Make ‘delete-trailing-whitespace’ delete spaces after form feed

* lisp/simple.el (delete-trailing-whitespace): Treat form fead as
a non-whitespace character (regradless of whether it’s character syntax
is whitespace) and delete any whitespace following it instead of leaving
lines with form feeds completely unchanged.  I.e. a line like "\f " will
now became "\f".

1 files changed, 6 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 2f2ae65da8d..bc8b097d460 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -187,6 +187,12 @@ questions, with a handy way to display help texts.
 'undo', undo the last replacement; bound to 'u'.
 'undo-all', undo all replacements; bound to 'U'.
 
+** 'delete-trailing-whitespace' deletes whitespace after form feed.
+In modes where form feed was treated as a whitespace character,
+'delete-trailing-whitespace' would keep lines containing it unchanged.
+It now deletes whitespace after the last form feed thus behaving the
+same as in modes where the character is not whitespace.
+
 
 * Changes in Specialized Modes and Packages in Emacs 25.2