multicol issue

[ultravioletcatastrophe]

Hi, I've read the tcolorbox documentation and know that I can't expect a perfect result when using breakable tcolorboxes and multicol, but i'm having a weird issue where paragraph breaks are actually being inserted and deleted, which I don't think is expected behavior. MWE and picture here: https://tex.stackexchange.com/questions/695327/tcolorbox-multicols-tufte-book-inserting-unwanted-paragraph-breaks

[muzimuzhi]

• The deletion of paragraph breaks is reported separately in #245, in its general form.

  • The problem reproduces when a fullwidth environment starts with a parbox=false tcolorbox.

    \documentclass[justified, nofonts, notitlepage, openany, debug]{tufte-book}
    \usepackage{tcolorbox}
    
    \begin{document}
    \begin{fullwidth}
    \begin{tcolorbox}[parbox=false]
      abc \par def \par ghi
    \end{tcolorbox}
    \end{fullwidth}
    \end{document}

  • Then the case is further simplified to "a list whose content starts with a parbox=false tcolorbox" . fullwidth is based on adjustwidth(*) environment from changepage package, and the latter is based on \list.
• The insertion of paragraph breaks is actually unwanted tcolorbox breakings. Setting skin=standard makes it more clear.
• The misalignment at the top of first column is also related to breakable option, which I don't know why as well.

[T-F-S]

As @muzimuzhi wrote, the deletion if paragraph breaks is problem/bug further discussed in https://github.com/T-F-S/tcolorbox/issues/245.

Automatic breakable boxes are not possible inside a multicol environment. On page 410ff of the documentation you will find examples how to use manual breaks with break at, if you still need to break boxes inside a multicols environment, but it is uncomfortable and a kind of final polish for a written document or multicols part.

The initial misalignment at the top results from using breakable and a sourrounding fullwidth environment. Removing one of them will remove the misalignment. Typically, a breakable box should not be inside other constructs, because the box will insert and remove stuff to calculate the remaining height. Inside other constructs, this process may leave visible space behind.