An app whose gesture/animation only moves an input-transparent subsurface (a slide-to-reveal panel over a static main surface) still paid a full main-surface re-raster on every frame of the slide, because the runtime force-dirties the main view on two paths it cannot tell apart from a real content change: `MoveOutcome::Swipe` calls `dirty_caches()` + `request_redraw()` per motion sample, and the `WlCallback` Main handler sets `view_dirty` + `request_redraw()` on every frame callback while `is_animating`. The subsurface reconcile already repositions the panel with a cheap `set_position` + bare parent commit, so the main re-raster is wasted work — and on slow targets (Librem5) it competes with the reposition and makes the slide stutter.
New opt-in `App::subsurface_motion_only` (default `false`, so existing apps are unaffected). When it returns `true`:
- the swipe dispatch (`input/dispatch/outcomes.rs`) still calls the `on_swipe_progress` family but skips `dirty_caches()` / `request_redraw()`; incoming motion events pump the loop and the per-iteration `reconcile_subsurfaces` carries the move.
- the frame-callback animation pump (`event_loop/handlers.rs`) keeps the vsync cadence without a re-raster by requesting a bare `wl.frame()` + `commit()` on the main surface (no buffer attach) instead of dirtying the view; `poll_external` advances the animation and the reconcile repositions each frame.
The main surface still redraws for genuine content changes (messages, resize, the one-shot redraw on swipe release) — only the per-frame slide raster is dropped.
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.
