shader-template.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-template.hpp>
#include <algorithm>
#include <engine/gl/shader-object.hpp>
#include <engine/gl/shader-program.hpp>
#include <engine/resources/resource-loader.hpp>
#include <engine/resources/resource-manager.hpp>
#include <engine/utility/text-file.hpp>
#include <engine/utility/hash/hash-combine.hpp>
#include <sstream>
#include <unordered_set>
 
namespace gl {
 
shader_template::shader_template(const text_file& source_code):
    m_template_source{source_code}
{
    find_directives();
    rehash();
}
 
shader_template::shader_template(text_file&& source_code):
    m_template_source{source_code}
{
    find_directives();
    rehash();
}
 
shader_template::shader_template(text_file&& source_code, std::vector<std::shared_ptr<text_file>>&& include_files):
    m_template_source{source_code},
    m_include_files{include_files}
{
    find_directives();
    rehash();
}
 
void shader_template::source(const text_file& source_code)
{
    m_template_source = source_code;
    m_include_files.clear();
    find_directives();
    rehash();
}
 
void shader_template::source(text_file&& source_code)
{
    m_template_source = source_code;
    m_include_files.clear();
    find_directives();
    rehash();
}
 
std::string shader_template::configure(gl::shader_stage stage, const dictionary_type& definitions) const
{
    replace_stage_directives(stage);
    replace_define_directives(definitions);
    
    // Join vector of source lines into single string
    std::string string;
    for (const auto& line: m_template_source.lines)
    {
        string += line;
        string += '\n';
    }
    
    return string;
}
 
std::unique_ptr<gl::shader_object> shader_template::compile(gl::shader_stage stage, const dictionary_type& definitions) const
{
    // Generate shader object source
    const std::string object_source = configure(stage, definitions);
    
    // Create shader object
    std::unique_ptr<gl::shader_object> object = std::make_unique<gl::shader_object>(stage);
    
    // Set shader object source
    object->source(object_source);
    
    // Compile shader object
    object->compile();
    
    return object;
}
 
std::unique_ptr<gl::shader_program> shader_template::build(const dictionary_type& definitions) const
{
    std::unique_ptr<gl::shader_object> vertex_object;
    std::unique_ptr<gl::shader_object> fragment_object;
    std::unique_ptr<gl::shader_object> geometry_object;
    
    // Create shader program
    std::unique_ptr<gl::shader_program> program = std::make_unique<gl::shader_program>();
    
    if (has_vertex_directive())
    {
        // Compile vertex shader object and attach to shader program
        vertex_object = compile(gl::shader_stage::vertex, definitions);
        program->attach(*vertex_object);
    }
    
    if (has_fragment_directive())
    {
        // Compile fragment shader object and attach to shader program
        fragment_object = compile(gl::shader_stage::fragment, definitions);
        program->attach(*fragment_object);
    }
    
    if (has_geometry_directive())
    {
        // Compile geometry shader object and attach to shader program
        geometry_object = compile(gl::shader_stage::geometry, definitions);
        program->attach(*geometry_object);
    }
    
    // Link attached shader objects into shader program
    program->link();
    
    // Detach all attached shader objects
    program->detach_all();
    
    return program;
}
 
void shader_template::find_directives()
{
    // Reset directives
    m_vertex_directives.clear();
    m_fragment_directives.clear();
    m_geometry_directives.clear();
    m_define_directives.clear();
    
    // Parse directives
    for (std::size_t i = 0; i < m_template_source.lines.size(); ++i)
    {
        std::istringstream line_stream(m_template_source.lines[i]);
        std::string token;
        
        // Detect `#pragma` directives
        if (line_stream >> token && token == "#pragma")
        {
            if (line_stream >> token)
            {
                // Map line numbers of supported directives
                if (token == "define")
                {
                    if (line_stream >> token)
                    {
                        m_define_directives.insert({token, i});
                    }
                }
                else if (token == "vertex")
                {
                    m_vertex_directives.insert(i);
                }
                else if (token == "fragment")
                {
                    m_fragment_directives.insert(i);
                }
                else if (token == "geometry")
                {
                    m_geometry_directives.insert(i);
                }
            }
        }
    }
}
 
void shader_template::rehash()
{
    m_hash = 0;
    for (const auto& line: m_template_source.lines)
    {
        m_hash = hash_combine(m_hash, std::hash<std::string>{}(line));
    }
}
 
void shader_template::replace_stage_directives(gl::shader_stage stage) const
{
    // Determine stage directives according to the shader stage being generated
    const char* vertex_directive = (stage == gl::shader_stage::vertex) ? "#define __VERTEX__" : "/* #undef __VERTEX__ */";
    const char* fragment_directive = (stage == gl::shader_stage::fragment) ? "#define __FRAGMENT__" : "/* #undef __FRAGMENT__ */";
    const char* geometry_directive = (stage == gl::shader_stage::geometry) ? "#define __GEOMETRY__" : "/* #undef __GEOMETRY__ */";
    
