bug#17829: 24.4.50; `C-t' in empty minibuffer traps user in read-only text

bug#17829: 24.4.50; `C-t' in empty minibuffer traps user in read-only text

[Drew Adams]

emacs -Q

`C-t' is `transpose-chars'. 

`M-x C-t' gives you a "Text is read-only" error, and it moves point
backward into the minibuffer prompt.  Repeating it does not move point
further backward but continues to raise the error.

Trying to type text then results in the same error message.  The user
can become confused, not realizing that point is in fact inside the
prompt area.  S?he can then use `C-f' to move back out of the prompt
area, but `C-t' should be smarter.

`transpose-chars' should presumably limit itself to field motion, or
should in some other way take such a situation into account.

In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-06-17 on ODIEONE
Bzr revision: 117359 monnier@iro.umontreal.ca-20140617193358-2t1nl1te9gc2mqrx
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''

bug#17829: 24.4.50; `C-t' in empty minibuffer traps user in read-only text

[Juri Linkov]

> `M-x C-t' gives you a "Text is read-only" error, and it moves point
> backward into the minibuffer prompt.  Repeating it does not move point
> further backward but continues to raise the error.

I often get into the same trap when mistyping C-t instead of C-y
to yank text into the minibuffer.  This is one of possible fixes:

=== modified file 'lisp/simple.el'
--- lisp/simple.el	2014-01-31 06:42:29 +0000
+++ lisp/simple.el	2014-06-21 21:54:06 +0000
@@ -5902,7 +5902,8 @@ (defun transpose-chars (arg)
 and drag it forward past ARG other characters (backward if ARG negative).
 If no argument and at end of line, the previous two chars are exchanged."
   (interactive "*P")
-  (and (null arg) (eolp) (forward-char -1))
+  (when (and (null arg) (eolp) (not (get-text-property (1- (point)) 'read-only)))
+    (forward-char -1))
   (transpose-subr 'forward-char (prefix-numeric-value arg)))
 
 (defun transpose-words (arg)

bug#17829: 24.4.50; `C-t' in empty minibuffer traps user in read-only text

[Juri Linkov]

Version: 24.4.50

> `M-x C-t' gives you a "Text is read-only" error, and it moves point
> backward into the minibuffer prompt.  Repeating it does not move point
> further backward but continues to raise the error.

Fixed in the trunk since it's not a regression.