ALL: Load savegame thumbnail only when necessary

This commit introduces the following changes:

1. Graphics::loadThumbnail()

   Now returns a boolean and takes a new argument skipThumbnail which
   defaults to false. In case of true, loadThumbnail() reads past the
   thumbnail data in the input stream instead of actually loading the
   thumbnail. This simplifies savegame handling where, up until now,
   many engines always read the whole savegame metadata (including
   the thumbnail) and then threw away the thumbnail when not needed
   (which is in almost all cases, the most common exception being
   MetaEngine::querySaveMetaInfos() which is responsible for loading
   savegame metadata for displaying it in the GUI launcher.

2. readSavegameHeader()

   Engines which already implement such a method (name varies) now take
   a new argument skipThumbnail (default: true) which is passed
   through to loadThumbnail(). This means that the default case for
   readSavegameHeader() is now _not_ loading the thumbnail from a
   savegame and just reading past it. In those cases, e.g.
   querySaveMetaInfos(), where we actually are interested in loading
   the thumbnail readSavegameHeader() needs to explicitely be called
   with skipThumbnail == false.

   Engines whose readSavegameHeader() (name varies) already takes an
   argument loadThumbnail have been adapted to have a similar
   prototype and semantics.
   I.e. readSaveHeader(in, loadThumbnail, header) now is
   readSaveHeader(in, header, skipThumbnail).

3. Error handling

   Engines which previously did not check the return value of
   readSavegameHeader() (name varies) now do so ensuring that possibly
   broken savegames (be it a broken thumbnail or something else) don't
   make it into the GUI launcher list in the first place.

4 files changed, 17 insertions, 17 deletions

diff --git a/engines/hopkins/detection.cpp b/engines/hopkins/detection.cpp
index 041afecaa8..ebefee6278 100644
--- a/engines/hopkins/detection.cpp
+++ b/engines/hopkins/detection.cpp
@@ -168,9 +168,6 @@ SaveStateList HopkinsMetaEngine::listSaves(const char *target) const {
 			if (in) {
 				if (Hopkins::SaveLoadManager::readSavegameHeader(in, header)) {
 					saveList.push_back(SaveStateDescriptor(slot, header._saveName));
-
-					header._thumbnail->free();
-					delete header._thumbnail;
 				}
 
 				delete in;
@@ -198,7 +195,11 @@ SaveStateDescriptor HopkinsMetaEngine::querySaveMetaInfos(const char *target, in
 
 	if (f) {
 		Hopkins::hopkinsSavegameHeader header;
-		Hopkins::SaveLoadManager::readSavegameHeader(f, header);
+		if (!Hopkins::SaveLoadManager::readSavegameHeader(f, header, false)) {
+			delete f;
+			return SaveStateDescriptor();
+		}
+
 		delete f;
 
 		// Create the return descriptor
diff --git a/engines/hopkins/dialogs.cpp b/engines/hopkins/dialogs.cpp
index fc613f892d..b8f1c73304 100644
--- a/engines/hopkins/dialogs.cpp
+++ b/engines/hopkins/dialogs.cpp
@@ -692,7 +692,7 @@ void DialogsManager::showSaveLoad(SaveLoadMode mode) {
 
 	for (int slotNumber = 1; slotNumber <= 6; ++slotNumber) {
 		hopkinsSavegameHeader header;
-		if (_vm->_saveLoad->readSavegameHeader(slotNumber, header)) {
+		if (_vm->_saveLoad->readSavegameHeader(slotNumber, header, false)) {
 			Graphics::Surface thumb8;
 			_vm->_saveLoad->convertThumb16To8(header._thumbnail, &thumb8);
 
diff --git a/engines/hopkins/saveload.cpp b/engines/hopkins/saveload.cpp
index 05c7fb8119..35a80458ff 100644
--- a/engines/hopkins/saveload.cpp
+++ b/engines/hopkins/saveload.cpp
@@ -77,9 +77,8 @@ void SaveLoadManager::load(const Common::String &file, byte *buf) {
 	delete savefile;
 }
 
-bool SaveLoadManager::readSavegameHeader(Common::InSaveFile *in, hopkinsSavegameHeader &header) {
+WARN_UNUSED_RESULT bool SaveLoadManager::readSavegameHeader(Common::InSaveFile *in, hopkinsSavegameHeader &header, bool skipThumbnail) {
 	char saveIdentBuffer[SAVEGAME_STR_SIZE + 1];
-	header._thumbnail = NULL;
 
 	// Validate the header Id
 	in->read(saveIdentBuffer, SAVEGAME_STR_SIZE + 1);
@@ -96,9 +95,9 @@ bool SaveLoadManager::readSavegameHeader(Common::InSaveFile *in, hopkinsSavegame
 	while ((ch = (char)in->readByte()) != '\0') header._saveName += ch;
 
 	// Get the thumbnail
-	header._thumbnail = Graphics::loadThumbnail(*in);
-	if (!header._thumbnail)
+	if (!Graphics::loadThumbnail(*in, header._thumbnail, skipThumbnail)) {
 		return false;
+	}
 
 	// Read in save date/time
 	header._year = in->readSint16LE();
@@ -186,10 +185,10 @@ Common::Error SaveLoadManager::loadGame(int slot) {
 
 	// Read in the savegame header
 	hopkinsSavegameHeader header;
-	readSavegameHeader(savefile, header);
-	if (header._thumbnail)
-		header._thumbnail->free();
-	delete header._thumbnail;
+	if (!readSavegameHeader(savefile, header)) {
+		delete savefile;
+		return Common::kReadingFailed;
+	}
 
 	// Read in the savegame data
 	syncSavegameData(serializer, header._version);
@@ -212,14 +211,14 @@ Common::Error SaveLoadManager::loadGame(int slot) {
 	return Common::kNoError;
 }
 
-bool SaveLoadManager::readSavegameHeader(int slot, hopkinsSavegameHeader &header) {
+WARN_UNUSED_RESULT bool SaveLoadManager::readSavegameHeader(int slot, hopkinsSavegameHeader &header, bool skipThumbnail) {
 	// Try and open the save file for reading
 	Common::InSaveFile *savefile = g_system->getSavefileManager()->openForLoading(
 		_vm->generateSaveName(slot));
 	if (!savefile)
 		return false;
 
-	bool result = readSavegameHeader(savefile, header);
+	bool result = readSavegameHeader(savefile, header, skipThumbnail);
 	delete savefile;
 	return result;
 }
diff --git a/engines/hopkins/saveload.h b/engines/hopkins/saveload.h
index 7b4ec307f5..33234f49fa 100644
--- a/engines/hopkins/saveload.h
+++ b/engines/hopkins/saveload.h
@@ -61,9 +61,9 @@ public:
 	bool saveFile(const Common::String &file, const void *buf, size_t n);
 	void load(const Common::String &file, byte *buf);
 
-	static bool readSavegameHeader(Common::InSaveFile *in, hopkinsSavegameHeader &header);
+	WARN_UNUSED_RESULT static bool readSavegameHeader(Common::InSaveFile *in, hopkinsSavegameHeader &header, bool skipThumbnail = true);
 	void writeSavegameHeader(Common::OutSaveFile *out, hopkinsSavegameHeader &header);
-	bool readSavegameHeader(int slot, hopkinsSavegameHeader &header);
+	WARN_UNUSED_RESULT bool readSavegameHeader(int slot, hopkinsSavegameHeader &header, bool skipThumbnail = true);
 	Common::Error saveGame(int slot, const Common::String &saveName);
 	Common::Error loadGame(int slot);