bug#52293: 29.0.50; [PATCH v2] Prevent further cases of duplicated separators in context menus

[Jim Porter <jporterbugs@gmail.com>]

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On 12/6/2021 1:23 AM, Juri Linkov wrote:
>> Updating this part of my config for Emacs 28 was actually what prompted me
>> to start looking into `context-menu-mode' in more detail. It would be
>> easier to implement this if context menu functions didn't rely on the
>> context menu title having a particular value.
> 
> I think the remaining problem we have to solve is to try to
> prevent such a situation when the user accidentally removes
> `context-menu-top-separator' from `context-menu-functions'.
> To not break the menu in this case, maybe we need to ensure
> that the menu always contains `top-separator' as well as
> `middle-separator' even when `context-menu-functions'
> doesn't contain a function that adds them?  I.e. just to check
> if these separators are missing, and add them at the top.

For the top separator, maybe instead of providing a function for users 
to put wherever they like in `context-menu-functions', we could just add 
it directly in `context-menu-map' immediately before calling the 
functions in `context-menu-functions'? Since it's supposed to be at the 
top, it doesn't make a lot of sense to be able to customize where it goes.

It does makes sense to customize where `middle-separator' goes though; 
what the user considers the "middle" depends on what other menu items 
are normally present. However, if the user didn't include 
`context-menu-middle-separator', then

   (define-key-after menu [foo] '(menu-item ...) 'middle-separator)

just adds `foo' to the end of the menu. That seems ok to me. Then, 
adding after `top-separator' puts your item at the beginning of the 
menu, and adding after `middle-separator' puts your item at the middle 
or the end, depending on the user's configuration. How does that sound 
to you?

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From 831ba55dd209fe5551733bbea1d33fc0e720227e Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Mon, 6 Dec 2021 19:40:40 -0800
Subject: [PATCH] Add a 'top-separator' to the context menu

This provides an anchor for context menu functions to use to insert
their menu items after it. Using 'define-key' doesn't work properly in
this case, since it inserts the items before the menu title, confusing
the separator de-duplication in 'context-menu-map'.

* lisp/mouse.el (context-menu-map): Add 'top-separator' to the menu.
* lisp/dired.el (dired-context-menu):
* lisp/help-mode.el (help-mode-context-menu):
* lisp/info.el (Info-context-menu):
* lisp/net/eww.el (eww-context-menu):
* lisp/net/goto-addr.el (goto-address-context-menu):
Use 'top-separator'.
---
 lisp/dired.el         |  5 +++--
 lisp/help-mode.el     | 10 ++++++----
 lisp/info.el          |  9 +++++----
 lisp/mouse.el         |  3 +++
 lisp/net/eww.el       | 14 ++++++++------
 lisp/net/goto-addr.el |  8 +++++---
 6 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/lisp/dired.el b/lisp/dired.el
index d0e547ba0b..b004d81495 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -2282,7 +2282,7 @@ dired-mode-operate-menu
 (defun dired-context-menu (menu click)
   "Populate MENU with Dired mode commands at CLICK."
   (when (mouse-posn-property (event-start click) 'dired-filename)
-    (define-key menu [dired-separator] menu-bar-separator)
+    (define-key-after menu [dired-separator] menu-bar-separator 'top-separator)
     (let ((easy-menu (make-sparse-keymap "Immediate")))
       (easy-menu-define nil easy-menu nil
         '("Immediate"
@@ -2292,7 +2292,8 @@ dired-context-menu
            :help "Edit file at mouse click in other window"]))
       (dolist (item (reverse (lookup-key easy-menu [menu-bar immediate])))
         (when (consp item)
-          (define-key menu (vector (car item)) (cdr item))))))
+          (define-key-after menu (vector (car item)) (cdr item)
+            'top-separator)))))
   menu)
 
 \f
diff --git a/lisp/help-mode.el b/lisp/help-mode.el
index 792f2e5af3..2ed20577f5 100644
--- a/lisp/help-mode.el
+++ b/lisp/help-mode.el
@@ -74,7 +74,8 @@ help-mode-menu
 
 (defun help-mode-context-menu (menu click)
   "Populate MENU with Help mode commands at CLICK."
-  (define-key menu [help-mode-separator] menu-bar-separator)
+  (define-key-after menu [help-mode-separator] menu-bar-separator
+    'top-separator)
   (let ((easy-menu (make-sparse-keymap "Help-Mode")))
     (easy-menu-define nil easy-menu nil
       '("Help-Mode"
@@ -86,14 +87,15 @@ help-mode-context-menu
          :active help-xref-forward-stack]))
     (dolist (item (reverse (lookup-key easy-menu [menu-bar help-mode])))
       (when (consp item)
-        (define-key menu (vector (car item)) (cdr item)))))
+        (define-key-after menu (vector (car item)) (cdr item) 'top-separator))))
 
