Which is taller.  This means that the Emacs frame changes size every
time you pop between these two windows, which is highly annoying.

I guess it has something to do with the former toolbar not having any
text?


In GNU Emacs 28.0.50 (build 31, x86_64-pc-linux-gnu, GTK+ Version 3.24.23, cairo version 1.16.0)
 of 2021-02-22 built on xo
Repository revision: c1712f55070d1fe861517d2c1a9fe53622f0e6a6
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux bullseye/sid


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   bloggy blog: http://lars.ingebrigtsen.no