Add a dummy backend

src/backend/producer/dummy.rs

@@ -0,0 +1,41 @@
+use std::io;
+use std::pin::Pin;
+use std::task::{Poll, Context};
+
+use futures_core::Stream;
+
+use crate::event::Event;
+use crate::producer::EventProducer;
+
+use crate::client::{ClientEvent, ClientHandle};
+
+pub struct DummyProducer {}
+
+impl DummyProducer {
+    pub fn new() -> Self {
+        Self {}
+    }
+}
+
+impl Default for DummyProducer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl EventProducer for DummyProducer {
+    fn notify(&mut self, _: ClientEvent) {}
+
+    fn release(&mut self) {}
+}
+
+impl Stream for DummyProducer {
+    type Item = io::Result<(ClientHandle, Event)>;
+
+    fn poll_next(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+    ) -> Poll<Option<Self::Item>> {
+        Poll::Pending
+    }
+}

src/backend/producer/libei.rs

@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use std::{io, task::Poll};
 
 use futures_core::Stream;
@@ -9,7 +9,7 @@ pub struct LibeiProducer {}
 
 impl LibeiProducer {
     pub fn new() -> Result<Self> {
-        Ok(Self {})
+        Err(anyhow!("not implemented"))
     }
 }
 

src/backend/producer/x11.rs

@@ -1,3 +1,4 @@
+use anyhow::{anyhow, Result};
 use std::io;
 use std::task::Poll;
 
@@ -11,14 +12,8 @@ use crate::client::{ClientEvent, ClientHandle};
 pub struct X11Producer {}
 
 impl X11Producer {
-    pub fn new() -> Self {
-        Self {}
-    }
-}
-
-impl Default for X11Producer {
-    fn default() -> Self {
-        Self::new()
+    pub fn new() -> Result<Self> {
+        return Err(anyhow!("not implemented"));
     }
 }