It happens with different overlays, and with the default monospaced font of my system (Ubuntu GNU/Linux), but it's easiest to reproduce doing isearch, and using Fira Mono (TrueType version, available from https://www.mozilla.org/en-US/styleguide/products/firefox-os/typeface/, see the bottom of the page). Steps from emacs -Q: 1. Evaluate (run-at-time nil 0.01 'ignore) 2. Evaluate (set-face-attribute 'default nil :height 105 :family "Fira Mono") This is optional, but with the default font the flickering is harder to reproduce. 3. Open a text file press C-s (or C-r), enter some letters, preferably common to that file, press C-s or C-r again. Repeat multiple times. Maybe do that for a couple of minutes, even. 4. Observe flickering letters, usually one to the left, or one to the right of the cursor. Most of the time the flickering happens 2 or 3 times and stops, but I've managed to record a couple of semi-stable loops of this on video, see the attachment. It demonstrates a somewhat extreme situation, usually I only see flickering once every handful searches or so. This is in no way limited to isearch. For example, I can also see it when typing, when using the fancy highlight-tail-mode (http://www.emacswiki.org/emacs-en/highlight-tail.el), at least with settings highlight-tail-steps 14, highlight-tail-timer 0.02. Let me know if the video format (h264) is not acceptable. In GNU Emacs 24.3.50.5 (x86_64-unknown-linux-gnu, GTK+ Version 3.8.6) of 2014-02-01 on axl Repository revision: 116234 address@hidden Windowing system distributor `The X.Org Foundation', version 11.0.11405000 System Description: Ubuntu 13.10
Screencast 2014-02-02 02:32:44.mp4
Description: screencast
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