data_device: let the compositor interact with the selection

anvil/src/udev.rs

@@ -108,7 +108,12 @@ pub fn run_udev(mut display: Display, mut event_loop: EventLoop<()>, log: Logger
 
     let udev_session_id = notifier.register(&mut udev_backend);
 
-    init_data_device(&mut display.borrow_mut(), ::misc::dnd_action_chooser, log.clone());
+    init_data_device(
+        &mut display.borrow_mut(),
+        |_| {},
+        ::misc::dnd_action_chooser,
+        log.clone(),
+    );
 
     let (mut w_seat, _) = Seat::new(&mut display.borrow_mut(), session.seat(), log.clone());
 

anvil/src/winit.rs

@@ -54,7 +54,7 @@ pub fn run_winit(display: &mut Display, event_loop: &mut EventLoop<()>, log: Log
 
     let (compositor_token, _, _, window_map) = init_shell(display, log.clone());
 
-    init_data_device(display, ::misc::dnd_action_chooser, log.clone());
+    init_data_device(display, |_| {}, ::misc::dnd_action_chooser, log.clone());
 
     let (mut seat, _) = Seat::new(display, "winit".into(), log.clone());
 

src/wayland/data_device/mod.rs

@@ -1,3 +1,4 @@
+use std::os::unix::io::RawFd;
 use std::sync::{Arc, Mutex};
 
 use wayland_server::{
@@ -16,9 +17,25 @@ mod dnd_grab;
 
 pub use self::data_source::{with_source_metadata, SourceMetadata};
 
+/// Events that are generated by interactions of the clients with the data device
+pub enum DataDeviceEvent {
+    /// A client has set the selection
+    NewSelection(Option<Resource<wl_data_source::WlDataSource>>),
+    /// A client started a drag'n'drop as response to a user pointer action
+    DnDStarted(Option<Resource<wl_data_source::WlDataSource>>),
+    /// A client requested to read the server-set selection
+    SendSelection {
+        // the requested mime type
+        mime_type: String,
+        // the fd to write into
+        fd: RawFd,
+    },
+}
+
 enum Selection {
     Empty,
     Client(Resource<wl_data_source::WlDataSource>),
+    Compositor(SourceMetadata),
 }
 
 struct SeatData {
@@ -109,6 +126,50 @@ impl SeatData {
                     dd.send(wl_data_device::Event::Selection { id: Some(offer) });
                 }
             }
+            Selection::Compositor(ref meta) => {
+                for dd in &self.known_devices {
+                    // skip data devices not belonging to our client
+                    if dd.client().map(|c| !c.equals(client)).unwrap_or(true) {
+                        continue;
+                    }
+                    let log = self.log.clone();
+                    let offer_meta = meta.clone();
+                    let callback = dd
+                        .user_data::<Arc<Mutex<FnMut(DataDeviceEvent) + Send + 'static>>>()
+                        .unwrap()
+                        .clone();
+                    // create a corresponding data offer
+                    let offer = client
+                        .create_resource::<wl_data_offer::WlDataOffer>(dd.version())
+                        .unwrap()
+                        .implement(
+                            move |req, _offer| match req {
+                                wl_data_offer::Request::Receive { fd, mime_type } => {
+                                    // check if the associated mime type is valid
+                                    if !offer_meta.mime_types.contains(&mime_type) {
+                                        // deny the receive
+                                        debug!(log, "Denying a wl_data_offer.receive with invalid source.");
+                                        let _ = ::nix::unistd::close(fd);
+                                    } else {
+                                        (&mut *callback.lock().unwrap())(DataDeviceEvent::SendSelection {
+                                            mime_type,
+                                            fd,
+                                        });
+                                    }
+                                }
+                                _ => { /* seleciton data offers only care about the `receive` event */ }
+                            },
+                            None::<fn(_)>,
+                            (),
+                        );
+                    // advertize the offer to the client
+                    dd.send(wl_data_device::Event::DataOffer { id: offer.clone() });
+                    for mime_type in meta.mime_types.iter().cloned() {
+                        offer.send(wl_data_offer::Event::Offer { mime_type })
+                    }
+                    dd.send(wl_data_device::Event::Selection { id: Some(offer) });
+                }
+            }
         }
     }
 }
@@ -131,19 +192,22 @@ impl SeatData {
 /// available actions (which is the intersection of the actions supported by the source and targets)
 /// and the second argument is the preferred action reported by the target. If no action should be
 /// chosen (and thus the drag'n'drop should abort on drop), return `DndAction::empty()`.
-pub fn init_data_device<F, L>(
+pub fn init_data_device<F, C, L>(
     display: &mut Display,
+    callback: C,
     action_choice: F,
     logger: L,
 ) -> Global<wl_data_device_manager::WlDataDeviceManager>
 where
     F: FnMut(DndAction, DndAction) -> DndAction + Send + 'static,
+    C: FnMut(DataDeviceEvent) + Send + 'static,
     L: Into<Option<::slog::Logger>>,
 {
     let log = ::slog_or_stdlog(logger).new(o!("smithay_module" => "data_device_mgr"));
     let action_choice = Arc::new(Mutex::new(action_choice));
+    let callback = Arc::new(Mutex::new(callback));
     let global = display.create_global(3, move |new_ddm, _version| {
-        implement_ddm(new_ddm, action_choice.clone(), log.clone());
+        implement_ddm(new_ddm, callback.clone(), action_choice.clone(), log.clone());
     });
 
