New option 'project-mode-line' to show project name on mode line (bug#66317)

* lisp/bindings.el (standard-mode-line-format):
Add '(project-mode-line project-mode-line-format)'.

* lisp/progmodes/project.el (project-mode-line): New user option.
(project-menu-entry, project-mode-line-map): New variables.
(project-mode-line-format): New variable.
(project-mode-line-format): New function.

etc/NEWS

@@ -889,6 +889,10 @@ showcases all their customization options.
 
 ** Project
 
+*** New user option 'project-mode-line'.
+When non-nil, display the name of the current project on
+the mode line.  Clicking mouse-1 pops up the project menu.
+
 *** New user option 'project-file-history-behavior'.
 Customizing it to 'relativize' makes commands like 'project-find-file'
 and 'project-find-dir' display previous history entries relative to

lisp/bindings.el

@@ -682,6 +682,7 @@ By default, this shows the information specified by `global-mode-string'.")
 	     'mode-line-buffer-identification
 	     "   "
 	     'mode-line-position
+	     '(project-mode-line project-mode-line-format)
 	     '(vc-mode vc-mode)
 	     "  "
 	     'mode-line-modes

lisp/progmodes/project.el

@@ -2010,5 +2010,38 @@ would otherwise have the same name."
           (file-relative-name dirname root))))
     dirname))
 
+;;; Project mode-line
+
+;;;###autoload
+(defcustom project-mode-line nil
+  "Show the current project name with the menu on the mode line.
+This feature requires the presence of the following item in
+`mode-line-format': `(project-mode-line project-mode-line-format)'."
+  :type 'boolean
+  :group 'project
+  :version "30.1")
+
+(defvar project-menu-entry
+  `(menu-item "Project" ,menu-bar-project-menu))
+
+(defvar project-mode-line-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map [mode-line down-mouse-1] project-menu-entry)
+    map))
+
+(defvar project-mode-line-format '(:eval (project-mode-line-format)))
+(put 'project-mode-line-format 'risky-local-variable t)
+
+(defun project-mode-line-format ()
+  "Compose the project mode-line."
+  (when-let ((project (project-current)))
+    (concat
+     " "
+     (propertize
+      (project-name project)
+      'mouse-face 'mode-line-highlight
+      'help-echo "mouse-1: Project menu"
+      'local-map project-mode-line-map))))
+
 (provide 'project)
 ;;; project.el ends here