inferno/src/inferno/render/texture.cpp

/*
 * Copyright (C) 2022 Riyyi
 *
 * SPDX-License-Identifier: MIT
 */

#include <climits> // UINT_MAX
#include <cstdint> // uint8_t, uint32_t
#include <memory>  // std::shared_ptr
#include <utility> // std::move

#include "glad/glad.h"
#include "ruc/format/log.h"
#include "ruc/meta/assert.h"
#define STB_IMAGE_IMPLEMENTATION
#include "stb/stb_image.h"

#include "inferno/render/texture.h"

namespace Inferno {

Texture::Texture(const std::string& path)
	: m_path(std::move(path))
{
	unsigned char* data = nullptr;
	int width = 0;
	int height = 0;
	int channels = 0;

	// Load image data
	stbi_set_flip_vertically_on_load(1);
	data = stbi_load(path.c_str(), &width, &height, &channels, STBI_default);
	VERIFY(data, "failed to load image: '{}'", path);

	init(data, width, height, channels);

	// Clean resources
	stbi_image_free(data);
}

Texture::Texture(unsigned char* data, uint32_t width, uint32_t height, uint8_t channels)
{
	init(data, width, height, channels);
}

Texture::~Texture()
{
	glDeleteTextures(1, &m_id);
}

void Texture::bind(uint32_t unit) const
{
	// Set active unit
	glActiveTexture(GL_TEXTURE0 + unit);

	glBindTexture(GL_TEXTURE_2D, m_id);

	// Reset unit
	glActiveTexture(GL_TEXTURE0);
}

void Texture::unbind() const
{
	glBindTexture(GL_TEXTURE_2D, 0);
}

// -----------------------------------------

void Texture::init(unsigned char* data, uint32_t width, uint32_t height, uint8_t channels)
{
	m_width = width;
	m_height = height;

	if (channels == 4) {
		m_internalFormat = GL_RGBA8;
		m_dataFormat = GL_RGBA;
	}
	else if (channels == 3) {
		m_internalFormat = GL_RGB8;
		m_dataFormat = GL_RGB;
	}

	create(data);
}

void Texture::create(unsigned char* data)
{
	m_id = UINT_MAX;

	// Create texture object
	glGenTextures(1, &m_id);

	// Bind texture object
	glBindTexture(GL_TEXTURE_2D, m_id);

	// Set unpacking of pixel data to byte-alignment,
	// this prevents alignment issues when using a single byte for color
	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

	// Generate texture
	glTexImage2D(
		GL_TEXTURE_2D,     // Texture target
		0,                 // Midmap level, base starts at level 0
		m_internalFormat,  // Texture format
		m_width, m_height, // Image width/height
		0,                 // Always 0 (legacy)
		m_dataFormat,      // Texture source format
		GL_UNSIGNED_BYTE,  // Texture source datatype
		data);             // Image data

	// Set the texture wrapping / filtering options
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);      // X
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);      // Y
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); // Minify
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); // Magnify

	// Automatically generate all mipmap levels
	glGenerateMipmap(GL_TEXTURE_2D);

	// Unbind texture object
	glBindTexture(GL_TEXTURE_2D, 0);
}

// -----------------------------------------

TextureManager::TextureManager(s)
{
	ruc::info("TextureManager initialized");
}

TextureManager::~TextureManager()
{
}

void TextureManager::add(const std::string& path, std::shared_ptr<Texture> texture)
{
	// Construct (key, value) pair and insert it into the unordered_map
	m_textureList.emplace(std::move(path), std::move(texture));
}

std::shared_ptr<Texture> TextureManager::load(const std::string& path)
{
	if (exists(path)) {
		return get(path);
	}

	std::shared_ptr<Texture> texture = std::make_shared<Texture>(path);
	add(path, texture);
	return get(path);
}

std::shared_ptr<Texture> TextureManager::get(const std::string& path)
{
	return exists(path) ? m_textureList.at(path) : nullptr;
}

bool TextureManager::exists(const std::string& path)
{
	return m_textureList.find(path) != m_textureList.end();
}

void TextureManager::remove(const std::string& path)
{
	if (exists(path)) {
		m_textureList.erase(path);
	}
}

void TextureManager::remove(std::shared_ptr<Texture> texture)
{
	if (exists(texture->path())) {
		m_textureList.erase(texture->path());
	}
}

} // namespace Inferno