Emacs post-command-hook redraws make touchpad scrolling lag

Under an Emacs-as-window-manager setup, scrolling felt like it took a second to render. Cause: a custom status bar redrawn from post-command-hook (about 13 ms per call); pixel-scroll-precision-mode turns a touchpad scroll into dozens of commands, so the redraws queue up. Benchmark candidate hooks with (benchmark-run 20 (fn)) and inspect post-command-hook before tuning redisplay variables. Fix: debounce the redraw with a 0.05 s run-with-timer, and skip it entirely when this-command is pixel-scroll-precision / mwheel-scroll, since scrolling changes nothing on the bar.