feat: drag the preview out

src/host.rs

@@ -5,9 +5,12 @@ use std::collections::BTreeSet;
 use std::io::{ErrorKind, Read, Write};
 use std::os::unix::net::{UnixListener, UnixStream};
 use std::path::Path;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::{Duration, Instant};
 
 use anyhow::{Context, Result};
+use smithay_client_toolkit::data_device_manager::{WritePipe, data_source::DragSource};
 use smithay_client_toolkit::reexports::calloop::{
     EventLoop, Interest, LoopHandle, Mode, PostAction,
     generic::Generic,
@@ -16,15 +19,16 @@ use smithay_client_toolkit::reexports::calloop::{
 use smithay_client_toolkit::reexports::calloop_wayland_source::WaylandSource;
 use smithay_client_toolkit::seat::pointer::{BTN_LEFT, PointerEvent, PointerEventKind};
 use smithay_client_toolkit::shell::wlr_layer::LayerSurface;
+use wayland_client::protocol::{wl_data_device_manager::DndAction, wl_data_source::WlDataSource};
 use wayland_client::{Connection, QueueHandle, protocol::wl_surface::WlSurface};
-use wayland_protocols::wp::cursor_shape::v1::client::wp_cursor_shape_device_v1::{
-    Shape, WpCursorShapeDeviceV1,
-};
+use wayland_protocols::wp::cursor_shape::v1::client::wp_cursor_shape_device_v1::Shape;
+use wayland_protocols::wp::viewporter::client::wp_viewport::WpViewport;
 
+use crate::dnd::{self, Outcome};
 use crate::ipc::{self, Reply, Request};
 use crate::lock::Lock;
 use crate::stack;
-use crate::thumbnail::{Action, Parts, Thumbnail};
+use crate::thumbnail::{Action, DragStart, Parts, Thumbnail};
 use crate::wayland::{State, Wayland};
 
 /// A host nobody connects to within this time gives up.
@@ -89,6 +93,19 @@ pub struct Host {
     conn: Connection,
     handle: LoopHandle<'static, State>,
     qh: QueueHandle<State>,
+    drag: Option<Drag>,
+    /// Threads still writing dropped data; the host waits for them, or the
+    /// receiving app would get a cut-off file.
+    writers: Arc<AtomicUsize>,
+    warned_no_dnd: bool,
+}
+
+/// The drag-out in progress. Dropping the source cancels the drag.
+struct Drag {
+    thumb: u64,
+    source: DragSource,
+    icon: WlSurface,
+    icon_viewport: WpViewport,
 }
 
 /// Runs the host until its last thumbnail closes. A second host exits
@@ -128,6 +145,9 @@ pub fn run() -> Result<()> {
         conn,
         handle: handle.clone(),
         qh,
+        drag: None,
+        writers: Arc::new(AtomicUsize::new(0)),
+        warned_no_dnd: false,
     });
 
     let mut next_client = 0u64;
@@ -152,7 +172,8 @@ pub fn run() -> Result<()> {
         .run(Duration::from_millis(500), &mut state, |state| {
             let host = state.preview.as_mut().expect("host state");
             host.tidy();
-            if host.core.should_exit(host.thumbs.len(), Instant::now()) {
+            let busy = host.thumbs.len() + host.writers.load(Ordering::SeqCst);
+            if host.core.should_exit(busy, Instant::now()) {
                 signal.stop();
             }
         })
@@ -253,38 +274,40 @@ impl Host {
         self.thumbs.retain(|t| !t.is_layer(layer));
     }
 
