emacs-27 19da602: Fix input method translation near read-only text

[Eli Zaretskii]

branch: emacs-27
commit 19da602991538e03648a82214cbb1bcc9a6ec14a
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix input method translation near read-only text
    
    * lisp/international/quail.el (quail-input-method): Don't disable
    input method when the character after point has the read-only
    property.  Suggested by Evgeny Zajcev <lg.zevlg@gmail.com>
    (Bug#44466)
    
    * doc/emacs/mule.texi (Input Methods): Document that input methods
    are inhibited in read-only text.
---
 doc/emacs/mule.texi         | 6 ++++++
 lisp/international/quail.el | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/doc/emacs/mule.texi b/doc/emacs/mule.texi
index 0f07d28..3421ce6 100644
--- a/doc/emacs/mule.texi
+++ b/doc/emacs/mule.texi
@@ -563,6 +563,12 @@ method's keys by defining key bindings in the keymap 
returned by the
 function @code{quail-translation-keymap}, using @code{define-key}.
 @xref{Init Rebinding}.
 
+  Input methods are inhibited when the text in the buffer is read-only
+for some reason.  This is so single-character key bindings work in
+modes that make buffer text or parts of it read-only, such as
+@code{read-only-mode} and @code{image-mode}, even when an input method
+is active.
+
   Another facility for typing characters not on your keyboard is by
 using @kbd{C-x 8 @key{RET}} (@code{insert-char}) to insert a single
 character based on its Unicode name or code-point; see @ref{Inserting
diff --git a/lisp/international/quail.el b/lisp/international/quail.el
index 3299cc5..63371bc 100644
--- a/lisp/international/quail.el
+++ b/lisp/international/quail.el
@@ -1330,7 +1330,8 @@ If STR has `advice' text property, append the following 
special event:
 
 (defun quail-input-method (key)
   (if (or (and (or buffer-read-only
-                   (get-char-property (point) 'read-only))
+                   (and (get-char-property (point) 'read-only)
+                        (get-char-property (point) 'front-sticky)))
               (not (or inhibit-read-only
                        (get-char-property (point) 'inhibit-read-only))))
          (and overriding-terminal-local-map