SCI32: Implement syncing planes+screen items from VM for restore

Fixes restoring saved games, when ScummVM dialogs are patched in
Removing clearing planes+screen items as well, because the scripts
actually did that, but did not clear everything.
Fixes "Invalid screen item" message when entering options menu,
after restoring in SQ6.

3 files changed, 14 insertions, 3 deletions

diff --git a/engines/sci/engine/savegame.cpp b/engines/sci/engine/savegame.cpp
index fcf951e4f2..1b56e667bf 100644
--- a/engines/sci/engine/savegame.cpp
+++ b/engines/sci/engine/savegame.cpp
@@ -1066,10 +1066,12 @@ void gamestate_restore(EngineState *s, Common::SeekableReadStream *fh) {
 	if (g_sci->_gfxScreen)
 		g_sci->_gfxScreen->clearForRestoreGame();
 #ifdef ENABLE_SCI32
-	// Also clear any SCI32 planes/screen items currently showing so they
-	// don't show up after the load.
+	// Delete current planes/elements of actively loaded VM, only when our ScummVM dialogs are patched in
+	// We MUST NOT delete all planes/screen items. At least Space Quest 6 has a few in memory like for example
+	// the options plane, which are not re-added and are in memory all the time right from the start of the
+	// game. Sierra SCI32 did not clear planes, only scripts cleared the ones inside planes::elements.
 	if (getSciVersion() >= SCI_VERSION_2)
-		g_sci->_gfxFrameout->clear();
+		g_sci->_gfxFrameout->syncWithScripts(false);
 #endif
 
 	s->reset(true);
@@ -1094,6 +1096,12 @@ void gamestate_restore(EngineState *s, Common::SeekableReadStream *fh) {
 	if (g_sci->_gfxPorts)
 		g_sci->_gfxPorts->saveLoadWithSerializer(ser);
 
+#ifdef ENABLE_SCI32
+	// Add current planes/screen elements of freshly loaded VM, only when our ScummVM dialogs are patched in
+	if (getSciVersion() >= SCI_VERSION_2)
+		g_sci->_gfxFrameout->syncWithScripts(true);
+#endif
+
 	Vocabulary *voc = g_sci->getVocabulary();
 	if (ser.getVersion() >= 30 && voc)
 		voc->saveLoadWithSerializer(ser);
diff --git a/engines/sci/engine/selector.cpp b/engines/sci/engine/selector.cpp
index b86e0ffd68..66f3793918 100644
--- a/engines/sci/engine/selector.cpp
+++ b/engines/sci/engine/selector.cpp
@@ -193,6 +193,7 @@ void Kernel::mapSelectors() {
 	FIND_SELECTOR(textBottom);
 	FIND_SELECTOR(textRight);
 	FIND_SELECTOR(magnifier);
+	FIND_SELECTOR(casts);
 #endif
 }
 
diff --git a/engines/sci/engine/selector.h b/engines/sci/engine/selector.h
index 6b724ed271..12074ed7d2 100644
--- a/engines/sci/engine/selector.h
+++ b/engines/sci/engine/selector.h
@@ -157,6 +157,8 @@ struct SelectorCache {
 	Selector textTop, textLeft, textBottom, textRight;
 
 	Selector magnifier;
+
+	Selector casts; // needed for sync'ing screen items/planes with scripts, when our save/restore code is patched in (see GfxFrameout::syncWithScripts)
 #endif
 };