Phase 1: Safety & performance foundation for Grid/Entity overhaul

- Fix Entity3D self-reference cycle: replace raw `self` pointer with
  `pyobject` strong-ref pattern matching UIEntity (closes #266)
- TileLayer inherits Grid texture when none set, in all three attachment
  paths: constructor, add_layer(), and .grid property (closes #254)
- Add SpatialHash::queryCell() for O(1) entity-at-cell lookup; fix
  missing spatial_hash.insert() in Entity.__init__ grid= kwarg path;
  use queryCell in GridPoint.entities (closes #253)
- Add FOV dirty flag and parameter cache to skip redundant computeFOV
  calls when map unchanged and params match (closes #292)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/3d/Entity3D.cpp

@@ -59,8 +59,8 @@ Entity3D::Entity3D(int grid_x, int grid_z)
 
 Entity3D::~Entity3D()
 {
-    // Cleanup cube geometry when last entity is destroyed?
+    // Release Python identity reference (handles viewport destruction edge case)
-    // For now, leave it - it's shared static data
+    releasePyIdentity();
 
     // Clean up Python animation callback
     Py_XDECREF(py_anim_callback_);
@@ -468,7 +468,7 @@ void Entity3D::updateAnimation(float dt)
             // Fire Python callback
             if (py_anim_callback_) {
                 PyObject* result = PyObject_CallFunction(py_anim_callback_, "(Os)",
-                    self, anim_clip_.c_str());
+                    pyobject, anim_clip_.c_str());
                 if (result) {
                     Py_DECREF(result);
                 } else {
@@ -722,7 +722,9 @@ int Entity3D::init(PyEntity3DObject* self, PyObject* args, PyObject* kwds)
 
     // Register in object cache
     self->data->serial_number = PythonObjectCache::getInstance().assignSerial();
-    self->data->self = (PyObject*)self;
+    // Set strong ref for Python subclass identity preservation
+    self->data->pyobject = (PyObject*)self;
+    Py_INCREF((PyObject*)self);
 
     return 0;
 }

src/3d/Entity3D.h

@@ -42,9 +42,18 @@ struct VoxelPointState {
 class Entity3D : public std::enable_shared_from_this<Entity3D> {
 public:
     // Python integration
-    PyObject* self = nullptr;  // Reference to Python object
+    PyObject* pyobject = nullptr;  // Strong ref: preserves Python subclass identity while in viewport
     uint64_t serial_number = 0;  // For object cache
 
+    /// Release Python identity reference (call at all viewport exit points)
+    void releasePyIdentity() {
+        if (pyobject) {
+            PyObject* tmp = pyobject;
+            pyobject = nullptr;
+            Py_DECREF(tmp);
+        }
+    }
+
     Entity3D();
     Entity3D(int grid_x, int grid_z);
     ~Entity3D();
@@ -383,6 +392,8 @@ inline PyTypeObject PyEntity3DType = {
     {
         PyEntity3DObject* obj = (PyEntity3DObject*)self;
         PyObject_GC_UnTrack(self);
+        // Clear the identity ref without DECREF - we ARE this object
+        if (obj->data) obj->data->pyobject = nullptr;
         if (obj->weakreflist != NULL) {
             PyObject_ClearWeakRefs(self);
         }

src/Animation.cpp

@@ -631,10 +631,10 @@ static PyObject* convertEntity3DToPython(std::shared_ptr<mcrf::Entity3D> entity)
         Py_RETURN_NONE;
     }
 
-    // Use the entity's cached Python self pointer if available
+    // Use the entity's cached Python pyobject pointer if available
-    if (entity->self) {
+    if (entity->pyobject) {
-        Py_INCREF(entity->self);
+        Py_INCREF(entity->pyobject);
-        return entity->self;
+        return entity->pyobject;
     }
 
     // Create a new wrapper

src/GridLayers.cpp

@@ -6,6 +6,7 @@
 #include "PyFOV.h"
 #include "PyPositionHelper.h"
 #include "PyHeightMap.h"
+#include "PythonObjectCache.h"
 #include <sstream>
 
