BLT-With-Graphics-Template/include/blt/gfx/renderer/postprocess.h

#pragma once
/*
 *  Copyright (C) 2024  Brett Terpstra
 *
 *  This program 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.
 *
 *  This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef BLT_GRAPHICS_POST_PROCESS_H
#define BLT_GRAPHICS_POST_PROCESS_H

#include <blt/std/types.h>
#include <blt/gfx/framebuffer.h>
#include <blt/gfx/shader.h>
#include <blt/gfx/model.h>
#include <vector>
#include <memory>

namespace blt::gfx
{
    class pp_engine_t;
    
    class pp_step_t;
    
    class pp_step_t
    {
        public:
            virtual void create()
            {}
            
            // only called on render()
            virtual void draw(pp_step_t&)
            {}
            
            // only called on bind()
            virtual void draw()
            {}
            
            auto& getBuffer()
            {
                return draw_buffer;
            }
            
            auto& getShader()
            {
                return *shader;
            }
            
            bool hasShader()
            {
                return shader != nullptr;
            }
            
            virtual ~pp_step_t() = default;
        
        protected:
            frame_buffer_t draw_buffer;
            std::unique_ptr<shader_t> shader;
    };
    
    class pp_render_target_t : public pp_step_t
    {
        public:
            void create() override;
            
            void draw() override;
    };
    
    class pp_to_screen_step_t : public pp_step_t
    {
        public:
            void create() override;
            
            void draw(pp_step_t& previous) override;
    };
    
    class pp_outline_target : public pp_step_t
    {
        public:
            void create() override;
            
            void draw() override;
    };
    
    class pp_outline_step_t : public pp_step_t
    {
        public:
            
            void create() override;
            
            void draw(pp_step_t& previous) override;
    };
    
    class pp_engine_t
    {
        public:
            void create();
            
            void bind();
            
            void render();
            
            void cleanup();
            
            void addStep(std::unique_ptr<pp_step_t> step)
            {
                steps.emplace_back(std::move(step));
            }
            
            static std::unique_ptr<shader_t> createShader(std::string_view fragment);
            
            static std::unique_ptr<pp_engine_t> make_basic_pp()
            {
                return make_single_pp(std::make_unique<pp_render_target_t>());
            }
            
            static std::unique_ptr<pp_engine_t> make_single_pp(std::unique_ptr<pp_step_t> step)
            {
                auto engine = new pp_engine_t();
                engine->addStep(std::move(step));
                return std::unique_ptr<pp_engine_t>(engine);
            }
            
            template<typename... Args>
            static std::unique_ptr<pp_engine_t> make_multi_pp(Args... steps)
            {
                auto engine = new pp_engine_t();
                (engine->addStep(std::move(steps)), ...);
                return std::unique_ptr<pp_engine_t>(engine);
            }
        
        private:
            pp_engine_t() = default;
            
            std::vector<std::unique_ptr<pp_step_t>> steps;
            std::unique_ptr<vertex_array_t> screen_vao;
    };
}

#endif //BLT_GRAPHICS_POST_PROCESS_H