Switched various Engine APIs to use Common::Error

svn-id: r34916

62 files changed, 244 insertions, 234 deletions

diff --git a/engines/agi/agi.cpp b/engines/agi/agi.cpp
index 3c1ec5efde..15af27b587 100644
--- a/engines/agi/agi.cpp
+++ b/engines/agi/agi.cpp
@@ -779,7 +779,7 @@ AgiEngine::~AgiEngine() {
 	free(_predictiveDictText);
 }
 
-int AgiBase::init() {
+Common::Error AgiBase::init() {
 
 	// Initialize backend
 	_system->beginGFXTransaction();
@@ -791,10 +791,10 @@ int AgiBase::init() {
 
 	_gfx->gfxSetPalette();
 
-	return 0;
+	return Common::kNoError;
 }
 
-int AgiEngine::go() {
+Common::Error AgiEngine::go() {
 	CursorMan.showMouse(true);
 
 	report(" \nAGI engine %s is ready.\n", gScummVMVersion);
@@ -808,7 +808,7 @@ int AgiEngine::go() {
 
 	runGame();
 
-	return 0;
+	return Common::kNoError;
 }
 
 void AgiEngine::syncSoundSettings() {
diff --git a/engines/agi/agi.h b/engines/agi/agi.h
index a1edcb2ad0..2e4710744b 100644
--- a/engines/agi/agi.h
+++ b/engines/agi/agi.h
@@ -696,7 +696,7 @@ struct StringData {
 class AgiBase : public ::Engine {
 protected:
 	// Engine API
-	virtual int init();
+	virtual Common::Error init();
 	virtual bool hasFeature(EngineFeature f) const;
 
 	virtual void initialize() = 0;
@@ -745,7 +745,7 @@ class AgiEngine : public AgiBase {
 
 protected:
 	// Engine APIs
-	virtual int go();
+	virtual Common::Error go();
 	virtual void syncSoundSettings();
 
 	void initialize();
diff --git a/engines/agi/preagi.cpp b/engines/agi/preagi.cpp
index 666d1b1b11..a3045a31cc 100644
--- a/engines/agi/preagi.cpp
+++ b/engines/agi/preagi.cpp
@@ -189,7 +189,7 @@ PreAgiEngine::~PreAgiEngine() {
 }
 
 
-int PreAgiEngine::go() {
+Common::Error PreAgiEngine::go() {
 	setflag(fSoundOn, true);	// enable sound
 
 /*
@@ -227,7 +227,7 @@ FIXME (Fingolfin asks): Why are Mickey, Winnie and Troll standalone classes
 		error("Unknown preagi engine");
 		break;
 	}
-	return 0;
+	return Common::kNoError;
 }
 
 } // End of namespace Agi
diff --git a/engines/agi/preagi.h b/engines/agi/preagi.h
index 73288de93c..10a46aa6ec 100644
--- a/engines/agi/preagi.h
+++ b/engines/agi/preagi.h
@@ -37,7 +37,7 @@ class PreAgiEngine : public AgiBase {
 	int _gameId;
 
 protected:
-	int go();
+	Common::Error go();
 	void initialize();
 
 public:
diff --git a/engines/agos/agos.cpp b/engines/agos/agos.cpp
index 3968646e63..e7669941b3 100644
--- a/engines/agos/agos.cpp
+++ b/engines/agos/agos.cpp
@@ -528,7 +528,7 @@ AGOSEngine::AGOSEngine(OSystem *syst)
 	syst->getEventManager()->registerRandomSource(_rnd, "agos");
 }
 
-int AGOSEngine::init() {
+Common::Error AGOSEngine::init() {
 	if (getGameId() == GID_DIMP) {
 		_screenWidth = 496;
 		_screenHeight = 400;
@@ -663,7 +663,7 @@ int AGOSEngine::init() {
 	if (gDebugLevel == 5)
 		_startVgaScript = true;
 
-	return 0;
+	return Common::kNoError;
 }
 
 static const uint16 initialVideoWindows_Simon[20] = {
@@ -958,7 +958,7 @@ void AGOSEngine::pause() {
 	}
 }
 
-int AGOSEngine::go() {
+Common::Error AGOSEngine::go() {
 	loadGamePcFile();
 
 	addTimeEvent(0, 1);
@@ -1023,7 +1023,7 @@ int AGOSEngine::go() {
 		delay(100);
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 
diff --git a/engines/agos/agos.h b/engines/agos/agos.h
index 4d1349b942..ada24fc032 100644
--- a/engines/agos/agos.h
+++ b/engines/agos/agos.h
@@ -164,8 +164,8 @@ class AGOSEngine : public Engine {
 	friend class MoviePlayer;
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual GUI::Debugger *getDebugger();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void syncSoundSettings();
diff --git a/engines/cine/cine.cpp b/engines/cine/cine.cpp
index d12ba61480..51f778610a 100644
--- a/engines/cine/cine.cpp
+++ b/engines/cine/cine.cpp
@@ -74,7 +74,7 @@ CineEngine::~CineEngine() {
 	Common::clearAllSpecialDebugLevels();
 }
 
-int CineEngine::init() {
+Common::Error CineEngine::init() {
 	// Initialize backend
 	_system->beginGFXTransaction();
 	initCommonGFX(false);
@@ -91,10 +91,10 @@ int CineEngine::init() {
 
 	initialize();
 
-	return 0;
+	return Common::kNoError;
 }
 
-int CineEngine::go() {
+Common::Error CineEngine::go() {
 	CursorMan.showMouse(true);
 	mainLoop(1);
 
@@ -102,7 +102,7 @@ int CineEngine::go() {
 	delete[] collisionPage;
 	delete g_sound;
 	
-	return 0;
+	return Common::kNoError;
 }
 
 int CineEngine::getTimerDelay() const {
diff --git a/engines/cine/cine.h b/engines/cine/cine.h
index ef643a115e..933f692ec2 100644
--- a/engines/cine/cine.h
+++ b/engines/cine/cine.h
@@ -71,8 +71,8 @@ class CineEngine : public Engine {
 
 protected:
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual bool hasFeature(EngineFeature f) const;
 
 	void shutdown();
diff --git a/engines/cruise/cruise.cpp b/engines/cruise/cruise.cpp
index f9487165e1..c84f4d7361 100644
--- a/engines/cruise/cruise.cpp
+++ b/engines/cruise/cruise.cpp
@@ -70,7 +70,7 @@ CruiseEngine::~CruiseEngine() {
 #endif
 }
 
-int CruiseEngine::init() {
+Common::Error CruiseEngine::init() {
 	// Initialize backend
 	_system->beginGFXTransaction();
 	initCommonGFX(false);
@@ -79,16 +79,16 @@ int CruiseEngine::init() {
 
 	initialize();
 
-	return 0;
+	return Common::kNoError;
 }
 
-int CruiseEngine::go() {
+Common::Error CruiseEngine::go() {
 	Cruise::changeCursor(Cruise::CURSOR_NORMAL);
 	CursorMan.showMouse(true);
 
 	Cruise::mainLoop();
 
-	return 0;
+	return Common::kNoError;
 }
 
 void CruiseEngine::initialize() {
diff --git a/engines/cruise/cruise.h b/engines/cruise/cruise.h
index 4a6bcff498..ad5b1100cb 100644
--- a/engines/cruise/cruise.h
+++ b/engines/cruise/cruise.h
@@ -44,8 +44,10 @@ struct CRUISEGameDescription;
 class CruiseEngine:public Engine {
 
 protected:
-	int init();
-	int go();
+	// Engine APIs
+	virtual Common::Error init();
+	virtual Common::Error go();
+
 	void shutdown();
 
 	bool initGame();
diff --git a/engines/drascula/drascula.cpp b/engines/drascula/drascula.cpp
index fce4fa73c6..8bd51123b5 100644
--- a/engines/drascula/drascula.cpp
+++ b/engines/drascula/drascula.cpp
@@ -104,7 +104,7 @@ DrasculaEngine::~DrasculaEngine() {
 	freeTexts(_textd1);
 }
 
-int DrasculaEngine::init() {
+Common::Error DrasculaEngine::init() {
 	// Initialize backend
 	_system->beginGFXTransaction();
 	initCommonGFX(false);
@@ -170,15 +170,15 @@ int DrasculaEngine::init() {
 	*textName = 0;
 
 	if (!loadDrasculaDat())
-		return 1;
+		return Common::kUnknownError;
 
 	setupRoomsTable();
 	loadArchives();
 
