> I see PResizeInc defined in nsgui.h but I nowhere see it used. Same
> goes for Wayland builds. AFAICT size increments are only recognized by
> X11. Everywhere else they are a pure nuisance.

Don't know what that means, sorry. And I don't know what is causing
this different behavior.

>> For transient-posframe child frames, when f-r-p is nil. things go wrong
>> because Posframe binds frame-resize-pixelwise to t, and transient uses
>> the default nil when fit-frame-to-buffer is called. That's what I showed
>> in the screen shot.
>
> That's a different issue.  If 'frame-resize-pixelwise' is nil,
> 'fit-frame-to-buffer-1' does all that silly rounding which blows frames
> up in your case.

It's the only reason I ask if we should change the default value. Or
Posframe shouldn't bind frame-resize-pixelwise, or Transient should not
call fit-buffer-to-frame, or whatever. As it stands, it will lead to bug
reports. Not that it matters much, of course.