ShaderManager.h

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/* Copyright (C) 2024 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. 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 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. 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 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef INCLUDED_SHADERMANAGER
#define INCLUDED_SHADERMANAGER
 
#include "graphics/ShaderDefines.h"
#include "graphics/ShaderProgram.h"
#include "graphics/ShaderTechnique.h"
#include "renderer/backend/IDevice.h"
#include "renderer/backend/PipelineState.h"
 
#include <functional>
#include <memory>
#include <set>
#include <unordered_map>
 
/**
 * Shader manager: loads and caches shader programs.
 *
 * For a high-level overview of shaders and materials, see
 * http://trac.wildfiregames.com/wiki/MaterialSystem
 */
class CShaderManager
{
public:
    CShaderManager(Renderer::Backend::IDevice* device);
    ~CShaderManager();
 
    /**
     * Load a shader effect.
     * Effects can be implemented via many techniques; this returns the best usable technique.
     * @param name name of effect XML specification (file is loaded from shaders/effects/${name}.xml)
     * @param defines key/value set of preprocessor definitions
     * @return loaded technique, or empty technique on error
     */
    CShaderTechniquePtr LoadEffect(CStrIntern name, const CShaderDefines& defines);
 
    /**
     * Load a shader effect, with empty defines.
     */
    CShaderTechniquePtr LoadEffect(CStrIntern name);
 
    /**
     * Load a shader effect with the pipeline state description overwriting.
     * TODO: we should set all needed states in XML.
     */
    using PipelineStateDescCallback = CShaderTechnique::PipelineStateDescCallback;
    CShaderTechniquePtr LoadEffect(
        CStrIntern name, const CShaderDefines& defines, const PipelineStateDescCallback& callback);
 
    /**
     * Returns the number of shader effects that are currently loaded.
     */
    size_t GetNumEffectsLoaded() const;
 
private:
    struct CacheKey
    {
        std::string name;
        CShaderDefines defines;
 
        bool operator<(const CacheKey& k) const
        {
            if (name < k.name) return true;
            if (k.name < name) return false;
            return defines < k.defines;
        }
    };
 
    Renderer::Backend::IDevice* m_Device = nullptr;
 
    // A CShaderProgram contains expensive backend state, so we ought to cache it.
    // The compiled state depends solely on the filename and list of defines,
    // so we store that in CacheKey.
    // TODO: is this cache useful when we already have an effect cache?
    std::map<CacheKey, CShaderProgramPtr> m_ProgramCache;
 
    /**
     * Key for effect cache lookups.
     * This stores two separate CShaderDefines because the renderer typically
     * has one set from the rendering context and one set from the material;
     * by handling both separately here, we avoid the cost of having to merge
     * the two sets into a single one before doing the cache lookup.
     */
    struct EffectCacheKey
    {
        CStrIntern name;
        CShaderDefines defines;
 
        bool operator==(const EffectCacheKey& b) const;
    };
 
    struct EffectCacheKeyHash
    {
        size_t operator()(const EffectCacheKey& key) const;
    };
 
    using EffectCacheMap = std::unordered_map<EffectCacheKey, CShaderTechniquePtr, EffectCacheKeyHash>;
    EffectCacheMap m_EffectCache;
 
    // Store the set of shaders that need to be reloaded when the given file is modified
    template<typename T>
    using HotloadFilesMap = std::unordered_map<
        VfsPath,
        std::set<std::weak_ptr<T>, std::owner_less<std::weak_ptr<T>>>>;
    HotloadFilesMap<CShaderTechnique> m_HotloadTechniques;
    HotloadFilesMap<CShaderProgram> m_HotloadPrograms;
 
    /**
     * Load a shader program.
     * @param name name of shader XML specification (file is loaded from shaders/${name}.xml)
     * @param defines key/value set of preprocessor definitions
     * @return loaded program, or null pointer on error
     */
    CShaderProgramPtr LoadProgram(const CStr& name, const CShaderDefines& defines);
 
    bool LoadTechnique(CShaderTechniquePtr& tech);
 
    static Status ReloadChangedFileCB(void* param, const VfsPath& path);
    Status ReloadChangedFile(const VfsPath& path);
 
    /**
     * Associates the file with the technique to be reloaded if the file has changed.
     */
    void AddTechniqueFileDependency(const CShaderTechniquePtr& technique, const VfsPath& path);
 
    /**
     * Associates the file with the program to be reloaded if the file has changed.
     */
    void AddProgramFileDependency(const CShaderProgramPtr& program, const VfsPath& path);
};
 
#endif // INCLUDED_SHADERMANAGER