    };

    QRectF sr = window->screen()->geometry();
    QRect r = window->window()->geometry();
    QPoint tl = r.topLeft();
    QPoint br = r.bottomRight();

    GLfloat x1 = (tl.x() / sr.width()) * 2 - 1;
    GLfloat x2 = (br.x() / sr.width()) * 2 - 1;
    GLfloat y1 = ((sr.height() - tl.y()) / sr.height()) * 2 - 1;
    GLfloat y2 = ((sr.height() - br.y()) / sr.height()) * 2 - 1;

    if (!raster)
        qSwap(y1, y2);

    const GLfloat vertexCoordinates[] = {
        x1, y1,
        x2, y1,
        x2, y2,
        x1, y2
    };

    glViewport(0, 0, sr.width(), sr.height());

    glEnableVertexAttribArray(m_vertexCoordEntry);
    glEnableVertexAttribArray(m_textureCoordEntry);

    glVertexAttribPointer(m_vertexCoordEntry, 2, GL_FLOAT, GL_FALSE, 0, vertexCoordinates);
    glVertexAttribPointer(m_textureCoordEntry, 2, GL_FLOAT, GL_FALSE, 0, textureCoordinates);

    glBindTexture(GL_TEXTURE_2D, texture);

    m_program->setUniformValue(m_isRasterEntry, raster);

    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    glBindTexture(GL_TEXTURE_2D, 0);
    glDisableVertexAttribArray(m_vertexCoordEntry);
    glDisableVertexAttribArray(m_textureCoordEntry);
}

QEglFSCompositor *QEglFSCompositor::instance()
{
    if (!compositor)
        compositor = new QEglFSCompositor;
    return compositor;
}

void QEglFSCompositor::destroy()
{
    delete compositor;
    compositor = 0;
}

QT_END_NAMESPACE