>From d001740b0f59cdc2165d62e05c7f2cb5ff8ab6b4 Mon Sep 17 00:00:00 2001
From: Alexander Gramiak <agrambot@gmail.com>
Date: Tue, 3 Oct 2017 17:11:08 -0600
Subject: [PATCH] Allow mouse clicks to be prefix keys (Bug#14793)

* src/keyboard.c (read_char): Check used_mouse_menu after calling
read_char_x_menu_prompt.
(read_char_x_menu_prompt): Pass used_mouse_menu to x_popup_menu and
return nil if it wasn't set to true.
* src/menu.c (Fx_popup_menu): Extract into a new function.
(x_popup_menu): New function. Don't error if used_mouse_menu is null,
and set used_mouse_menu if there was no error.
* src/keyboard.h: Declare x_popup_menu.
---
 src/keyboard.c | 21 +++++++++++++--------
 src/keyboard.h |  3 +++
 src/menu.c     | 11 ++++++++++-
 3 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/src/keyboard.c b/src/keyboard.c
index e8701b8870..5912f89115 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -2682,11 +2682,15 @@ read_char (int commandflag, Lisp_Object map,
     {
       c = read_char_x_menu_prompt (map, prev_event, used_mouse_menu);
 
-      /* Now that we have read an event, Emacs is not idle.  */
-      if (!end_time)
-	timer_stop_idle ();
+      /* Only exit if a mouse menu was actually used successfully.  */
+      if (*used_mouse_menu)
+        {
+          /* Now that we have read an event, Emacs is not idle.  */
+          if (!end_time)
+            timer_stop_idle ();
 
-      goto exit;
+          goto exit;
+        }
     }
 
   /* Maybe autosave and/or garbage collect due to idleness.  */
@@ -8457,8 +8461,11 @@ read_char_x_menu_prompt (Lisp_Object map,
       /* Display the menu and get the selection.  */
       Lisp_Object value;
 
-      value = Fx_popup_menu (prev_event, get_keymap (map, 0, 1));
-      if (CONSP (value))
+      value = x_popup_menu (prev_event, get_keymap (map, 0, 1), used_mouse_menu);
+
+      if (!*used_mouse_menu)
+        value = Qnil;
+      else if (CONSP (value))
 	{
 	  Lisp_Object tem;
 
@@ -8489,8 +8496,6 @@ read_char_x_menu_prompt (Lisp_Object map,
 	}
       else if (NILP (value))
 	value = Qt;
-      if (used_mouse_menu)
-	*used_mouse_menu = true;
       return value;
     }
   return Qnil ;
diff --git a/src/keyboard.h b/src/keyboard.h
index a2a5f8f21d..954485c78b 100644
--- a/src/keyboard.h
+++ b/src/keyboard.h
@@ -360,6 +360,9 @@ enum menu_item_idx
 
 extern void unuse_menu_items (void);
 
+extern Lisp_Object
+x_popup_menu (Lisp_Object position, Lisp_Object menu, bool *used_mouse_menu);
+
 /* This is how to deal with multibyte text if HAVE_MULTILINGUAL_MENU
    isn't defined.  The use of HAVE_MULTILINGUAL_MENU could probably be
    confined to an extended version of this with sections of code below
diff --git a/src/menu.c b/src/menu.c
index d569b4b29b..257c67f6a4 100644
--- a/src/menu.c
+++ b/src/menu.c
@@ -1157,6 +1157,12 @@ keyboard input, then this normally results in a quit and
 event (indicating that the user invoked the menu with the mouse) then
 no quit occurs and `x-popup-menu' returns nil.  */)
   (Lisp_Object position, Lisp_Object menu)
+{
+  return x_popup_menu (position, menu, NULL);
+}
+
+Lisp_Object
+x_popup_menu (Lisp_Object position, Lisp_Object menu, bool *used_mouse_menu)
 {
   Lisp_Object keymap, tem, tem2;
   int xpos = 0, ypos = 0;
@@ -1439,7 +1445,10 @@ no quit occurs and `x-popup-menu' returns nil.  */)
     FRAME_DISPLAY_INFO (f)->grabbed = 0;
 #endif
 
-  if (error_name) error ("%s", error_name);
+  if (error_name && !used_mouse_menu)
+    error ("%s", error_name);
+  else if (!error_name && used_mouse_menu)
+    *used_mouse_menu = true;
   return selection;
 }
 
-- 
2.14.2