ShaderManager.h

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/* Copyright (C) 2012 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

#define USE_SHADER_XML_VALIDATION 1

#include <boost/unordered_map.hpp>
#include <boost/weak_ptr.hpp>

#include "graphics/ShaderDefines.h"
#include "graphics/ShaderProgram.h"
#include "graphics/ShaderTechnique.h"

#if USE_SHADER_XML_VALIDATION
# include "ps/XML/RelaxNG.h"
#endif

#include <set>

/**
 * 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();
    ~CShaderManager();

    /**
     * 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 char* name, const CShaderDefines& defines);

    /**
     * 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 defines1,defines2 key/value set of preprocessor definitions; defines2 has higher precedence
     * @return loaded technique, or empty technique on error
     */
    CShaderTechniquePtr LoadEffect(CStrIntern name, const CShaderDefines& defines1, const CShaderDefines& defines2);

    /**
     * Load a shader effect, with default system defines (from CRenderer::GetSystemShaderDefines).
     */
    CShaderTechniquePtr LoadEffect(CStrIntern name);

    /**
     * Returns the number of shader effects that are currently loaded.
     */
    size_t GetNumEffectsLoaded();

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;
        }
    };

    // A CShaderProgram contains expensive GL 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 defines1;
        CShaderDefines defines2;

        bool operator==(const EffectCacheKey& b) const;
    };

    struct EffectCacheKeyHash
    {
        size_t operator()(const EffectCacheKey& key) const;
    };

    typedef boost::unordered_map<EffectCacheKey, CShaderTechniquePtr, EffectCacheKeyHash> EffectCacheMap;
    EffectCacheMap m_EffectCache;

    // Store the set of shaders that need to be reloaded when the given file is modified
    typedef boost::unordered_map<VfsPath, std::set<boost::weak_ptr<CShaderProgram> > > HotloadFilesMap;
    HotloadFilesMap m_HotloadFiles;

#if USE_SHADER_XML_VALIDATION
    RelaxNGValidator m_Validator;
#endif

    bool NewProgram(const char* name, const CShaderDefines& defines, CShaderProgramPtr& program);
    bool NewEffect(const char* name, const CShaderDefines& defines, CShaderTechniquePtr& tech);

    static Status ReloadChangedFileCB(void* param, const VfsPath& path);
    Status ReloadChangedFile(const VfsPath& path);
};

#endif // INCLUDED_SHADERMANAGER