From 84fa2bcb7a91874c0e7fd0a4ef9e707326d9181c Mon Sep 17 00:00:00 2001
From: Afloat <132809511+Afloat16@users.noreply.github.com>
Date: Tue, 3 Nov 2026 08:12:47 -0500
Subject: [PATCH] fix(mobile): clip occupancy updates to grid bounds

---
 src/roboticstoolbox/mobile/OccGrid.py |  8 +++++--
 tests/test_mobile_maps.py             | 31 +++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/roboticstoolbox/mobile/OccGrid.py b/src/roboticstoolbox/mobile/OccGrid.py
index 8b490acb2..1c7fb9484 100644
--- a/src/roboticstoolbox/mobile/OccGrid.py
+++ b/src/roboticstoolbox/mobile/OccGrid.py
@@ -285,11 +285,15 @@ def set(self, region: ArrayLike4, value: float | bool) -> None:
         :param value: value to set cells to
 
         The cells that contain the corners of the region, and all those between
-        them, are set.
+        them, are set.  Only cells inside the grid are changed; a region
+        entirely outside the grid has no effect.
         """
         bl = self.w2g([region[0], region[2]])
         tr = self.w2g([region[1], region[3]])
-        self.grid[bl[1] : tr[1] + 1, bl[0] : tr[0] + 1] = value
+        bl = np.maximum(bl, 0)
+        tr = np.minimum(tr, np.array(self.grid.shape[::-1]) - 1)
+        if np.all(bl <= tr):
+            self.grid[bl[1] : tr[1] + 1, bl[0] : tr[0] + 1] = value
 
     def grid_to_world(self, p: ArrayLike2) -> R2:
         """
diff --git a/tests/test_mobile_maps.py b/tests/test_mobile_maps.py
index c5c31ffdd..60c249f44 100644
--- a/tests/test_mobile_maps.py
+++ b/tests/test_mobile_maps.py
@@ -11,11 +11,42 @@
 import matplotlib.pyplot as plt
 import numpy as np
 import numpy.testing as nt
+import pytest
 from spatialmath import Polygon2
 
 from roboticstoolbox import BinaryOccupancyGrid, LandmarkMap, PolygonMap
 
 
+@pytest.mark.parametrize("cellsize, origin", [(1.0, (0.0, 0.0)), (0.5, (10.0, -3.0))])
+@pytest.mark.parametrize(
+    "bounds",
+    [
+        (-2, 2, -1, 1),
+        (4, 8, 2, 5),
+        (-5, -3, 1, 2),
+        (7, 9, 1, 2),
+        (1, 2, -4, -2),
+        (1, 2, 5, 7),
+    ],
+)
+def test_set_region_clips_to_grid(
+    cellsize: float, origin: tuple[float, float], bounds: tuple[int, int, int, int]
+) -> None:
+    grid = BinaryOccupancyGrid(np.zeros((4, 6)), cellsize=cellsize, origin=origin)
+    region = np.array(bounds) * cellsize + np.repeat(origin, 2)
+    columns, rows = np.meshgrid(np.arange(6), np.arange(4))
+    expected = (
+        (columns >= bounds[0])
+        & (columns <= bounds[1])
+        & (rows >= bounds[2])
+        & (rows <= bounds[3])
+    )
+
+    grid.set(region, True)
+
+    nt.assert_array_equal(grid.grid, expected)
+
+
 class TestOccupancyGrid(unittest.TestCase):
     def test_unknown_argument_is_an_error(self):
         # ``size`` used to be silently ignored, the argument is ``cellsize``