X11: Split off the event loop into a separate module

Author: prokopyl

src/x11/event_loop.rs

@@ -0,0 +1,303 @@
+use crate::x11::keyboard::{convert_key_press_event, convert_key_release_event, key_mods};
+use crate::x11::{ParentHandle, Window, WindowInner};
+use crate::{
+    Event, MouseButton, MouseEvent, PhyPoint, PhySize, ScrollDelta, WindowEvent, WindowHandler,
+    WindowInfo,
+};
+use std::error::Error;
+use std::os::fd::AsRawFd;
+use std::time::{Duration, Instant};
+use x11rb::connection::Connection;
+use x11rb::protocol::Event as XEvent;
+
+pub(super) struct EventLoop {
+    handler: Box<dyn WindowHandler>,
+    window: WindowInner,
+    parent_handle: Option<ParentHandle>,
+
+    new_physical_size: Option<PhySize>,
+    frame_interval: Duration,
+    event_loop_running: bool,
+}
+
+impl EventLoop {
+    pub fn new(
+        window: WindowInner, handler: impl WindowHandler + 'static,
+        parent_handle: Option<ParentHandle>,
+    ) -> Self {
+        Self {
+            window,
+            handler: Box::new(handler),
+            parent_handle,
+            frame_interval: Duration::from_millis(15),
+            event_loop_running: false,
+            new_physical_size: None,
+        }
+    }
+
+    #[inline]
+    fn drain_xcb_events(&mut self) -> Result<(), Box<dyn Error>> {
+        // the X server has a tendency to send spurious/extraneous configure notify events when a
+        // window is resized, and we need to batch those together and just send one resize event
+        // when they've all been coalesced.
+        self.new_physical_size = None;
+
+        while let Some(event) = self.window.xcb_connection.conn.poll_for_event()? {
+            self.handle_xcb_event(event);
+        }
+
+        if let Some(size) = self.new_physical_size.take() {
+            self.window.window_info =
+                WindowInfo::from_physical_size(size, self.window.window_info.scale());
+
+            let window_info = self.window.window_info;
+
+            self.handler.on_event(
+                &mut crate::Window::new(Window { inner: &self.window }),
+                Event::Window(WindowEvent::Resized(window_info)),
+            );
+        }
+
+        Ok(())
+    }
+
+    // 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 mut last_frame = Instant::now();
+        self.event_loop_running = true;
+
+        while self.event_loop_running {
+            // We'll try to keep a consistent frame pace. If the last frame couldn't be processed in
+            // the expected frame time, this will throttle down to prevent multiple frames from
+            // being queued up. The conditional here is needed because event handling and frame
+            // drawing is interleaved. The `poll()` function below will wait until the next frame
+            // can be drawn, or until the window receives an event. We thus need to manually check
+            // if it's already time to draw a new frame.
+            let next_frame = last_frame + self.frame_interval;
+            if Instant::now() >= next_frame {
+                self.handler.on_frame(&mut crate::Window::new(Window { inner: &self.window }));
+                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()?;
+                }
+            }
+
+            // Check if the parents's handle was dropped (such as when the host
+            // requested the window to close)
+            //
+            // FIXME: This will need to be changed from just setting an atomic to somehow
+            // synchronizing with the window being closed (using a synchronous channel, or
+            // by joining on the event loop thread).
+            if let Some(parent_handle) = &self.parent_handle {
+                if parent_handle.parent_did_drop() {
+                    self.handle_must_close();
+                    self.window.close_requested.set(false);
+                }
+            }
+
+            // Check if the user has requested the window to close
+            if self.window.close_requested.get() {
+                self.handle_must_close();
+                self.window.close_requested.set(false);
+            }
+        }
+
+        Ok(())
+    }
+
+    fn handle_xcb_event(&mut self, event: XEvent) {
+        // For all the keyboard and mouse events, you can fetch
+        // `x`, `y`, `detail`, and `state`.
+        // - `x` and `y` are the position inside the window where the cursor currently is
+        //   when the event happened.
+        // - `detail` will tell you which keycode was pressed/released (for keyboard events)
+        //   or which mouse button was pressed/released (for mouse events).
+        //   For mouse events, here's what the value means (at least on my current mouse):
+        //      1 = left mouse button
+        //      2 = middle mouse button (scroll wheel)
+        //      3 = right mouse button
+        //      4 = scroll wheel up
+        //      5 = scroll wheel down
+        //      8 = lower side button ("back" button)
+        //      9 = upper side button ("forward" button)
+        //   Note that you *will* get a "button released" event for even the scroll wheel
+        //   events, which you can probably ignore.
+        // - `state` will tell you the state of the main three mouse buttons and some of
+        //   the keyboard modifier keys at the time of the event.
+        //   http://rtbo.github.io/rust-xcb/src/xcb/ffi/xproto.rs.html#445
+
+        match event {
+            ////
+            // window
+            ////
+            XEvent::ClientMessage(event) => {
+                if event.format == 32
+                    && event.data.as_data32()[0]
+                        == self.window.xcb_connection.atoms.WM_DELETE_WINDOW
