# Dividing Scrolling text

Based on the video available here : http://www.youtube.com/watch?v=vkBCeOBbAmM I try to understand what the following code does

\def\text{\setbox\galley=\vbox\bgroup
\hsize= 5cm
\hrule}

\makeatletter
\def\endtext{\vskip-\prevdepth
\vfil\egroup
\setbox0=\vsplit\galley to\z@}
\makeatother

\def\lines#1{\vsplit\galley
to #1\baselineskip}


unfortunately, I am not sucessful. In the video, he speaks about "floating, scrolling text" which you can cut in pieces and place the different pieces in the page. But I fail to understand how to do that with the previous code lines. I begin in macro writing so it could be I do not understand because I do not undestand the effect of the different commands put under these macros.

I tried

\text blablablabla \endtext


to check the effect but the page does not display any text at all then.

Here's a working example:

\input plipsum

\newbox\galley
\def\text{\setbox\galley=\vbox\bgroup
\hsize=10cm \hrule height 0pt}

\catcode\@=11
\def\endtext{\vskip-\prevdepth
\vfil\egroup
\setbox0=\vsplit\galley to \z@}
\catcode\@=12

\def\lines#1{\vsplit\galley to #1\baselineskip}

\text
\lipsum 1,3
\endtext

\noindent{\bf Four lines:}\par\medskip

\setbox0=\lines{4}\box0

\bigskip

\noindent{\bf Five lines:}\par\medskip

\setbox0=\lines{5}\box0

\bye


The big text has much more than nine lines. We gather it in a \vbox, then chop off the initial (invisible) rule. With \lines{x} we can chop x lines from the top of the paragraph and set them in a box which we can do anything with. In the example we just print it.