//////////////////
// DISPLAY.H
//////////////////

#ifndef DISPLAY_H
#define DISPLAY_H

#include <QOpenGLWidget>
#include <QOpenGLFunctions>

class Display : public QOpenGLWidget
{
public:
    Display(QWidget* parent);
    ~Display();

    void render();
    static QSize displaySize() { return QSize(displayWidth, displayHeight); }

    void doTest();

protected:
    void initializeGL() override;
    void paintGL() override;
    void resizeGL(int width, int height) override;

private:
    static const quint32 displayWidth = 256;
    static const quint32 displayHeight = 240;

    void setPixelColor(quint32 x, quint32 y, quint32 color);

    QColor clearColor;

    quint32* textureBuffer;
    GLuint texture;
};

#endif // DISPLAY_H


//////////////////
// DISPLAY.CPP
//////////////////

#include "display.h"

Display::Display(QWidget* parent)
    : QOpenGLWidget(parent), clearColor(Qt::black)
{
    textureBuffer = new quint32[displayWidth*displayHeight];

    setMinimumSize(displayWidth, displayHeight);
}

Display::~Display()
{
    delete[] textureBuffer;
}

void Display::initializeGL()
{
    glDisable(GL_DEPTH_TEST);
    glDisable(GL_ALPHA_TEST);
    glDisable(GL_STENCIL_TEST);

    glEnable(GL_TEXTURE_2D);
    glEnable(GL_DITHER);

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glPixelStorei(GL_UNPACK_ROW_LENGTH, displayWidth);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, displayWidth, displayHeight, 0,
                 GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, textureBuffer);
}

void Display::paintGL()
{
    glClearColor(clearColor.redF(), clearColor.greenF(), clearColor.blueF(), 1.0f);

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

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, width(), 0, height(), -1, 1);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();


    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, displayWidth, displayHeight, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, textureBuffer);


    glBindTexture(GL_TEXTURE_2D, texture);
    glBegin(GL_TRIANGLE_STRIP);

    glTexCoord2f(0.0, 1.0);
    glVertex3i(0, 0, 0);

    glTexCoord2f(1.0, 1.0);
    glVertex3i(width(), 0, 0);

    glTexCoord2f(0.0, 0.0);
    glVertex3i(0, height(), 0);

    glTexCoord2f(1.0, 0.0);
    glVertex3i(width(), height(), 0);

    glEnd();
}

void Display::resizeGL(int width, int height)
{
    Q_UNUSED(width);
    Q_UNUSED(height);

    // Do some aspect ratio stuff here eventually...
}