Symmetrically spread extra row height in cells adjacent to a tall multirow cell

[Sonja-K]

tabularray seems to avoid overflowing contents of tall \multirow cells by enlarging the height of the last row that the \multirow cell spans. Is there already a way to instead evenly distribute the extra row height over all rows that the \multirow cell spans or is such a feature planned?

Here is a MWE comparing the current output using tabularray as well as two mock-up versions showing such an evenly distributed additional row height:

\documentclass{article}
\usepackage{tabularray}
\usepackage{multirow}

\begin{document}

\begin{tblr}{hlines,vlines, colspec={lp{3.25cm}}}
  Column1 & Column2  \\
  Row1 & \multirow{3}{=}{Long text that needs multiple lines. Long text that needs multiple lines.  Long text that needs multiple lines.}  \\ 
  Row2 &  \\  
  Row3 &  \\ 
  Row4 &  short text  \\ 
\end{tblr}

\bigskip
\begin{tabular}{|l|p{3.25cm}|}
  \hline
  Column1 & Column2  \\ 
  \hline
  Row1 & \multirow{6}{=}{Long text that needs multiple lines. Long text that needs multiple lines. Long text that needs multiple lines.} \\
  &\\ 
  \cline{1-1}
  Row2 &  \\
  &\\
  \cline{1-1}
  Row3 &  \\
  &\\
  \hline  
  Row4 &  short text  \\
  \hline
\end{tabular}
\quad
\begin{tabular}{|l|p{3.25cm}|}
  \hline
  Column1 & Column2  \\ 
  \hline
  \multirow{2}{*}{Row1} & \multirow{6}{=}{Long text that needs multiple lines. Long text that needs multiple lines. Long text that needs multiple lines.} \\
  &\\  
  \cline{1-1}
  \multirow{2}{*}{Row2} &  \\
  &\\
  \cline{1-1}
  \multirow{2}{*}{Row3} &  \\
  &\\ 
  \hline 
  Row4 &  short text  \\ 
  \hline
\end{tabular}

\end{document} 

Some related questions/comments:

https://tex.stackexchange.com/q/581298
https://tex.stackexchange.com/q/359003
https://tex.stackexchange.com/questions/343779/multirow-cell-content-overflows#comment843635_343779

[lvjr]

In tabularray, the default behaviors of \multicolumn and \multirow follow the span algorithm in TeXbook (see page 245 in chapter 22). It is in my todo list to add two options hspan=even and vspan=even as you described above. But I'm refactoring the code to make it run faster, there maybe some days later when I start to add this feature.

[lvjr]

As long as we have a proper algorithm, it's not hard to implement it. The problem is, if we have many multirow cells which span different rows, how could we find the minimal height to extend? It's complex if we want to add the same height to each row. Do you know of any algorithms about this situation?

[lvjr]

I have added hspan=even and vspan=even options, and this issue could be closed now.

\begin{tblr}{hlines, vlines, colspec={lp{3.25cm}}}
  Column1 & Column2  \\
  Row1 & \multirow{3}{=}{Long text that needs multiple lines. Long text that needs multiple lines. Long text that needs multiple lines.}  \\ 
  Row2 &  \\  
  Row3 &  \\ 
  Row4 &  short text  \\ 
\end{tblr}
\qquad
\begin{tblr}{hlines, vlines, colspec={lp{3.25cm}}, vspan=even}
  Column1 & Column2  \\
  Row1 & \multirow{3}{=}{Long text that needs multiple lines. Long text that needs multiple lines. Long text that needs multiple lines.}  \\ 
  Row2 &  \\  
  Row3 &  \\ 
  Row4 &  short text  \\ 
\end{tblr}

[Sonja-K]

Thanks a lot. The vspan=equal option works just as I had envisaged.