 // =============================================================================
@@ -1632,17 +1633,31 @@ PyObject* PyGridLayerAPI::ColorLayer_get_grid(PyColorLayerObject* self, void* cl
         Py_RETURN_NONE;
     }
 
-    // Create Python Grid wrapper for the parent grid
+    // Check cache first — preserves identity (layer.grid is layer.grid)
-    auto* grid_type = (PyTypeObject*)PyObject_GetAttrString(
+    if (self->grid->serial_number != 0) {
-        PyImport_ImportModule("mcrfpy"), "Grid");
+        PyObject* cached = PythonObjectCache::getInstance().lookup(self->grid->serial_number);
-    if (!grid_type) return NULL;
+        if (cached) {
+            return cached;
+        }
+    }
 
+    // No cached wrapper — allocate a new one
+    auto* grid_type = &mcrfpydef::PyUIGridType;
     PyUIGridObject* py_grid = (PyUIGridObject*)grid_type->tp_alloc(grid_type, 0);
-    Py_DECREF(grid_type);
     if (!py_grid) return NULL;
 
     py_grid->data = self->grid;
     py_grid->weakreflist = NULL;
+
+    // Register in cache
+    if (self->grid->serial_number == 0) {
+        self->grid->serial_number = PythonObjectCache::getInstance().assignSerial();
+    }
+    PyObject* weakref = PyWeakref_NewRef((PyObject*)py_grid, NULL);
+    if (weakref) {
+        PythonObjectCache::getInstance().registerObject(self->grid->serial_number, weakref);
+        Py_DECREF(weakref);
+    }
     return (PyObject*)py_grid;
 }
 
@@ -2267,17 +2282,31 @@ PyObject* PyGridLayerAPI::TileLayer_get_grid(PyTileLayerObject* self, void* clos
         Py_RETURN_NONE;
     }
 
-    // Create Python Grid wrapper for the parent grid
+    // Check cache first — preserves identity (layer.grid is layer.grid)
-    auto* grid_type = (PyTypeObject*)PyObject_GetAttrString(
+    if (self->grid->serial_number != 0) {
-        PyImport_ImportModule("mcrfpy"), "Grid");
+        PyObject* cached = PythonObjectCache::getInstance().lookup(self->grid->serial_number);
-    if (!grid_type) return NULL;
+        if (cached) {
+            return cached;
+        }
+    }
 
+    // No cached wrapper — allocate a new one
+    auto* grid_type = &mcrfpydef::PyUIGridType;
     PyUIGridObject* py_grid = (PyUIGridObject*)grid_type->tp_alloc(grid_type, 0);
-    Py_DECREF(grid_type);
     if (!py_grid) return NULL;
 
     py_grid->data = self->grid;
     py_grid->weakreflist = NULL;
+
+    // Register in cache
+    if (self->grid->serial_number == 0) {
+        self->grid->serial_number = PythonObjectCache::getInstance().assignSerial();
+    }
+    PyObject* weakref = PyWeakref_NewRef((PyObject*)py_grid, NULL);
+    if (weakref) {
+        PythonObjectCache::getInstance().registerObject(self->grid->serial_number, weakref);
+        Py_DECREF(weakref);
+    }
     return (PyObject*)py_grid;
 }
 
@@ -2360,6 +2389,11 @@ int PyGridLayerAPI::TileLayer_set_grid(PyTileLayerObject* self, PyObject* value,
     py_grid->data->layers_need_sort = true;
     self->grid = py_grid->data;
 
+    // Inherit grid texture if TileLayer has none (#254)
+    if (!self->data->texture) {
+        self->data->texture = py_grid->data->getTexture();
+    }
+
     return 0;
 }
 

src/SpatialHash.cpp

@@ -72,6 +72,28 @@ void SpatialHash::update(std::shared_ptr<UIEntity> entity, float old_x, float ol
     buckets[new_bucket].push_back(entity);
 }
 