-	return 0;
+	return Common::kNoError;
 }
 
-int DrasculaEngine::go() {
+Common::Error DrasculaEngine::go() {
 	currentChapter = 1; // values from 1 to 6 will start each part of game
 	loadedDifferentChapter = 0;
 
@@ -274,7 +274,7 @@ int DrasculaEngine::go() {
 		currentChapter++;
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void DrasculaEngine::endChapter() {
diff --git a/engines/drascula/drascula.h b/engines/drascula/drascula.h
index 4a00d35d10..a03e5c16da 100644
--- a/engines/drascula/drascula.h
+++ b/engines/drascula/drascula.h
@@ -275,9 +275,9 @@ class DrasculaEngine : public ::Engine {
 	Common::KeyState _keyPressed;
 
 protected:
-	int init();
-	int go();
-//	void shutdown();
+	// Engine APIs
+	virtual Common::Error init();
+	virtual Common::Error go();
 
 public:
 	DrasculaEngine(OSystem *syst, const DrasculaGameDescription *gameDesc);
diff --git a/engines/engine.cpp b/engines/engine.cpp
index 52b4cc4ad3..fc13adf9c7 100644
--- a/engines/engine.cpp
+++ b/engines/engine.cpp
@@ -255,9 +255,9 @@ void Engine::syncSoundSettings() {
 	_mixer->setVolumeForSoundType(Audio::Mixer::kSpeechSoundType, soundVolumeSpeech);
 }
 
-int Engine::loadGameState(int slot) {
+Common::Error Engine::loadGameState(int slot) {
 	// Do nothing by default
-	return 0;
+	return Common::kNoError;
 }
 
 bool Engine::canLoadGameStateCurrently() {
@@ -265,9 +265,9 @@ bool Engine::canLoadGameStateCurrently() {
 	return false;
 }
 
-int Engine::saveGameState(int slot, const char *desc) {
+Common::Error Engine::saveGameState(int slot, const char *desc) {
 	// Do nothing by default
-	return 0;
+	return Common::kNoError;
 }
 
 bool Engine::canSaveGameStateCurrently() {
diff --git a/engines/engine.h b/engines/engine.h
index 2a631e069f..5444293a36 100644
--- a/engines/engine.h
+++ b/engines/engine.h
@@ -26,6 +26,7 @@
 #define ENGINES_ENGINE_H
 
 #include "common/scummsys.h"
+#include "common/error.h"
 #include "common/fs.h"
 #include "common/str.h"
 
@@ -127,17 +128,17 @@ public:
 
 	/**
 	 * Init the engine.
-	 * @return 0 for success, else an error code.
+	 * @return returns kNoError on success, else an error code.
 	 */
-	virtual int init() = 0;
+	virtual Common::Error init() = 0;
 
 	/**
 	 * Start the main engine loop.
 	 * The return value is not yet used, but could indicate whether the user
 	 * wants to return to the launch or to fully quit ScummVM.
-	 * @return 0 for success, else an error code.
+	 * @return returns kNoError on success, else an error code.
 	 */
-	virtual int go() = 0;
+	virtual Common::Error go() = 0;
 
 	/**
 	 * Prepare an error string, which is printed by the error() function.
@@ -168,11 +169,9 @@ public:
 	/** 
 	 * Load a game state.
 	 * @param slot	the slot from which a savestate should be loaded
-	 * @return returns 0 on success, anything else indicates failure
-	 *
-	 * @todo define proper error values
+	 * @return returns kNoError on success, else an error code.
 	 */
-	virtual int loadGameState(int slot);
+	virtual Common::Error loadGameState(int slot);
 
 	/**
 	 * Indicates whether a game state can be loaded.
@@ -183,11 +182,9 @@ public:
 	 * 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 0 on success, anything else indicates failure
-	 *
-	 * @todo define proper error values
+	 * @return returns kNoError on success, else an error code.
 	 */
-	virtual int saveGameState(int slot, const char *desc);
+	virtual Common::Error saveGameState(int slot, const char *desc);
 
 	/**
 	 * Indicates whether a game state can be saved.
diff --git a/engines/gob/gob.cpp b/engines/gob/gob.cpp
index e1543e9277..de369c5528 100644
--- a/engines/gob/gob.cpp
+++ b/engines/gob/gob.cpp
@@ -110,10 +110,10 @@ GobEngine::~GobEngine() {
 	delete[] _startTot0;
 }
 
-int GobEngine::go() {
+Common::Error GobEngine::go() {
 	_init->initGame(0);
 
-	return 0;
+	return Common::kNoError;
 }
 
 const char *GobEngine::getLangDesc(int16 language) const {
@@ -177,10 +177,10 @@ bool GobEngine::hasAdlib() const {
 	return (_features & kFeaturesAdlib) != 0;
 }
 
-int GobEngine::init() {
+Common::Error GobEngine::init() {
 	if (!initGameParts()) {
 		GUIErrorMessage("GobEngine::init(): Unknown version of game engine");
-		return -1;
+		return Common::kUnknownError;
 	}
 
 	_video->setSize(is640());
@@ -259,7 +259,7 @@ int GobEngine::init() {
 	//        640x480.
 
 	g_system->setFeatureState(OSystem::kFeatureAutoComputeDirtyRects, true);
-	return 0;
+	return Common::kNoError;
 }
 
 void GobEngine::pauseEngineIntern(bool pause) {
diff --git a/engines/gob/gob.h b/engines/gob/gob.h
index 599d7085fb..69f4a20632 100644
--- a/engines/gob/gob.h
+++ b/engines/gob/gob.h
@@ -191,8 +191,8 @@ private:
 	uint32 _pauseStart;
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void pauseEngineIntern(bool pause);
 
diff --git a/engines/igor/igor.cpp b/engines/igor/igor.cpp
index 4d4fb97762..d68aeb7c3e 100644
--- a/engines/igor/igor.cpp
+++ b/engines/igor/igor.cpp
@@ -88,14 +88,14 @@ IgorEngine::~IgorEngine() {
 	delete _midiPlayer;
 }
 
-int IgorEngine::init() {
+Common::Error IgorEngine::init() {
 	_system->beginGFXTransaction();
 		initCommonGFX(false);
 		_system->initSize(320, 200);
 	_system->endGFXTransaction();
 
 	_mixer->setVolumeForSoundType(Audio::Mixer::kSFXSoundType, ConfMan.getInt("sfx_volume"));
-	return 0;
+	return Common::kNoError;
 }
 
 void IgorEngine::restart() {
@@ -169,7 +169,7 @@ void IgorEngine::restart() {
 	_gameTicks = 0;
 }
 
-int IgorEngine::go() {
+Common::Error IgorEngine::go() {
 	restart();
 	setupDefaultPalette();
 	_currentPart = ConfMan.getInt("boot_param");
@@ -192,7 +192,7 @@ int IgorEngine::go() {
 	PART_MAIN();
 	_ovlFile.close();
 	_sndFile.close();
-	return 0;
+	return Common::kNoError;
 }
 
 void IgorEngine::readTableFile() {
diff --git a/engines/igor/igor.h b/engines/igor/igor.h
index 418a7ad6b4..4ded9d1eb3 100644
--- a/engines/igor/igor.h
+++ b/engines/igor/igor.h
@@ -312,8 +312,8 @@ public:
 	IgorEngine(OSystem *system, const DetectedGameVersion *dgv);
 	virtual ~IgorEngine();
 
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 
 	void handleOptionsMenu_paintSave();
 	bool handleOptionsMenu_handleKeyDownSave(int key);
@@ -427,8 +427,8 @@ protected:
 	void dialogueReplyToQuestion(int x, int y, int r, int g, int b, int reply = 0);
 
 	void saveOrLoadGameState(TypeSerializer &typeSerializer);
-	int loadGameState(int slot);
-	int saveGameState(int slot);
+	Common::Error loadGameState(int slot);
+	Common::Error saveGameState(int slot);
 	void generateGameStateFileName(int num, char *dst, int len) const;
 
 	MidiPlayer *_midiPlayer;
diff --git a/engines/igor/saveload.cpp b/engines/igor/saveload.cpp
index a87ecc0ba5..cbae77a343 100644
--- a/engines/igor/saveload.cpp
+++ b/engines/igor/saveload.cpp
@@ -156,7 +156,7 @@ void IgorEngine::saveOrLoadGameState(TypeSerializer &typeSerializer) {
 	}
 }
 