-    pub fn pointer(
-        &mut self,
-        events: &[PointerEvent],
-        cursor: Option<&WpCursorShapeDeviceV1>,
-        qh: &QueueHandle<State>,
-    ) {
-        for event in events {
-            let Some(t) = self.thumb(&event.surface) else {
-                continue;
-            };
-            let (x, y) = event.position;
-            match event.kind {
-                PointerEventKind::Enter { serial } => {
-                    if let Some(cursor) = cursor {
-                        cursor.set_shape(serial, Shape::Pointer);
-                    }
-                }
-                PointerEventKind::Press {
-                    button: BTN_LEFT, ..
-                } => t.press(x, y),
-                PointerEventKind::Motion { .. } => t.motion(x, qh),
-                PointerEventKind::Release {
-                    button: BTN_LEFT, ..
-                } => {
-                    let action = t.release(x, y, qh);
-                    if action == Some(Action::OpenEditor) {
-                        open_editor(&t.path);
-                    }
-                }
-                _ => {}
+    /// Writes the dragged screenshot for the receiving app, on its own
+    /// thread: a large PNG fills the pipe, and blocking here would freeze
+    /// every thumbnail.
+    pub fn send(&self, source: &WlDataSource, mime: String, fd: WritePipe) {
+        let Some(drag) = self.drag.as_ref().filter(|d| d.source.inner() == source) else {
+            return;
+        };
+        let Some(thumb) = self.thumbs.iter().find(|t| t.id == drag.thumb) else {
+            return;
+        };
+        let path = thumb.path.clone();
+        let writers = Arc::clone(&self.writers);
+        writers.fetch_add(1, Ordering::SeqCst);
+        std::thread::spawn(move || {
+            let mut fd = fd;
+            if let Err(e) = dnd::write_offer(&mime, &path, &mut fd) {
+                tracing::warn!("could not send the screenshot as {mime}: {e:#}");
             }
+            drop(fd);
+            writers.fetch_sub(1, Ordering::SeqCst);
+        });
+    }
+
+    pub fn drag_ended(&mut self, source: &WlDataSource, outcome: Outcome, qh: &QueueHandle<State>) {
+        let Some(drag) = self.drag.take_if(|d| d.source.inner() == source) else {
+            return;
+        };
+        tracing::info!("drag-out {outcome:?}");
+        drag.icon_viewport.destroy();
+        drag.icon.destroy();
+        if let Some(t) = self.thumbs.iter_mut().find(|t| t.id == drag.thumb) {
+            t.end_drag(outcome, qh);
         }
+        let _ = self.conn.flush();
     }
 
     fn expire(&mut self, id: u64) {
@@ -306,6 +329,78 @@ impl Host {
     }
 }
 
+/// Pointer events on thumbnails. A free function: starting a drag needs
+/// more of `State` than the host.
+pub fn pointer(state: &mut State, events: &[PointerEvent], qh: &QueueHandle<State>) {
+    for event in events {
+        let Some(host) = state.preview.as_mut() else {
+            return;
+        };
+        let Some(i) = host.thumbs.iter().position(|t| t.is(&event.surface)) else {
+            continue;
+        };
+        let (x, y) = event.position;
+        match event.kind {
+            PointerEventKind::Enter { serial } => {
+                if let Some(cursor) = &state.cursor_device {
+                    cursor.set_shape(serial, Shape::Pointer);
+                }
+            }
+            PointerEventKind::Press {
+                button: BTN_LEFT,
+                serial,
+                ..
+            } => host.thumbs[i].press(x, y, serial),
+            PointerEventKind::Motion { .. } => {
+                let start = host.thumbs[i].motion(x, y, qh);
+                if let Some(start) = start {
+                    start_drag(state, i, start, qh);
+                }
+            }
+            PointerEventKind::Release {
+                button: BTN_LEFT, ..
+            } => {
+                let t = &mut host.thumbs[i];
+                if t.release(x, y, qh) == Some(Action::OpenEditor) {
+                    open_editor(&t.path);
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+fn start_drag(state: &mut State, i: usize, start: DragStart, qh: &QueueHandle<State>) {
+    let host = state.preview.as_mut().expect("host state");
+    let (Some(manager), Some(device), Some(viewporter)) =
+        (&state.data_devices, &state.data_device, &state.viewporter)
+    else {
+        if !host.warned_no_dnd {
+            host.warned_no_dnd = true;
+            tracing::warn!("the compositor has no wl_data_device_manager; drag-out is off");
+        }
+        return;
+    };
+    if host.drag.is_some() {
+        return;
+    }
+    let source = manager.create_drag_and_drop_source(qh, dnd::MIME_TYPES, DndAction::Copy);
+    let icon = state.compositor.create_surface(qh);
+    let icon_viewport = viewporter.get_viewport(&icon, qh, ());
+    let thumb = &mut host.thumbs[i];
+    source.start_drag(device, thumb.surface(), Some(&icon), start.serial);
+    thumb.draw_icon(&icon, &icon_viewport, start.grab);
+    thumb.begin_drag(qh);
+    tracing::info!("drag-out started for {}", thumb.path.display());
+    host.drag = Some(Drag {
+        thumb: thumb.id,
+        source,
+        icon,
+        icon_viewport,
+    });
+    let _ = host.conn.flush();
+}
+
 fn disconnect(state: &mut State, id: u64) {
     let Some(host) = &mut state.preview else {
         return;

