LaTeX: excessive whitespace since v4.4.0

[rhssk]

Describe the bug

Hi,

I'm using Sphinx together with Breathe and Doxygen to generate LaTeX -> PDF documentation.

Since v4.4.0 I've noticed that undocumented variables/structure members have large amount of whitespace added below them.
Bisecting shows that this is caused by b230365 (#9941).

HEAD (799385f):

With revert:

How to Reproduce

Input RST:

.. cpp:class:: Data

   .. cpp:union:: @data

      .. cpp:var:: int a

      .. cpp:var:: double b

MWE.zip

Expected behavior

No response

Your project

---

Screenshots

No response

OS

Linux

Python version

3.10.2

Sphinx version

v4.4.0

Sphinx extensions

No response

Extra tools

No response

Additional context

No response

[jakobandersen]

It indeed looks excessive, but note that the layout is tuned for when you have documentation of the entities, e.g.,

.. cpp:class:: Data

   A class that models either this or that.

   .. cpp:union:: @data

      A nested union storing the data different in this and that.

      .. cpp:var:: int a

         If it models a this, then this member is valid.

      .. cpp:var:: double b

         If it models a that, then this member is valid.

@jfbu may be able to provide at bit more details in what is going on with the whitespace and may be doable.

[jfbu]

Hi thanks for report. In fact the problem caused by the commit you identified (#9941) had already been fixed at #10087 which I have now merged into 4.x, so whitespace will be better at 4.5.0:

[jfbu]

Fixed at 6768577

[rhssk]

Hi. I've applied the fix locally and it indeed improves the spacing issues but does not completely bring spacing back to the pre-v4.4.0 state.

Here's a comparison of v4.4.0, current HEAD (b8789b4) and the revert of b230365 (left-to-right):

Nevertheless, this is good enough for me, so thanks for the fix.

[jfbu]

Thanks for the feedback and nice visual diff! Yes indeed the merge of #10087 is not a revert of b230365, and deliberately injects some more spacing for better grouping, see #10087 (comment).

Although there is no way to reproduce exactly former behaviour (which had quite a few issues, and the LaTeX code has been changed significantly), it might be that adding this to conf.py

latex_elements = {
    'preamble': r'\setlength{\sphinxsignaturesep}{0pt}',
}

will mimick close enough. The default setting \smallskipamount rather than 0pt is responsible for some extra vertical whitespace. It is very difficult to provide a customizable interface because Sphinx sticks to legacy situation that object descriptions are rendered using LaTeX list/\item syntax which in hindsight is not adapted for such things, in particular to get multiple such "labels" share a common description, which is what #10087 in particular is about.