-int IgorEngine::loadGameState(int slot) {
+Common::Error IgorEngine::loadGameState(int slot) {
 	char name[64];
 	generateGameStateFileName(slot, name, 63);
 	Common::InSaveFile *isf = _saveFileMan->openForLoading(name);
@@ -176,10 +176,10 @@ int IgorEngine::loadGameState(int slot) {
 		debug(0, "Loaded state, current part %d", _currentPart);
 	}
 
-	return 0;	// TODO: return success/failure
+	return Common::kNoError;	// TODO: return success/failure
 }
 
-int IgorEngine::saveGameState(int slot) {
+Common::Error IgorEngine::saveGameState(int slot) {
 	char name[64];
 	generateGameStateFileName(slot, name, 63);
 	Common::OutSaveFile *osf = _saveFileMan->openForSaving(name);
@@ -190,7 +190,7 @@ int IgorEngine::saveGameState(int slot) {
 		delete osf;
 	}
 
-	return 0;	// TODO: return success/failure
+	return Common::kNoError;	// TODO: return success/failure
 }
 
 void IgorEngine::generateGameStateFileName(int num, char *dst, int len) const {
diff --git a/engines/kyra/kyra_hof.cpp b/engines/kyra/kyra_hof.cpp
index a0213c0be3..bc5a59b7a9 100644
--- a/engines/kyra/kyra_hof.cpp
+++ b/engines/kyra/kyra_hof.cpp
@@ -219,7 +219,7 @@ void KyraEngine_HoF::pauseEngineIntern(bool pause) {
 	}
 }
 
-int KyraEngine_HoF::init() {
+Common::Error KyraEngine_HoF::init() {
 	_screen = new Screen_HoF(this, _system);
 	assert(_screen);
 	_screen->setResolution();
@@ -261,7 +261,7 @@ int KyraEngine_HoF::init() {
 
 	// No mouse display in demo
 	if (_flags.isDemo && !_flags.isTalkie)
-		return 0;
+		return Common::kNoError;
 
 	_res->exists("PWGMOUSE.SHP", true);
 	uint8 *shapes = _res->fileData("PWGMOUSE.SHP", 0);
@@ -273,10 +273,10 @@ int KyraEngine_HoF::init() {
 	delete[] shapes;
 
 	_screen->setMouseCursor(0, 0, getShapePtr(0));
-	return 0;
+	return Common::kNoError;
 }
 
-int KyraEngine_HoF::go() {
+Common::Error KyraEngine_HoF::go() {
 	if (_gameToLoad == -1) {
 		if (_flags.platform == Common::kPlatformFMTowns || _flags.platform == Common::kPlatformPC98)
 			seq_showStarcraftLogo();
@@ -326,7 +326,7 @@ int KyraEngine_HoF::go() {
 			seq_playSequences(kSequenceFunters, kSequenceFrash);
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void KyraEngine_HoF::startup() {
diff --git a/engines/kyra/kyra_hof.h b/engines/kyra/kyra_hof.h
index dc4161f0c1..62039cb80a 100644
--- a/engines/kyra/kyra_hof.h
+++ b/engines/kyra/kyra_hof.h
@@ -292,8 +292,8 @@ protected:
 	void seq_init();
 	void seq_uninit();
 
-	int init();
-	int go();
+	Common::Error init();
+	Common::Error go();
 
 	Screen_HoF *_screen;
 	TextDisplayer_HoF *_text;
diff --git a/engines/kyra/kyra_lok.cpp b/engines/kyra/kyra_lok.cpp
index e8db3467fc..e995c74fd2 100644
--- a/engines/kyra/kyra_lok.cpp
+++ b/engines/kyra/kyra_lok.cpp
@@ -155,7 +155,7 @@ KyraEngine_LoK::~KyraEngine_LoK() {
 		delete[] _sceneAnimTable[i];
 }
 
-int KyraEngine_LoK::init() {
+Common::Error KyraEngine_LoK::init() {
 	_screen = new Screen_LoK(this, _system);
 	assert(_screen);
 	_screen->setResolution();
@@ -284,10 +284,10 @@ int KyraEngine_LoK::init() {
 
 	_lastMusicCommand = 0;
 
-	return 0;
+	return Common::kNoError;
 }
 
-int KyraEngine_LoK::go() {
+Common::Error KyraEngine_LoK::go() {
 	if (_res->getFileSize("6.FNT"))
 		_screen->loadFont(Screen::FID_6_FNT, "6.FNT");
 	_screen->loadFont(Screen::FID_8_FNT, "8FAT.FNT");
@@ -304,7 +304,7 @@ int KyraEngine_LoK::go() {
 			setGameFlag(0xEF);
 			seq_intro();
 			if (shouldQuit())
-				return 0;
+				return Common::kNoError;
 			if (_skipIntroFlag && _abortIntroFlag)
 				resetGameFlag(0xEF);
 		}
@@ -312,7 +312,7 @@ int KyraEngine_LoK::go() {
 		resetGameFlag(0xEF);
 		mainLoop();
 	}
-	return 0;
+	return Common::kNoError;
 }
 
 
diff --git a/engines/kyra/kyra_lok.h b/engines/kyra/kyra_lok.h
index e6fc0dc774..c345dd4df8 100644
--- a/engines/kyra/kyra_lok.h
+++ b/engines/kyra/kyra_lok.h
@@ -144,8 +144,8 @@ public:
 	const uint8 * const*palTable2() { return &_specialPalettes[29]; }
 
 protected:
-	virtual int go();
-	virtual int init();
+	virtual Common::Error go();
+	virtual Common::Error init();
 
 public:
 	// sequences
diff --git a/engines/kyra/kyra_mr.cpp b/engines/kyra/kyra_mr.cpp
index 7dea56a5fa..c461bfa494 100644
--- a/engines/kyra/kyra_mr.cpp
+++ b/engines/kyra/kyra_mr.cpp
@@ -202,7 +202,7 @@ KyraEngine_MR::~KyraEngine_MR() {
 	delete _album.rightPage.wsa;
 }
 
-int KyraEngine_MR::init() {
+Common::Error KyraEngine_MR::init() {
 	_screen = new Screen_MR(this, _system);
 	assert(_screen);
 	_screen->setResolution();
@@ -233,10 +233,10 @@ int KyraEngine_MR::init() {
 	_res->loadFileToBuf("PALETTE.COL", _screen->getPalette(0), 768);
 	_screen->setScreenPalette(_screen->getPalette(0));
 
-	return 0;
+	return Common::kNoError;
 }
 
-int KyraEngine_MR::go() {
+Common::Error KyraEngine_MR::go() {
 	bool running = true;
 	preinit();
 	_screen->hideMouse();
@@ -324,7 +324,7 @@ int KyraEngine_MR::go() {
 	if (_showOutro)
 		playVQA("CREDITS");
 
-	return 0;
+	return Common::kNoError;
 }
 
 void KyraEngine_MR::initMainMenu() {
diff --git a/engines/kyra/kyra_mr.h b/engines/kyra/kyra_mr.h
index a6fb9af20c..0bf5e663b4 100644
--- a/engines/kyra/kyra_mr.h
+++ b/engines/kyra/kyra_mr.h
@@ -62,7 +62,7 @@ public:
 	int language() const { return _lang; }
 	bool heliumMode() const { return _configHelium; }
 
-	int go();
+	Common::Error go();
 
 	void playVQA(const char *name);
 
@@ -84,7 +84,7 @@ private:
 	Screen_MR *_screen;
 	SoundDigital *_soundDigital;
 
-	int init();
+	Common::Error init();
 
 	void preinit();
 	void startup();
diff --git a/engines/kyra/kyra_v1.cpp b/engines/kyra/kyra_v1.cpp
index 0d398f6c64..11a303c27a 100644
--- a/engines/kyra/kyra_v1.cpp
+++ b/engines/kyra/kyra_v1.cpp
@@ -92,7 +92,7 @@ void KyraEngine_v1::pauseEngineIntern(bool pause) {
 	_timer->pause(pause);
 }
 
-int KyraEngine_v1::init() {
+Common::Error KyraEngine_v1::init() {
 	registerDefaultSettings();
 
 	// Setup mixer
@@ -186,7 +186,7 @@ int KyraEngine_v1::init() {
 	// Prevent autosave on game startup
 	_lastAutosave = _system->getMillis();
 