+std::vector<std::shared_ptr<UIEntity>> SpatialHash::queryCell(int x, int y) const
+{
+    std::vector<std::shared_ptr<UIEntity>> result;
+
+    auto bucket_coord = getBucket(static_cast<float>(x), static_cast<float>(y));
+    auto it = buckets.find(bucket_coord);
+    if (it == buckets.end()) return result;
+
+    for (const auto& wp : it->second) {
+        auto entity = wp.lock();
+        if (!entity) continue;
+
+        // Exact integer position match
+        if (static_cast<int>(entity->position.x) == x &&
+            static_cast<int>(entity->position.y) == y) {
+            result.push_back(entity);
+        }
+    }
+
+    return result;
+}
+
 std::vector<std::pair<int, int>> SpatialHash::getBucketsInRadius(float x, float y, float radius) const
 {
     std::vector<std::pair<int, int>> result;

src/SpatialHash.h

@@ -33,6 +33,10 @@ public:
     // This removes from old bucket and inserts into new bucket if needed
     void update(std::shared_ptr<UIEntity> entity, float old_x, float old_y);
 
+    // Query all entities at a specific cell (exact integer position match)
+    // O(n) where n = entities in the bucket containing this cell
+    std::vector<std::shared_ptr<UIEntity>> queryCell(int x, int y) const;
+
     // Query all entities within radius of a point
     // Returns entities whose positions are within the circular radius
     std::vector<std::shared_ptr<UIEntity>> queryRadius(float x, float y, float radius) const;

src/UIEntity.cpp

@@ -281,6 +281,8 @@ int UIEntity::init(PyUIEntityObject* self, PyObject* args, PyObject* kwds) {
         self->data->grid = pygrid->data;
         // Append entity to grid's entity list
         pygrid->data->entities->push_back(self->data);
+        // Insert into spatial hash for O(1) cell queries (#253)
+        pygrid->data->spatial_hash.insert(self->data);
 
         // Don't initialize gridstate here - lazy initialization to support large numbers of entities
         // gridstate will be initialized when visibility is updated or accessed
@@ -634,14 +636,33 @@ PyObject* UIEntity::get_grid(PyUIEntityObject* self, void* closure)
         Py_RETURN_NONE;
     }
 
-    // Return a Python Grid object wrapping the C++ grid
+    auto& grid = self->data->grid;
-    auto grid_type = &mcrfpydef::PyUIGridType;
 
+    // Check cache first — preserves identity (entity.grid is entity.grid)
+    if (grid->serial_number != 0) {
+        PyObject* cached = PythonObjectCache::getInstance().lookup(grid->serial_number);
+        if (cached) {
+            return cached;  // Already INCREF'd by lookup
+        }
+    }
+
+    // No cached wrapper — allocate a new one
+    auto grid_type = &mcrfpydef::PyUIGridType;
     auto pyGrid = (PyUIGridObject*)grid_type->tp_alloc(grid_type, 0);
 
     if (pyGrid) {
-        pyGrid->data = self->data->grid;
+        pyGrid->data = grid;
         pyGrid->weakreflist = NULL;
+
+        // Register in cache so future accesses return the same wrapper
+        if (grid->serial_number == 0) {
+            grid->serial_number = PythonObjectCache::getInstance().assignSerial();
+        }
+        PyObject* weakref = PyWeakref_NewRef((PyObject*)pyGrid, NULL);
+        if (weakref) {
+            PythonObjectCache::getInstance().registerObject(grid->serial_number, weakref);
+            Py_DECREF(weakref);
+        }
     }
     return (PyObject*)pyGrid;
 }

src/UIGrid.cpp

@@ -575,6 +575,7 @@ void UIGrid::syncTCODMap()
             tcod_map->setProperties(x, y, point.transparent, point.walkable);
         }
     }
+    fov_dirty = true;  // #292: map changed, FOV needs recomputation
 }
 
 void UIGrid::syncTCODMapCell(int x, int y)
@@ -583,14 +584,32 @@ void UIGrid::syncTCODMapCell(int x, int y)
 
     const UIGridPoint& point = at(x, y);
     tcod_map->setProperties(x, y, point.transparent, point.walkable);
+    fov_dirty = true;  // #292: cell changed, FOV needs recomputation
 }
 
 void UIGrid::computeFOV(int x, int y, int radius, bool light_walls, TCOD_fov_algorithm_t algo)
 {
     if (!tcod_map || x < 0 || x >= grid_w || y < 0 || y >= grid_h) return;
 
