event_loop, a11y, text_shaping: AccessKit AT-SPI2 bridge, cross-app clipboard, xdg-activation, HarfBuzz shaping, multi-touch hooks

Five orthogonal capabilities land together because they share the same `try_run` plumbing: an optional global is bound at startup, a piece of state is added to `AppData`, the run-loop iteration drains an inbox / pushes a frame snapshot, and the public surface gains a small set of opt-in `App` hooks. Nothing here breaks an existing app — every new path degrades to a no-op when the compositor does not advertise the relevant global or when the platform adapter cannot start.
AT-SPI2 accessibility via AccessKit. A new `src/a11y/` module owns the platform adapter and the inbound `ActionRequest` channel. `A11yState::try_new` constructs an `accesskit_unix::Adapter`; when the AT-SPI2 daemon is not on the session bus (headless CI, locked-down compositors) the constructor returns `None` and the rest of the pipeline runs unchanged. After every successful `draw_frame`, the run loop builds a fresh `accesskit::TreeUpdate` from `widget_rects` and pushes it through the adapter — main surface plus every visible overlay, each translated to global coordinates via `surface_offset_for` so screen readers report positions in the same frame the user sees. Buttons / toggles / checkboxes / radios / list items / sliders / text edits map to the matching `Role`s; `Click` and `Focus` actions are advertised on every interactive node; inbound action requests are drained at the top of each iteration and translated into a synthetic press / focus on the matching widget. The integration is documented as best-effort in `docs/architecture.md` under "Known gaps and non-goals": hierarchical nesting, per-widget accessible names, live regions and `Action::SetValue` are listed as the natural follow-ups that the foundation now supports but does not yet wire.
Cross-application clipboard via `wl_data_device_manager`. A new `src/event_loop/data_device.rs` bridges the existing process-local `clipboard: String` to the Wayland selection. Outbound (Ctrl+C / Cut): after the local clipboard is populated, `publish_clipboard_selection` creates a `CopyPasteSource` offering `text/plain;charset=utf-8` and installs it as the seat's selection; `DataSourceHandler::send` writes the cached string into the fd the peer hands us. Inbound (Ctrl+V from another app): `DataDeviceHandler::selection` asks for the offered text via `WlDataOffer::receive`, spawns a tiny worker thread to drain the read pipe with a 16 MiB cap to prevent paste-bomb DoS, and posts the result back through an `mpsc::Sender` that the run loop drains each iteration into `data.clipboard`. The `clipboard:` field's doc-comment is updated to reflect the new behaviour: process-local when the compositor does not advertise the global, synchronised with the seat selection otherwise.
External drag-and-drop reception. The same `data_device` module handles `DragOffer` enter / motion / leave / drop_performed: `on_drop_motion( x, y )` fires while the drag hovers over the surface, `on_drop_leave()` when it withdraws without dropping, and `on_drop_received( x, y, mime, text )` when an external payload (`text/uri-list`, `text/plain`, …) is released on top of an ltk window. The receive path reuses the same worker-thread / channel pattern as the clipboard so the run loop never blocks on the read fd. Three new `App` hooks expose the events with no-op defaults; apps that ignore them get the previous behaviour.
`xdg-activation-v1`. The global is bound optionally; when it is present, `try_run` reads `$XDG_ACTIVATION_TOKEN` from the environment, removes it immediately (single-use; preventing leaks into child processes) and stashes it on `AppData::activation_token_pending`. After the first successful configure of the main surface — the earliest point at which `xdg_activation_v1.activate` is meaningful — the token is consumed once and the surface raised to focus. Compositors without the global leave `activation_state` as `None` and the inbound path silently degrades. An `App::request_activation_token` outbound path is reserved on the trait but not yet exercised here.
HarfBuzz shaping. A new `src/text_shaping.rs::shape_line` drives both renderers: the logical-order string is run through `unicode-bidi`, split into per-font sub-runs, and shaped through `rustybuzz`. Each `PositionedGlyph` carries the per-font `glyph_id`, the visual advance and the ink offsets — exactly what `fontdue::Font::rasterize_indexed` needs to render Arabic connected forms, Devanagari clusters and CJK shaped glyphs correctly. The GLES atlas is re-keyed on `(glyph_id, size_bits, font_id)` so glyphs from different fonts at the same size no longer collide, and the atlas format is selected per ES profile (`GL_R8` / `GL_RED` on ES3, `GL_LUMINANCE` on ES2) — the fragment shader samples `.r` for both, since `GL_LUMINANCE` replicates the coverage byte into `.r=.g=.b`. Software path follows the same key. New `Cargo.toml` deps: `unicode-bidi = "0.3"`, `rustybuzz = "0.14"`.
Multi-touch hooks. `App::on_touch_down / on_touch_move / on_touch_up( id, x, y )` expose the raw `wl_touch.id` of every secondary finger. The first finger to land remains the *primary slot* and is fed through the regular gesture machine (`on_pointer_*`, swipe, scroll, long-press, drag-and-drop). Every additional finger fires the new callbacks instead, leaving the existing single-slot behaviour untouched for apps that do not override them. This is the substrate for app-defined pinch-zoom / two-finger pan; the toolkit itself does not yet ship a built-in pinch gesture (called out in the same "Known gaps" doc section).
`event_loop::frame` extracted from `draw/mod.rs`. The `draw_frame` orchestrator and its per-format SHM helper (`pick_shm_format`) move into `src/event_loop/frame.rs`, leaving `draw/` strictly responsible for per-surface paint primitives. The import in `event_loop/run.rs` is rewritten accordingly; `draw/mod.rs` shrinks from 192-line orchestrator to a thin module index.
Overlay teardown safety. `AppData::discard_overlay( id )` synchronously removes a destroyed overlay from the map and rewrites every per-device focus that pointed at it (pointer, keyboard, every touch slot), migrating an in-flight long-press drag to the main surface the same way `reconcile_overlays` does. Used by the compositor-driven destruction paths (`PopupHandler::done`, `LayerShellHandler::closed`) where waiting for the next reconcile would leave a window in which `surface()` / `surface_mut()` panic. The non-panicking siblings `try_surface` / `try_surface_mut` are added for callers on async dispatch paths (IME `Done`, tooltip arm) that may race a teardown.
Miscellaneous. CI: `master` → `main` to match the actual default branch. `Makefile` adds `cargo run --example dialog` to the examples target. `src/lib.rs` re-exports `widget::scroll::ScrollAxis` so apps can configure a `scroll()` axis without reaching into a `pub(crate)` module. `Cargo.toml` adds `accesskit = "0.17"` and `accesskit_unix = "0.13"`. `docs/architecture.md` gains the "Known gaps and non-goals" section that enumerates the new capabilities, what still ships flat, and what is deferred (per-widget a11y labels, primary selection, intra-process multi-touch gestures, `wp_fractional_scale_v1`).

src/a11y/mod.rs

@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: LGPL-2.1-only
+// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>
+
+//! AT-SPI2 accessibility via AccessKit.
+//!
+//! ltk does not implement the D-Bus AT-SPI2 protocol itself — that is
+//! delegated to [`accesskit_unix`], which translates a backend-neutral
+//! [`accesskit::TreeUpdate`] into the corresponding D-Bus calls,
+//! registers the application against `org.a11y.Bus`, and emits the
+//! property / state / focus change signals Orca and friends listen
+//! for. Our job is two-way:
+//!
+//! 1. **Outbound**: every frame, after the layout pass has populated
+//!    `widget_rects`, build a fresh [`accesskit::TreeUpdate`] from
+//!    those rects and push it into the adapter through
+//!    [`A11yState::update`]. The runtime calls this from the same
+//!    place that runs `draw_frame`, so the accessible tree is always
+//!    in sync with what the user can see.
+//!
+//! 2. **Inbound**: an [`accesskit::ActionRequest`] from an assistive
+//!    technology (Orca pressing the "Default Action" on a button, a
+//!    switch-control device focusing the next node, …) lands on the
+//!    [`ActionForwarder`] running inside the adapter's worker
+//!    thread; the forwarder pushes it through an `mpsc::Sender` into
+//!    the run loop, which drains the channel each iteration and
+//!    translates the request into a synthetic press / focus on the
+//!    target widget.
+//!
+//! The adapter is constructed unconditionally — `accesskit_unix`
+//! never refuses creation, it just stays inactive when no AT client
+//! attaches to the session bus. Nothing else in the pipeline reads
+//! the field except the per-frame tree update and the per-iteration
+//! action inbox drain, so the rest of the runtime is unaware of
+//! whether an AT is listening or not.
