Persian & RTL specifics

The HIG covers layout mirroring rules (RTL & Persian). This page collects the implementation-level details: what to do in code and data.

Numerals

Persian UI strings use Persian digits (۱۲۳۴۵۶۷۸۹۰) for human-facing numbers when the locale is fa; format through the platform's locale formatting rather than hand-converting.
Versions, package names, file sizes in technical contexts, and anything copy-pasteable (commands, URLs) stay Latin digits.
Calendars: Gregorian is the default. Where a Solar Hijri option is offered (desktop settings), it is opt-in.

Typography in code

/* Correct stack: Latin falls to Saira, Persian to Estedad */
font-family: "Saira", "Estedad", sans-serif;
/* Estedad needs ~1.05x line-height vs Latin at equal size */

Never letter-space Arabic-script text; joining breaks.
Font sizes in relative units (rem) so Estedad's taller metrics scale with user preferences.
Bold Persian text renders from Estedad Bold; do not synthesize bold via stroke on the Light weight.

Mixed direction (bidi)

Persian sentences routinely contain LTR islands: package names, versions, paths. Rules:

# Rendered inside a Persian sentence, this stays LTR and unbroken:
# «بسته‌ی plasma-desktop به‌روزرسانی شد»

Isolate LTR islands: in HTML/CSS with unicode-bidi: isolate or <bdi>; in Qt with QTextLayout bidi support (automatic in labels); in GTK with Pango markup where needed.
Never assemble mixed-direction strings by concatenation; keep the full sentence in the catalog with placeholders, so the translator controls ordering.

Locale defaults of record

Setting	Value
Locale	`fa_IR.UTF-8` (with `en_US.UTF-8` generated as fallback)
Timezone	`Asia/Tehran`
Keyboard	`fa` layout available from the live session
First-run language	Persian for Iranian installs, selectable everywhere

These are set by the installer (Calamares) and documented as defaults, not constraints: an English install in Germany works identically.

Number/date formatting in practice

# Inspect what the locale produces before hardcoding anything:
$ LC_ALL=fa_IR.UTF-8 python3 -c \
  "import locale; print(locale.format_string('%d', 1234567, grouping=True))"

Prefer platform APIs (locale.format_string, Intl.NumberFormat, Qt QLocale) over hand-rolled formatting; they follow the user's actual locale, which may not be fa.