# trees with nice straight spines and not too vertical

I want to be able to typeset syntactic trees in a way that will achieve the following:

• straight spine when there is no label on the nonterminal node
• obtuse angle at each (binary) branch (so the tree is not too tall)

I'm having trouble making forest or (tikz-)qtree to achieve this easily. Surely there is someone with a solution to this problem out there.

Basically I want to achieve this:

but what I get with tikz-qtree is

which I got using the following code:

\usepackage{tikz,tikz-qtree-compat}
\tikzset{baseline=0pt,level distance=20pt,sibling distance=0pt}
\begin{document}
\Tree [.CP [.who ] [ [.$\lambda_1$ ]
[.IP [.$t_1$ ] [.registered ] ] ] ]
\end{document}


or, with forest:

using the following code:

\usepackage[linguistics]{forest}
\newcommand{\tree}[1]{
\begin{forest}
for tree={
inner sep=0pt,
% where n children=0{font=\itshape}{},
%    calign=fixed edge angles,
parent anchor=south,
},
before typesetting nodes={% page 52: example (81)
where content={}{% shape=coordinate gives an error if used here but this is *almost* right - it just leaves a little, tiny gap
text width=.001pt,
inner sep=0pt,
before drawing tree={% here we make sure that the tiny gap disappears so only the size is not quite dimensionless
shape=coordinate,
typeset node,
},
for parent={
for children={
anchor=north,
}
}
}{}
}
#1
\end{forest}
}

\begin{document}
\tree{
[CP [who] [ [$\lambda_1$]
[IP [$t_1$] [registered]]]]
}
\end{document}


Does anyone have an easy way of getting nice trees like in the first image (where not all nonterminals have labels, but some do, and the spine is nice and straight, but the trees are not too tall? I'd be happy to learn there's an easy way of doing this... thanks!

• Yes, that's true... width is another problem with large trees. But, right now I'm just trying to find a way to get forest's small trees to be smaller vertically, or qtree's trees to be straight-spined, in either case without making the angles too acute. The way these packages deal with larger trees is subject to a different list of desired behaviors, ha! – postylem Jan 17 '19 at 18:19