+
+pub( crate ) mod tree;
+
+use std::sync::mpsc;
+
+use accesskit::{ ActionRequest, Rect as A11yRect, TreeUpdate };
+
+/// Channel carrying inbound action requests from the AccessKit
+/// adapter thread to the run loop.
+pub( crate ) type ActionInbox = mpsc::Receiver<ActionRequest>;
+
+/// Top-level accessibility state owned by `AppData`. Holds the
+/// platform adapter alongside the receiver half of the action
+/// channel.
+pub( crate ) struct A11yState
+{
+	adapter:                accesskit_unix::Adapter,
+	pub( crate ) action_rx: ActionInbox,
+}
+
+impl A11yState
+{
+	/// Bring up the AccessKit adapter. Returns `None` only when we
+	/// reserve the right to refuse creation in the future (currently
+	/// always `Some` — `accesskit_unix::Adapter::new` is infallible
+	/// and stays inactive when no AT client is attached). Keeping
+	/// the `Option` lets us toggle accessibility off at runtime via
+	/// an env var or feature flag without re-plumbing every call
+	/// site.
+	pub( crate ) fn try_new( _app_name: &str, _app_id: &str ) -> Option<Self>
+	{
+		let ( action_tx, action_rx ) = mpsc::channel();
+		let adapter = accesskit_unix::Adapter::new(
+			ActivationStub,
+			ActionForwarder { tx: action_tx },
+			DeactivationStub,
+		);
+		Some( Self { adapter, action_rx } )
+	}
+
+	/// Push a freshly-built tree into the adapter. The closure is
+	/// invoked synchronously **only** when AT-SPI2 is currently
+	/// observing the application (an AT client connected to the
+	/// daemon and queried us at least once), so the cost of
+	/// constructing the tree is paid only when something is actually
+	/// listening.
+	pub( crate ) fn update<F>( &mut self, factory: F )
+	where
+		F: FnOnce() -> TreeUpdate,
+	{
+		self.adapter.update_if_active( factory );
+	}
+
+	/// AT-SPI clients filter by window focus; without it Orca skips
+	/// the surface entirely.
+	pub( crate ) fn set_window_focus( &mut self, focused: bool )
+	{
+		self.adapter.update_window_focus_state( focused );
+	}
+
+	pub( crate ) fn set_window_bounds( &mut self, width: f64, height: f64 )
+	{
+		let r = A11yRect { x0: 0.0, y0: 0.0, x1: width, y1: height };
+		self.adapter.set_root_window_bounds( r, r );
+	}
+
+	#[ allow( dead_code ) ]
+	pub( crate ) fn notify_focus( &mut self, new_focus: accesskit::NodeId )
+	{
+		self.adapter.update_if_active( ||
+		{
+			TreeUpdate
+			{
+				nodes: vec![],
+				tree:  None,
+				focus: new_focus,
+			}
+		} );
+	}
+}
+
+/// Activation handler the adapter calls when an assistive technology
+/// first attaches and asks for the initial tree. We hand back an
+/// empty root — the first proper update comes from the run loop on
+/// the very next frame, which is the natural moment to materialise a
+/// real tree (the widget_rects are populated by then).
+struct ActivationStub;
+
+impl accesskit::ActivationHandler for ActivationStub
+{
+	fn request_initial_tree( &mut self ) -> Option<TreeUpdate>
+	{
+		Some( tree::empty_root() )
+	}
+}
+
+/// Action handler that simply forwards every incoming request to the
+/// main event loop. The translation from `ActionRequest` to a
+/// synthetic press / focus happens on the main thread so it can
+/// touch the rest of `AppData` without locking.
+struct ActionForwarder
+{
+	tx: mpsc::Sender<ActionRequest>,
+}
+
+impl accesskit::ActionHandler for ActionForwarder
+{
+	fn do_action( &mut self, request: ActionRequest )
+	{
+		let _ = self.tx.send( request );
+	}
+}
+
+/// Deactivation handler. AccessKit invokes this when every AT client
+/// detaches; we have no per-client cleanup so it's a no-op.
+struct DeactivationStub;
+
+impl accesskit::DeactivationHandler for DeactivationStub
+{
+	fn deactivate_accessibility( &mut self ) {}
+}