FontDb cataloged the system fonts only when a character needed a fallback
(nothing else calls load_system_fonts), so a document set in an installed
family was composed in Source Sans 3, and font.list and preflight reported
the family missing (#22).
Every lookup by family name now waits for one scan of the font folders per
session, as VectorCraft does since #130: the app starts the scan in the
background at startup, other processes run it on first use. The scan reads
only each file's table directory and name table, and skips folders it has
already read, so a symlink loop can't hang it. has_family counts installed
families. FontDb::with_font_dirs and system_font_dirs let tests use their
own font folder.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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