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/event_loop/handlers.rs

@@ -143,10 +143,15 @@ impl<A: App> LayerShellHandler for AppData<A>
 			}
 			Some( super::SurfaceFocus::Overlay( id ) ) =>
 			{
-				// Compositor asked us to destroy this overlay. Remove it;
-				// the next reconcile will not recreate it unless the app
-				// still returns its id from `App::overlays()`.
-				self.overlays.remove( &id );
+				// Compositor asked us to destroy this overlay. Drop it
+				// synchronously *and* rewrite every per-device focus that
+				// pointed at it — otherwise the next event in this same
+				// dispatch (touch up, IME done, pointer leave) lands on a
+				// freed surface and `surface()` / `surface_mut()` panic.
+				// `reconcile_overlays` will still run afterwards and skip
+				// re-creating the entry as long as the app stops returning
+				// its id from `overlays()`.
+				self.discard_overlay( id );
 			}
 		}
 	}
@@ -266,8 +271,23 @@ impl<A: App> SeatHandler for AppData<A>
 	}
 
 	fn new_seat(
-		&mut self, _conn: &Connection, _qh: &QueueHandle<Self>, _seat: WlSeat,
-	) {}
+		&mut self, _conn: &Connection, qh: &QueueHandle<Self>, seat: WlSeat,
+	)
+	{
+		// First seat → first data device. We only need one device
+		// regardless of how many seats appear (the typical desktop
+		// session has exactly one); additional seats reuse the same
+		// device-bound clipboard semantics by construction because
+		// `wl_data_device_manager.get_data_device` takes the seat as
+		// argument and the compositor manages routing.
+		if self.data_device.is_none()
+		{
+			if let Some( ref ddm ) = self.data_device_manager
+			{
+				self.data_device = Some( ddm.get_data_device( qh, &seat ) );
+			}
+		}
+	}
 
 	fn new_capability(
 		&mut self,
@@ -369,7 +389,9 @@ impl<A: App> PopupHandler for AppData<A>
 			{
 				self.pending_msgs.push( msg );
 			}
-			self.overlays.remove( &id );
+			// Synchronous teardown plus per-device focus cleanup. See
+			// `discard_overlay` for the panic case this prevents.
+			self.discard_overlay( id );
 		}
 	}
 }
@@ -389,6 +411,27 @@ delegate_xdg_window!(  @<A: App> AppData<A> );
 delegate_xdg_popup!(   @<A: App> AppData<A> );
 delegate_foreign_toplevel_list!( @<A: App> AppData<A> );
 delegate_registry!(    @<A: App> AppData<A> );
+smithay_client_toolkit::delegate_activation!( @<A: App> AppData<A> );
+smithay_client_toolkit::delegate_data_device!( @<A: App> AppData<A> );
+
+// --- `xdg-activation-v1` handler ---
+//
+// We only honour inbound activation here: when a token issued for our
+// own request gets delivered, we activate the main surface. Outbound
+// requests (so the app can pass a token to another app) are out of
+// scope for now — adding them only requires a new public method on
+// `AppData` and an extra trait method on `App`.
+impl<A: App> smithay_client_toolkit::activation::ActivationHandler for AppData<A>
+{
+	type RequestData = smithay_client_toolkit::activation::RequestData;
+	fn new_token( &mut self, token: String, _data: &Self::RequestData )
+	{
+		if let ( Some( ref activation ), Some( wl ) ) = ( self.activation_state.as_ref(), self.main.surface.try_wl_surface() )
+		{
+			activation.activate::<Self>( &wl, token );
+		}
+	}
+}
 
 impl<A: App> ProvidesRegistryState for AppData<A>
 {
@@ -581,16 +624,16 @@ impl<A: App> Dispatch<ZwpTextInputV3, ()> for AppData<A>
 					}
 				}
 			}
-			zwp_text_input_v3::Event::DeleteSurroundingText { before_length, .. } =>
+			zwp_text_input_v3::Event::DeleteSurroundingText { before_length, after_length } =>
 			{
-				for _ in 0..before_length
-				{
-					state.handle_backspace( focus );
-				}
+				state.handle_delete_surrounding( focus, before_length, after_length );
 			}
 			zwp_text_input_v3::Event::Done { .. } =>
 			{
-				state.surface_mut( focus ).request_redraw();
+				if let Some( ss ) = state.try_surface_mut( focus )
+				{
+					ss.request_redraw();
+				}
 			}
 			_ => {}
 		}