Note that there is not point to have an equation in a full math
mode in a title (etc..). Only the inline formula mode is
acceptable in a title (etc..).
This is precisely what you have in the document: A displayed equation
as part of the title of the section. I agree that it's unclear why one
would ever want to do this, but LaTeX does allow it, and so LyX allows
it, too. Maybe if you had a really long equation that needed to be
part of the title, you'd want to do it that way.
I do see the difference you are talking about now, though. In both
cases, it looks like a displayed equation immediately follows the
section title. However, in one case, it is actually part of the
section title. In the other case, it is not, but is in a separate
paragraph.
Here is the LaTeX output:
\section{This $$x=y&=$$}
One two
\section{That}
$$x=y$$ One two.
Note that I've simplified this a bit, to make it easier to see what's
happening.
The result, in the PDF output, is that there is additional whitespace
above the equation in the second case. This is LaTeX's doing, and has
nothing to do with LyX itself. If you wanted to counteract this, then
you'd have to put some negative vertical space in there somewhere.
See
https://tex.stackexchange.com/questions/763938/correct-way-to-reduce-space-above-displayed-equation-which-shows-right-below-sec
for the way to do this. It is not trivial.
The difference is not completely obvious in the LyX display. But if
you look closely, you'll see that there is additional whitespace above
the equation there as well. If you had pilcrows displayed, then it
would be clearer. (Preferences> Display> Mark end of paragraphs)
On 8/3/26 2:37 PM, Patrick Dupre wrote:
I disagree, the management of the vertical spacing in lyx have been
modified.
You are right, latex manages this vertical spacing between the section
title and the formula in displayed mode.
Actually, if I remember correctly, there is a proper way to manage
this spacing.
Anyway, lyx has now the tendency to add newlines where it did not used
to do it before.
If what you mean is that, *in the LyX display*, LyX shows additional
space above a displayed formula, when such a formula begins a paragraph,
then that may be correct. I do think this may have changed in the 2.5.x
series. There was lots of work on this sort of thing for 2.5.0 (which I
have just checked does the same thing as 2.5.1). But it would also
correspond to what LaTeX does, so I would regard that as an improvement.
Otherwise, there is no visual difference between the two cases mentioned.
All these behaviors are simply due to the fact that a displayed equation
can either be part of the paragraph that precedes it or not. If it is,
then changing the paragraph the text is in will of course affect the
type of paragraph the equation is in. As it should.
In LaTeX, the difference is:
test
$$x=y$$ % part of same paragraph
test
$$x=y$$ % starts a new paragraph
You get more space in the latter case, even without any special
paragraph type. Again, I think it may be correct that LyX *shows* more
space in the latter case, whereas it did not do so before. And that
would be intentional, and correct, as a way of indicating the difference
visually.
File a bug report if you wish, and we can see what others think.
Riki
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