Recently I've had an odd problem with Emacs:occasionally, and somewhat randomly, as I wrote code, and only when I wroteEmacs Lisp code, and only when working inemacs-lisp-mode, I'd find that the buffer I was working in woulddisappear. Not just fully disappear, but more like if I'd usedquit-window. Worse still, once this started happening, it wouldn't go awayunless I turned Emacs off and on again.Very un-Emacs!Normally this would happen when I'm in full flow on something, so I'd justrestart Emacs and crack on with the thing I was writing; because of this Iwasn't diagnosing what was actually going on.Then, today, as I was writing require in some code, and kept seeing thebuffer go away when I hit q, it dawned on me.Recently, when I cleaned upexpando.el, I added the ability toclose the window with q.--- a/expando.el+++ b/expando.el@@ -58,7 +58,8 @@ Pass LEVEL as 2 (or prefix a call with \\[universal-argument] and (let ((form (preceding-sexp))) (with-current-buffer-window "*Expando Macro*" nil nil (emacs-lisp-mode)- (pp (funcall (expando--expander level) form)))))+ (local-set-key (kbd "q") #'quit-window)+ (pp (funcall (expando--expander level) form))))) (provide 'expando)So, after opening a window for the purposes of displaying the expandedmacro, switch to emacs-lisp-mode, locally set the binding so qwill call on quit-window, and I'm all good.Except... not, as it turns out.To quote from the documentation for local-set-key:The binding goes in the current buffer’s local map, which in most cases isshared with all other buffers in the same major mode.D'oh!Point being, any time I used expando-macro, I was changing the meaning ofq in the keyboard map for emacs-lisp-mode. :-/And so v1.6 of expando.el is now athing, in which I introduce a derived mode of emacs-lisp-mode and setq in its keyboard map. In fact, I keep the keyboard map nice andsimple.(defvar expando-view-mode-map (let ((map (make-sparse-keymap))) (define-key map (kbd "q") #'quit-window) map) "Mode map for `expando-view-mode'.")(define-derived-mode expando-view-mode emacs-lisp-mode "expando" "Major mode for viewing expanded macros.The key bindings for `expando-view-mode' are:\\{expando-view-mode-map}")From now on I should be able to code in full flow state without the worrythat my window will disappear at any given moment...