New set_text_scale / text_scale process global (clamped [0.5, 3.0]) multiplied into every resolved font size — Canvas::resolve_font for explicit Lengths and the Physical branch of font_px (the Fluid branch routes through resolve_font) — so the whole tree's text follows the accessibility "large text" factor while geometry stays untouched, mirroring GNOME's text-scaling-factor semantics. Unit test covers fonts-scale-geometry-doesn't.
The run loop keeps the factor synced on its own: a watcher thread (event_loop/text_scale.rs) reads org.gnome.desktop.interface text-scaling-factor via gsettings get at startup and streams external changes from gsettings monitor into a calloop channel; on a change the loop stores the factor, invalidates the view caches and repaints main and overlays. Since fonts resolve at paint time nothing else needs rebuilding. Every ltk app tracks the settings slider live with zero app-side wiring, the same way GTK apps follow the key; missing gsettings degrades silently to a fixed 1.0. Embedders driving core::UiSurface (forge) call set_text_scale themselves — the multiplication only runs at widget font resolution, so raw Canvas::draw_text callers keep hand-computed sizes.
architecture.md documents the multiplier in the font-space paragraph and CHANGELOG gains the entry.
Pedro M. de Echanove Pasquin
d9652dce98