Inconsistent TC Section Title Indentation in mm?

Hi all,

while familiarizing myself with the capabilities of the mm macros, I
noticed that the section titles on the table of contents pages, list
of figures, tables, etc. pages—produced by the TC macro—appear
misaligned, i.e. not properly centered.

To validate my assumption I replaced the section title strings with
a line-length rule to visualize page offsets and line-lengths.

Reading through m.tmac I found that adding an `.in` macro call before
writing the section title in the print-ds macro definition seems
to remedy the issue.

Quite possibly this approach is just a workaround and the actual
issues lies elsewhere. Hence I kindly request other groff and mm
users to validate or refute the behaviour I'm observing and my
attempt to resolve it.

Please find attached a patch, a minimal working example to demonstrate
the issue, and two PDFs showing the mwe output before and after the
patch was applied.


Thanks
Alexis



—————
P.S: I'm using a groff built from the latest changeset; as of this
writing that is 2542eb3f2ef12be6696e0e305937f82f87549df5
from Fri Dec 5 07:02:13 2025 -0600 and have the following environment
variables set:
GROFF_ENCODING=utf-8
GROFF_TYPESETTER=pdf

diff --git i/contrib/mm/m.tmac w/contrib/mm/m.tmac
index 4181c195a..99835f43e 100644
--- i/contrib/mm/m.tmac
+++ w/contrib/mm/m.tmac
@@ -3107,0 +3108 @@ exceeds depth of nested lists (\\n[li*lvl])
+.	in

.ds Rule \l'\\n[.l]u'
.als Captc Rule
.als Licon Rule
.als Le Rule
.als Lf Rule
.als Lt Rule
.als Lx Rule
.
.ND 2025-12-05
.TL
Minimal Working Example for
.br
Inconsistent TC Section Title Indentation
.AU
.MT \*[mt]
.H 1 "Heading Example"
.EC "Equation Caption Example"
.EX "Exhibit Caption Example"
.FG "Figure Caption Example"
.TB "Table Caption Example"
.TC