   (when (mouse-posn-property (event-start click) 'mouse-face)
-    (define-key menu [help-mode-push-button]
+    (define-key-after menu [help-mode-push-button]
       '(menu-item "Follow Link" (lambda (event)
                                   (interactive "e")
                                   (push-button event))
-                  :help "Follow the link at click")))
+                  :help "Follow the link at click")
+      'top-separator))
 
   menu)
 
diff --git a/lisp/info.el b/lisp/info.el
index 559460e8d2..05e9277698 100644
--- a/lisp/info.el
+++ b/lisp/info.el
@@ -4193,7 +4193,7 @@ Info-check-pointer
 
 (defun Info-context-menu (menu click)
   "Populate MENU with Info commands at CLICK."
-  (define-key menu [Info-separator] menu-bar-separator)
+  (define-key-after menu [Info-separator] menu-bar-separator 'top-separator)
   (let ((easy-menu (make-sparse-keymap "Info")))
     (easy-menu-define nil easy-menu nil
       '("Info"
@@ -4203,12 +4203,13 @@ Info-context-menu
          :help "Go forward in history"]))
     (dolist (item (reverse (lookup-key easy-menu [menu-bar info])))
       (when (consp item)
-        (define-key menu (vector (car item)) (cdr item)))))
+        (define-key-after menu (vector (car item)) (cdr item) 'top-separator))))
 
   (when (mouse-posn-property (event-start click) 'mouse-face)
-    (define-key menu [Info-mouse-follow-nearest-node]
+    (define-key-after menu [Info-mouse-follow-nearest-node]
       '(menu-item "Follow Link" Info-mouse-follow-nearest-node
-                  :help "Follow a link where you click")))
+                  :help "Follow a link where you click")
+      'top-separator))
 
   menu)
 
diff --git a/lisp/mouse.el b/lisp/mouse.el
index af1eca12f4..36003a1db8 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -319,6 +319,9 @@ context-menu-map
          (click (or click last-input-event))
          (fun (mouse-posn-property (event-start click)
                                    'context-menu-function)))
+    ;; Add a separator to the top of the menu to provide an anchor for
+    ;; context menu functions to use.
+    (define-key-after menu [top-separator] menu-bar-separator)
 
     (if (functionp fun)
         (setq menu (funcall fun menu click))
diff --git a/lisp/net/eww.el b/lisp/net/eww.el
index e86d21f889..7303e01a37 100644
--- a/lisp/net/eww.el
+++ b/lisp/net/eww.el
@@ -1106,7 +1106,7 @@ eww-mode-map
 
 (defun eww-context-menu (menu click)
   "Populate MENU with eww commands at CLICK."
-  (define-key menu [eww-separator] menu-bar-separator)
+  (define-key-after menu [eww-separator] menu-bar-separator 'top-separator)
   (let ((easy-menu (make-sparse-keymap "Eww")))
     (easy-menu-define nil easy-menu nil
       '("Eww"
@@ -1117,20 +1117,22 @@ eww-context-menu
 	["Reload" eww-reload t]))
     (dolist (item (reverse (lookup-key easy-menu [menu-bar eww])))
       (when (consp item)
-        (define-key menu (vector (car item)) (cdr item)))))
+        (define-key-after menu (vector (car item)) (cdr item) 'top-separator))))
 
   (when (or (mouse-posn-property (event-start click) 'shr-url)
             (mouse-posn-property (event-start click) 'image-url))
-    (define-key menu [shr-mouse-browse-url-new-window]
+    (define-key-after menu [shr-mouse-browse-url-new-window]
       `(menu-item "Follow URL in new window" ,(if browse-url-new-window-flag
                                                   'shr-mouse-browse-url
                                                 'shr-mouse-browse-url-new-window)
-                  :help "Browse the URL under the mouse cursor in a new window"))
-    (define-key menu [shr-mouse-browse-url]
+                  :help "Browse the URL under the mouse cursor in a new window")
+      'top-separator)
+    (define-key-after menu [shr-mouse-browse-url]
       `(menu-item "Follow URL" ,(if browse-url-new-window-flag
                                     'shr-mouse-browse-url-new-window
                                   'shr-mouse-browse-url)
-                  :help "Browse the URL under the mouse cursor")))
+                  :help "Browse the URL under the mouse cursor")
+      'top-separator))
 
   menu)
 
diff --git a/lisp/net/goto-addr.el b/lisp/net/goto-addr.el
index 848bad3b0d..bb0f0b00ee 100644
--- a/lisp/net/goto-addr.el
+++ b/lisp/net/goto-addr.el
@@ -127,10 +127,12 @@ goto-address-highlight-keymap
 (defun goto-address-context-menu (menu click)
   "Populate MENU with `goto-address' commands at CLICK."
   (when (mouse-posn-property (event-start click) 'goto-address)
-    (define-key menu [goto-address-separator] menu-bar-separator)
-    (define-key menu [goto-address-at-mouse]
+    (define-key-after menu [goto-address-separator] menu-bar-separator
+      'top-separator)
+    (define-key-after menu [goto-address-at-mouse]
       '(menu-item "Follow Link" goto-address-at-mouse
-                  :help "Follow a link where you click")))
+                  :help "Follow a link where you click")
+      'top-separator))
   menu)
 
 (defcustom goto-address-url-face 'link
-- 
2.25.1