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/render/setup.rs

@@ -10,29 +10,36 @@ use std::sync::{ Arc, OnceLock };
 use fontdue::{ Font, FontSettings };
 use tiny_skia::{ Pixmap, PixmapPaint, Transform };
 
+use crate::system_fonts::FontHandle;
 use crate::theme::{ FontRegistry, FontStyle };
 
 use super::helpers::load_default_font_bytes;
 use super::SoftwareCanvas;
 
-/// Process-wide cache of the default font face. Avoids re-reading +
-/// re-parsing the file on every surface bring-up. Sora is small
-/// (~50 KB) so the cost was minor in absolute terms — but a layer
-/// shell that brings up a launcher overlay, a QS panel, a calendar
-/// popup and a handful of toast surfaces would still pay the parse
-/// cost a dozen times in a single session, all of which is wasted
-/// work.
-static DEFAULT_FONT: OnceLock<Arc<Font>> = OnceLock::new();
+/// Process-wide cache of the default font face. The handle keeps the
+/// raw bytes (`Arc<Vec<u8>>`) alongside the fontdue `Arc<Font>` so
+/// the HarfBuzz shaper can be invoked without re-reading the file.
+/// Sora is small (~50 KB) so the cost was minor in absolute terms —
+/// but a layer shell that brings up a launcher overlay, a QS panel,
+/// a calendar popup and a handful of toast surfaces would still pay
+/// the parse cost a dozen times in a single session, all of which
+/// is wasted work.
+static DEFAULT_FONT: OnceLock<FontHandle> = OnceLock::new();
 
-fn default_font() -> Arc<Font>
+fn default_handle() -> FontHandle
 {
-	Arc::clone( DEFAULT_FONT.get_or_init( ||
+	DEFAULT_FONT.get_or_init( ||
 	{
 		let bytes = load_default_font_bytes();
 		let font  = Font::from_bytes( bytes.as_slice(), FontSettings::default() )
 			.expect( "bad font" );
-		Arc::new( font )
-	} ) )
+		FontHandle
+		{
+			font:  Arc::new( font ),
+			bytes: Arc::new( bytes ),
+			face:  0,
+		}
+	} ).clone()
 }
 
 impl SoftwareCanvas
@@ -47,10 +54,13 @@ impl SoftwareCanvas
 	/// process reuses the cached `Arc<Font>`.
 	pub fn new( width: u32, height: u32 ) -> Self
 	{
+		let handle = default_handle();
 		Self
 		{
 			pixmap:          Pixmap::new( width, height ).expect( "pixmap" ),
-			font:            default_font(),
+			font:            handle.font.clone(),
+			font_bytes:      handle.bytes.clone(),
+			font_face:       handle.face,
 			font_registry:   None,
 			dpi_scale:       1.0,
 			global_alpha:    1.0,
@@ -67,6 +77,8 @@ impl SoftwareCanvas
 		{
 			pixmap:         Pixmap::new( width, height ).expect( "pixmap" ),
 			font:           Arc::clone( &self.font ),
+			font_bytes:     Arc::clone( &self.font_bytes ),
+			font_face:      self.font_face,
 			font_registry:  self.font_registry.as_ref().map( Arc::clone ),
 			dpi_scale:      self.dpi_scale,
 			global_alpha:   self.global_alpha,
@@ -110,6 +122,33 @@ impl SoftwareCanvas
 		crate::system_fonts::lookup( ch ).unwrap_or_else( || Arc::clone( &self.font ) )
 	}
 
+	/// Bytes-aware variant of [`Self::font_for_char`]. Returns the
+	/// full `FontHandle` so callers that invoke the HarfBuzz shaper
+	/// can hand the raw bytes directly to rustybuzz. The primary
+	/// font supplies the bytes from
+	/// [`Self::font_bytes`]; fallback chars borrow the bytes that
+	/// were loaded into the system fallback cache.
+	pub fn font_handle_for_char( &self, ch: char ) -> crate::system_fonts::FontHandle
+	{
+		if self.font.lookup_glyph_index( ch ) != 0
+		{
+			return crate::system_fonts::FontHandle
+			{
+				font:  Arc::clone( &self.font ),
+				bytes: Arc::clone( &self.font_bytes ),
+				face:  self.font_face,
+			};
+		}
+		crate::system_fonts::lookup_handle( ch ).unwrap_or_else( ||
+			crate::system_fonts::FontHandle
+			{
+				font:  Arc::clone( &self.font ),
+				bytes: Arc::clone( &self.font_bytes ),
+				face:  self.font_face,
+			}
+		)
+	}
+
 	pub fn blit( &mut self, src: &SoftwareCanvas, dest_x: i32, dest_y: i32 )
 	{
 		let paint = PixmapPaint::default();