Fixes for handling of oversized map dwellings

- Marked large version of H3 Unicorn's Glade as not usable for random
dwelling replacement
- Shifted oversized dwellings - that have at most 2x2 as blocked tile,
but have non-blocked tile column will now be placed correctly
- This fixes incorrect random dwelling replacement of the only oversized
H3 dwelling - Portal of Glory
- Game will now detect & report invalid dwelling templates from mods
- Updated docs to clarify dwellings format

lib/mapObjects/CGObjectInstance.cpp

@@ -121,7 +121,7 @@ const std::set<int3> & CGObjectInstance::getBlockedOffsets() const
 void CGObjectInstance::setType(MapObjectID newID, MapObjectSubID newSubID)
 {
 	auto position = visitablePos();
-	auto oldOffset = getVisitableOffset();
+	auto oldOffset = appearance->getCornerOffset();
 	auto &tile = cb->gameState().getMap().getTile(position);
 
 	//recalculate blockvis tiles - new appearance might have different blockmap than before
@@ -144,11 +144,12 @@ void CGObjectInstance::setType(MapObjectID newID, MapObjectSubID newSubID)
 	// instead, appearance update & pos adjustment occurs in GiveHero::applyGs
 	needToAdjustOffset |= this->ID == Obj::PRISON && newID == Obj::HERO;
 	needToAdjustOffset |= newID == Obj::MONSTER;
+	needToAdjustOffset |= newID == Obj::CREATURE_GENERATOR1 || newID == Obj::CREATURE_GENERATOR2 || newID == Obj::CREATURE_GENERATOR3 || newID == Obj::CREATURE_GENERATOR4;
 
 	if(needToAdjustOffset)
 	{
 		// adjust position since object visitable offset might have changed
-		auto newOffset = getVisitableOffset();
+		auto newOffset = appearance->getCornerOffset();
 		pos = pos - oldOffset + newOffset;
 	}
 

lib/mapObjects/ObjectTemplate.cpp

@@ -500,6 +500,23 @@ void ObjectTemplate::calculateVisitableOffset()
 	visitableOffset = int3(0, 0, 0);
 }
 
+int3 ObjectTemplate::getCornerOffset() const
+{
+	assert(isVisitable());
+
+	int3 ret = visitableOffset;
+	for (const auto & tile : blockedOffsets)
+	{
+		ret = {
+			std::min(-tile.x, ret.x),
+			std::min(-tile.y, ret.y),
+			ret.z
+		};
+	}
+
+	return ret;
+}
+
 bool ObjectTemplate::canBePlacedAt(TerrainId terrainID) const
 {
 	if (anyLandTerrain)

lib/mapObjects/ObjectTemplate.h

@@ -124,6 +124,11 @@ public:
 	// Checks if object can be placed on specific terrain
 	bool canBePlacedAt(TerrainId terrain) const;
 
+	/// Returns number of completely empty rows & columns in template
+	/// Such as shifted wandering monster def's from hota, or Portal of Glory dwelling from H3
+	/// object must be visitable
+	int3 getCornerOffset() const;
+
 	CompoundMapObjectID getCompoundID() const;
 
 	ObjectTemplate();