>> Isn't this a bug that the tool bar and menu bar incorrectly calculate lines?
>
> The lines are calculated correctly by rounding up when we divide the
> object's pixel height by the default character height of the frame.  But
> that calculated value is useless on a GUI.

Accoring to window-total-height, the currently used rounding
in x_change_tab_bar_height corresponds to 'ceiling':

      return make_fixnum (EQ (round, Qceiling)
			  ? ((w->pixel_height + unit - 1) /unit)

On a TTY where the frame line height is 1, this gives the correct result.
But not on a GUI where the frame line height is measured in pixels.

When the argument 'round' of window-total-height is 'floor',
it uses the formula without subtracting 1 that works on a GUI too:

			  : (w->pixel_height / unit));

This patch fixes this in x_change_tab_bar_height.  Do you think the same
fix should be applied to x_change_tool_bar_height as well?