OpenRCT2/src/openrct2-ui/drawing/engines/opengl/OpenGLFramebuffer.cpp

#pragma region Copyright (c) 2014-2017 OpenRCT2 Developers
/*****************************************************************************
 * OpenRCT2, an open source clone of Roller Coaster Tycoon 2.
 *
 * OpenRCT2 is the work of many authors, a full list can be found in contributors.md
 * For more information, visit https://github.com/OpenRCT2/OpenRCT2
 *
 * OpenRCT2 is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * A full copy of the GNU General Public License can be found in licence.txt
 *****************************************************************************/
#pragma endregion

#ifndef DISABLE_OPENGL

#include <algorithm>
#include <memory>
#include <openrct2/common.h>
#include <SDL_video.h>
#include "OpenGLFramebuffer.h"

constexpr GLuint BACKBUFFER_ID = 0;

OpenGLFramebuffer::OpenGLFramebuffer(SDL_Window * window)
{
    _id = BACKBUFFER_ID;
    _texture = 0;
    _depth = 0;
    SDL_GetWindowSize(window, &_width, &_height);
}

OpenGLFramebuffer::OpenGLFramebuffer(sint32 width, sint32 height, bool depth, bool integer)
{
    _width = width;
    _height = height;

    glGenTextures(1, &_texture);
    glBindTexture(GL_TEXTURE_2D, _texture);
    if (integer)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_R8UI, width, height, 0, GL_RED_INTEGER, GL_UNSIGNED_BYTE, nullptr);
    }
    else
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr);
    }
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    if (depth)
    {
        _depth = CreateDepthTexture(width, height);
    }
    else
    {
        _depth = 0;
    }

    glGenFramebuffers(1, &_id);
    glBindFramebuffer(GL_FRAMEBUFFER, _id);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _texture, 0);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, _depth, 0);
}

OpenGLFramebuffer::~OpenGLFramebuffer()
{
    if (_id != BACKBUFFER_ID)
    {
        glDeleteTextures(1, &_texture);
        glDeleteTextures(1, &_depth);
        glDeleteFramebuffers(1, &_id);
    }
}

void OpenGLFramebuffer::Bind() const
{
    glBindFramebuffer(GL_FRAMEBUFFER, _id);
    glViewport(0, 0, (GLsizei)_width, (GLsizei)_height);
}

void OpenGLFramebuffer::BindDraw() const
{
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, _id);
}

void OpenGLFramebuffer::BindRead() const
{
    glBindFramebuffer(GL_READ_FRAMEBUFFER, _id);
}

void OpenGLFramebuffer::GetPixels(rct_drawpixelinfo &dpi) const
{
    assert(dpi.width == _width && dpi.height == _height);

    auto pixels = std::make_unique<uint8[]>(_width * _height);
    glBindTexture(GL_TEXTURE_2D, _texture);
    glPixelStorei(GL_PACK_ALIGNMENT, 1);
    glGetTexImage(GL_TEXTURE_2D, 0, GL_RED_INTEGER, GL_UNSIGNED_BYTE, pixels.get());

    // Flip pixels vertically on copy
    uint8 * src = pixels.get() + ((_height - 1) * _width);
    uint8 * dst = dpi.bits;
    for (sint32 y = 0; y < _height; y++)
    {
        std::copy_n(src, _width, dst);
        src -= _width;
        dst += dpi.width + dpi.pitch;
    }
}

void OpenGLFramebuffer::SwapColourBuffer(OpenGLFramebuffer &other)
{
    std::swap(_texture, other._texture);

    glBindFramebuffer(GL_FRAMEBUFFER, _id);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _texture, 0);

    glBindFramebuffer(GL_FRAMEBUFFER, other._id);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, other._texture, 0);
}

GLuint OpenGLFramebuffer::SwapDepthTexture(GLuint depth)
{
    std::swap(_depth, depth);

    glBindFramebuffer(GL_FRAMEBUFFER, _id);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, _depth, 0);

    return depth;
}

void OpenGLFramebuffer::Copy(OpenGLFramebuffer &src, GLenum filter)
{
    BindDraw();
    src.BindRead();
    glBlitFramebuffer(
        0, 0, src.GetWidth(), src.GetHeight(),
        0, 0, _width, _height, GL_COLOR_BUFFER_BIT, filter
    );
    Bind();
}

GLuint OpenGLFramebuffer::CreateDepthTexture(sint32 width, sint32 height)
{
    GLuint depth;
    glGenTextures(1, &depth);
    glBindTexture(GL_TEXTURE_2D, depth);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT24, width, height, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, nullptr);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_NONE);
    return depth;
}

#endif /* DISABLE_OPENGL */