src/main.rs

@@ -1,6 +1,3 @@
-// Drag-out modules land before the host uses them; Task 3 removes this.
-#![allow(dead_code)]
-
 mod capture;
 mod config;
 mod detach;

src/thumbnail.rs

@@ -16,12 +16,16 @@ use smithay_client_toolkit::{
         slot::{Buffer, SlotPool},
     },
 };
-use wayland_client::{QueueHandle, protocol::wl_shm};
+use wayland_client::{
+    Proxy, QueueHandle,
+    protocol::{wl_shm, wl_surface::WlSurface},
+};
 use wayland_protocols::wp::viewporter::client::{
     wp_viewport::WpViewport, wp_viewporter::WpViewporter,
 };
 
-use crate::stack::{self, Anim, EDGE_MARGIN, Release};
+use crate::dnd::{self, AfterDrag, Outcome};
+use crate::stack::{self, Anim, EDGE_MARGIN, Gesture, Release};
 use crate::wayland::{Output, State};
 
 pub const NAMESPACE: &str = "valw-preview";
@@ -93,6 +97,24 @@ pub enum Action {
     OpenEditor,
 }
 
+/// A press turned into a drag-out: the host starts the drag with these.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct DragStart {
+    /// Serial of the press; the compositor only accepts a drag for it.
+    pub serial: u32,
+    /// Where on the image the press was, so it stays under the pointer.
+    pub grab: (f64, f64),
+}
+
+/// A press in progress and what it turned into once the pointer moved.
+#[derive(Debug, Clone, Copy)]
+struct Press {
+    x: f64,
+    y: f64,
+    serial: u32,
+    gesture: Option<Gesture>,
+}
+
 pub struct Thumbnail {
     pub id: u64,
     pub output: String,
@@ -108,13 +130,17 @@ pub struct Thumbnail {
     /// How far right of its resting place the image is drawn, logical px.
     offset: f64,
     anim: Option<(Anim, Instant)>,
-    drag: Option<(f64, f64)>,
+    press: Option<Press>,
     margin: u32,
     /// Input region while visible (the image) and while hidden (nothing).
     input: Region,
     no_input: Region,
     /// Hidden for a capture: drawn fully transparent, clicks pass through.
     hidden: bool,
+    /// Being dragged out: the drag icon shows it, so this one hides too.
+    /// Separate from `hidden` so a capture ending mid-drag can't bring it back.
+    dragging: bool,
+    icon_buffer: Option<Buffer>,
     configured: bool,
     frame_pending: bool,
     started: bool,
@@ -178,11 +204,13 @@ impl Thumbnail {
             scale: output.scale,
             offset: travel(size.0),
             anim: None,
-            drag: None,
+            press: None,
             margin: EDGE_MARGIN,
             input,
             no_input,
             hidden: false,
+            dragging: false,
+            icon_buffer: None,
             configured: false,
             frame_pending: false,
             started: false,
@@ -191,10 +219,14 @@ impl Thumbnail {
         })
     }
 
-    pub fn is(&self, surface: &wayland_client::protocol::wl_surface::WlSurface) -> bool {
+    pub fn is(&self, surface: &WlSurface) -> bool {
         self.layer.wl_surface() == surface
     }
 
+    pub fn surface(&self) -> &WlSurface {
+        self.layer.wl_surface()
+    }
+
     pub fn is_layer(&self, layer: &LayerSurface) -> bool {
         self.layer.wl_surface() == layer.wl_surface()
     }
@@ -205,7 +237,23 @@ impl Thumbnail {
 
     /// The slide-out has finished (or is invisible anyway).
     pub fn is_finished(&self) -> bool {
-        self.closing && (self.hidden || anim_over(self.anim, Instant::now()))
+        self.closing && (!self.visible() || anim_over(self.anim, Instant::now()))
+    }
+
+    fn visible(&self) -> bool {
+        !self.hidden && !self.dragging
+    }
+
+    /// Clicks reach the image only while it is visible.
+    fn apply_input(&self) {
+        let region = if self.visible() {
+            &self.input
+        } else {
+            &self.no_input
+        };
+        self.layer
+            .wl_surface()
+            .set_input_region(Some(region.wl_region()));
     }
 
