> 
> I see no alternative to current icons because ASCII art
> characters have own problems explained by Eli in
> https://lists.gnu.org/archive/html/emacs-devel/2019-09/msg00268.html
> 
> This is why the tab-bar moved from Unicode characters to images,
> but another attempt to use SVG failed as was demonstrated in
> https://lists.gnu.org/archive/html/emacs-devel/2019-09/msg00414.html
> 
> But in any case feel free to try other options.
> 
> BTW, if you want to see a funny effect, try typing 'r' when point
> is on the arrow in the customize buffer - it will rotate the image :-)
> 
> There are other image keys used in the customize buffer,
> e.g. '+' will zoom the image (function 'image-increase-size'),
> so maybe you could just increase image size instead of using
> 2x image files.

Aha, that’s pretty cool :-) 

To be clear, I’m not looking for a larger icon, but one with higher resolution. “2x” basically means I make a 18x18 px image and render it in “9x9 size”, which looks better than a 9x9 image on a HiDPI screen. Maybe Apple can explain it better than I do: https://developer.apple.com/design/human-interface-guidelines/ios/icons-and-images/image-size-and-resolution/ <https://developer.apple.com/design/human-interface-guidelines/ios/icons-and-images/image-size-and-resolution/>. You can have a look at the images my previous message, the 9x9 one looks a bit fuzzy and the high-res one looks sharp.

Yuan