fix glitch with \t tabs

.gitignore

@@ -0,0 +1,2 @@
+*~
+*.elc

tests/bench11.el

@@ -0,0 +1,28 @@
+;;; uniline.el --- Draw lines, boxes, & arrows with the keyboard  -*- coding:utf-8; lexical-binding: t; -*-
+
+;; Copyright (C) 2024  Thierry Banel
+
+;; Author: Thierry Banel tbanelwebmin at free dot fr
+;; Version: 1.0
+;; URL: https://github.com/tbanel/uniline
+
+;; Uniline is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; Uniline is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+(uniline-bench
+"C-q <tab> t a b s SPC ? <return> <down> C-a C-q <tab> C-q <tab> 2 SPC t a b s <down> <home> <kp-subtract> <right> <right> <up> <up> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <down> <down> <insert> s"
+"\
+  ╭─────tabs╮? 
+  │         │   2 tabs         
+╶─╯         □          
+")

uniline.el

@@ -154,8 +154,9 @@ Exchange left with right, up with down."
 Add blanks if line is too short: ensure that cursor
 points to a character, not \\n.
 Move to 0 if X negative."
-  (move-to-column (1+ (max x 0)) t)
-  (backward-char))
+  (let ((x (max x 0))) ;; let is faster than setq when byte-compiled
+    (move-to-column (1+ x) t)
+    (move-to-column     x  t)))
 
 (defun uniline--move-to-delta-column (x)
   "Move X characters, staying on the same line.