     /// Makes the thumbnail invisible and click-through. The surface stays
@@ -215,9 +263,7 @@ impl Thumbnail {
             return;
         }
         self.hidden = true;
-        self.layer
-            .wl_surface()
-            .set_input_region(Some(self.no_input.wl_region()));
+        self.apply_input();
         self.draw(qh, true);
     }
 
@@ -226,9 +272,7 @@ impl Thumbnail {
             return;
         }
         self.hidden = false;
-        self.layer
-            .wl_surface()
-            .set_input_region(Some(self.input.wl_region()));
+        self.apply_input();
         self.draw(qh, true);
     }
 
@@ -252,15 +296,16 @@ impl Thumbnail {
 
     pub fn frame_done(&mut self, qh: &QueueHandle<State>) {
         self.frame_pending = false;
-        if self.anim.is_some() || self.drag.is_some() {
+        if self.anim.is_some() || self.press.is_some() {
             self.draw(qh, false);
         }
     }
 
-    /// The timeout fired: slide out, unless the user is dragging it.
+    /// The timeout fired: slide out, unless the user is holding or
+    /// dragging it; then it is decided when they let go.
     pub fn expire(&mut self, qh: &QueueHandle<State>) {
         self.expired = true;
-        if self.drag.is_none() {
+        if self.press.is_none() && !self.dragging {
             self.slide_out(qh);
         }
     }
@@ -277,23 +322,46 @@ impl Thumbnail {
         self.draw(qh, false);
     }
 
-    pub fn press(&mut self, x: f64, y: f64) {
-        if !self.closing {
+    pub fn press(&mut self, x: f64, y: f64, serial: u32) {
+        if !self.closing && !self.dragging {
             self.anim = None;
-            self.drag = Some((x, y));
+            self.press = Some(Press {
+                x,
+                y,
+                serial,
+                gesture: None,
+            });
         }
     }
 
-    pub fn motion(&mut self, x: f64, qh: &QueueHandle<State>) {
-        if let Some((x0, _)) = self.drag {
-            self.offset = stack::drag_offset(x - x0);
+    /// Follows a swipe, or returns a `DragStart` the moment the press turns
+    /// into a drag-out.
+    pub fn motion(&mut self, x: f64, y: f64, qh: &QueueHandle<State>) -> Option<DragStart> {
+        let press = self.press.as_mut()?;
+        let (dx, dy) = (x - press.x, y - press.y);
+        if press.gesture.is_none() {
+            press.gesture = stack::classify(dx, dy);
+            if press.gesture == Some(Gesture::DragOut) {
+                return Some(DragStart {
+                    serial: press.serial,
+                    grab: (press.x, press.y),
+                });
+            }
+        }
+        if press.gesture == Some(Gesture::Swipe) {
+            self.offset = stack::drag_offset(dx);
             self.draw(qh, false);
         }
+        None
     }
 
     pub fn release(&mut self, x: f64, y: f64, qh: &QueueHandle<State>) -> Option<Action> {
-        let (x0, y0) = self.drag.take()?;
-        match stack::release(x - x0, y - y0, self.size.0 as f64) {
+        let press = self.press.take()?;
+        if press.gesture == Some(Gesture::DragOut) {
+            // The drag never started (no data device); nothing moved.
+            return None;
+        }
+        match stack::release(x - press.x, y - press.y, self.size.0 as f64) {
             Release::Click => {
                 self.slide_out(qh);
                 Some(Action::OpenEditor)
@@ -314,6 +382,63 @@ impl Thumbnail {
         }
     }
 
