On Tue, Sep 19, 2017 at 04:49:16PM +0100, Duncan Harvey wrote:
> 
> On macOS Sierra, creating the new frame appears to create a macOS-style tab in the same 'space'.
> On El Capitan, creating the new frame creates a new Mac OS X 'space'.

Emacs 26 shouldn’t create a new tab any more.

> Animating the creation of a new space certainly appears to be
> relatively slow (when running under a VM, at least), which lends
> weight to your suspicion that it's timing related.

I can’t see any way around this in C. I can’t even find a way to
prevent native fullscreen from animating, so I’ve gone with just
causing toggle-frame-fullscreen to pause for 1 second on macOS.

I don’t think anyone will be too bothered by this as I don’t think you
can realistically do anything in Emacs while the animation is running
anyway.

BTW, running your script with native fullscreen disabled causes a
crash here, and this pause fixes that too. In theory non‐native
fullscreen should happen instantly, but there’s a pause in the C code
too to fix another issue, so whatever. (see bug#28443)

Patch attached.
-- 
Alan Third