Use polling crate for open_blocking on X11 (#264)

Author: prokopyl

Cargo.toml

@@ -38,7 +38,7 @@ raw-window-handle = "0.5"
 [target.'cfg(target_os="linux")'.dependencies]
 x11rb = { version = "0.13.2", features = ["cursor", "resource_manager", "allow-unsafe-code", "dl-libxcb"], default-features = false }
 x11-dl = { version = "2.21" }
-nix = "0.22.0"
+polling = "3.11.0"
 percent-encoding = "2.3.1"
 bytemuck = "1.15.0"
 

src/wrappers.rs

@@ -19,6 +19,9 @@ pub mod xlib;
 #[cfg(all(target_os = "linux", feature = "opengl"))]
 pub mod glx;
 
+#[cfg(target_os = "linux")]
+pub mod connection_poller;
+
 /// Wrappers and utilities around the Win32 API
 #[cfg(target_os = "windows")]
 pub mod win32;

src/wrappers/connection_poller.rs

@@ -0,0 +1,66 @@
+use polling::{Event, Events, Poller};
+use std::io;
+use std::os::fd::{AsFd, BorrowedFd};
+use std::time::Instant;
+
+pub struct ConnectionPoller<'a> {
+    poller: Poller,
+    events: Events,
+    fd: BorrowedFd<'a>,
+}
+
+const CONNECTION_KEY: usize = 42;
+
+impl<'a> ConnectionPoller<'a> {
+    pub fn new(source: &'a impl AsFd) -> io::Result<Self> {
+        let poller = Poller::new()?;
+        let fd = source.as_fd();
+        unsafe { poller.add(&fd, Event::readable(CONNECTION_KEY))? };
+
+        Ok(Self { poller, fd, events: Events::new() })
+    }
+
+    pub fn wait(&mut self, deadline: Instant) -> io::Result<PollStatus> {
+        self.events.clear();
+        // NOTE: polling crate already handles retrying on EINTR
+        let new_events_count = self.poller.wait_deadline(&mut self.events, deadline)?;
+
+        if new_events_count == 0 {
+            return Ok(PollStatus::Nothing);
+        }
+
+        for event in self.events.iter() {
+            if event.key != CONNECTION_KEY {
+                continue;
+            }
+
+            if let Some(true) = event.is_err() {
+                panic!("xcb connection poll error")
+            }
+
+            if event.is_interrupt() {
+                return Ok(PollStatus::ConnectionClosed);
+            }
+
+            return Ok(PollStatus::ReadAvailable);
+        }
+
+        Ok(PollStatus::Nothing)
+    }
+
+    pub fn delete(self) -> io::Result<()> {
+        self.poller.delete(self.fd)
+    }
+}
+
+impl<'a> Drop for ConnectionPoller<'a> {
+    fn drop(&mut self) {
+        let _ = self.poller.delete(self.fd);
+    }
+}
+
+pub enum PollStatus {
+    Nothing,
+    ReadAvailable,
+    ConnectionClosed,
+}

src/wrappers/xlib/xlib_xcb.rs

@@ -1,6 +1,7 @@
 use crate::wrappers::xlib::xlib_connection::XlibConnection;
 use std::error::Error;
 use std::ops::Deref;
+use std::os::fd::{AsFd, BorrowedFd};
 use std::os::raw::c_int;
 use x11_dl::xlib::Display;
 use x11_dl::xlib_xcb::Xlib_xcb;
@@ -72,3 +73,9 @@ impl Deref for XlibXcbConnection {
         &self.xcb_connection
     }
 }
+
+impl AsFd for XlibXcbConnection {
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        self.xcb_connection.as_fd()
+    }
+}

src/x11/event_loop.rs

@@ -1,3 +1,4 @@
+use crate::wrappers::connection_poller::{ConnectionPoller, PollStatus};
 use crate::x11::drag_n_drop::DragNDropState;
 use crate::x11::keyboard::{convert_key_press_event, convert_key_release_event, key_mods};
 use crate::x11::{ParentHandle, Window, WindowInner};
@@ -6,7 +7,7 @@ use crate::{
     WindowInfo,
 };
 use std::error::Error;
-use std::os::fd::AsRawFd;
+use std::rc::Rc;
 use std::time::{Duration, Instant};
 use x11rb::connection::Connection;
 use x11rb::protocol::Event as XEvent;
@@ -63,13 +64,9 @@ impl EventLoop {
     }
 
     // Event loop
-    // FIXME: poll() acts fine on linux, sometimes funky on *BSD. XCB upstream uses a define to
-    // switch between poll() and select() (the latter of which is fine on *BSD), and we should do
-    // the same.
     pub fn run(&mut self) -> Result<(), Box<dyn Error>> {
-        use nix::poll::*;
-
-        let xcb_fd = self.window.xcb_connection.conn.as_raw_fd();
+        let connection = Rc::clone(&self.window.xcb_connection);
+        let mut poller = ConnectionPoller::new(&connection.conn)?;
 
         let mut last_frame = Instant::now();
         self.event_loop_running = true;
@@ -87,24 +84,13 @@ impl EventLoop {
                 last_frame = Instant::max(next_frame, Instant::now() - self.frame_interval);
             }
 
-            let mut fds = [PollFd::new(xcb_fd, PollFlags::POLLIN)];
-
             // Check for any events in the internal buffers
             // before going to sleep:
             self.drain_xcb_events()?;
 
             // FIXME: handle errors
-            poll(&mut fds, next_frame.duration_since(Instant::now()).subsec_millis() as i32)
-                .unwrap();
-
-            if let Some(revents) = fds[0].revents() {
-                if revents.contains(PollFlags::POLLERR) {
-                    panic!("xcb connection poll error");
-                }
-
-                if revents.contains(PollFlags::POLLIN) {
-                    self.drain_xcb_events()?;
-                }
+            if let PollStatus::ReadAvailable = poller.wait(next_frame).unwrap() {
+                self.drain_xcb_events()?;
             }
 
             // Check if the parents's handle was dropped (such as when the host
@@ -123,6 +109,8 @@ impl EventLoop {
             }
         }
 
+        poller.delete()?;
+
         Ok(())
     }