memoir \vplace / \vspace that breaks pages on content starting with a section header

Question

When using memoir's \vplace environment, I've noticed that LaTeX tends prefer break before a \vplace when its content starts with a \{sub}section.

So for example:

\documentclass[oneside,11pt]{memoir}
\usepackage{lipsum}
\begin{document}
\lipsum[1] % A
\begin{vplace}
  \subsection{Title}  % Starts a new page if the number of pages is > 1
  \lipsum[1] % B
 \end{vplace}
\lipsum[1] % C
\end{document}

When the content is contained to one page it works as expected. When there is more than one page, the break occurs at the Title, even if a visually preferable break occurs after the paragraphs in the vplace.

One can see this by increasing the number of ipsum sections to e.g. [1-2].

The vplace environment is simply defined as:

\newenvironment{vplace}[1][1]
  {\par\vspace*{\stretch{#1}}}
  {\vspace*{\stretch{1}}\par}

This only appears to occur when the vplace starts with a section.

It appears that the vplace environment is not suitable for spanning multiple pages. Is there an environment or alternative that is, or a way to make the vplace macro's page breaking effects more suitable?

Answer 1

This is perfectly normal. If I set \tracingpages=1 in the \lipsum[1-2] case, I get in the log

%% goal height=541.40024, max depth=5.5
% t=0.0 g=541.40024 b=10000 p=0 c=100000#
% t=11.0 g=541.40024 b=10000 p=1000 c=100000#
% t=24.6 g=541.40024 b=10000 p=0 c=100000#
% t=38.20001 g=541.40024 b=10000 p=0 c=100000#
% t=51.80002 g=541.40024 b=10000 p=100 c=100000#
% t=65.40002 g=541.40024 b=10000 p=0 c=100000#
% t=79.00003 g=541.40024 b=10000 p=100 c=100000#
% t=92.60004 g=541.40024 b=10000 p=0 c=100000#
% t=106.20004 g=541.40024 b=10000 p=0 c=100000#
% t=119.80005 g=541.40024 b=10000 p=0 c=100000#
% t=133.40005 g=541.40024 b=10000 p=0 c=100000#
% t=147.00006 g=541.40024 b=10000 p=1000 c=100000#
% t=160.60007 g=541.40024 b=10000 p=0 c=100000#
% t=174.20007 plus 1.0 g=541.40024 b=10000 p=1000 c=100000#
% t=187.80008 plus 1.0 g=541.40024 b=10000 p=0 c=100000#
% t=201.40009 plus 1.0 g=541.40024 b=10000 p=0 c=100000#
% t=215.00009 plus 1.0 g=541.40024 b=10000 p=100 c=100000#
% t=228.6001 plus 1.0 g=541.40024 b=10000 p=0 c=100000#
% t=242.2001 plus 1.0 g=541.40024 b=10000 p=0 c=100000#
% t=255.80011 plus 1.0 g=541.40024 b=10000 p=1000 c=100000#
% t=269.40012 plus 1.0 plus 1.0fill g=541.40024 b=0 p=-300 c=-300#
% t=333.49432 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=347.09433 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=360.69434 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=100 c=100
% t=374.29434 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=387.89435 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=100 c=100
% t=401.49435 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=415.09436 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=428.69437 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=442.29437 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=455.89438 plus 7.65746 plus 1.0fill minus 0.94289 g=541.40024 b=0 p=1000 c=1000
% t=483.09439 plus 8.65746 plus 2.0fill minus 0.94289 g=541.40024 b=0 p=1000 c=1000
% t=496.6944 plus 8.65746 plus 2.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=510.2944 plus 8.65746 plus 2.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=523.89441 plus 8.65746 plus 2.0fill minus 0.94289 g=541.40024 b=0 p=100 c=100
% t=537.49442 plus 8.65746 plus 2.0fill minus 0.94289 g=541.40024 b=0 p=0 c=0
% t=551.09442 plus 8.65746 plus 2.0fill minus 0.94289 g=541.40024 b=* p=100 c=*

Each line in the output records the height of the accumulated material after each typeset line, the goal height, the badness if a page break had to be taken there, the penalty for a break after the line and the “cost” of the break. The “cheapest cost so far” is marked with #. The formula for the cost of a page break can be found on page 111 of the TeXbook.

We see that when \vspace*{\stretch{1} appears, an available stretch of 1fill is shown and also a -300 penalty (it's due to the section title and \penalty\@secpenalty that's issued before it). This produces, according to the formula in the TeX book, a cost of -300. Later costs are larger, so the break is taken after the \vspace{\stretch{\fill}.

In the \lipsum[1] case, the copy fits on one page, so the best cost comes to be the -10000 that's found at \end{document} in consequence of the routine for ending a job.

You get two pages also if you use \lipsum[1-2] at the end, because the copy doesn't fit on one page any more.

Possible solution

Change locally \@secpenalty to be 0.

\documentclass[oneside,11pt]{memoir}
\usepackage{xpatch}
\usepackage{lipsum}

\makeatletter
\xapptocmd{\vplace}{\@secpenalty\z@}{}{}
\makeatother

\begin{document}
\lipsum[1-2] % A
\begin{vplace}
  \subsection{Title}
  \lipsum[1] % B
 \end{vplace}
\lipsum[1] % C
\end{document}

However you still have the stretchable glue that can come into play again.