+    /// The drag started: the icon carries the image, this one hides.
+    pub fn begin_drag(&mut self, qh: &QueueHandle<State>) {
+        self.press = None;
+        self.dragging = true;
+        self.anim = None;
+        self.offset = 0.0;
+        self.apply_input();
+        self.draw(qh, true);
+    }
+
+    pub fn end_drag(&mut self, outcome: Outcome, qh: &QueueHandle<State>) {
+        self.dragging = false;
+        self.icon_buffer = None;
+        self.apply_input();
+        match dnd::after_drag(outcome, self.expired) {
+            AfterDrag::Close => {
+                // Already invisible; nothing to animate.
+                self.closing = true;
+                self.anim = None;
+            }
+            AfterDrag::ComeBack => {
+                self.anim = Some((Anim::slide_in(travel(self.size.0)), Instant::now()));
+                self.draw(qh, true);
+            }
+            AfterDrag::SlideOut => self.slide_out(qh),
+        }
+    }
+
+    /// Draws the drag icon: the image alone, sharp at the output's scale,
+    /// placed so the grabbed point stays under the pointer.
+    pub fn draw_icon(&mut self, icon: &WlSurface, viewport: &WpViewport, grab: (f64, f64)) {
+        let (width, height) = self.small.dimensions();
+        let Ok((buffer, canvas)) = self.pool.create_buffer(
+            width as i32,
+            height as i32,
+            width as i32 * 4,
+            wl_shm::Format::Argb8888,
+        ) else {
+            tracing::warn!("could not allocate a drag icon buffer");
+            return;
+        };
+        paint(canvas, width, &self.small, 0);
+        viewport.set_destination(self.size.0 as i32, self.size.1 as i32);
+        // wl_surface.offset needs version 5; older compositors put the
+        // icon's corner at the pointer instead.
+        if icon.version() >= 5 {
+            icon.offset(-(grab.0.round() as i32), -(grab.1.round() as i32));
+        }
+        icon.damage_buffer(0, 0, width as i32, height as i32);
+        if buffer.attach_to(icon).is_err() {
+            tracing::warn!("could not attach the drag icon");
+            return;
+        }
+        icon.commit();
+        self.icon_buffer = Some(buffer);
+    }
+
     fn draw(&mut self, qh: &QueueHandle<State>, force: bool) {
         if let Some((anim, start)) = self.anim {
             let (offset, done) = anim.at(start.elapsed().as_secs_f64() * 1000.0);
@@ -328,6 +453,7 @@ impl Thumbnail {
         }
         let width = canvas_width(self.size.0, self.scale);
         let height = self.small.height();
+        let visible = self.visible();
         let Ok((buffer, canvas)) = self.pool.create_buffer(
             width as i32,
             height as i32,
@@ -337,7 +463,7 @@ impl Thumbnail {
             tracing::warn!("could not allocate a thumbnail buffer");
             return;
         };
-        if self.hidden {
+        if !visible {
             canvas.fill(0);
         } else {
             paint(
@@ -351,7 +477,7 @@ impl Thumbnail {
         surface.damage_buffer(0, 0, width as i32, height as i32);
         // Keep drawing while something moves; motion that arrives while a
         // frame is pending is picked up by the next frame callback.
-        if self.anim.is_some() || self.drag.is_some() {
+        if self.anim.is_some() || self.press.is_some() {
             surface.frame(qh, FrameCallbackData(surface.clone()));
             self.frame_pending = true;
         }

src/wayland.rs

@@ -4,6 +4,12 @@ use anyhow::{Context, Result, bail};
 use rustix::event::{PollFd, PollFlags, Timespec, poll};
 use smithay_client_toolkit::{
     compositor::{CompositorHandler, CompositorState},
+    data_device_manager::{
+        DataDeviceManagerState, WritePipe,
+        data_device::{DataDevice, DataDeviceHandler},
+        data_offer::{DataOfferHandler, DragOffer},
+        data_source::DataSourceHandler,
+    },
     delegate_registry,
     output::{OutputHandler, OutputState},
     registry::{ProvidesRegistryState, RegistryState},
@@ -19,7 +25,10 @@ use smithay_client_toolkit::{
 use wayland_client::{
     Connection, EventQueue, QueueHandle,
     globals::{GlobalList, registry_queue_init},
-    protocol::{wl_buffer::WlBuffer, wl_keyboard, wl_output, wl_pointer, wl_seat, wl_surface},
+    protocol::{
+        wl_buffer::WlBuffer, wl_data_device::WlDataDevice, wl_data_device_manager::DndAction,
+        wl_data_source::WlDataSource, wl_keyboard, wl_output, wl_pointer, wl_seat, wl_surface,
+    },
 };
 use wayland_protocols::wp::cursor_shape::v1::client::wp_cursor_shape_device_v1::WpCursorShapeDeviceV1;
 use wayland_protocols::wp::viewporter::client::{
@@ -28,6 +37,7 @@ use wayland_protocols::wp::viewporter::client::{
 use wayland_protocols_wlr::screencopy::v1::client::zwlr_screencopy_manager_v1::ZwlrScreencopyManagerV1;
 
 use crate::capture::Pending;
+use crate::dnd::Outcome;
 use crate::error::HintExt;
 use crate::frame::OutputGeom;
 use crate::host::Host;
@@ -61,6 +71,9 @@ pub struct State {
     pub viewporter: Option<WpViewporter>,
     pub cursor_shape: Option<CursorShapeManager>,
     pub cursor_device: Option<WpCursorShapeDeviceV1>,
+    /// For dragging a preview out; the host never receives drops.
+    pub data_devices: Option<DataDeviceManagerState>,
+    pub data_device: Option<DataDevice>,
     pub keyboard: Option<wl_keyboard::WlKeyboard>,
     pub pointer: Option<wl_pointer::WlPointer>,
     /// Screencopy requests in flight.
@@ -92,6 +105,8 @@ impl Wayland {
             viewporter: globals.bind(&qh, 1..=1, ()).ok(),
             cursor_shape: CursorShapeManager::bind(&globals, &qh).ok(),
             cursor_device: None,
+            data_devices: DataDeviceManagerState::bind(&globals, &qh).ok(),
+            data_device: None,
             keyboard: None,
             pointer: None,
             captures: Vec::new(),
@@ -370,6 +385,10 @@ impl SeatHandler for State {
                 .cursor_shape
                 .as_ref()
                 .map(|m| m.get_shape_device(&pointer, qh));
+            self.data_device = self
+                .data_devices
+                .as_ref()
+                .map(|m| m.get_data_device(qh, &seat));
             self.pointer = Some(pointer);
         }
     }
@@ -481,12 +500,94 @@ impl PointerHandler for State {
         if let Some(overlay) = &mut self.overlay {
             overlay.pointer(events, self.cursor_device.as_ref(), qh);
         }
-        if let Some(preview) = &mut self.preview {
-            preview.pointer(events, self.cursor_device.as_ref(), qh);
+        if self.preview.is_some() {
+            crate::host::pointer(self, events, qh);
         }
     }
 }
 
+impl DataSourceHandler for State {
+    fn accept_mime(
+        &mut self,
+        _: &Connection,
+        _: &QueueHandle<Self>,
+        _: &WlDataSource,
+        _: Option<String>,
+    ) {
+    }
+
+    fn send_request(
+        &mut self,
+        _: &Connection,
+        _: &QueueHandle<Self>,
+        source: &WlDataSource,
+        mime: String,
+        fd: WritePipe,
+    ) {
+        if let Some(preview) = &self.preview {
+            preview.send(source, mime, fd);
+        }
+    }
+
+    fn cancelled(&mut self, _: &Connection, qh: &QueueHandle<Self>, source: &WlDataSource) {
+        if let Some(preview) = &mut self.preview {
+            preview.drag_ended(source, Outcome::Cancelled, qh);
+        }
+    }
+
+    fn dnd_dropped(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &WlDataSource) {}
+
+    fn dnd_finished(&mut self, _: &Connection, qh: &QueueHandle<Self>, source: &WlDataSource) {
+        if let Some(preview) = &mut self.preview {
+            preview.drag_ended(source, Outcome::Dropped, qh);
+        }
+    }
+
+    fn action(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &WlDataSource, _: DndAction) {}
+}
+
+// valw only ever starts drags; incoming offers are ignored.
+impl DataDeviceHandler for State {
+    fn enter(
+        &mut self,
+        _: &Connection,
+        _: &QueueHandle<Self>,
+        _: &WlDataDevice,
+        _: f64,
+        _: f64,
+        _: &wl_surface::WlSurface,
+    ) {
+    }
+
+    fn leave(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &WlDataDevice) {}
+
+    fn motion(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &WlDataDevice, _: f64, _: f64) {}
+
+    fn selection(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &WlDataDevice) {}
+
+    fn drop_performed(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &WlDataDevice) {}
+}
+
+impl DataOfferHandler for State {
+    fn source_actions(
+        &mut self,
+        _: &Connection,
+        _: &QueueHandle<Self>,
+        _: &mut DragOffer,
+        _: DndAction,
+    ) {
+    }
+
+    fn selected_action(
+        &mut self,
+        _: &Connection,
+        _: &QueueHandle<Self>,
+        _: &mut DragOffer,
+        _: DndAction,
+    ) {
+    }
+}
+
 impl ShmHandler for State {
     fn shm_state(&mut self) -> &mut Shm {
         &mut self.shm