Add option to consider buildings as destroyable pathfinding obstacles

CREDITS.md

@@ -223,6 +223,7 @@ This page lists all the individual contributions to the project by their author.
   - Projectile return weapon
   - Aircraft landing / docking direction
   - `DeploysInto` cursor desync fix
+  - Buildings considered as destroyable pathfinding obstacles
 - **Morton (MortonPL)**:
   - `XDrawOffset` for animations
   - Shield passthrough & absorption

docs/New-or-Enhanced-Logics.md

@@ -322,6 +322,16 @@ PowersUp.Owner=Self ; list of Affected House Enumeration (none|owner/self|allies
 PowersUp.Buildings= ; list of BuildingTypes
 ```
 
+### Destroyable pathfinding obstacles
+
+It is possible to make buildings be considered pathfinding obstacles that can be destroyed by setting `IsDestroyableBlockage` to true. What this does is make the building be considered impassable and impenetrable pathfinding obstacle to every unit that is not flying or have appropriate `MovementZone` (ones that allow destroyable obstacles to be overcome, e.g `(Infantry|Amphibious)Destroyer`) akin to wall overlays and TerrainTypes.
+
+In `rulesmd.ini`:
+```ini
+[SOMEBUILDING]               ; BuildingType
+IsDestroyableObstacle=false  ; boolean
+```
+
 ### Power plant enhancer
 
 - When it exists, it can increase the power amount generated by the power plants.

docs/Whats-New.md

@@ -389,6 +389,7 @@ New:
 - Allow upgrade animations to use `Powered` & `PoweredLight/Effect/Special` keys (by Starkku)
 - Toggle for `Explodes=true` BuildingTypes to not explode during buildup or being sold (by Starkku)
 - Toggleable height-based shadow scaling for voxel air units (by Trsdy & Starkku)
+- Buildings considered as destroyable pathfinding obstacles (by Starkku)
 
 Vanilla fixes:
 - Allow AI to repair structures built from base nodes/trigger action 125/SW delivery in single player missions (by Trsdy)

src/Ext/Building/Body.cpp

@@ -328,6 +328,51 @@ bool BuildingExt::HandleInfiltrate(BuildingClass* pBuilding, HouseClass* pInfilt
 	return true;
 }
 
+// Get all cells covered by the building, optionally including those covered by OccupyHeight.
+const std::vector<CellStruct> BuildingExt::GetFoundationCells(BuildingClass* const pThis, CellStruct const baseCoords, bool includeOccupyHeight)
+{
+	const CellStruct foundationEnd = { 0x7FFF, 0x7FFF };
+	auto const pFoundation = pThis->GetFoundationData(false);
+
+	int occupyHeight = includeOccupyHeight ? pThis->Type->OccupyHeight : 1;
+
+	if (occupyHeight <= 0)
+		occupyHeight = 1;
+
+	auto pCellIterator = pFoundation;
+
+	while (*pCellIterator != foundationEnd)
+		++pCellIterator;
+
+	std::vector<CellStruct> foundationCells;
+	foundationCells.reserve(static_cast<int>(std::distance(pFoundation, pCellIterator + 1)) * occupyHeight);
+	pCellIterator = pFoundation;
+
+	while (*pCellIterator != foundationEnd)
+	{
+		auto actualCell = baseCoords + *pCellIterator;
+
+		for (auto i = occupyHeight; i > 0; --i)
+		{
+			foundationCells.push_back(actualCell);
+			--actualCell.X;
+			--actualCell.Y;
+		}
+		++pCellIterator;
+	}
+
+	std::sort(foundationCells.begin(), foundationCells.end(),
+		[](const CellStruct& lhs, const CellStruct& rhs) -> bool
+	{
+		return lhs.X > rhs.X || lhs.X == rhs.X && lhs.Y > rhs.Y;
+	});
+
+	auto const it = std::unique(foundationCells.begin(), foundationCells.end());