-	return 0;
+	return Common::kNoError;
 }
 
 KyraEngine_v1::~KyraEngine_v1() {
diff --git a/engines/kyra/kyra_v1.h b/engines/kyra/kyra_v1.h
index 81eea7420c..f85ddade50 100644
--- a/engines/kyra/kyra_v1.h
+++ b/engines/kyra/kyra_v1.h
@@ -168,7 +168,7 @@ public:
 
 protected:
 	// Engine APIs
-	virtual int init();
+	virtual Common::Error init();
 	virtual ::GUI::Debugger *getDebugger();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void pauseEngineIntern(bool pause);
@@ -304,7 +304,7 @@ protected:
 
 	static kReadSaveHeaderError readSaveHeader(Common::SeekableReadStream *file, bool loadThumbnail, SaveHeader &header);
 
-	int loadGameState(int slot);
+	Common::Error loadGameState(int slot);
 	virtual void loadGame(const char *fileName) = 0;
 	virtual void saveGame(const char *fileName, const char *saveName, const Graphics::Surface *thumbnail) = 0;
 
diff --git a/engines/kyra/lol.cpp b/engines/kyra/lol.cpp
index 91c9b65d1e..0b1a63ecf6 100644
--- a/engines/kyra/lol.cpp
+++ b/engines/kyra/lol.cpp
@@ -74,7 +74,7 @@ Screen *LoLEngine::screen() {
 	return _screen;
 }
 
-int LoLEngine::init() {
+Common::Error LoLEngine::init() {
 	_screen = new Screen_LoL(this, _system);
 	assert(_screen);
 	_screen->setResolution();
@@ -90,10 +90,10 @@ int LoLEngine::init() {
 	if (!_sound->init())
 		error("Couldn't init sound");
 
-	return 0;
+	return Common::kNoError;
 }
 
-int LoLEngine::go() {
+Common::Error LoLEngine::go() {
 	setupPrologueData(true);
 	showIntro();
 	_sound->playTrack(6);
@@ -102,7 +102,7 @@ int LoLEngine::go() {
 	_screen->fadeToBlack();
 	setupPrologueData(false);
 
-	return 0;
+	return Common::kNoError;
 }
 
 #pragma mark - Input
diff --git a/engines/kyra/lol.h b/engines/kyra/lol.h
index 71d184f062..3ece9b28a4 100644
--- a/engines/kyra/lol.h
+++ b/engines/kyra/lol.h
@@ -47,8 +47,8 @@ private:
 	Screen_LoL *_screen;
 	TIMInterpreter *_tim;
 
-	int init();
-	int go();
+	Common::Error init();
+	Common::Error go();
 
 	// input
 	void updateInput();
diff --git a/engines/kyra/saveload.cpp b/engines/kyra/saveload.cpp
index e85346a9ba..5f94c1321d 100644
--- a/engines/kyra/saveload.cpp
+++ b/engines/kyra/saveload.cpp
@@ -244,14 +244,14 @@ bool KyraEngine_v1::saveFileLoadable(int slot) {
 	return false;
 }
 
-int KyraEngine_v1::loadGameState(int slot) {
+Common::Error KyraEngine_v1::loadGameState(int slot) {
 	if (!_isSaveAllowed)
-		return -1;
+		return Common::kUnknownError;	// FIXME
 	
 	const char *filename = getSavegameFilename(slot);
 	loadGame(filename);
 
-	return 0;
+	return Common::kNoError;
 }
 
 void KyraEngine_v1::checkAutosave() {
diff --git a/engines/lure/lure.cpp b/engines/lure/lure.cpp
index 32eb0dbe21..282aa9801d 100644
--- a/engines/lure/lure.cpp
+++ b/engines/lure/lure.cpp
@@ -48,7 +48,7 @@ LureEngine::LureEngine(OSystem *system, const LureGameDescription *gameDesc): En
 	Common::addSpecialDebugLevel(kLureDebugStrings, "strings", "Strings debugging");
 }
 
-int LureEngine::init() {
+Common::Error LureEngine::init() {
 	int_engine = this;
 	_initialised = false;
 
@@ -62,7 +62,7 @@ int LureEngine::init() {
 	VersionStructure version;
 	if (!f.open(SUPPORT_FILENAME)) {
 		GUIError("Could not locate Lure support file");
-		return 1;
+		return Common::kUnknownError;
 	}
 
 	f.seek(0xbf * 8);
@@ -71,12 +71,12 @@ int LureEngine::init() {
 
 	if (READ_LE_UINT16(&version.id) != 0xffff) {
 		GUIError("Error validating %s - file is invalid or out of date", SUPPORT_FILENAME);
-		return 1;
+		return Common::kUnknownError;
 	} else if ((version.vMajor != LURE_DAT_MAJOR) || (version.vMinor != LURE_DAT_MINOR)) {
 		GUIError("Incorrect version of %s file - expected %d.%d but got %d.%d",
 			SUPPORT_FILENAME, LURE_DAT_MAJOR, LURE_DAT_MINOR,
 			version.vMajor, version.vMinor);
-		return 1;
+		return Common::kUnknownError;
 	}
 
 	_disk = new Disk();
@@ -92,7 +92,7 @@ int LureEngine::init() {
 
 	_gameToLoad = -1;
 	_initialised = true;
-	return 0;
+	return Common::kNoError;
 }
 
 LureEngine::~LureEngine() {
@@ -119,7 +119,7 @@ LureEngine &LureEngine::getReference() {
 	return *int_engine;
 }
 
-int LureEngine::go() {
+Common::Error LureEngine::go() {
 	Game *gameInstance = new Game();
 	
 	// If requested, load a savegame instead of showing the intro
@@ -135,7 +135,7 @@ int LureEngine::go() {
 			bool result = dialog->show();
 			delete dialog;
 			if (shouldQuit())
-				return 0;
+				return Common::kNoError;
 
 			if (!result)
 				error("Sorry - copy protection failed");
@@ -158,7 +158,7 @@ int LureEngine::go() {
 	}
 
 	delete gameInstance;
-	return 0;
+	return Common::kNoError;
 }
 
 void LureEngine::pauseEngineIntern(bool pause) {
diff --git a/engines/lure/lure.h b/engines/lure/lure.h
index a1e1448e0f..38029a0601 100644
--- a/engines/lure/lure.h
+++ b/engines/lure/lure.h
@@ -70,8 +70,8 @@ public:
 	static LureEngine &getReference();
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void syncSoundSettings();
 	virtual void pauseEngineIntern(bool pause);
diff --git a/engines/m4/m4.cpp b/engines/m4/m4.cpp
index 67201c2aff..45185b3b86 100644
--- a/engines/m4/m4.cpp
+++ b/engines/m4/m4.cpp
@@ -141,7 +141,7 @@ M4Engine::~M4Engine() {
 	delete _resourceManager;
 }
 
-int M4Engine::init() {
+Common::Error M4Engine::init() {
 	// Initialize backend
 	_system->beginGFXTransaction();
 	initCommonGFX(isM4());
@@ -197,7 +197,7 @@ int M4Engine::init() {
 	_random = new Common::RandomSource();
 	g_system->getEventManager()->registerRandomSource(*_random, "m4");
 
-	return 0;
+	return Common::kNoError;
 }
 
 void M4Engine::eventHandler() {
@@ -272,14 +272,14 @@ void M4Engine::loadMenu(MenuType menuType, bool loadSaveFromHotkey, bool calledF
 	_viewManager->moveToFront(view);
 }
 
-int M4Engine::go() {
+Common::Error M4Engine::go() {
 	if (isM4())
 		return goM4();
 	else
 		return goMADS();
 }
 
-int M4Engine::goMADS() {
+Common::Error M4Engine::goMADS() {
 	_palette->setMadsSystemPalette();
 
 	_mouse->init("cursor.ss", NULL);
@@ -351,10 +351,10 @@ int M4Engine::goMADS() {
 		g_system->delayMillis(10);
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
-int M4Engine::goM4() {
+Common::Error M4Engine::goM4() {
 
 	_script->open("m4.dat");
 
