menu-bar-mode makes frame continuously shrink in height

[PierGianLuca]

Hi everyone,

Emacs 29.1 on Ubuntu 20.04 here. Emacs was installed from tarball with options:
--with-native-compilation --with-json --enable-link-time-optimization 
--with-x-toolkit=lucid --without-toolkit-scroll-bars


I see a curious behaviour from calling "menu-bar-mode" and "tool-bar-mode". 
Before submitting it as a bug I wanted to ask here if it's something known, or if not how I can 
track the source of the problem myself.

I have frames set at height=77 in "default-frame-alist", and "menu-bar-mode" and 
"tool-bar-mode" both set to nil (all via Customize).


(A) If I call "M-x menu-bar-mode", the menu bar appears, and the frame shrinks vertically 
by one line. If I call "M-x menu-bar-mode" again, the menu bar disappears, and the frame 
shrinks vertically once more. So the more I make the menu bar appear and disappear, the more the 
frame shrinks.

I tried adding and removing "menu-bar-lines" in "frame-inhibit-implied-resize", 
but the problem remains either way.


(B) Exactly the same problem with tool-bar-mode. There's one difference here:

this continuous-shrinking behaviour happens if "tool-bar-lines" is in 
"frame-inhibit-implied-resize". Otherwise, the frame increases in vertical size when tool-bar-mode 
is enabled, and decrease to the original size when tool-bar-mode is is disabled. (This seems to me contrary 
to what's explained under "tool-bar-lines".)


(C) If I call Emacs with "-Q" (no init file), the continuous shrinking does 
*not* happen with menu-bar-mode – but it *does* happen with tool-bar-mode.


This makes me think that there's both a bug somewhere, but also something 
strange in my init file.

Appreciate any thoughts or suggestions about which tests to make!

Cheers,
Luca