Straight diagonal rule by using Tikz and Tree diagrams

Question

My code are follows:

\documentclass[10pt]{book}
\usepackage[T1]{fontenc}
\usepackage{newtxmath,newtxtext}
\usepackage{linguex}%
\usepackage{tikz}%
\usetikzlibrary{decorations.text,calc,arrows.meta}%
\usepackage{tikz-qtree}%

\usepackage{adjustbox}
%\usepackage{showframe}
\begin{document}

\ex.
\Tree [.CauseP [.DP \edge[roof]; {`the zog'} ] [ [.{\scshape
cause} ] [ [.{\scshape past} ] [.vP \edge[roof]; {`dissolved the
house'} ]]] ]

Throughout this monograph, I will
focus on the reusable linguistic ingredients of the system and how
they are efficiently deployed in the recursive combinatorics in
building propositions. Reusability (and by extension polysemy)
will be a seen as a design feature of the system rather than a
bug. As a methodological principle, then, I will be guided by the
fact of polysemous items and seek analytic unities to underlie
them.

\ex. \textit{Achievements and accomplishments with result states}\\
%\begin{tikzpicture}[baseline=(current bounding box.north)]
\begin{adjustbox}{max width=0.91\textwidth}
\Tree [.InitP [.{\textsc{initiator}} ] [ [.Init ] [.ProcP
[.{\textsc{undergoer}} ] [ [.Proc ] [.ResP
[.{\textsc{resultee}} ] [ [.Res ] [.XP \edge[roof];
{\sc ground/final state} ] ] ] ] ] ] ]
%\end{tikzpicture}
\end{adjustbox}

\end{document}

and the output came as:

Is this possible to make the diagonal lines to be straight as marked in the below picture?

Diagonal line should be straight in all Trees. Please suggest...

Answer 1

Forest can do this - sort of - if that's an option. However, Forest's trees tend to be rather more ungainly by default, at least in a range of pertinent cases.

Here's an example using nice empty nodes:

\documentclass[border=10pt]{standalone}
\usepackage[linguistics]{forest}
\begin{document}
\begin{forest}
  scshape/.style={font=\scshape},
  nice empty nodes,
  for tree={
    calign angle=50,
  }
  [CauseP
    [DP[`the zog', roof]]
    [[cause, scshape]
      [[past, scshape][vP[`dissolved the house', roof]]
      ]
    ]
  ]
\end{forest}
\end{document}