@@ -375,7 +375,7 @@ int M4Engine::goM4() {
 	}
 #endif
 
-	return 0;
+	return Common::kNoError;
 #endif
 
 	// Set up the inventory
@@ -520,7 +520,7 @@ int M4Engine::goM4() {
 		g_system->delayMillis(10);
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void M4Engine::dumpFile(const char* filename, bool uncompress) {
diff --git a/engines/m4/m4.h b/engines/m4/m4.h
index e989bcc4e6..ac3262e7b8 100644
--- a/engines/m4/m4.h
+++ b/engines/m4/m4.h
@@ -107,12 +107,14 @@ FORCEINLINE long FixedDiv(long a, long b) { return (long)(((float)a / (float)b)
 
 class M4Engine : public Engine {
 private:
-	int goMADS();
-	int goM4();
+	Common::Error goMADS();
+	Common::Error goM4();
 
 protected:
-	int init();
-	int go();
+	// Engine APIs
+	virtual Common::Error init();
+	virtual Common::Error go();
+
 	void shutdown();
 	
 	MidiPlayer *_midi;
diff --git a/engines/made/made.cpp b/engines/made/made.cpp
index dc45dc4d2f..2b7411fb3d 100644
--- a/engines/made/made.cpp
+++ b/engines/made/made.cpp
@@ -138,14 +138,14 @@ MadeEngine::~MadeEngine() {
 	delete _music;
 }
 
-int MadeEngine::init() {
+Common::Error MadeEngine::init() {
 	// Initialize backend
 	_system->beginGFXTransaction();
 	initCommonGFX(false);
 	_system->initSize(320, 200);
 	_system->endGFXTransaction();
 
-	return 0;
+	return Common::kNoError;
 }
 
 int16 MadeEngine::getTicks() {
@@ -244,7 +244,7 @@ void MadeEngine::handleEvents() {
 
 }
 
-int MadeEngine::go() {
+Common::Error MadeEngine::go() {
 
 	for (int i = 0; i < ARRAYSIZE(_timers); i++)
 		_timers[i] = -1;
@@ -297,7 +297,7 @@ int MadeEngine::go() {
 	_script->runScript(_dat->getMainCodeObjectIndex());
 #endif
 
-	return 0;
+	return Common::kNoError;
 }
 
 } // End of namespace Made
diff --git a/engines/made/made.h b/engines/made/made.h
index 971961c867..e06d0fd0b1 100644
--- a/engines/made/made.h
+++ b/engines/made/made.h
@@ -78,8 +78,9 @@ class MadeEngine : public ::Engine {
 
 protected:
 
-	int init();
-	int go();
+	// Engine APIs
+	virtual Common::Error init();
+	virtual Common::Error go();
 
 public:
 	MadeEngine(OSystem *syst, const MadeGameDescription *gameDesc);
diff --git a/engines/parallaction/parallaction.cpp b/engines/parallaction/parallaction.cpp
index 388675e31a..5abc308bee 100644
--- a/engines/parallaction/parallaction.cpp
+++ b/engines/parallaction/parallaction.cpp
@@ -109,7 +109,7 @@ Parallaction::~Parallaction() {
 }
 
 
-int Parallaction::init() {
+Common::Error Parallaction::init() {
 
 	_engineFlags = 0;
 	_objectsNames = NULL;
@@ -145,7 +145,7 @@ int Parallaction::init() {
 
 	setupBalloonManager();
 
-	return 0;
+	return Common::kNoError;
 }
 
 void Parallaction::updateView() {
diff --git a/engines/parallaction/parallaction.h b/engines/parallaction/parallaction.h
index b1baa28530..5b56f29e94 100644
--- a/engines/parallaction/parallaction.h
+++ b/engines/parallaction/parallaction.h
@@ -228,7 +228,7 @@ public:
 	~Parallaction();
 
 	// Engine APIs
-	virtual int init();
+	virtual Common::Error init();
 	virtual bool hasFeature(EngineFeature f) const;
 
 	// info
@@ -363,8 +363,8 @@ public:
 	~Parallaction_ns();
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 
 public:
 	virtual void 	parseLocation(const char *filename);
@@ -451,8 +451,8 @@ public:
 	Parallaction_br(OSystem* syst, const PARALLACTIONGameDescription *gameDesc) : Parallaction_ns(syst, gameDesc) { }
 	~Parallaction_br();
 
-	int init();
-	int go();
+	Common::Error init();
+	Common::Error go();
 
 public:
 	virtual void parseLocation(const char* name);
diff --git a/engines/parallaction/parallaction_br.cpp b/engines/parallaction/parallaction_br.cpp
index 2988350cb4..fe179a0ba4 100644
--- a/engines/parallaction/parallaction_br.cpp
+++ b/engines/parallaction/parallaction_br.cpp
@@ -42,7 +42,7 @@ const char *Parallaction_br::_partNames[] = {
 	"PART4"
 };
 
-int Parallaction_br::init() {
+Common::Error Parallaction_br::init() {
 
 	_screenWidth = 640;
 	_screenHeight = 400;
@@ -89,7 +89,7 @@ int Parallaction_br::init() {
 
 	Parallaction::init();
 
-	return 0;
+	return Common::kNoError;
 }
 
 Parallaction_br::~Parallaction_br() {
@@ -102,7 +102,7 @@ void Parallaction_br::callFunction(uint index, void* parm) {
 	(this->*_callables[index])(parm);
 }
 
-int Parallaction_br::go() {
+Common::Error Parallaction_br::go() {
 
 	bool splash = true;
 
@@ -127,7 +127,7 @@ int Parallaction_br::go() {
 		cleanupGame();
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 
diff --git a/engines/parallaction/parallaction_ns.cpp b/engines/parallaction/parallaction_ns.cpp
index a0fba08287..efb5f94b84 100644
--- a/engines/parallaction/parallaction_ns.cpp
+++ b/engines/parallaction/parallaction_ns.cpp
@@ -143,7 +143,7 @@ void LocationName::bind(const char *s) {
 
 
 
-int Parallaction_ns::init() {
+Common::Error Parallaction_ns::init() {
 
 	_screenWidth = 320;
 	_screenHeight = 200;
@@ -193,7 +193,7 @@ int Parallaction_ns::init() {
 
 	Parallaction::init();
 
-	return 0;
+	return Common::kNoError;
 }
 
 Parallaction_ns::~Parallaction_ns() {
@@ -228,7 +228,7 @@ void Parallaction_ns::callFunction(uint index, void* parm) {
 }
 
 
-int Parallaction_ns::go() {
+Common::Error Parallaction_ns::go() {
 	_saveLoad->renameOldSavefiles();
 
 	_globalFlagsNames = _disk->loadTable("global");
@@ -239,7 +239,7 @@ int Parallaction_ns::go() {
 		runGame();
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void Parallaction_ns::switchBackground(const char* background, const char* mask) {
diff --git a/engines/queen/queen.cpp b/engines/queen/queen.cpp
index 1232b12288..995c2aff60 100644
--- a/engines/queen/queen.cpp
+++ b/engines/queen/queen.cpp
@@ -312,9 +312,10 @@ bool QueenEngine::canLoadOrSave() const {
 	return !_input->cutawayRunning() && !(_resource->isDemo() || _resource->isInterview());
 }
 
-int QueenEngine::saveGameState(int slot, const char *desc) {
+Common::Error QueenEngine::saveGameState(int slot, const char *desc) {
 	debug(3, "Saving game to slot %d", slot);
 	char name[20];
+	Common::Error err = Common::kNoError;
 	makeGameStateName(slot, name);
 	Common::OutSaveFile *file = _saveFileMan->openForSaving(name);
 	if (file) {
@@ -345,18 +346,21 @@ int QueenEngine::saveGameState(int slot, const char *desc) {
 		// check for errors
 		if (file->ioFailed()) {
 			warning("Can't write file '%s'. (Disk full?)", name);
+			err = Common::kWritingFailed;
 		}
 		delete[] saveData;
 		delete file;
 	} else {
 		warning("Can't create file '%s', game not saved", name);
+		err = Common::kCreatingFileFailed;
 	}
 	
-	return 0;
+	return err;
 }
 
-int QueenEngine::loadGameState(int slot) {
+Common::Error QueenEngine::loadGameState(int slot) {
 	debug(3, "Loading game from slot %d", slot);
+	Common::Error err = Common::kNoError;
 	GameStateHeader header;
 	Common::InSaveFile *file = readGameStateHeader(slot, &header);
 	if (file && header.dataSize != 0) {
@@ -364,6 +368,7 @@ int QueenEngine::loadGameState(int slot) {
 		byte *p = saveData;
 		if (file->read(saveData, header.dataSize) != header.dataSize) {
 			warning("Error reading savegame file");
+			err = Common::kReadingFailed;
 		} else {
 			_bam->loadState(header.version, p);
 			_grid->loadState(header.version, p);
@@ -371,15 +376,18 @@ int QueenEngine::loadGameState(int slot) {
 			_sound->loadState(header.version, p);
 			if (header.dataSize != (uint32)(p - saveData)) {
 				warning("Corrupted savegame file");
+				err = Common::kReadingFailed;	// FIXME
 			} else {
 				_logic->setupRestoredGame();
 			}
 		}
 		delete[] saveData;
 		delete file;
+	} else {
+		err = Common::kReadingFailed;
 	}
 
