\vskip should always(?) break the line

[xworld21]

This normally compiles to two lines

\documentclass{article}
\begin{document}
First line
\vskip0.01em
second line
\end{document}

but LaTeXML does not add a line break because of

LaTeXML/lib/LaTeXML/Engine/TeX_Glue.pool.ltxml

Lines 89 to 98 in f82b733

	DefConstructor('\vskip Glue', sub {
	my ($document, $length) = @_;
	$length = $length->ptValue;
	if ($length > 10) { # Or what!?!?!?!
	if ($document->isCloseable('ltx:para')) {
	$document->closeElement('ltx:para'); }
	elsif ($document->isOpenable('ltx:break')) {
	$document->insertElement('ltx:break'); } }
	return; },
	properties => sub { (height => $_[1], isSpace => 1,, isSkip => 1, isVerticalSpace => 1, isBreak => 1); });

Checking for > 10 is very intentional, obviously, but why is that?

[xworld21]

Some clarification: \vskip always switches to vertical mode. I suspect the >10 test has more to do with \vspace

LaTeXML/lib/LaTeXML/Engine/LaTeX.pool.ltxml

Line 4814 in f82b733

DefMacro('\vspace OptionalMatch:* {}', '\vskip #2\relax');

The problem is that \vspace is the same as \vskip only in vertical mode. In horizontal mode, it shifts the line spacing (https://tex.stackexchange.com/a/30065). I suggest: \vskip removes the >10 test and adds margin-bottom to the previous block, \vspace instead checks if it is 'horizontal mode' (same test as for ltx:inline-block vs ltx:block) and if so inserts an inline-block with margin/vertical-align/??? to dynamically affect the space on the current line.

We were just talking about distinguishing vertical vs horizontal mode... should there be a common function isVertical somewhere?