SCI32: "Improve" comparison algorithm for planes and screen items

This adds a slightly more accurate comparison algorithm that will
at least ensure that all the engine-generated planes and screen
items with matching priorities will be sorted above
script-generated planes and screen items, like in the original
engine. It still does not sort script-generated items by memory
handle order, so if that is ever a thing that actually happens,
those may still be in the wrong order.

3 files changed, 35 insertions, 5 deletions

diff --git a/engines/sci/graphics/plane32.cpp b/engines/sci/graphics/plane32.cpp
index 7d1487bd7c..0a0b0ad561 100644
--- a/engines/sci/graphics/plane32.cpp
+++ b/engines/sci/graphics/plane32.cpp
@@ -447,7 +447,20 @@ void Plane::calcLists(Plane &visiblePlane, const PlaneList &planeList, DrawList
 					if (j < _screenItemList.size() && sli) {
 						if (!sli->_updated && !sli->_deleted && !sli->_created) {
 							ScreenItem *item = dli->screenItem;
-							if (sli->_priority > item->_priority /* TODO: || (sli->_priority == item->_priority && sli->_object > item->_object)*/) {
+
+							bool isAbove = false;
+							if (sli->_priority > item->_priority) {
+								isAbove = true;
+							}
+							else if (sli->_priority == item->_priority) {
+								if (sli->_object.isNumber() && item->_object.isNumber()) {
+									isAbove = sli->_object > item->_object;
+								} else if (sli->_object.isNumber()) {
+									isAbove = true;
+								}
+							}
+
+							if (isAbove) {
 								if (dli->rect.intersects(sli->_screenRect)) {
 									drawList.add(sli, dli->rect.findIntersectingRect(sli->_screenRect));
 								}
diff --git a/engines/sci/graphics/plane32.h b/engines/sci/graphics/plane32.h
index 65df19d924..c9b9d6a099 100644
--- a/engines/sci/graphics/plane32.h
+++ b/engines/sci/graphics/plane32.h
@@ -272,7 +272,19 @@ public:
 		// However, this whole comparison is quite ugly, and if it still
 		// fails, we should try to change it to something equivalent, to avoid
 		// adding loads of workarounds just for this
-		return _priority < other._priority || (_priority == other._priority && _priority > -1 && _object.getOffset() < other._object.getOffset());
+		if (_priority < other._priority) {
+			return true;
+		}
+
+		if (_priority == other._priority) {
+			if (_object.isNumber() && other._object.isNumber()) {
+				return _object < other._object;
+			} else if (other._object.isNumber()) {
+				return true;
+			}
+		}
+
+		return false;
 	}
 
 	/**
diff --git a/engines/sci/graphics/screen_item32.h b/engines/sci/graphics/screen_item32.h
index e054cf32f3..1c4d87d24c 100644
--- a/engines/sci/graphics/screen_item32.h
+++ b/engines/sci/graphics/screen_item32.h
@@ -228,9 +228,14 @@ public:
 			}
 
 			if (_position.y + _z == other._position.y + other._z) {
-				return false;
-				// TODO: Failure in SQ6 room 220
-//				return _object < other._object;
+				// TODO: Failure in SQ6 room 220 when using SCI logic
+				// to compare pointer and numeric memory handles
+
+				if (_object.isNumber() && other._object.isNumber()) {
+					return _object < other._object;
+				} else if (other._object.isNumber()) {
+					return true;
+				}
 			}
 		}