emacs-mac scrolling performance

[Calvin-Xu]

Hi! I just want to provide some feedback on the recommendation in the README:

If you are using MacOS, install emacs from homebrew using the emacs-mac package (aka Mitsuharu's Emacs build), since it uses WebKit to render SVG, resulting in beautifully crisp images.

I have been using emacs-mac for the longest time, and it does render SVG beautifully. However, I mainly use xenops in org mode buffers with hundreds of overlays. Scrolling in emacs-mac quickly grinds to a halt and I often have to kill Emacs completely. This got so bad I started hiding subtrees & overlays before moving around, and seriously considered writing a separate viewer for my org notes from pandoc-parsed AST.

After tweaking my config I noticed emacs-mac has no issues in the same buffer when the overlays are png (dvipng), even if a very high DPI is set. I still want to use SVGs, and switching to emacs-plus@30 the entire problem just went away. It scrolls like butter in pixel-scroll-precision-mode and I can tell no difference in render quality.

I think this may be related to railwaycat/homebrew-emacsmacport#380. A word of caution here if anyone else runs into something similar.

(I am not sure if installing librsvg solves this for emacs-mac, but then again it seems to defeat the point)

edit: searching for librsvg yields more context

railwaycat/homebrew-emacsmacport#312
railwaycat/homebrew-emacsmacport#366