    // Handle `#pragma <stage>` directives
    for (const auto directive_line: m_vertex_directives)
    {
        m_template_source.lines[directive_line] = vertex_directive;
    }
    for (const auto directive_line: m_fragment_directives)
    {
        m_template_source.lines[directive_line] = fragment_directive;
    }
    for (const auto directive_line: m_geometry_directives)
    {
        m_template_source.lines[directive_line] = geometry_directive;
    }
}
 
void shader_template::replace_define_directives(const dictionary_type& definitions) const
{
    // For each `#pragma define <key>` directive
    for (const auto& define_directive: m_define_directives)
    {
        // Get a reference to the directive line
        std::string& line = m_template_source.lines[define_directive.second];
        
        // Check if the corresponding definition was given by the configuration
        auto definitions_it = definitions.find(define_directive.first);
        if (definitions_it != definitions.end())
        {
            // Definition found, replace `#pragma define <key>` with `#define <key>` or `#define <key> <value>`
            line = "#define " + define_directive.first;
            if (!definitions_it->second.empty())
            {
                line += " " + definitions_it->second;
            }
        }
        else
        {
            // Definition not found, replace `#pragma define <key>` with the comment `/* #undef <key> */`.
            line = "/* #undef " + define_directive.first + " */";
        }
    }
}
 
bool shader_template::has_define_directive(const std::string& key) const
{
    return (m_define_directives.find(key) != m_define_directives.end());
}
 
} // namespace gl
 
static bool has_pragma_once(const text_file& source)
{
    for (const auto& line: source.lines)
    {
        std::istringstream line_stream(line);
        std::string token;
        
        // If line contains a `#pragma once` directive
        if (line_stream >> token && token == "#pragma")
        {
            if (line_stream >> token && token == "once")
            {
                return true;
            }
        }
    }
    
    return false;
}
 
static void handle_includes(std::vector<std::shared_ptr<text_file>>& include_files, text_file& source, std::unordered_set<std::filesystem::path>& include_once, resource_manager& resource_manager)
{
    // For each line in the source
    for (std::size_t i = 0; i < source.lines.size(); ++i)
    {
        std::string token;
        std::istringstream line_stream(source.lines[i]);
        
        // If line contains a `#pragma include` directive
        if (line_stream >> token && token == "#pragma" &&
            line_stream >> token && token == "include")
        {
            // If third token is enclosed in quotes or angled brackets
            if (line_stream >> token && token.size() > 2 &&
                ((token.front() == '\"' && token.back() == '\"') ||
                (token.front() == '<' && token.back() == '>')))
            {
                // Extract include path
                const std::filesystem::path path = token.substr(1, token.length() - 2);
                
                // Skip pre-included files that contain a `#pragma once` directive
                if (include_once.contains(path))
                {
                    source.lines[i] = "/* #pragma exclude " + token + " */";
                    continue;
                }
                
                // Load include file
                auto include_file = resource_manager.load<text_file>(path);
                if (!include_file)
                {
                    source.lines[i] = "#error file not found: " + path.string();
                    continue;
                }
                else
                {
                    include_files.emplace_back(include_file);
                }
                
                // If file has `#pragma once` directive
                if (has_pragma_once(*include_file))
                {
                    // Add file to set of files to include once
                    include_once.insert(path);
                }
                
                // Create a copy of the include file
                text_file include_file_copy = *include_file;
                
                // Handle `#pragma include` directives inside include file
                handle_includes(include_files, include_file_copy, include_once, resource_manager);
                
                // Replace #pragma include directive with include file contents
                source.lines.erase(source.lines.begin() + i);
                source.lines.insert(source.lines.begin() + i, include_file_copy.lines.begin(), include_file_copy.lines.end());
                i += include_file_copy.lines.size() - 1;
            }
            else
            {
                source.lines[i] = "#error malformed include directive: \"" + source.lines[i] + "\"";
            }
        }
    }
}
 
template <>
std::unique_ptr<gl::shader_template> resource_loader<gl::shader_template>::load(::resource_manager& resource_manager, deserialize_context& ctx)
{
    // Load shader template source file
    const auto source_file = resource_loader<text_file>::load(resource_manager, ctx);
    
    // Make a copy of the shader template source file
    text_file source_file_copy = *source_file;
    
    std::vector<std::shared_ptr<text_file>> include_files;
    
    // Handle `#pragma include` directives
    std::unordered_set<std::filesystem::path> include_once;
    include_once.insert(ctx.path());
    handle_includes(include_files, source_file_copy, include_once, resource_manager);
    
    // Construct shader template
    return std::make_unique<gl::shader_template>(std::move(source_file_copy), std::move(include_files));
}