-	return 0;	// TODO: return success/failure
+	return err;
 }
 
 Common::InSaveFile *QueenEngine::readGameStateHeader(int slot, GameStateHeader *gsh) {
@@ -436,7 +444,7 @@ GUI::Debugger *QueenEngine::getDebugger() {
 	return _debugger;
 }
 
-int QueenEngine::go() {
+Common::Error QueenEngine::go() {
 	_logic->start();
 	if (ConfMan.hasKey("save_slot") && canLoadOrSave()) {
 		loadGameState(ConfMan.getInt("save_slot"));
@@ -461,10 +469,10 @@ int QueenEngine::go() {
 			update(true);
 		}
 	}
-	return 0;
+	return Common::kNoError;
 }
 
-int QueenEngine::init() {
+Common::Error QueenEngine::init() {
 	_system->beginGFXTransaction();
 		initCommonGFX(false);
 		_system->initSize(GAME_SCREEN_WIDTH, GAME_SCREEN_HEIGHT);
@@ -496,7 +504,7 @@ int QueenEngine::init() {
 	registerDefaultSettings();
 	readOptionSettings();
 
-	return 0;
+	return Common::kNoError;
 }
 
 } // End of namespace Queen
diff --git a/engines/queen/queen.h b/engines/queen/queen.h
index df218a64a2..34ba0ab8e7 100644
--- a/engines/queen/queen.h
+++ b/engines/queen/queen.h
@@ -106,8 +106,8 @@ public:
 	void update(bool checkPlayerInput = false);
 
 	bool canLoadOrSave() const;
-	int saveGameState(int slot, const char *desc);
-	int loadGameState(int slot);
+	Common::Error saveGameState(int slot, const char *desc);
+	Common::Error loadGameState(int slot);
 	void makeGameStateName(int slot, char *buf) const;
 	int getGameStateSlot(const char *filename) const;
 	void findGameStateDescriptions(char descriptions[100][32]);
@@ -129,8 +129,8 @@ public:
 protected:
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual GUI::Debugger *getDebugger();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void syncSoundSettings();
diff --git a/engines/saga/detection.cpp b/engines/saga/detection.cpp
index d5f3659dd4..c49661a052 100644
--- a/engines/saga/detection.cpp
+++ b/engines/saga/detection.cpp
@@ -245,7 +245,7 @@ int SagaEngine::getDisplayHeight() const {
 	return di.logicalHeight;
 }
 
-int SagaEngine::loadGameState(int slot) {
+Common::Error SagaEngine::loadGameState(int slot) {
 	// Init the current chapter to 8 (character selection) for IHNM
 	if (getGameType() == GType_IHNM)
 		_scene->changeScene(-2, 0, kTransitionFade, 8);
@@ -262,7 +262,7 @@ int SagaEngine::loadGameState(int slot) {
 	load(calcSaveFileName((uint)slot));
 	syncSoundSettings();
 
-	return 0;	// TODO: return success/failure
+	return Common::kNoError;	// TODO: return success/failure
 }
 
 } // End of namespace Saga
diff --git a/engines/saga/saga.cpp b/engines/saga/saga.cpp
index 4ee81269d2..ee471f9330 100644
--- a/engines/saga/saga.cpp
+++ b/engines/saga/saga.cpp
@@ -140,7 +140,7 @@ SagaEngine::~SagaEngine() {
 	delete _resource;
 }
 
-int SagaEngine::init() {
+Common::Error SagaEngine::init() {
 	_musicVolume = ConfMan.getInt("music_volume");
 	_subtitlesEnabled = ConfMan.getBool("subtitles");
 	_readingSpeed = getTalkspeed();
@@ -156,7 +156,7 @@ int SagaEngine::init() {
 	// Detect game and open resource files
 	if (!initGame()) {
 		GUIErrorMessage("Error loading game resources.");
-		return FAILURE;
+		return Common::kUnknownError;
 	}
 
 	// Initialize engine modules
@@ -197,7 +197,7 @@ int SagaEngine::init() {
 	_music->setAdlib(adlib);
 	_render = new Render(this, _system);
 	if (!_render->initialized()) {
-		return FAILURE;
+		return Common::kUnknownError;
 	}
 
 	// Initialize system specific sound
@@ -232,10 +232,10 @@ int SagaEngine::init() {
 	if (getGameType() == GType_ITE)
 		_system->setFeatureState(OSystem::kFeatureAutoComputeDirtyRects, true);
 
-	return SUCCESS;
+	return Common::kNoError;
 }
 
-int SagaEngine::go() {
+Common::Error SagaEngine::go() {
 	int msec = 0;
 
 	_previousTicks = _system->getMillis();
@@ -310,7 +310,7 @@ int SagaEngine::go() {
 		_system->delayMillis(10);
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void SagaEngine::loadStrings(StringsTable &stringsTable, const byte *stringsPointer, size_t stringsLength) {
diff --git a/engines/saga/saga.h b/engines/saga/saga.h
index 86c91c2f3a..6563cd30d6 100644
--- a/engines/saga/saga.h
+++ b/engines/saga/saga.h
@@ -488,8 +488,8 @@ class SagaEngine : public Engine {
 
 public:
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void syncSoundSettings();
 
@@ -652,7 +652,7 @@ public:
 	const Common::Rect &getDisplayClip() const { return _displayClip;}
 	int getDisplayWidth() const;
 	int getDisplayHeight() const;
-	int loadGameState(int slot);
+	Common::Error loadGameState(int slot);
 	bool canLoadGameStateCurrently();
 	bool canSaveGameStateCurrently();
 	const GameDisplayInfo &getDisplayInfo();
diff --git a/engines/scumm/detection.cpp b/engines/scumm/detection.cpp
index 6ca3406230..e4694cf68b 100644
--- a/engines/scumm/detection.cpp
+++ b/engines/scumm/detection.cpp
@@ -794,18 +794,18 @@ Common::Error ScummMetaEngine::createInstance(OSystem *syst, Engine **engine) co
 	// Fetch the list of files in the current directory
 	Common::FSList fslist;
 	Common::FSNode dir(ConfMan.get("path"));
-	if (!dir.getChildren(fslist, Common::FSNode::kListFilesOnly)) {
+	if (!dir.isDirectory())
 		return Common::kInvalidPathError;
-	}
+	if (!dir.getChildren(fslist, Common::FSNode::kListFilesOnly))
+		return Common::kNoGameDataFoundError;
 
 	// Invoke the detector, but fixed to the specified gameid.
 	Common::List<DetectorResult> results;
 	::detectGames(fslist, results, gameid);
 
 	// Unable to locate game data
-	if (results.empty()) {
+	if (results.empty())
 		return Common::kNoGameDataFoundError;
-	}
 
 	// No unique match found. If a platform override is present, try to
 	// narrow down the list a bit more.
@@ -831,9 +831,8 @@ Common::Error ScummMetaEngine::createInstance(OSystem *syst, Engine **engine) co
 	}
 
 	// Still no unique match found -> print a warning
-	if (results.size() > 1) {
+	if (results.size() > 1)
 		warning("Engine_SCUMM_create: No unique game candidate found, using first one");
-	}
 
 	// Simply use the first match
 	DetectorResult res(*(results.begin()));
diff --git a/engines/scumm/he/intern_he.h b/engines/scumm/he/intern_he.h
index 8fd9122503..3b9bd40b17 100644
--- a/engines/scumm/he/intern_he.h
+++ b/engines/scumm/he/intern_he.h
@@ -669,8 +669,8 @@ public:
 	ScummEngine_vCUPhe(OSystem *syst, const DetectorResult &dr);
 	~ScummEngine_vCUPhe();
 
-	int init();
-	int go();
+	Common::Error init();
+	Common::Error go();
 
 	void parseEvents();
 
diff --git a/engines/scumm/saveload.cpp b/engines/scumm/saveload.cpp
index bb8a6bac65..069302482c 100644
--- a/engines/scumm/saveload.cpp
+++ b/engines/scumm/saveload.cpp
@@ -75,9 +75,9 @@ struct SaveInfoSection {
 
