Fix highlighting right at the edge of a non-scrolled line

babi/file.py

@@ -805,7 +805,7 @@ class File:
                     else:
                         h_s_x = region.x - l_x
 
-                    if region.end >= l_x_max:
+                    if region.end >= l_x_max and l_x_max < len(self.buf[l_y]):
                         if file_hl.include_edge:
                             h_e_x = curses.COLS
                         else:

tests/features/syntax_highlight_test.py

@@ -113,3 +113,12 @@ def test_syntax_highlighting_one_off_left_of_screen(run, tmpdir):
         h.press('End')
         h.await_text_missing('?')
         h.assert_screen_attr_equals(1, [(236, 40, 0)] * 20)
+
+
+def test_syntax_highlighting_to_edge_of_screen(run, tmpdir):
+    f = tmpdir.join('f.demo')
+    f.write(f'# {"x" * 18}')
+
+    with run(str(f), term='screen-256color', width=20) as h, and_exit(h):
+        h.await_text('# xxx')
+        h.assert_screen_attr_equals(1, [(243, 40, 0)] * 20)