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`.
Subsurfaces can now be parented to an overlay surface, not just the main surface. `SubsurfaceSpec` gains `parent: SubsurfaceParent { Main, Overlay(id) }` so a sliding panel can ride above app windows the way an overlay panel does, and an optional `gpu: bool` so content that uses the `surface-panel` backdrop-filter glass (a GLES-only pass) keeps it while sliding instead of dropping to the software rasteriser. `reconcile_subsurfaces` resolves each spec's parent independently — skipping an `Overlay` parent that is absent, unconfigured, or zero-sized — tracks the rastered size on the slot, and commits each touched parent once per frame. The ~14 GLES shader programs are compiled once into a shared `AppData::subsurface_gles_canvas` reused across every subsurface, so a lazily re-created sliding panel never recompiles them (hundreds of ms on a mobile GPU).
Vertical and horizontal swipes are now mutually exclusive: a gesture locks onto its dominant axis within the first 8 px of travel (new `SwipeAxis`) and ignores the perpendicular axis for the rest of the gesture, so a vertical swipe that drifts sideways no longer also drives the pager (and vice-versa). The upward swipe progress is no longer clamped at 1.0 — follow-the-finger panels can keep tracking the finger past the commit threshold — and a release below threshold delivers a final `progress = 0.0` cancellation pulse. A vertical swipe also no longer re-rasters the full-screen main surface on every motion event: only the overlays it drives are refreshed, while the horizontal pager (which does move the main surface) still redraws it. Re-rastering the main on every frame of a vertical drag was wasted work that stalled the loop and made the gesture feel laggy to start on a slow GPU.
Layout-affecting `Length` values (widths, paddings, gaps, widget sizes, including `Vw` / `Vh`) now resolve against the physical viewport via the new `Canvas::viewport_layout()` — the space the layout tree is actually computed in — so a `Vw(100)` fills the surface on a HiDPI (scale 2) output instead of covering half of it. Font sizes are unchanged: they still resolve against the logical viewport and are scaled at raster time. Switched column, row, spacer, wrap_grid, container, image, and vslider over to it; `img_widget` and `vslider` now document `Length::vw` / `vh` sizing and the showcase example demonstrates a viewport-relative image.
Touch gesture state is reset when the touch capability is added or removed — suspend / resume on devices that power the touchscreen down. A yanked capability never delivers the pending `up` / `cancel`, so the shared `reset_touch_state()` (also used by the `wl_touch.cancel` handler) drops the stranded `primary_touch_id` / slot state across the main surface and every overlay, keeping the first post-resume gesture clean. Also drops an accidental duplicate `on_scale_changed` call from the scale-change handler.
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.
