shader-program.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-program.hpp>
#include <engine/gl/shader-object.hpp>
#include <engine/gl/opengl/gl-shader-variables.hpp>
#include <glad/gl.h>
#include <stdexcept>
#include <string_view>
 
namespace gl {
 
shader_program::shader_program()
{
    // Create an OpenGL shader program
    gl_program_id = glCreateProgram();
    
    // Handle OpenGL errors
    if (!gl_program_id)
    {
        throw std::runtime_error("Unable to create OpenGL shader program");
    }
}
 
shader_program::~shader_program()
{
    // Detach all shader objects
    detach_all();
    
    // Delete the OpenGL shader program
    glDeleteProgram(gl_program_id);
}
 
void shader_program::attach(const shader_object& object)
{
    if (attached_objects.find(&object) != attached_objects.end())
    {
        throw std::runtime_error("OpenGL shader object already attached to the shader program");
    }
    else
    {
        // Check that both the OpenGL shader program and OpenGL shader object are valid
        if (glIsProgram(gl_program_id) != GL_TRUE)
        {
            throw std::runtime_error("Invalid OpenGL shader program");
        }
        if (glIsShader(object.gl_shader_id) != GL_TRUE)
        {
            throw std::runtime_error("Invalid OpenGL shader object");
        }
        
        // Attach the OpenGL shader object to the OpenGL shader program
        glAttachShader(gl_program_id, object.gl_shader_id);
        
        // Add shader object to set of attached objects
        attached_objects.insert(&object);
    }
}
 
void shader_program::detach(const shader_object& object)
{
    if (attached_objects.find(&object) == attached_objects.end())
    {
        throw std::runtime_error("Shader object is not attached to the shader program.");
    }
    else
    {
        // Check that both the OpenGL shader program and OpenGL shader object are valid
        if (glIsProgram(gl_program_id) != GL_TRUE)
        {
            throw std::runtime_error("Invalid OpenGL shader program");
        }
        if (glIsShader(object.gl_shader_id) != GL_TRUE)
        {
            throw std::runtime_error("Invalid OpenGL shader object");
        }
        
        // Detach the OpenGL shader object from the OpenGL shader program
        glDetachShader(gl_program_id, object.gl_shader_id);
        
        // Remove shader object from set of attached objects
        attached_objects.erase(&object);
    }
}
 
void shader_program::detach_all()
{
    while (!attached_objects.empty())
    {
        detach(**attached_objects.begin());
    }
}
 
bool shader_program::link()
{
    m_linked = false;
    info_log.clear();
    variable_map.clear();
    
    // Check that the OpenGL shader program is valid
    if (glIsProgram(gl_program_id) != GL_TRUE)
    {
        throw std::runtime_error("Invalid OpenGL shader program");
    }
    
    // Link OpenGL shader program
    glLinkProgram(gl_program_id);
    
    // Get OpenGL shader program linking status
    GLint gl_link_status;
    glGetProgramiv(gl_program_id, GL_LINK_STATUS, &gl_link_status);
    m_linked = (gl_link_status == GL_TRUE);
    
    // Populate info log string
    if (m_linked)
    {
        // Load shader variables
        load_variables();
    }
    else
    {
        // Get OpenGL shader program info log length
        GLint gl_info_log_length;
        glGetProgramiv(gl_program_id, GL_INFO_LOG_LENGTH, &gl_info_log_length);
        
        if (gl_info_log_length > 0)
        {
            // Resize string to accommodate OpenGL shader program info log
            info_log.resize(gl_info_log_length);
            
            // Read OpenGL shader program info log into string
            glGetProgramInfoLog(gl_program_id, gl_info_log_length, &gl_info_log_length, info_log.data());
            
            // Remove redundant null terminator from string
            info_log.pop_back();
        }
    }
    
    return m_linked;
}
 
void shader_program::load_variables()
{
    variable_map.clear();
    
    // Get maximum uniform name length
    GLint max_uniform_name_length = 0;
    glGetProgramiv(gl_program_id, GL_ACTIVE_UNIFORM_MAX_LENGTH, &max_uniform_name_length);
    
    // Allocate uniform name buffer
    std::string uniform_name(static_cast<std::size_t>(max_uniform_name_length), '\0');
    
    // Get number of active uniforms in the shader
    GLint active_uniform_count = 0;
    glGetProgramiv(gl_program_id, GL_ACTIVE_UNIFORMS, &active_uniform_count);
    
    // Init texture unit index
    GLint texture_index = 0;
    
    // For each active uniform
    for (GLint uniform_index = 0; uniform_index < active_uniform_count; ++uniform_index)
    {
        // Get uniform info
        GLsizei uniform_name_length;
        GLint uniform_size;
        GLenum uniform_type;
        glGetActiveUniform(gl_program_id, static_cast<GLuint>(uniform_index), static_cast<GLsizei>(max_uniform_name_length), &uniform_name_length, &uniform_size, &uniform_type, uniform_name.data());
        
