source/src/gl/framebuffer.cpp

/*
 * Copyright (C) 2021  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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.
 *
 * Antkeeper source code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "gl/framebuffer.hpp"
#include "gl/texture-2d.hpp"
#include <glad/glad.h>

namespace gl {

static constexpr GLenum attachment_lut[] =
{
	GL_COLOR_ATTACHMENT0,
	GL_DEPTH_ATTACHMENT,
	GL_STENCIL_ATTACHMENT
};

framebuffer::framebuffer(int width, int height):
	gl_framebuffer_id(0),
	dimensions({width, height}),
	color_attachment(nullptr),
	depth_attachment(nullptr),
	stencil_attachment(nullptr)
{
	glGenFramebuffers(1, &gl_framebuffer_id);
}

framebuffer::framebuffer():
	gl_framebuffer_id(0),
	dimensions({0, 0}),
	color_attachment(nullptr),
	depth_attachment(nullptr),
	stencil_attachment(nullptr)
{}

framebuffer::~framebuffer()
{
	if (gl_framebuffer_id)
	{
		glDeleteFramebuffers(1, &gl_framebuffer_id);
	}
}

void framebuffer::resize(const std::array<int, 2>& dimensions)
{
	this->dimensions = dimensions;
}

void framebuffer::attach(framebuffer_attachment_type attachment_type, texture_2d* texture)
{
	glBindFramebuffer(GL_FRAMEBUFFER, gl_framebuffer_id);
	
	GLenum gl_attachment = attachment_lut[static_cast<std::size_t>(attachment_type)];
	glFramebufferTexture2D(GL_FRAMEBUFFER, gl_attachment, GL_TEXTURE_2D, texture->gl_texture_id, 0);
	
	if (attachment_type == framebuffer_attachment_type::color)
		color_attachment = texture;
	else if (attachment_type == framebuffer_attachment_type::depth)
		depth_attachment = texture;
	else if (attachment_type == framebuffer_attachment_type::stencil)
		stencil_attachment = texture;
	
	if (!color_attachment)
	{
		glDrawBuffer(GL_NONE);
		glReadBuffer(GL_NONE);
	}
	else
	{
		glDrawBuffer(GL_COLOR_ATTACHMENT0);
		glReadBuffer(GL_COLOR_ATTACHMENT0);
	}
	
	glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

} // namespace gl