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engine.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 2
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL: https://scummvm.svn.sourceforge.net/svnroot/scummvm/scummvm/tags/release-1-2-0/engines/engine.h $
 * $Id: engine.h 48934 2010-05-04 11:58:12Z fingolfin $
 */

#ifndef ENGINES_ENGINE_H
#define ENGINES_ENGINE_H

#include "common/scummsys.h"
#include "common/error.h"
#include "common/str.h"

class OSystem;

namespace Audio {
      class Mixer;
}
namespace Common {
      class EventManager;
      class SaveFileManager;
      class TimerManager;
}
namespace GUI {
      class Debugger;
      class Dialog;
}

/**
 * Initializes graphics and shows error message.
 */
void GUIErrorMessage(const Common::String msg);


class Engine {
public:
      OSystem *_system;
      Audio::Mixer *_mixer;

protected:
      Common::TimerManager *_timer;
      Common::EventManager *_eventMan;
      Common::SaveFileManager *_saveFileMan;

      GUI::Dialog *_mainMenuDialog;
      virtual int runDialog(GUI::Dialog &dialog);

      const Common::String _targetName; // target name for saves

private:
      /**
       * The pause level, 0 means 'running', a positive value indicates
       * how often the engine has been paused (and hence how often it has
       * to be un-paused before it resumes running). This makes it possible
       * to nest code which pauses the engine.
       */
      int _pauseLevel;

public:


      /**
       * A feature in this context means an ability of the engine which can be
       * either available or not.
       * @see Engine::hasFeature()
       */
      enum EngineFeature {
            /**
             * Enables the subtitle speed and toggle items in the Options section
             * of the global main menu.
             */
            kSupportsSubtitleOptions,

            /**
             * 'Return to launcher' feature is supported, i.e., EVENT_RTL is handled
             * either directly, or indirectly (that is, the engine calls and honors
             * the result of the Engine::shouldQuit() method appropriately).
             */
            kSupportsRTL,

            /**
             * Loading savestates during runtime is supported, that is, this engine
             * implements loadGameState() and canLoadGameStateCurrently().
             * If this feature is supported, then the corresponding MetaEngine *must*
             * support the kSupportsListSaves feature.
             */
            kSupportsLoadingDuringRuntime,

            /**
             * Loading savestates during runtime is supported, that is, this engine
             * implements saveGameState() and canSaveGameStateCurrently().
             * If this feature is supported, then the corresponding MetaEngine *must*
             * support the kSupportsListSaves feature.
             */
            kSupportsSavingDuringRuntime
      };



      /** @name Overloadable methods
       *
       *  All Engine subclasses should consider overloading some or all of the following methods.
       */
      //@{

      Engine(OSystem *syst);
      virtual ~Engine();

      /**
       * Init the engine and start its main loop.
       * @return returns kNoError on success, else an error code.
       */
      virtual Common::Error run() = 0;

      /**
       * Prepare an error string, which is printed by the error() function.
       */
      virtual void errorString(const char *buf_input, char *buf_output, int buf_output_size);

      /**
       * Return the engine's debugger instance, if any. Used by error() to
       * invoke the debugger when a severe error is reported.
       */
      virtual GUI::Debugger *getDebugger() { return 0; }

      /**
       * Determine whether the engine supports the specified feature.
       */
      virtual bool hasFeature(EngineFeature f) const { return false; }

//    virtual EnginePlugin *getMetaEnginePlugin() const;

      /**
       * Notify the engine that the sound settings in the config manager may have
       * changed and that it hence should adjust any internal volume etc. values
       * accordingly.
       * @todo find a better name for this
       */
      virtual void syncSoundSettings();

      /**
       * Flip mute all sound option.
       */
      virtual void flipMute();

      /**
       * Load a game state.
       * @param slot    the slot from which a savestate should be loaded
       * @return returns kNoError on success, else an error code.
       */
      virtual Common::Error loadGameState(int slot);

      /**
       * Indicates whether a game state can be loaded.
       */
      virtual bool canLoadGameStateCurrently();

      /**
       * Save a game state.
       * @param slot    the slot into which the savestate should be stored
       * @param desc    a description for the savestate, entered by the user
       * @return returns kNoError on success, else an error code.
       */
      virtual Common::Error saveGameState(int slot, const char *desc);

      /**
       * Indicates whether a game state can be saved.
       */
      virtual bool canSaveGameStateCurrently();

protected:

      /**
       * Actual implementation of pauseEngine by subclasses. See there
       * for details.
       */
      virtual void pauseEngineIntern(bool pause);

      //@}


public:

      /**
       * Request the engine to quit. Sends a EVENT_QUIT event to the Event
       * Manager.
       */
      static void quitGame();

      /**
       * Return whether the ENGINE should quit respectively should return to the
       * launcher.
       */
      static bool shouldQuit();

      /**
       * Pause or resume the engine. This should stop/resume any audio playback
       * and other stuff. Called right before the system runs a global dialog
       * (like a global pause, main menu, options or 'confirm exit' dialog).
       *
       * This is a convenience tracker which automatically keeps track on how
       * often the engine has been paused, ensuring that after pausing an engine
       * e.g. twice, it has to be unpaused twice before actuallying resuming.
       *
       * @param pause         true to pause the engine, false to resume it
       */
      void pauseEngine(bool pause);

      /**
       * Return whether the engine is currently paused or not.
       */
      bool isPaused() const { return _pauseLevel != 0; }

      /**
       * Run the Global Main Menu Dialog
       */
      void openMainMenuDialog();

      inline Common::TimerManager *getTimerManager() { return _timer; }
      inline Common::EventManager *getEventManager() { return _eventMan; }
      inline Common::SaveFileManager *getSaveFileManager() { return _saveFileMan; }

public:

      /** On some systems, check if the game appears to be run from CD. */
      void checkCD();

protected:

      /**
       * Indicate whether an autosave should be performed.
       */
      bool shouldPerformAutoSave(int lastSaveTime);

};

// FIXME: HACK for MidiEmu & error()
extern Engine *g_engine;

#endif

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