#include "svpointcloudviewer.h"

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

SvPointCloudViewer::SvPointCloudViewer(QQuickItem *parent) :
    QQuickPaintedItem(parent)
{
    setRenderTarget(QQuickPaintedItem::FramebufferObject);
}

void SvPointCloudViewer::paint(QPainter *painter)
{
    painter->beginNativePainting();

    if (!m_program) {
        m_program = new QOpenGLShaderProgram();
        m_program->addShaderFromSourceCode(QOpenGLShader::Vertex,
                                           "attribute highp vec4 vertices;"
                                           "varying highp vec2 coords;"
                                           "void main() {"
                                           "    gl_Position = vertices;"
                                           "    coords = vertices.xy;"
                                           "}");
        m_program->addShaderFromSourceCode(QOpenGLShader::Fragment,
                                           "uniform lowp float t;"
                                           "varying highp vec2 coords;"
                                           "void main() {"
                                           "    lowp float i = 1. - (pow(abs(coords.x), 4.) + pow(abs(coords.y), 4.));"
                                           "    i = smoothstep(t - 0.8, t + 0.8, i);"
                                           "    i = floor(i * 20.) / 20.;"
                                           "    gl_FragColor = vec4(coords * .5 + .5, i, i);"
                                           "}");

        m_program->bindAttributeLocation("vertices", 0);
        m_program->link();

    }

    m_program->bind();

        m_program->enableAttributeArray(0);

        float values[] = {
            -1, -1,
            1, -1,
            -1, 1,
            1, 1
        };
        m_program->setAttributeArray(0, GL_FLOAT, values, 2);
        m_program->setUniformValue("t", (float) 1);

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

        glDisable(GL_DEPTH_TEST);

        glClearColor(0, 0, 0, 1);
        glClear(GL_COLOR_BUFFER_BIT);

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

        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

        m_program->disableAttributeArray(0);
        m_program->release();

    painter->endNativePainting();
}