+    // #292: Skip redundant FOV computation if map hasn't changed and params match
+    if (!fov_dirty &&
+        x == fov_last_x && y == fov_last_y &&
+        radius == fov_last_radius &&
+        light_walls == fov_last_light_walls &&
+        algo == fov_last_algo) {
+        return;
+    }
+
     std::lock_guard<std::mutex> lock(fov_mutex);
     tcod_map->computeFov(x, y, radius, light_walls, algo);
+
+    // Cache parameters for deduplication
+    fov_dirty = false;
+    fov_last_x = x;
+    fov_last_y = y;
+    fov_last_radius = radius;
+    fov_last_light_walls = light_walls;
+    fov_last_algo = algo;
 }
 
 bool UIGrid::isInFOV(int x, int y) const
@@ -1101,6 +1120,12 @@ int UIGrid::init(PyUIGridObject* self, PyObject* args, PyObject* kwds) {
                 self->data->layers.push_back(layer);
                 py_layer->grid = self->data;
 
+                // Inherit grid texture if TileLayer has none (#254)
+                auto tile_layer_ptr = std::static_pointer_cast<TileLayer>(layer);
+                if (!tile_layer_ptr->texture) {
+                    tile_layer_ptr->texture = self->data->getTexture();
+                }
+
             } else {
                 Py_DECREF(item);
                 Py_DECREF(iterator);
@@ -1720,6 +1745,12 @@ PyObject* UIGrid::py_add_layer(PyUIGridObject* self, PyObject* args) {
         self->data->layers_need_sort = true;
         py_layer->grid = self->data;
 
+        // Inherit grid texture if TileLayer has none (#254)
+        auto tile_layer = std::static_pointer_cast<TileLayer>(layer);
+        if (!tile_layer->texture) {
+            tile_layer->texture = self->data->getTexture();
+        }
+
     } else {
         Py_DECREF(color_layer_type);
         Py_DECREF(tile_layer_type);

src/UIGrid.h

@@ -135,6 +135,13 @@ public:
     TCOD_fov_algorithm_t fov_algorithm;           // Default FOV algorithm (from mcrfpy.default_fov)
     int fov_radius;                               // Default FOV radius
 
+    // #292 - FOV deduplication: skip redundant computations
+    bool fov_dirty = true;                        // Set true when TCOD map changes
+    int fov_last_x = -1, fov_last_y = -1;        // Last FOV computation parameters
+    int fov_last_radius = -1;
+    bool fov_last_light_walls = true;
+    TCOD_fov_algorithm_t fov_last_algo = FOV_BASIC;
+
     // #142, #230 - Grid cell mouse events
     // Cell hover callbacks take only (cell_pos); cell click still takes (cell_pos, button, action)
     std::unique_ptr<PyCellHoverCallable> on_cell_enter_callable;

src/UIGridPoint.cpp

@@ -41,11 +41,12 @@ sf::Color PyObject_to_sfColor(PyObject* obj) {
 // #150 - Removed get_color/set_color - now handled by layers
 
 // Helper to safely get the GridPoint data from coordinates
+// Routes through UIGrid::at() which handles both flat and chunked storage
 static UIGridPoint* getGridPointData(PyUIGridPointObject* self) {
     if (!self->grid) return nullptr;
-    int idx = self->y * self->grid->grid_w + self->x;
+    if (self->x < 0 || self->x >= self->grid->grid_w ||
-    if (idx < 0 || idx >= static_cast<int>(self->grid->points.size())) return nullptr;
+        self->y < 0 || self->y >= self->grid->grid_h) return nullptr;
-    return &self->grid->points[idx];
+    return &self->grid->at(self->x, self->y);
 }
 
