shader-object.cpp

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/*
 * Copyright (C) 2023  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 <engine/gl/shader-object.hpp>
#include <glad/gl.h>
#include <stdexcept>
 
namespace gl {
 
static constexpr GLenum gl_shader_type_lut[] =
{
    GL_VERTEX_SHADER,
    GL_FRAGMENT_SHADER,
    GL_GEOMETRY_SHADER
};
 
shader_object::shader_object(shader_stage stage):
    m_stage{stage}
{
    // Look up OpenGL shader type enumeration that corresponds to the given stage 
    const GLenum gl_shader_type = gl_shader_type_lut[static_cast<std::size_t>(m_stage)];
    
    // Create an OpenGL shader object
    gl_shader_id = glCreateShader(gl_shader_type);
    if (!gl_shader_id)
    {
        throw std::runtime_error("Unable to create OpenGL shader object");
    }
}
 
shader_object::~shader_object()
{
    glDeleteShader(gl_shader_id);
}
 
void shader_object::source(std::string_view source_code)
{
    // Replace OpenGL shader object source code
    const GLint gl_length = static_cast<GLint>(source_code.length());
    const GLchar* gl_string = source_code.data();
    glShaderSource(gl_shader_id, 1, &gl_string, &gl_length);
}
 
bool shader_object::compile()
{
    m_compiled = false;
    info_log.clear();
    
    // Compile OpenGL shader object
    glCompileShader(gl_shader_id);
    
    // Get OpenGL shader object compilation status
    GLint gl_compile_status;
    glGetShaderiv(gl_shader_id, GL_COMPILE_STATUS, &gl_compile_status);
    m_compiled = (gl_compile_status == GL_TRUE);
    
    // Get OpenGL shader object info log length
    GLint gl_info_log_length;
    glGetShaderiv(gl_shader_id, GL_INFO_LOG_LENGTH, &gl_info_log_length);
    
    if (gl_info_log_length > 0)
    {
        // Resize string to accommodate OpenGL shader object info log
        info_log.resize(gl_info_log_length);
        
        // Read OpenGL shader object info log into string
        glGetShaderInfoLog(gl_shader_id, gl_info_log_length, &gl_info_log_length, info_log.data());
        
        // Remove redundant null terminator from string
        info_log.pop_back();
    }
    
    // Return compilation status
    return m_compiled;
}
 
} // namespace gl