`Viewport::local_viewport()` resolves the child's viewport-relative (vw / vh / vmin) and fluid Lengths against the viewport's own rect instead of the root layout viewport the sub-canvas inherits since the fluid-resolution inheritance change. That inheritance is right for scroll-like clips (content renders the same size inside and outside), but it is exactly wrong for a fixed-size floating mini-UI — crustace's phone-shaped quick-settings pill pinned to a corner of a desktop-wide surface resolved its vw text and fluid stock geometry against the whole monitor, inflating the content past the pill's fixed clip and cutting off the bottom stripe. The flag pins the sub-canvas's layout viewport to its own size via the new crate-internal Canvas::set_local_layout_viewport, nested sub-canvases keep propagating the pinned value, and a unit test covers the override plus propagation.
`ListItem::height( impl Into<Length> )` and `ListItem::font_size( impl Into<Length> )` mirror the Toggle / Radio height() builders: override the theme row height (floored at the label's rendered height so the text never clips) and the primary-label font size (subtitle and trailing keep their theme sizes), letting dense context menus trade the stock touch-target generosity for row density.
Docs: widgets.md gains both builder sets, architecture.md documents the layout-viewport inheritance model next to the per-canvas density it parallels, the cookbook slide-in panel recipe notes when the pill needs local_viewport(), and the toggle / radio height() rustdoc demotes its private theme::HEIGHT link to a code span so cargo doc is warning-free again. CHANGELOG entries added.
Responsive scaling. ltk now offers two first-class ways to size a UI so it adapts across screens, chosen per process via `WidgetScaling { Fluid, Physical }` (`set_widget_scaling` / `widget_scaling`, default `Fluid`). Fluid sizing (`Length::fluid( px )`) makes a design pixel a proportion of the surface's smaller side, calibrated against a reference width (`set_fluid_reference` / `fluid_reference`, 412 px default) and bounded by `FLUID_MIN` / `FLUID_MAX`; physical sizing (`Length::dp( px )`) is a constant-physical-size pixel scaled by display density (`set_density` / `density`). `Length` gains `orient( portrait, landscape )` — resolve one value in portrait, another in landscape — plus `widget( px )`, which picks fluid or dp per the active mode. Canvas exposes `geom_px` (geometry, resolved in physical layout space) and `font_px` (font size, bridging logical / physical per mode) so widgets and apps share one resolution path. Note the rename: `set_design_reference` / `design_reference` became `set_fluid_reference` / `fluid_reference`, and `Length::dp` changed meaning — the old surface-proportional behaviour now lives on `Length::fluid`.
Widgets. Every stock widget resolves its default geometry and font through the widget-scaling mode instead of frozen pixels, so a whole UI scales coherently without per-call units. New size builders where they were missing: `button` gains `font_size` / `height`, `text_edit` gains `height` / `font_size_fluid`, `separator` gains `pad_v`, and assorted widgets accept a `Length` where they previously took only `f32`.
Overlays. `OverlaySpec::size` is now `( Length, Length )` instead of `( u32, u32 )`, resolved against the main surface when the overlay is materialized, so overlays can scale with the display; `Length::px( … )` reproduces the old fixed sizing.
API stabilization (toward 1.0). Widget struct fields are now `pub( crate )` — they are configured through builders, not field access — except the value / state types apps genuinely read or construct (`Time`, `Date`, `ComboState`), which stay public. The internal `test_support` helpers move behind a `test-support` Cargo feature (off by default, so third-party builds never see them; ltk's own `make test` enables it). `Separator` drops its `0.0`-means-mode sentinel for `Option<Length>`, so an explicit `pad_v( 0.0 )` is a real flush divider distinct from the mode-following default.
Performance guardrails. Opt-in diagnostics via `LTK_PERF_WARN=1` warn about stuck animations, sustained software-render animation, and low `poll_interval`; software-rendered animation is capped near 30 Hz to spare CPU on machines that fall back off EGL. Apps can override the cap with `App::cap_software_animation`.
Docs and build. The two scaling modes are documented in README, onboarding and architecture, with the earlier gradient / backdrop doc drift cleaned up. The Makefile now ships the `locales/` directory into the packaged crate (fixing i18n keys rendering raw for downstreams), builds the new `responsive` example, and runs tests with `--features test-support`.
Each source file that had grown beyond a single concern is replaced by an identically-named directory containing focused submodules. `src/event_loop/mod.rs` (878 lines) becomes a directory with clipboard, context_menu, cursor_shape, drag, focus, handlers, invalidation, overlays_reconcile, repeat, run, surface, text_editing, and tooltip. Every widget, input handler, and theme component follows the same split. Public interfaces are unchanged — only the internal file layout moves.
image bumped from 0.25.2 to 0.25.9.