 PyObject* UIGridPoint::get_bool_member(PyUIGridPointObject* self, void* closure) {
@@ -94,7 +95,7 @@ int UIGridPoint::set_bool_member(PyUIGridPointObject* self, PyObject* value, voi
 
 // #150 - Removed get_int_member/set_int_member - now handled by layers
 
-// #114 - Get list of entities at this grid cell
+// #114, #253 - Get list of entities at this grid cell (uses spatial hash for O(1) lookup)
 PyObject* UIGridPoint::get_entities(PyUIGridPointObject* self, void* closure) {
     if (!self->grid) {
         PyErr_SetString(PyExc_RuntimeError, "GridPoint has no parent grid");
@@ -107,25 +108,23 @@ PyObject* UIGridPoint::get_entities(PyUIGridPointObject* self, void* closure) {
     PyObject* list = PyList_New(0);
     if (!list) return NULL;
 
-    // Iterate through grid's entities and find those at this position
+    // Use spatial hash for O(bucket_size) lookup instead of O(n) iteration
-    for (auto& entity : *(self->grid->entities)) {
+    auto entities = self->grid->spatial_hash.queryCell(target_x, target_y);
-        if (static_cast<int>(entity->position.x) == target_x &&
+    for (auto& entity : entities) {
-            static_cast<int>(entity->position.y) == target_y) {
+        // Create Python Entity object for this entity
-            // Create Python Entity object for this entity
+        auto type = &mcrfpydef::PyUIEntityType;
-            auto type = &mcrfpydef::PyUIEntityType;
+        auto obj = (PyUIEntityObject*)type->tp_alloc(type, 0);
-            auto obj = (PyUIEntityObject*)type->tp_alloc(type, 0);
+        if (!obj) {
-            if (!obj) {
+            Py_DECREF(list);
-                Py_DECREF(list);
+            return NULL;
-                return NULL;
-            }
-            obj->data = entity;
-            if (PyList_Append(list, (PyObject*)obj) < 0) {
-                Py_DECREF(obj);
-                Py_DECREF(list);
-                return NULL;
-            }
-            Py_DECREF(obj);  // List now owns the reference
         }
+        obj->data = entity;
+        if (PyList_Append(list, (PyObject*)obj) < 0) {
+            Py_DECREF(obj);
+            Py_DECREF(list);
+            return NULL;
+        }
+        Py_DECREF(obj);  // List now owns the reference
     }
 
     return list;

