Identify position after a newline as the start of the next line

Closes gh-10814

IPython/utils/tests/test_tokenutil.py

@@ -108,6 +108,12 b' def test_line_at_cursor():'
     assert line == "", ("Expected '', got %r" % line)
     assert offset == 0, ("Expected '', got %r" % line)
 
+    # The position after a newline should be the start of the following line.
+    cell = "One\nTwo\n"
+    (line, offset) = line_at_cursor(cell, cursor_pos=4)
+    nt.assert_equal(line, "Two\n")
+    nt.assert_equal(offset, 4)
+
 def test_muliline_statement():
     cell = """a = (1,
     3)

IPython/utils/tokenutil.py

@@ -44,7 +44,7 b' def line_at_cursor(cell, cursor_pos=0):'
     lines = cell.splitlines(True)
     for line in lines:
         next_offset = offset + len(line)
-        if next_offset >= cursor_pos:
+        if next_offset > cursor_pos:
             break
         offset = next_offset
     else: