Hi there! I know that we've switched to a IOSurface based rendering for nsterm in master branch. Now master renders more precisely than emacs-27 (i.e. less flickers or blank screens.) But I feel that its rendering performance is much worse due to the new buffering mechanism backed by IOSurface. Several cases that I can feel this worse performance: 1. moving a maximized emacs frame from a larger screen to a smaller screen (I use hammerspoon to do that) I can see the emacs-28 frame shrink to the smaller screen size, then move to the smaller screen 2. scrolling I set `scroll-conservatively' to 101 in order to achieve the smooth-scrolling effect. When I scroll down a large text buffer constantly (hold `j' in evil-mode or `C-n' in emacs-mode), emacs-28 hangs more times than emacs-27 (emacs-27 scrolls very smoothly except it would flicker from time to time) See also for a previous discussion. 3. child-frame child-frame like company-box appears more slowly in emacs-28 than emacs-27 Sorry I haven't found a way to measure the rendering performance except the `scroll-up-benchmark' script from Alan Third in the reddit comment mentioned above. I think this poor rendering performance obscures the improvements brought by native-compile. So I want to fix this performance issue and make Emacs runs on macOS as fast as on Linux. I've spent the last several days trying to understand how nsterm works and if we can use a more efficient rendering API. But I failed completely, mostly because I have no Cocoa development experience before. Here are the 3 steps I want to take to improve the rendering performance: 1. Try to restore the nsterm behavior from Emacs27 (which is much simpler than master IMHO), and start again from there I've reverted the code and made it compile (see ) But Emacs failed to start and raised an error `Font ‘Menlo’ is not defined' 2. Use layer-based view for rendering I found that macvim also faced the similar issue when macOS 10.14 came out (). They used NSImage to implement a double rendering solution (), which was also slower than before. Then they switched from NSImage to layer-based view in . So I wonder if we can do the same. 3. Switch to CALayer (Core Animation) to use GPU (Metal) rendering for even better performance than before If 2 (layer-based view) is possible, then I hope we can leverage CALayer to make nsterm renders even faster. I was so desperate about this issue, so I also tried other window systems on macOS: 1. emacs-pgtk (): technically emacs-pgtk should work on macOS with gtk3, but the performance was even worse 2. emacs-ng + webrender () webrender hasn't been working on macOS neither If anyone can point a direction for me so I can investigate more, that would be the best. Thanks in advance! Cheers, Yiming