+                {
+                    self.handle_close_requested();
+                }
+            }
+
+            XEvent::ConfigureNotify(event) => {
+                let new_physical_size = PhySize::new(event.width as u32, event.height as u32);
+
+                if self.new_physical_size.is_some()
+                    || new_physical_size != self.window.window_info.physical_size()
+                {
+                    self.new_physical_size = Some(new_physical_size);
+                }
+            }
+
+            ////
+            // mouse
+            ////
+            XEvent::MotionNotify(event) => {
+                let physical_pos = PhyPoint::new(event.event_x as i32, event.event_y as i32);
+                let logical_pos = physical_pos.to_logical(&self.window.window_info);
+
+                self.handler.on_event(
+                    &mut crate::Window::new(Window { inner: &self.window }),
+                    Event::Mouse(MouseEvent::CursorMoved {
+                        position: logical_pos,
+                        modifiers: key_mods(event.state),
+                    }),
+                );
+            }
+
+            XEvent::EnterNotify(event) => {
+                self.handler.on_event(
+                    &mut crate::Window::new(Window { inner: &self.window }),
+                    Event::Mouse(MouseEvent::CursorEntered),
+                );
+                // since no `MOTION_NOTIFY` event is generated when `ENTER_NOTIFY` is generated,
+                // we generate a CursorMoved as well, so the mouse position from here isn't lost
+                let physical_pos = PhyPoint::new(event.event_x as i32, event.event_y as i32);
+                let logical_pos = physical_pos.to_logical(&self.window.window_info);
+                self.handler.on_event(
+                    &mut crate::Window::new(Window { inner: &self.window }),
+                    Event::Mouse(MouseEvent::CursorMoved {
+                        position: logical_pos,
+                        modifiers: key_mods(event.state),
+                    }),
+                );
+            }
+
+            XEvent::LeaveNotify(_) => {
+                self.handler.on_event(
+                    &mut crate::Window::new(Window { inner: &self.window }),
+                    Event::Mouse(MouseEvent::CursorLeft),
+                );
+            }
+
+            XEvent::ButtonPress(event) => match event.detail {
+                4..=7 => {
+                    self.handler.on_event(
+                        &mut crate::Window::new(Window { inner: &self.window }),
+                        Event::Mouse(MouseEvent::WheelScrolled {
+                            delta: match event.detail {
+                                4 => ScrollDelta::Lines { x: 0.0, y: 1.0 },
+                                5 => ScrollDelta::Lines { x: 0.0, y: -1.0 },
+                                6 => ScrollDelta::Lines { x: -1.0, y: 0.0 },
+                                7 => ScrollDelta::Lines { x: 1.0, y: 0.0 },
+                                _ => unreachable!(),
+                            },
+                            modifiers: key_mods(event.state),
+                        }),
+                    );
+                }
+                detail => {
+                    let button_id = mouse_id(detail);
+                    self.handler.on_event(
+                        &mut crate::Window::new(Window { inner: &self.window }),
+                        Event::Mouse(MouseEvent::ButtonPressed {
+                            button: button_id,
+                            modifiers: key_mods(event.state),
+                        }),
+                    );
+                }
+            },
+
+            XEvent::ButtonRelease(event) => {
+                if !(4..=7).contains(&event.detail) {
+                    let button_id = mouse_id(event.detail);
+                    self.handler.on_event(
+                        &mut crate::Window::new(Window { inner: &self.window }),
+                        Event::Mouse(MouseEvent::ButtonReleased {
+                            button: button_id,
+                            modifiers: key_mods(event.state),
+                        }),
+                    );
+                }
+            }
+
+            ////
+            // keys
+            ////
+            XEvent::KeyPress(event) => {
+                self.handler.on_event(
+                    &mut crate::Window::new(Window { inner: &self.window }),
+                    Event::Keyboard(convert_key_press_event(&event)),
+                );
+            }
+
+            XEvent::KeyRelease(event) => {
+                self.handler.on_event(
+                    &mut crate::Window::new(Window { inner: &self.window }),
+                    Event::Keyboard(convert_key_release_event(&event)),
+                );
+            }
+
+            _ => {}
+        }
+    }
+
+    fn handle_close_requested(&mut self) {
+        // FIXME: handler should decide whether window stays open or not
+        self.handle_must_close();
+    }
+
+    fn handle_must_close(&mut self) {
+        self.handler.on_event(
+            &mut crate::Window::new(Window { inner: &self.window }),
+            Event::Window(WindowEvent::WillClose),
+        );
+
+        self.event_loop_running = false;
+    }
+}
+
+fn mouse_id(id: u8) -> MouseButton {
+    match id {
+        1 => MouseButton::Left,
+        2 => MouseButton::Middle,
+        3 => MouseButton::Right,
+        8 => MouseButton::Back,
+        9 => MouseButton::Forward,
+        id => MouseButton::Other(id),
+    }
+}

src/x11/mod.rs

@@ -5,5 +5,6 @@ mod window;
 pub use window::*;
 
 mod cursor;
+mod event_loop;
 mod keyboard;
 mod visual_info;