Fix byte-counting error in ‘format’

Problem reported by Paul Pogonyshev (Bug#38191).
* src/editfns.c (styled_format): When checking for adjacent
%-sequences, use byte position rather than character position.
* test/src/editfns-tests.el (format-properties): Test for fix.

1 files changed, 4 insertions, 0 deletions

diff --git a/test/src/editfns-tests.el b/test/src/editfns-tests.el
index a1060808f66..238fb409f0b 100644
--- a/test/src/editfns-tests.el
+++ b/test/src/editfns-tests.el
@@ -90,6 +90,10 @@
                                    (propertize "45" 'face 'italic)))
            #("012345    "
              0 2 (face bold) 2 4 (face underline) 4 10 (face italic))))
+  ;; Bug #38191
+  (should (ert-equal-including-properties
+           (format (propertize "‘foo’ %s bar" 'face 'bold) "xxx")
+           #("‘foo’ xxx bar" 0 13 (face bold))))
   ;; Bug #32404
   (should (ert-equal-including-properties
            (format (concat (propertize "%s" 'face 'bold)