Eli Zaretskii writes: >> Date: Thu, 29 Sep 2022 19:38:28 +0200 >> From: miha--- via "Bug reports for GNU Emacs, >> the Swiss army knife of text editors" >> >> 1. (setq highlight-nonselected-windows t) >> 2. 'C-x 2' >> 3. Click with mouse-1 somewhere to move point >> >> Notice that for the duration mouse-1 being held down for the click, >> region highlighting appears in the non-selected window. Usually the >> click is short so the region only appears for a short time, which can be >> perceived as a somewhat annoying flicker. > > It's a direct consequence of the fact that point is different in each > window. I don't see any bug here, FWIW. If you don't like this side > effect of highlight-nonselected-windows, then don't set it non-nil. Well, maybe we could try a bit harder to reduce the flicker for ordinary non-dragging mouse-1 clicks. One idea could be to prevent down-mouse-1 from activating mark until the region becomes non-zero length, so something like this patch. diff --git a/lisp/mouse.el b/lisp/mouse.el index e38a4f8a71..a0f48de923 100644 --- a/lisp/mouse.el +++ b/lisp/mouse.el @@ -1729,7 +1729,7 @@ mouse-drag-track '(only) (cons 'only transient-mark-mode))) (let ((range (mouse-start-end start-point start-point click-count))) - (push-mark (nth 0 range) t t) + (push-mark (nth 0 range) t (not (eql (nth 0 range) (nth 1 range)))) (goto-char (nth 1 range))) (setf (terminal-parameter nil 'mouse-drag-start) start-event) @@ -1794,7 +1794,10 @@ mouse--drag-set-mark-and-point (goto-char beg)) (t (set-mark beg) - (goto-char end))))) + (goto-char end))) + (unless mark-active + (unless (eql beg end) + (activate-mark 'no-tmm))))) ;; Commands to handle xterm-style multiple clicks. (defun mouse-skip-word (dir)