using half-open intervals for GridCell boundary checks

Author: kimit0310

src/graphomotor/core/models.py

@@ -167,7 +167,8 @@ def contains_points(self, points: pd.DataFrame) -> bool:
         """Check if a stroke belongs to this cell based on its centroid.
 
         Computes the centroid (mean x, mean y) of the provided points and checks
-        whether it falls within the cell boundaries (inclusive).
+        whether it falls within the cell boundaries. Uses half-open intervals
+        [min, max) to prevent double-assignment on shared grid edges.
 
         Args:
             points: DataFrame with 'x' and 'y' columns representing a stroke.
@@ -178,8 +179,8 @@ def contains_points(self, points: pd.DataFrame) -> bool:
         centroid_x = points["x"].mean()
         centroid_y = points["y"].mean()
         return (
-            self.x_min <= centroid_x <= self.x_max
-            and self.y_min <= centroid_y <= self.y_max
+            self.x_min <= centroid_x < self.x_max
+            and self.y_min <= centroid_y < self.y_max
         )
 
 

tests/unit/test_grid_cell.py

@@ -47,12 +47,18 @@ def test_stroke_centroid_outside_cell(cell: models.GridCell) -> None:
     assert not cell.contains_points(stroke_points)
 
 
-def test_stroke_centroid_on_boundary(cell: models.GridCell) -> None:
-    """Stroke whose centroid lands exactly on the cell boundary should be contained."""
+def test_stroke_centroid_on_lower_boundary(cell: models.GridCell) -> None:
+    """Stroke whose centroid lands on the lower/left boundary (min) is included."""
     stroke_points = pd.DataFrame({"x": [10.0, 10.0], "y": [88.0, 89.0]})
     assert cell.contains_points(stroke_points)
 
 
+def test_stroke_centroid_on_upper_boundary(cell: models.GridCell) -> None:
+    """Stroke whose centroid lands on the upper/right boundary (max) is excluded."""
+    stroke_points = pd.DataFrame({"x": [17.0, 18.0], "y": [97.0, 97.0]})
+    assert not cell.contains_points(stroke_points)
+
+
 def test_stroke_points_span_outside_but_centroid_inside(
     cell: models.GridCell,
 ) -> None: