The previous approach built tooltip strings by formatting a translated
category name (e.g. "Month") into a generic "Previous %1$s" template.
This is a classic gettext concatenation anti-pattern: languages with
grammatical gender (French, Spanish, German, …) need the adjective to
agree with the noun, and word order can differ from English, so
translators of the format string have no way to produce a correct
result.
Replace the format strings and their helper callbacks with two explicit
GObject properties on GcalMultiChoice: prev-button-tooltip-text and
next-button-tooltip-text. The buttons in the template now bind to
these properties directly. Each widget instance in gcal-date-chooser.blp
sets its own fully self-contained translatable string ("Previous month",
"Next month", "Previous year", "Next year"), giving translators all the
context they need to handle gender and word order correctly.
Closes: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1547
Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/721>
Guillaume Bernard