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/input/gesture/mod.rs

@@ -67,7 +67,7 @@ pub struct GestureState<Msg: Clone>
 	pub pressed_idx:             Option<usize>,
 	/// Index of the Scroll viewport that owns the current gesture, if
 	/// the press landed inside one.
-	pub scrolling_widget:        Option<usize>,
+	pub scrolling_widget:        Option<( usize, crate::widget::scroll::ScrollAxis )>,
 	/// Scroll-viewport drag exceeded the 8 px start tolerance — the
 	/// release will be consumed as a scroll instead of a tap.
 	pub scroll_drag_started:     bool,
@@ -161,7 +161,7 @@ impl<Msg: Clone> GestureState<Msg>
 		&mut self,
 		pos:          Point,
 		widget_rects: &[LaidOutWidget<Msg>],
-		scroll_rects: &[( Rect, usize )],
+		scroll_rects: &[( Rect, usize, crate::widget::scroll::ScrollAxis )],
 	) -> PressOutcome<Msg>
 	{
 		let hit = find_widget_at( widget_rects, pos );
@@ -176,8 +176,8 @@ impl<Msg: Clone> GestureState<Msg>
 
 		self.start                   = Some( pos );
 		self.scrolling_widget        = scroll_rects.iter().rev()
-			.find( |( r, _ )| r.contains( pos ) )
-			.map( |( _, idx )| *idx );
+			.find( |( r, _, _ )| r.contains( pos ) )
+			.map( |( _, idx, ax )| ( *idx, *ax ) );
 		self.scroll_drag_started     = false;
 		self.horizontal_drag_started = false;
 		self.vertical_drag_started   = false;
@@ -238,7 +238,7 @@ impl<Msg: Clone> GestureState<Msg>
 		&mut self,
 		pos:            Point,
 		widget_rects:   &[LaidOutWidget<Msg>],
-		scroll_offsets: &mut HashMap<usize, f32>,
+		scroll_offsets: &mut HashMap<usize, ( f32, f32 )>,
 		swipe:          &SwipeConfig,
 		global_drag:    bool,
 	) -> MoveOutcome<Msg>
@@ -292,15 +292,23 @@ impl<Msg: Clone> GestureState<Msg>
 		// Scroll viewport drag: mutate offset in place and advance the
 		// gesture origin so the next delta is frame-to-frame, not
 		// press-to-now (otherwise the first 8 px trip the threshold
-		// and the entire scroll gets absorbed into one delta).
-		if let Some( scroll_idx ) = self.scrolling_widget
+		// and the entire scroll gets absorbed into one delta). Both
+		// axes are routed independently; an axis the viewport does not
+		// allow is just ignored (delta still consumed by the gesture,
+		// so the swipe handler does not fight the scroll for it).
+		if let Some( ( scroll_idx, axis ) ) = self.scrolling_widget
 		{
 			if let Some( start ) = self.start
 			{
+				let dx    = pos.x - start.x;
 				let dy    = pos.y - start.y;
-				let entry = scroll_offsets.entry( scroll_idx ).or_insert( 0.0 );
-				*entry    = ( *entry - dy ).max( 0.0 );
-				if dy.abs() > 8.0 { self.scroll_drag_started = true; }
+				let entry = scroll_offsets.entry( scroll_idx ).or_insert( ( 0.0, 0.0 ) );
+				if axis.allows_x() { entry.0 = ( entry.0 - dx ).max( 0.0 ); }
+				if axis.allows_y() { entry.1 = ( entry.1 - dy ).max( 0.0 ); }
+				let moved = if axis.allows_x() && axis.allows_y() { dx.hypot( dy ) }
+				            else if axis.allows_x()               { dx.abs() }
+				            else                                   { dy.abs() };
+				if moved > 8.0 { self.scroll_drag_started = true; }
 				self.start = Some( pos );
 				return MoveOutcome::Scroll;
 			}