 #pragma mark -
 
-int ScummEngine::loadGameState(int slot) {
+Common::Error ScummEngine::loadGameState(int slot) {
 	requestLoad(slot);
-	return 0;
+	return Common::kNoError;
 }
 
 bool ScummEngine::canLoadGameStateCurrently() {
@@ -85,9 +85,9 @@ bool ScummEngine::canLoadGameStateCurrently() {
 	return true;
 }
 
-int ScummEngine::saveGameState(int slot, const char *desc) {
+Common::Error ScummEngine::saveGameState(int slot, const char *desc) {
 	requestSave(slot, desc);
-	return 0;
+	return Common::kNoError;
 }
 
 bool ScummEngine::canSaveGameStateCurrently() {
diff --git a/engines/scumm/scumm.cpp b/engines/scumm/scumm.cpp
index bb22ee6381..8ee880691b 100644
--- a/engines/scumm/scumm.cpp
+++ b/engines/scumm/scumm.cpp
@@ -821,21 +821,21 @@ ScummEngine_vCUPhe::~ScummEngine_vCUPhe() {
 	delete _cupPlayer;
 }
 
-int ScummEngine_vCUPhe::init() {
+Common::Error ScummEngine_vCUPhe::init() {
 	_system->beginGFXTransaction();
 		_system->initSize(CUP_Player::kDefaultVideoWidth, CUP_Player::kDefaultVideoHeight);
 		initCommonGFX(true);
 	_system->endGFXTransaction();
 
-	return 0;
+	return Common::kNoError;
 }
 
-int ScummEngine_vCUPhe::go() {
+Common::Error ScummEngine_vCUPhe::go() {
 	if (_cupPlayer->open(_filenamePattern.pattern)) {
 		_cupPlayer->play();
 		_cupPlayer->close();
 	}
-	return 0;
+	return Common::kNoError;
 }
 
 void ScummEngine_vCUPhe::parseEvents() {
@@ -907,7 +907,7 @@ ScummEngine_v8::~ScummEngine_v8() {
 #pragma mark --- Initialization ---
 #pragma mark -
 
-int ScummEngine::init() {
+Common::Error ScummEngine::init() {
 
 	// Add default file directories.
 	if (((_game.platform == Common::kPlatformAmiga) || (_game.platform == Common::kPlatformAtariST)) && (_game.version <= 4)) {
@@ -1106,7 +1106,7 @@ int ScummEngine::init() {
 
 	syncSoundSettings();
 
-	return 0;
+	return Common::kNoError;
 }
 
 void ScummEngine::setupScumm() {
@@ -1712,7 +1712,7 @@ int ScummEngine::getTalkDelay() {
 #pragma mark --- Main loop ---
 #pragma mark -
 
-int ScummEngine::go() {
+Common::Error ScummEngine::go() {
 	_engineStartTime = _system->getMillis() / 1000;
 
 	// If requested, load a save game instead of running the boot script
@@ -1763,7 +1763,7 @@ int ScummEngine::go() {
 		}
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void ScummEngine::waitForTimer(int msec_delay) {
diff --git a/engines/scumm/scumm.h b/engines/scumm/scumm.h
index 80f5784351..582d9fdf60 100644
--- a/engines/scumm/scumm.h
+++ b/engines/scumm/scumm.h
@@ -443,16 +443,16 @@ public:
 	virtual ~ScummEngine();
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual void errorString(const char *buf_input, char *buf_output);
 	virtual GUI::Debugger *getDebugger();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void syncSoundSettings();
 
-	virtual int loadGameState(int slot);
+	virtual Common::Error loadGameState(int slot);
 	virtual bool canLoadGameStateCurrently();
-	virtual int saveGameState(int slot, const char *desc);
+	virtual Common::Error saveGameState(int slot, const char *desc);
 	virtual bool canSaveGameStateCurrently();
 
 	virtual void pauseEngineIntern(bool pause);
diff --git a/engines/sky/sky.cpp b/engines/sky/sky.cpp
index 1abb3d94f6..7e8250aa1f 100644
--- a/engines/sky/sky.cpp
+++ b/engines/sky/sky.cpp
@@ -349,7 +349,7 @@ void SkyEngine::handleKey(void) {
 	_keyPressed.reset();
 }
 
-int SkyEngine::go() {
+Common::Error SkyEngine::go() {
 
 	_keyPressed.reset();
 
@@ -428,10 +428,10 @@ int SkyEngine::go() {
 	_skyMusic->stopMusic();
 	ConfMan.flushToDisk();
 	delay(1500);
-	return 0;
+	return Common::kNoError;
 }
 
-int SkyEngine::init() {
+Common::Error SkyEngine::init() {
 	_system->beginGFXTransaction();
 		initCommonGFX(false);
 		_system->initSize(320, 200);
@@ -549,7 +549,7 @@ int SkyEngine::init() {
 	_skyMusic->setVolume(ConfMan.getInt("music_volume") >> 1);
 
 	_debugger = new Debugger(_skyLogic, _skyMouse, _skyScreen, _skyCompact);
-	return 0;
+	return Common::kNoError;
 }
 
 void SkyEngine::initItemList() {
diff --git a/engines/sky/sky.h b/engines/sky/sky.h
index f3d2e564c8..47c67c743b 100644
--- a/engines/sky/sky.h
+++ b/engines/sky/sky.h
@@ -89,8 +89,8 @@ public:
 
 protected:
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual GUI::Debugger *getDebugger();
 	virtual bool hasFeature(EngineFeature f) const;
 
diff --git a/engines/sword1/sword1.cpp b/engines/sword1/sword1.cpp
index 9a6bfac030..7f942f3b2d 100644
--- a/engines/sword1/sword1.cpp
+++ b/engines/sword1/sword1.cpp
@@ -309,7 +309,7 @@ SwordEngine::~SwordEngine() {
 	delete _resMan;
 }
 
-int SwordEngine::init() {
+Common::Error SwordEngine::init() {
 
 	_system->beginGFXTransaction();
 		initCommonGFX(true);
@@ -377,7 +377,7 @@ int SwordEngine::init() {
 	_mouse->initialize();
 	_control = new Control(_saveFileMan, _resMan, _objectMan, _system, _mouse, _sound, _music);
 
-	return 0;
+	return Common::kNoError;
 }
 
 void SwordEngine::reinitialize(void) {
@@ -719,7 +719,7 @@ void SwordEngine::checkCdFiles(void) { // check if we're running from cd, hdd or
 #endif
 }
 
-int SwordEngine::go() {
+Common::Error SwordEngine::go() {
 	uint16 startPos = ConfMan.getInt("boot_param");
 	if (startPos) {
 		_logic->startPositions(startPos);
@@ -757,7 +757,7 @@ int SwordEngine::go() {
 		}
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void SwordEngine::checkCd(void) {
diff --git a/engines/sword1/sword1.h b/engines/sword1/sword1.h
index 8397f30705..8f77f3119a 100644
--- a/engines/sword1/sword1.h
+++ b/engines/sword1/sword1.h
@@ -81,8 +81,8 @@ public:
 	uint32 _features;
 protected:
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void syncSoundSettings();
 
diff --git a/engines/sword2/sword2.cpp b/engines/sword2/sword2.cpp
index c596e2f8c0..f1f880c11e 100644
--- a/engines/sword2/sword2.cpp
+++ b/engines/sword2/sword2.cpp
@@ -218,7 +218,7 @@ Common::Error Sword2MetaEngine::createInstance(OSystem *syst, Engine **engine) c
 	Common::FSList fslist;
 	Common::FSNode dir(ConfMan.get("path"));
 	if (!dir.getChildren(fslist, Common::FSNode::kListAll)) {
-		return Common::kInvalidPathError;
+		return Common::kNoGameDataFoundError;
 	}
 
 	// Invoke the detector
@@ -349,7 +349,7 @@ void Sword2Engine::setupPersistentResources() {
 	_resman->openResource(CUR_PLAYER_ID);
 }
 
-int Sword2Engine::init() {
+Common::Error Sword2Engine::init() {
 	// Get some falling RAM and put it in your pocket, never let it slip
 	// away
 
@@ -378,7 +378,7 @@ int Sword2Engine::init() {
 	_resman = new ResourceManager(this);
 
 	if (!_resman->init())
-		return 1;
+		return Common::kUnknownError;
 