     global
@@ -165,13 +229,38 @@ pub fn set_data_device_focus(seat: &Seat, client: Option<Client>) {
     seat_data.lock().unwrap().set_focus(client);
 }
 
-fn implement_ddm<F>(
+/// Set a compositor-provided selection for this seat
+///
+/// You need to provide the available mime types for this selection.
+///
+/// Whenever a client requests to read the selection, your callback will
+/// receive a `DataDeviceEvent::SendSelection` event.
+pub fn set_data_device_selection(seat: &Seat, mime_types: Vec<String>) {
+    // TODO: same question as in set_data_device_focus
+    seat.user_data().insert_if_missing(|| {
+        Mutex::new(SeatData::new(
+            seat.arc.log.new(o!("smithay_module" => "data_device_mgr")),
+        ))
+    });
+    let seat_data = seat.user_data().get::<Mutex<SeatData>>().unwrap();
+    seat_data
+        .lock()
+        .unwrap()
+        .set_selection(Selection::Compositor(SourceMetadata {
+            mime_types,
+            dnd_action: DndAction::empty(),
+        }));
+}
+
+fn implement_ddm<F, C>(
     new_ddm: NewResource<wl_data_device_manager::WlDataDeviceManager>,
+    callback: Arc<Mutex<C>>,
     action_choice: Arc<Mutex<F>>,
     log: ::slog::Logger,
 ) -> Resource<wl_data_device_manager::WlDataDeviceManager>
 where
     F: FnMut(DndAction, DndAction) -> DndAction + Send + 'static,
+    C: FnMut(DataDeviceEvent) + Send + 'static,
 {
     use self::wl_data_device_manager::Request;
     new_ddm.implement(
@@ -185,8 +274,13 @@ where
                     seat.user_data()
                         .insert_if_missing(|| Mutex::new(SeatData::new(log.clone())));
                     let seat_data = seat.user_data().get::<Mutex<SeatData>>().unwrap();
-                    let data_device =
+                    let data_device = implement_data_device(
-                        implement_data_device(id, seat.clone(), action_choice.clone(), log.clone());
+                        id,
+                        seat.clone(),
+                        callback.clone(),
+                        action_choice.clone(),
+                        log.clone(),
+                    );
                     seat_data.lock().unwrap().known_devices.push(data_device);
                 }
                 None => {
@@ -199,16 +293,19 @@ where
     )
 }
 
-fn implement_data_device<F>(
+fn implement_data_device<F, C>(
     new_dd: NewResource<wl_data_device::WlDataDevice>,
     seat: Seat,
+    callback: Arc<Mutex<C>>,
     action_choice: Arc<Mutex<F>>,
     log: ::slog::Logger,
 ) -> Resource<wl_data_device::WlDataDevice>
 where
     F: FnMut(DndAction, DndAction) -> DndAction + Send + 'static,
+    C: FnMut(DataDeviceEvent) + Send + 'static,
 {
     use self::wl_data_device::Request;
+    let callback2 = callback.clone();
     new_dd.implement(
         move |req, dd| match req {
             Request::StartDrag {
@@ -221,6 +318,7 @@ where
                 if let Some(pointer) = seat.get_pointer() {
                     if pointer.has_grab(serial) {
                         // The StartDrag is in response to a pointer implicit grab, all is good
+                        (&mut *callback.lock().unwrap())(DataDeviceEvent::DnDStarted(source.clone()));
                         pointer.set_grab(
                             dnd_grab::DnDGrab::new(source, origin, seat.clone(), action_choice.clone()),
                             serial,
@@ -239,6 +337,7 @@ where
                         .unwrap_or(false)
                     {
                         let seat_data = seat.user_data().get::<Mutex<SeatData>>().unwrap();
+                        (&mut *callback.lock().unwrap())(DataDeviceEvent::NewSelection(source.clone()));
                         // The client has kbd focus, it can set the selection
                         seat_data
                             .lock()
@@ -261,6 +360,6 @@ where
             }
         },
         None::<fn(_)>,
-        (),
+        callback2 as Arc<Mutex<FnMut(DataDeviceEvent) + Send + 'static>>,
     )
 }