fixup! SceneGadget : Add normalAt` method

src/GafferSceneUI/SceneGadget.cpp

@@ -653,8 +653,8 @@ std::optional<V3f> SceneGadget::normalAt( const IECore::LineSegment3f &lineInGad
 
 	// Transforming from raster to gadget space (done by `Widget`) and back to raster space
 	// can introduce enough floating point error to make positions, and therefore normals,
-	// incorrect. We know that the incoming `lineInGadgetSpace` has been calculated from
-	// an integeer pixel value so we snap to the nearest integer as a corrective.
+	// incorrect. We expect that `lineInGadgetSpace` corresponds to the center of a pixel,
+	// so we snap to the nearest center as a corrective.
 	V2f centerRasterP = viewportGadget->gadgetToRasterSpace( lineInGadgetSpace.p0, this );
 	centerRasterP.x = (int)centerRasterP.x + 0.5f;
 	centerRasterP.y = (int)centerRasterP.y + 0.5f;