tests/regression/issue_253_spatial_hash_test.py

@@ -0,0 +1,73 @@
+"""Regression test for #253: GridPoint.entities uses spatial hash for O(1) lookup."""
+import mcrfpy
+import sys
+
+def test_gridpoint_entities_basic():
+    """Entities at known positions are returned correctly."""
+    scene = mcrfpy.Scene("test253")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    # Place entities at specific cells
+    e1 = mcrfpy.Entity((5, 5), grid=grid)
+    e2 = mcrfpy.Entity((5, 5), grid=grid)
+    e3 = mcrfpy.Entity((10, 10), grid=grid)
+
+    # Query cell (5, 5) - should have 2 entities
+    cell_5_5 = grid.at(5, 5)
+    ents = cell_5_5.entities
+    assert len(ents) == 2, f"Expected 2 entities at (5,5), got {len(ents)}"
+    print("PASS: 2 entities at (5,5)")
+
+    # Query cell (10, 10) - should have 1 entity
+    cell_10_10 = grid.at(10, 10)
+    ents = cell_10_10.entities
+    assert len(ents) == 1, f"Expected 1 entity at (10,10), got {len(ents)}"
+    print("PASS: 1 entity at (10,10)")
+
+def test_gridpoint_entities_empty():
+    """Empty cells return empty list."""
+    scene = mcrfpy.Scene("test253b")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    # No entities placed - empty cell should return empty list
+    cell = grid.at(0, 0)
+    ents = cell.entities
+    assert len(ents) == 0, f"Expected 0 entities, got {len(ents)}"
+    print("PASS: empty cell returns empty list")
+
+def test_gridpoint_entities_after_move():
+    """Moving an entity updates spatial hash so GridPoint.entities reflects new position."""
+    scene = mcrfpy.Scene("test253c")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    e = mcrfpy.Entity((3, 3), grid=grid)
+
+    # Verify entity is at (3, 3)
+    assert len(grid.at(3, 3).entities) == 1, "Entity should be at (3,3)"
+
+    # Move entity to (7, 7)
+    e.grid_pos = (7, 7)
+
+    # Old cell should be empty, new cell should have the entity
+    assert len(grid.at(3, 3).entities) == 0, "Old cell should be empty after move"
+    assert len(grid.at(7, 7).entities) == 1, "New cell should have entity after move"
+    print("PASS: entity move updates spatial hash correctly")
+
+if __name__ == "__main__":
+    test_gridpoint_entities_basic()
+    test_gridpoint_entities_empty()
+    test_gridpoint_entities_after_move()
+    print("All #253 tests passed")
+    sys.exit(0)

tests/regression/issue_254_tilelayer_texture_test.py

@@ -0,0 +1,67 @@
+"""Regression test for #254: TileLayer inherits Grid texture when none set."""
+import mcrfpy
+import sys
+
+def test_tilelayer_texture_inheritance():
+    """TileLayer without texture should inherit grid's texture on attachment."""
+    scene = mcrfpy.Scene("test254")
+    mcrfpy.current_scene = scene
+
+    # Create grid with texture
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(10, 10), texture=tex, pos=(0, 0), size=(160, 160))
+    scene.children.append(grid)
+
+    # Create TileLayer WITHOUT texture
+    layer_no_tex = mcrfpy.TileLayer(name="terrain", z_index=0)
+    grid.add_layer(layer_no_tex)
+
+    # Verify it inherited the grid's texture
+    assert layer_no_tex.texture is not None, "TileLayer should inherit grid texture"
+    print("PASS: TileLayer without texture inherits grid texture")
+
+    # Create TileLayer WITH explicit texture
+    tex2 = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    layer_with_tex = mcrfpy.TileLayer(name="overlay", z_index=1, texture=tex2)
+    grid.add_layer(layer_with_tex)
+
+    # Verify it kept its own texture
+    assert layer_with_tex.texture is not None, "TileLayer with texture should keep it"
+    print("PASS: TileLayer with explicit texture keeps its own")
+
+def test_tilelayer_texture_via_constructor():
+    """TileLayer passed in Grid constructor should also inherit texture."""
+    scene = mcrfpy.Scene("test254b")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    layer = mcrfpy.TileLayer(name="base", z_index=0)
+
+    grid = mcrfpy.Grid(grid_size=(10, 10), texture=tex, pos=(0, 0), size=(160, 160),
+                        layers=[layer])
+    scene.children.append(grid)
+
+    assert layer.texture is not None, "TileLayer in constructor should inherit grid texture"
+    print("PASS: TileLayer in constructor inherits grid texture")
+
+def test_tilelayer_texture_via_grid_property():
+    """TileLayer attached via layer.grid = grid should inherit texture."""
+    scene = mcrfpy.Scene("test254c")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(10, 10), texture=tex, pos=(0, 0), size=(160, 160))
+    scene.children.append(grid)
+
+    layer = mcrfpy.TileLayer(name="via_prop", z_index=0)
+    layer.grid = grid
+
+    assert layer.texture is not None, "TileLayer attached via .grid should inherit texture"
+    print("PASS: TileLayer via .grid property inherits grid texture")
+
+if __name__ == "__main__":
+    test_tilelayer_texture_inheritance()
+    test_tilelayer_texture_via_constructor()
+    test_tilelayer_texture_via_grid_property()
+    print("All #254 tests passed")
+    sys.exit(0)

tests/regression/issue_292_fov_dedup_test.py

@@ -0,0 +1,118 @@
+"""Regression test for #292: Deduplicate FOV computation via dirty flag."""
+import mcrfpy
+import sys
+
+def test_fov_basic_correctness():
+    """FOV computation still works correctly with dirty flag."""
+    scene = mcrfpy.Scene("test292")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    # Make all cells transparent and walkable
+    for y in range(20):
+        for x in range(20):
+            pt = grid.at(x, y)
+            pt.walkable = True
+            pt.transparent = True
+
+    # Compute FOV from center
+    grid.compute_fov((10, 10), radius=5)
+
+    # Center should be visible
+    assert grid.is_in_fov((10, 10)), "Center should be in FOV"
+    # Nearby cell should be visible
+    assert grid.is_in_fov((10, 11)), "Adjacent cell should be in FOV"
+    # Far cell should NOT be visible
+    assert not grid.is_in_fov((0, 0)), "Far cell should not be in FOV"
+    print("PASS: FOV basic correctness")
+
+def test_fov_duplicate_call():
+    """Calling computeFOV twice with same params should still give correct results."""
+    scene = mcrfpy.Scene("test292b")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    for y in range(20):
+        for x in range(20):
+            pt = grid.at(x, y)
+            pt.walkable = True
+            pt.transparent = True
+
+    # Compute FOV twice with same params (second should be skipped internally)
+    grid.compute_fov((10, 10), radius=5)
+    result1 = grid.is_in_fov((10, 11))
+
+    grid.compute_fov((10, 10), radius=5)
+    result2 = grid.is_in_fov((10, 11))
+
+    assert result1 == result2, "Duplicate FOV call should give same result"
+    print("PASS: Duplicate FOV call gives same result")
+
+def test_fov_updates_after_map_change():
+    """FOV should recompute after a cell's walkable/transparent changes."""
+    scene = mcrfpy.Scene("test292c")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    for y in range(20):
+        for x in range(20):
+            pt = grid.at(x, y)
+            pt.walkable = True
+            pt.transparent = True
+
+    # Compute FOV - cell (10, 12) should be visible
+    grid.compute_fov((10, 10), radius=5)
+    assert grid.is_in_fov((10, 12)), "Cell should be visible initially"
+
+    # Block line of sight by making (10, 11) opaque
+    grid.at(10, 11).transparent = False
+
+    # Recompute FOV with same params - dirty flag should force recomputation
+    grid.compute_fov((10, 10), radius=5)
+    assert not grid.is_in_fov((10, 12)), "Cell behind wall should not be visible after map change"
+    print("PASS: FOV updates correctly after map change")
+
+def test_fov_different_params_recompute():
+    """FOV should recompute when params change even if map hasn't."""
+    scene = mcrfpy.Scene("test292d")
+    mcrfpy.current_scene = scene
+
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    for y in range(20):
+        for x in range(20):
+            pt = grid.at(x, y)
+            pt.walkable = True
+            pt.transparent = True
+
+    # Compute from (10, 10) with radius 3
+    grid.compute_fov((10, 10), radius=3)
+    visible_3 = grid.is_in_fov((10, 14))
+
+    # Compute from (10, 10) with radius 5 - different params should recompute
+    grid.compute_fov((10, 10), radius=5)
+    visible_5 = grid.is_in_fov((10, 14))
+
+    # Radius 3 shouldn't see (10, 14), but radius 5 should
+    assert not visible_3, "(10,14) should not be visible with radius 3"
+    assert visible_5, "(10,14) should be visible with radius 5"
+    print("PASS: Different FOV params force recomputation")
+
+if __name__ == "__main__":
+    test_fov_basic_correctness()
+    test_fov_duplicate_call()
+    test_fov_updates_after_map_change()
+    test_fov_different_params_recompute()
+    print("All #292 tests passed")
+    sys.exit(0)