        // Get uniform location
        const GLint uniform_location = glGetUniformLocation(gl_program_id, uniform_name.c_str());
        if (uniform_location == -1)
        {
            throw std::runtime_error("Unable to get shader uniform location");
        }
        
        // Get length of variable name by stripping array notation from uniform name
        std::size_t uniform_base_name_length = static_cast<std::size_t>(uniform_name_length);
        if (std::size_t i = std::string_view(uniform_name.c_str(), uniform_name_length).find_first_of("["); i != std::string::npos)
        {
            uniform_base_name_length = i;
        }
        
        // Hash variable name to get variable key
        const hash::fnv1a32_t variable_key = hash::fnv1a32<char>({uniform_name.c_str(), uniform_base_name_length});
        
        // Get size of variable
        const std::size_t variable_size = static_cast<std::size_t>(uniform_size);
        
        // Construct shader variable
        std::unique_ptr<const gl::shader_variable> variable;
        switch (uniform_type)
        {
            case GL_BOOL:
                variable = std::make_unique<const gl_shader_bool>(variable_size, uniform_location);
                break;
            case GL_BOOL_VEC2:
                variable = std::make_unique<const gl_shader_bvec2>(variable_size, uniform_location);
                break;
            case GL_BOOL_VEC3:
                variable = std::make_unique<const gl_shader_bvec3>(variable_size, uniform_location);
                break;
            case GL_BOOL_VEC4:
                variable = std::make_unique<const gl_shader_bvec4>(variable_size, uniform_location);
                break;
            
            case GL_INT:
                variable = std::make_unique<const gl_shader_int>(variable_size, uniform_location);
                break;
            case GL_INT_VEC2:
                variable = std::make_unique<const gl_shader_ivec2>(variable_size, uniform_location);
                break;
            case GL_INT_VEC3:
                variable = std::make_unique<const gl_shader_ivec3>(variable_size, uniform_location);
                break;
            case GL_INT_VEC4:
                variable = std::make_unique<const gl_shader_ivec4>(variable_size, uniform_location);
                break;
            
            case GL_UNSIGNED_INT:
                variable = std::make_unique<const gl_shader_uint>(variable_size, uniform_location);
                break;
            case GL_UNSIGNED_INT_VEC2:
                variable = std::make_unique<const gl_shader_uvec2>(variable_size, uniform_location);
                break;
            case GL_UNSIGNED_INT_VEC3:
                variable = std::make_unique<const gl_shader_uvec3>(variable_size, uniform_location);
                break;
            case GL_UNSIGNED_INT_VEC4:
                variable = std::make_unique<const gl_shader_uvec4>(variable_size, uniform_location);
                break;
            
            case GL_FLOAT:
                variable = std::make_unique<const gl_shader_float>(variable_size, uniform_location);
                break;
            case GL_FLOAT_VEC2:
                variable = std::make_unique<const gl_shader_fvec2>(variable_size, uniform_location);
                break;
            case GL_FLOAT_VEC3:
                variable = std::make_unique<const gl_shader_fvec3>(variable_size, uniform_location);
                break;
            case GL_FLOAT_VEC4:
                variable = std::make_unique<const gl_shader_fvec4>(variable_size, uniform_location);
                break;
            
            case GL_FLOAT_MAT2:
                variable = std::make_unique<const gl_shader_fmat2>(variable_size, uniform_location);
                break;
            case GL_FLOAT_MAT3:
                variable = std::make_unique<const gl_shader_fmat3>(variable_size, uniform_location);
                break;
            case GL_FLOAT_MAT4:
                variable = std::make_unique<const gl_shader_fmat4>(variable_size, uniform_location);
                break;
            
            case GL_SAMPLER_1D:
            case GL_SAMPLER_1D_SHADOW:
                variable = std::make_unique<const gl_shader_texture_1d>(variable_size, uniform_location, texture_index);
                texture_index += uniform_size;
                break;
            
            case GL_SAMPLER_2D:
            case GL_SAMPLER_2D_SHADOW:
                variable = std::make_unique<const gl_shader_texture_2d>(variable_size, uniform_location, texture_index);
                texture_index += uniform_size;
                break;
            
            case GL_SAMPLER_3D:
                variable = std::make_unique<const gl_shader_texture_3d>(variable_size, uniform_location, texture_index);
                texture_index += uniform_size;
                break;
            
            case GL_SAMPLER_CUBE:
                variable = std::make_unique<const gl_shader_texture_cube>(variable_size, uniform_location, texture_index);
                texture_index += uniform_size;
                break;
            
            default:
                throw std::runtime_error("Unsupported to shader uniform type");
                break;
        }
        
        // Map variable to variable key
        variable_map.emplace(variable_key, std::move(variable));
    }
}
 
} // namespace gl