 	_logic = new Logic(this);
 	_fontRenderer = new FontRenderer(this);
@@ -426,7 +426,7 @@ int Sword2Engine::init() {
 		// will either have killed the music, or done a crossfade.
 
 		if (shouldQuit())
-			return 0;
+			return Common::kNoError;
 
 		if (result)
 			startGame();
@@ -435,10 +435,10 @@ int Sword2Engine::init() {
 
 	_screen->initialiseRenderCycle();
 
-	return 0;
+	return Common::kNoError;
 }
 
-int Sword2Engine::go() {
+Common::Error Sword2Engine::go() {
 	while (1) {
 		if (_debugger->isAttached())
 			_debugger->onFrame();
@@ -514,7 +514,7 @@ int Sword2Engine::go() {
 #endif
 	}
 
-	return 0;
+	return Common::kNoError;
 }
 
 void Sword2Engine::restartGame() {
diff --git a/engines/sword2/sword2.h b/engines/sword2/sword2.h
index 06d6292ec2..172dcea35c 100644
--- a/engines/sword2/sword2.h
+++ b/engines/sword2/sword2.h
@@ -127,8 +127,8 @@ public:
 	~Sword2Engine();
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual GUI::Debugger *getDebugger();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void pauseEngineIntern(bool pause);
diff --git a/engines/tinsel/tinsel.cpp b/engines/tinsel/tinsel.cpp
index 1ac36efb13..e876fbc40c 100644
--- a/engines/tinsel/tinsel.cpp
+++ b/engines/tinsel/tinsel.cpp
@@ -658,7 +658,7 @@ TinselEngine::~TinselEngine() {
 	delete _scheduler;
 }
 
-int TinselEngine::init() {
+Common::Error TinselEngine::init() {
 	// Initialize backend
 	_system->beginGFXTransaction();
 		initCommonGFX(false);
@@ -707,7 +707,7 @@ int TinselEngine::init() {
 	// Actors, globals and inventory icons
 	LoadBasicChunks();
 
-	return 0;
+	return Common::kNoError;
 }
 
 Common::String TinselEngine::getSavegameFilename(int16 saveNum) const {
@@ -718,7 +718,7 @@ Common::String TinselEngine::getSavegameFilename(int16 saveNum) const {
 
 #define GAME_FRAME_DELAY (1000 / ONE_SECOND)
 
-int TinselEngine::go() {
+Common::Error TinselEngine::go() {
 	uint32 timerVal = 0;
 
 	// Continuous game processes
@@ -774,7 +774,7 @@ int TinselEngine::go() {
 	// Write configuration
 	WriteConfig();
 
-	return 0;
+	return Common::kNoError;
 }
 
 
diff --git a/engines/tinsel/tinsel.h b/engines/tinsel/tinsel.h
index 9820be7ddd..080e539f69 100644
--- a/engines/tinsel/tinsel.h
+++ b/engines/tinsel/tinsel.h
@@ -91,8 +91,9 @@ class TinselEngine : public Engine {
 
 protected:
 
-	int init();
-	int go();
+	// Engine APIs
+	virtual Common::Error init();
+	virtual Common::Error go();
 
 public:
 	TinselEngine(OSystem *syst, const TinselGameDescription *gameDesc);
diff --git a/engines/touche/menu.cpp b/engines/touche/menu.cpp
index 2d7af18da3..fbc73d027e 100644
--- a/engines/touche/menu.cpp
+++ b/engines/touche/menu.cpp
@@ -331,14 +331,14 @@ void ToucheEngine::handleMenuAction(void *menu, int actionId) {
 		break;
 	case kActionPerformSaveLoad:
 		if (menuData->mode == kMenuLoadStateMode) {
-			if (loadGameState(_saveLoadCurrentSlot) == 0) {
+			if (loadGameState(_saveLoadCurrentSlot) == Common::kNoError) {
 				menuData->quit = true;
 			}
 		} else if (menuData->mode == kMenuSaveStateMode) {
 			_system->setFeatureState(OSystem::kFeatureVirtualKeyboard, false);
 			const char *description = menuData->saveLoadDescriptionsTable[_saveLoadCurrentSlot];
 			if (strlen(description) > 0) {
-				if (saveGameState(_saveLoadCurrentSlot, description)) {
+				if (saveGameState(_saveLoadCurrentSlot, description) == Common::kNoError) {
 					menuData->quit = true;
 				}
 			}
diff --git a/engines/touche/saveload.cpp b/engines/touche/saveload.cpp
index 0890d4688f..5d63d45bb5 100644
--- a/engines/touche/saveload.cpp
+++ b/engines/touche/saveload.cpp
@@ -316,7 +316,7 @@ void ToucheEngine::loadGameStateData(Common::ReadStream *stream) {
 	debug(0, "Loaded state, current episode %d", _currentEpisodeNum);
 }
 
-int ToucheEngine::saveGameState(int num, const char *description) {
+Common::Error ToucheEngine::saveGameState(int num, const char *description) {
 	bool saveOk = false;
 	char gameStateFileName[64];
 	generateGameStateFileName(num, gameStateFileName, 63);
@@ -337,10 +337,10 @@ int ToucheEngine::saveGameState(int num, const char *description) {
 		}
 		delete f;
 	}
-	return saveOk;
+	return saveOk ? Common::kNoError : Common::kUnknownError;
 }
 
-int ToucheEngine::loadGameState(int num) {
+Common::Error ToucheEngine::loadGameState(int num) {
 	bool loadOk = false;
 	char gameStateFileName[64];
 	generateGameStateFileName(num, gameStateFileName, 63);
@@ -360,7 +360,7 @@ int ToucheEngine::loadGameState(int num) {
 		}
 		delete f;
 	}
-	return loadOk ? 0 : 1;
+	return loadOk ? Common::kNoError : Common::kUnknownError;
 }
 
 void ToucheEngine::readGameStateDescription(int num, char *description, int len) {
diff --git a/engines/touche/touche.cpp b/engines/touche/touche.cpp
index 26170e2734..0033d80cb2 100644
--- a/engines/touche/touche.cpp
+++ b/engines/touche/touche.cpp
@@ -81,7 +81,7 @@ ToucheEngine::~ToucheEngine() {
 	delete _midiPlayer;
 }
 
-int ToucheEngine::init() {
+Common::Error ToucheEngine::init() {
 	_system->beginGFXTransaction();
 		initCommonGFX(true);
 		_system->initSize(kScreenWidth, kScreenHeight);
@@ -96,10 +96,10 @@ int ToucheEngine::init() {
 	_mixer->setVolumeForSoundType(Audio::Mixer::kSFXSoundType, ConfMan.getInt("sfx_volume"));
 	_mixer->setVolumeForSoundType(Audio::Mixer::kSpeechSoundType, ConfMan.getInt("speech_volume"));
 	_mixer->setVolumeForSoundType(Audio::Mixer::kMusicSoundType, ConfMan.getInt("music_volume"));
-	return 0;
+	return Common::kNoError;
 }
 
-int ToucheEngine::go() {
+Common::Error ToucheEngine::go() {
 	res_openDataFile();
 	res_allocateTables();
 	res_loadSpriteImage(18, _menuKitData);
@@ -111,7 +111,7 @@ int ToucheEngine::go() {
 
 	res_deallocateTables();
 	res_closeDataFile();
-	return 0;
+	return Common::kNoError;
 }
 
 void ToucheEngine::restart() {
diff --git a/engines/touche/touche.h b/engines/touche/touche.h
index 9d66d839a0..b5256a9d8f 100644
--- a/engines/touche/touche.h
+++ b/engines/touche/touche.h
@@ -362,8 +362,8 @@ public:
 	virtual ~ToucheEngine();
 
 	// Engine APIs
-	virtual int init();
-	virtual int go();
+	virtual Common::Error init();
+	virtual Common::Error go();
 	virtual bool hasFeature(EngineFeature f) const;
 	virtual void syncSoundSettings();
 
@@ -497,8 +497,8 @@ protected:
 
 	void saveGameStateData(Common::WriteStream *stream);
 	void loadGameStateData(Common::ReadStream *stream);
-	int saveGameState(int num, const char *description);
-	int loadGameState(int num);
+	Common::Error saveGameState(int num, const char *description);
+	Common::Error loadGameState(int num);
 	void readGameStateDescription(int num, char *description, int len);
 	void generateGameStateFileName(int num, char *dst, int len, bool prefixOnly = false) const;
 	int getGameStateFileSlot(const char *filename) const;