src/xdisp.c (try_window_id): Update commentary.

1 files changed, 9 insertions, 2 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index de553a71f97..99471d1df19 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -17333,9 +17333,16 @@ row_containing_pos (struct window *w, ptrdiff_t charpos,
 
    Value is
 
-   1    if display has been updated
-   0    if otherwise unsuccessful
+   >= 1 if successful, i.e. display has been updated
+         specifically:
+         1 means the changes were in front of a newline that precedes
+           the window start, and the whole current matrix was reused
+         2 means the changes were after the last position displayed
+           in the window, and the whole current matrix was reused
+         3 means portions of the current matrix were reused, while
+           some of the screen lines were redrawn
    -1   if redisplay with same window start is known not to succeed
+   0    if otherwise unsuccessful
 
    The following steps are performed: