feat: method for peeking dnd offer data

examples/clipboard.rs

@@ -85,6 +85,18 @@ fn main() {
                 let s = smithay_clipboard::text::Text::try_from((data, mime_type)).unwrap();
                 println!("Received DnD data for {}: {}", id.unwrap_or_default(), s.0);
             },
+            smithay_clipboard::dnd::DndEvent::Offer(id, OfferEvent::Motion { x, y }) => {
+                if id != state.offer_hover_id {
+                    state.offer_hover_id = id;
+                    if let Ok(data) = state.clipboard.peek_offer::<smithay_clipboard::text::Text>(
+                        MimeType::Text(smithay_clipboard::mime::Text::TextPlain),
+                    ) {
+                        println!("Peeked the data: {}", data.0);
+                    }
+                }
+                println!("Received DnD Motion for {id:?}: at {x}, {y}");
+            },
+
             smithay_clipboard::dnd::DndEvent::Offer(id, OfferEvent::Leave) => {
                 if state.internal_dnd {
                     if state.pointer_focus {
@@ -97,12 +109,25 @@ fn main() {
                         state.clipboard.end_dnd();
                     }
                 } else {
+                    state.offer_hover_id = None;
                     println!("Dnd offer left {id:?}.");
                 }
             },
+            smithay_clipboard::dnd::DndEvent::Offer(id, OfferEvent::Enter { mime_types, .. }) => {
+                println!("Received DnD Enter for {id:?}");
+                state.offer_hover_id = id;
+                if let Some(mime) = mime_types.get(0) {
+                    if let Ok(data) =
+                        state.clipboard.peek_offer::<smithay_clipboard::text::Text>(mime.clone())
+                    {
+                        println!("Peeked the data: {}", data.0);
+                    }
+                }
+            },
             smithay_clipboard::dnd::DndEvent::Source(SourceEvent::Finished) => {
                 println!("Finished sending data.");
                 state.internal_dnd = false;
+                state.offer_hover_id = None;
             },
             e => {
                 dbg!(e);
@@ -172,6 +197,7 @@ fn main() {
         internal_dnd: false,
         keyboard_focus: false,
         pointer_focus: false,
+        offer_hover_id: None,
         loop_handle: event_loop.handle(),
     };
 
@@ -204,6 +230,7 @@ struct SimpleWindow {
     internal_dnd: bool,
     keyboard_focus: bool,
     pointer_focus: bool,
+    offer_hover_id: Option<u128>,
     loop_handle: LoopHandle<'static, SimpleWindow>,
 }
 

src/dnd/mod.rs

@@ -8,7 +8,7 @@ use sctk::reexports::client::protocol::wl_surface::WlSurface;
 use sctk::reexports::client::{Connection, Proxy};
 use wayland_backend::client::{InvalidId, ObjectId};
 
-use crate::mime::{AsMimeTypes, MimeType};
+use crate::mime::{AllowedMimeTypes, AsMimeTypes, MimeType};
 use crate::Clipboard;
 
 pub mod state;
@@ -139,6 +139,8 @@ pub enum DndRequest<T> {
         content: Box<dyn AsMimeTypes + Send>,
         actions: DndAction,
     },
+    /// Peek the data of an active DnD offer
+    Peek(MimeType),
     /// Set the DnD action chosen by the user.
     SetAction(DndAction),
     /// End an active DnD Source
@@ -201,6 +203,8 @@ impl<T: RawSurface> Clipboard<T> {
 
     /// Register a surface for receiving DnD offers
     /// Rectangles should be provided in order of decreasing priority.
+    /// This method can be called multiple time for a single surface if the
+    /// rectangles change.
     pub fn register_dnd_destination(&self, surface: T, rectangles: Vec<DndDestinationRectangle>) {
         let s = DndSurface::new(surface, &self.connection).unwrap();
 
@@ -215,4 +219,30 @@ impl<T: RawSurface> Clipboard<T> {
             .request_sender
             .send(crate::worker::Command::DndRequest(DndRequest::SetAction(action)));
     }
+
+    /// Peek at the contents of a DnD offer
+    pub fn peek_offer<D: AllowedMimeTypes + 'static>(
+        &self,
+        mime_type: MimeType,
+    ) -> std::io::Result<D> {
+        self.request_sender
+            .send(crate::worker::Command::DndRequest(DndRequest::Peek(mime_type)))
+            .map_err(|_| {
+            std::io::Error::new(std::io::ErrorKind::Other, "Failed to send Peek request.")
+        })?;
+
+        self.request_receiver
+            .recv()
+            .map_err(|_| {
+                std::io::Error::new(std::io::ErrorKind::Other, "Failed to receive data request.")
+            })
+            .and_then(|ret| {
+                D::try_from(ret?).map_err(|_| {
+                    std::io::Error::new(
+                        std::io::ErrorKind::Other,
+                        "Failed to convert data to requested type.",
+                    )
+                })
+            })
+    }
 }

src/dnd/state.rs

@@ -162,7 +162,7 @@ where
         dnd_state.set_actions(self.dnd_state.selected_action, self.dnd_state.selected_action);
         dnd_state.accept_mime_type(dnd_state.serial, Some(mime.to_string()));
 
-        _ = self.load_dnd(mime);
+        _ = self.load_dnd(mime, false);
     }
 
     pub(crate) fn offer_enter(
@@ -263,6 +263,11 @@ where
                 self.dnd_state.source_content = None;
                 self.dnd_state.dnd_source = None;
             },
+            DndRequest::Peek(mime_type) => {
+                if let Err(err) = self.load_dnd(mime_type, true) {
+                    _ = self.reply_tx.send(Err(err));
+                }
+            },
         };
     }
 
@@ -341,13 +346,13 @@ where
         offer.set_actions(a, a);
 
         if let Some(mime_type) = self.dnd_state.selected_mime.clone() {
-            _ = self.load_dnd(mime_type);
+            _ = self.load_dnd(mime_type, false);
         }
         Ok(())
     }
 
     /// Load data for the given target.
-    pub fn load_dnd(&mut self, mut mime_type: MimeType) -> std::io::Result<()> {
+    pub fn load_dnd(&mut self, mut mime_type: MimeType, peek: bool) -> std::io::Result<()> {
         let cur_id = self.cur_id();
         let latest = self
             .latest_seat
@@ -375,23 +380,33 @@ where
         let mut content = Vec::new();
         let _ = self.loop_handle.insert_source(read_pipe, move |_, file, state| {
             let file = unsafe { file.get_mut() };
-            let Some(tx) = state.dnd_state.sender.as_ref() else {
-                return PostAction::Remove;
-            };
+
             loop {
                 match file.read(&mut reader_buffer) {
                     Ok(0) => {
-                        offer.finish();
-                        let _ = tx.send(DndEvent::Offer(cur_id, OfferEvent::Data {
-                            data: mem::take(&mut content),
-                            mime_type: mem::take(&mut mime_type),
-                        }));
+                        // only finish if not peeking
+                        if !peek {
+                            offer.finish();
+                        }
+
+                        if peek {
+                            _ = state
+                                .reply_tx
+                                .send(Ok((mem::take(&mut content), mem::take(&mut mime_type))));
+                        } else if let Some(tx) = state.dnd_state.sender.as_ref() {
+                            let _ = tx.send(DndEvent::Offer(cur_id, OfferEvent::Data {
+                                data: mem::take(&mut content),
+                                mime_type: mem::take(&mut mime_type),
+                            }));
+                        }
                         break PostAction::Remove;
                     },
                     Ok(n) => content.extend_from_slice(&reader_buffer[..n]),
                     Err(err) if err.kind() == ErrorKind::WouldBlock => break PostAction::Continue,
-                    Err(_) => {
-                        // let _ = state.dnd_state.sender.unwrap().send(Err(err));
+                    Err(err) => {
+                        if peek {
+                            let _ = state.reply_tx.send(Err(err));
+                        }
                         break PostAction::Remove;
                     },
                 };