Avoid: multicol Error: Error saving partial page

Question

In my package I am using in the dtx file the ltxdoc class which uses multicol for the index.

Currently I get this error:

! Package multicol Error: Error saving partial page.

See the multicol package documentation for explanation.

l.1 \begin{theindex}

The part of the page before the multicols environment was nearly full with the result that starting the environment will produce an overfull page. Some text may be lost! Please increase \premulticols either generally or for this environment by specifying a suitable value in the second optional argument to the multicols environment.

However even if I include something like

\setlength\premulticols{10\baselineskip}

this does not change anything.

In the document pdf the error is that the index runs into the bottom of the page instead of starting at a new page.

An obvious solution would be to add an \clearpage at the end of the dtx file

% \clearpage
% \Finale
\endinput

but if this can be solved otherwise I would like to know it.

Answer 1

doc package uses

    {\begin{multicols}\c@IndexColumns[\index@prologue][\IndexMin]%

So the second optional argument of multicols is used, so the default value of that argument \premulticols is never referenced. Instead you need to set the length \IndexMin (which defaults to 80pt)