+	foundationCells.erase(it, foundationCells.end());
+
+	return foundationCells;
+}
+
 // =============================
 // load / save
 

src/Ext/Building/Body.h

@@ -104,4 +104,5 @@ class BuildingExt
 	static bool DoGrindingExtras(BuildingClass* pBuilding, TechnoClass* pTechno, int refund);
 	static bool HandleInfiltrate(BuildingClass* pBuilding, HouseClass* pInfiltratorHouse);
 	static bool CanUndeployOnSell(BuildingClass* pThis);
+	static const std::vector<CellStruct> GetFoundationCells(BuildingClass* pThis, CellStruct baseCoords, bool includeOccupyHeight = false);
 };

src/Ext/Building/Hooks.cpp

@@ -419,3 +419,69 @@ DEFINE_HOOK(0x4511D6, BuildingClass_AnimationAI_SellBuildup, 0x7)
 
 	return pTypeExt->SellBuildupLength == pThis->Animation.Value ? Continue : Skip;
 }
+
+#pragma region DestroyableObstacle
+
+template <bool remove = false>
+static void RecalculateCells(BuildingClass* pThis)
+{
+	auto const cells = BuildingExt::GetFoundationCells(pThis, pThis->GetMapCoords());
+
+	auto& map = MapClass::Instance;
+
+	for (auto const& cell : cells)
+	{
+		if (auto pCell = map->TryGetCellAt(cell))
+		{
+			pCell->RecalcAttributes(DWORD(-1));
+
+			if constexpr (remove)
+				map->ResetZones(cell);
+			else
+				map->RecalculateZones(cell);
+
+			map->RecalculateSubZones(cell);
+
+		}
+	}
+}
+
+DEFINE_HOOK(0x440D01, BuildingClass_Unlimbo_DestroyableObstacle, 0x6)
+{
+	GET(BuildingClass*, pThis, ESI);
+
+	auto const pTypeExt = BuildingTypeExt::ExtMap.Find(pThis->Type);
+
+	if (pTypeExt->IsDestroyableObstacle)
+		RecalculateCells(pThis);
+
+	return 0;
+}
+
+DEFINE_HOOK(0x445D87, BuildingClass_Limbo_DestroyableObstacle, 0x6)
+{
+	GET(BuildingClass*, pThis, ESI);
+
+	auto const pTypeExt = BuildingTypeExt::ExtMap.Find(pThis->Type);
+
+	if (pTypeExt->IsDestroyableObstacle)
+		RecalculateCells<true>(pThis);
+
+	return 0;
+}
+
+DEFINE_HOOK(0x483D8E, CellClass_CheckPassability_DestroyableObstacle, 0x6)
+{
+	enum { IsBlockage = 0x483CD4 };
+
+	GET(BuildingClass*, pBuilding, ESI);
+
+	auto const pTypeExt = BuildingTypeExt::ExtMap.Find(pBuilding->Type);
+
+	if (pTypeExt->IsDestroyableObstacle)
+		return IsBlockage;
+
+	return 0;
+}
+
+#pragma endregion

src/Ext/BuildingType/Body.cpp

@@ -147,6 +147,7 @@ void BuildingTypeExt::ExtData::LoadFromINIFile(CCINIClass* const pINI)
 
 	this->ConsideredVehicle.Read(exINI, pSection, "ConsideredVehicle");
 	this->SellBuildupLength.Read(exINI, pSection, "SellBuildupLength");
+	this->IsDestroyableObstacle.Read(exINI, pSection, "IsDestroyableObstacle");
 
 	if (pThis->NumberOfDocks > 0)
 	{
@@ -259,6 +260,7 @@ void BuildingTypeExt::ExtData::Serialize(T& Stm)
 		.Process(this->ZShapePointMove_OnBuildup)
 		.Process(this->SellBuildupLength)
 		.Process(this->AircraftDockingDirs)
+		.Process(this->IsDestroyableObstacle)
 		;
 }
 

src/Ext/BuildingType/Body.h

@@ -61,6 +61,7 @@ class BuildingTypeExt
 		Nullable<bool> ConsideredVehicle;
 		Valueable<bool> ZShapePointMove_OnBuildup;
 		Valueable<int> SellBuildupLength;
+		Valueable<bool> IsDestroyableObstacle;
 
 		std::vector<OptionalStruct<DirType, true>> AircraftDockingDirs;
 
@@ -101,6 +102,7 @@ class BuildingTypeExt
 			, ZShapePointMove_OnBuildup { false }
 			, SellBuildupLength { 23 }
 			, AircraftDockingDirs {}
+			, IsDestroyableObstacle { false }
 		{ }
 
 		// Ares 0.A functions