bug#31662: [PATCH] fix double counting bug in term.el

[John Shahid]

Hi all,

Today I was trying to run fzf[1] in term when I ran into a weird issue
that will cause the term output to be clobbered with certain output. The
root cause seems to be a double counting in the column offset. This is
usually fine, unless `2*len(inserted text)' causes the point to be equal
to the window width. I fixed the issue and added a new test in the
attached patch

[1] https://github.com/junegunn/fzf

>From efeec7bb556084f7004a83faf679f724bb8a0fe8 Mon Sep 17 00:00:00 2001
From: John Shahid <jvshahid@gmail.com>
Date: Wed, 30 May 2018 23:55:16 -0400
Subject: [PATCH] * lisp/term.el (term-emulate-terminal): fix column double
 counting

---
 lisp/term.el            | 3 ++-
 test/lisp/term-tests.el | 7 +++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/lisp/term.el b/lisp/term.el
index 19e68ddb49..67cebda1be 100644
--- a/lisp/term.el
+++ b/lisp/term.el
@@ -2904,7 +2904,8 @@ term-emulate-terminal
                   (when (not (or (eobp) term-insert-mode))
                     (let ((pos (point)))
                       (term-move-columns columns)
-                      (delete-region pos (point))))
+                      (delete-region pos (point))
+                      (term-move-columns (- columns))))
                   ;; In insert mode if the current line
                   ;; has become too long it needs to be
                   ;; chopped off.
diff --git a/test/lisp/term-tests.el b/test/lisp/term-tests.el
index 8aaa61a210..e27dd0354d 100644
--- a/test/lisp/term-tests.el
+++ b/test/lisp/term-tests.el
@@ -89,6 +89,13 @@ term-test-screen-from-input
                                               "\e[2;1Hc"
                                               "\e[1;2Hb"
                                               "\e[1;1Ha") "" t))))
+  (should (equal "abcde    j"
+                 (term-test-screen-from-input
+                  10 12 (concat "\e[mabcdefghij"
+                                "\e[H"  ;move back to point-min
+                                "\e[mabcde"
+                                "\e[m    j"))))
+
   ;; Relative positioning.
   (should (equal "ab\ncd"
                  (term-test-screen-from-input
-- 
2.17.0