Scroll right and left using wheel-right and wheel-left.

These changes also make use of touchpad and trackpad (Bug#26347).

* doc/emacs/frames.texi (Mouse Commands): Document horizontal
scrolling using the mouse wheel.

* lisp/mwheel.el (mwheel-scroll): Respond to wheel-right and wheel-left.
(mwheel-tilt-scroll-p, mwheel-flip-direction)
(mwheel-scroll-left-function, mwheel-scroll-right-function): New
defcustoms.
(mouse-wheel-left-event, mouse-wheel-right-event): New variables,
events that calls wheel-left/right.

* etc/NEWS: Mention horizontal scrolling using the mouse wheel.

1 files changed, 9 insertions, 0 deletions

diff --git a/doc/emacs/frames.texi b/doc/emacs/frames.texi
index d1fd4d0446e..68c12d272f8 100644
--- a/doc/emacs/frames.texi
+++ b/doc/emacs/frames.texi
@@ -207,6 +207,15 @@ buffers are scrolled.  The variable
 @code{mouse-wheel-progressive-speed} determines whether the scroll
 speed is linked to how fast you move the wheel.
 
+@vindex mwheel-tilt-scroll-p
+@vindex mwheel-flip-direction
+Emacs can also support horizontal scrolling if your mouse's wheel can
+be tilted.  This feature is off by default; the variable
+@code{mwheel-tilt-scroll-p} turns it on.  If you'd like to reverse the
+direction of horizontal scrolling, customize the variable
+@code{mwheel-flip-direction} to a non-@code{nil} value.
+
+
 @node Word and Line Mouse
 @section Mouse Commands for Words and Lines