Merge from origin/emacs-26

a5da653 * src/editfns.c (Fnarrow_to_region): Doc fix.  (Bug#35163)
646d33d Fix doc strings of 'vc-version-diff' and 'vc-version-ediff'
a30a6c3 Improve documentation of set-window-start
92ce2dd Improve documentation of window parameters
6dc42c5 Improve commentary in frame.el
a8cffcf Fix typo in a doc string
9e79f19 (emacs-26) ; * src/fontset.c (set-fontset-font): Use uppercas...

# Conflicts:
#	lisp/vc/vc.el

1 files changed, 6 insertions, 1 deletions

diff --git a/src/window.c b/src/window.c
index f911c0c7d44..ef2ed638508 100644
--- a/src/window.c
+++ b/src/window.c
@@ -1796,7 +1796,12 @@ DEFUN ("set-window-start", Fset_window_start, Sset_window_start, 2, 3, 0,
        doc: /* Make display in WINDOW start at position POS in WINDOW's buffer.
 WINDOW must be a live window and defaults to the selected one.  Return
 POS.  Optional third arg NOFORCE non-nil inhibits next redisplay from
-overriding motion of point in order to display at this exact start.  */)
+overriding motion of point in order to display at this exact start.
+
+For reliable setting of WINDOW start position, make sure point is
+at a position that will be visible when that start is in effect,
+otherwise there's a chance POS will be disregarded, e.g., if point
+winds up in a partially-visible line.  */)
   (Lisp_Object window, Lisp_Object pos, Lisp_Object noforce)
 {
   register struct window *w = decode_live_window (window);