window.rs

// Copyright 2020 The Druid Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! X11 window creation and window management.

use std::any::Any;
use std::cell::RefCell;
use std::convert::{TryFrom, TryInto};
use std::collections::BinaryHeap;
use std::os::unix::io::RawFd;
use std::rc::{Rc, Weak};
use std::sync::{Arc, Mutex};
use std::time::Instant;

use anyhow::{anyhow, Context, Error};
use cairo::{XCBConnection as CairoXCBConnection, XCBDrawable, XCBSurface, XCBVisualType};
use x11rb::atom_manager;
use x11rb::connection::Connection;
use x11rb::protocol::present::{CompleteNotifyEvent, ConnectionExt as _, IdleNotifyEvent};
use x11rb::protocol::xfixes::{ConnectionExt as _, Region};
use x11rb::protocol::xproto::{
    self, AtomEnum, ConfigureNotifyEvent, ConnectionExt, CreateGCAux, EventMask, Gcontext, Pixmap,
    PropMode, Rectangle, Visualtype, WindowClass,
};
use x11rb::wrapper::ConnectionExt as _;
use x11rb::xcb_ffi::XCBConnection;

use crate::common_util::IdleCallback;
use crate::dialog::{FileDialogOptions, FileInfo};
use crate::error::Error as ShellError;
use crate::keyboard::{KeyEvent, KeyState, Modifiers};
use crate::kurbo::{Point, Rect, Size, Vec2};
use crate::mouse::{Cursor, MouseButton, MouseButtons, MouseEvent};
use crate::piet::{Piet, RenderContext};
use crate::scale::Scale;
use crate::window::{IdleToken, Text, TimerToken, WinHandler};

use super::application::Application;
use super::keycodes;
use super::menu::Menu;
use super::util::{self, Timer};

/// A version of XCB's `xcb_visualtype_t` struct. This was copied from the [example] in x11rb; it
/// is used to interoperate with cairo.
///
/// The official upstream reference for this struct definition is [here].
///
/// [example]: https://github.com/psychon/x11rb/blob/master/cairo-example/src/main.rs
/// [here]: https://xcb.freedesktop.org/manual/structxcb__visualtype__t.html
#[derive(Debug, Clone, Copy)]
#[repr(C)]
pub struct xcb_visualtype_t {
    pub visual_id: u32,
    pub class: u8,
    pub bits_per_rgb_value: u8,
    pub colormap_entries: u16,
    pub red_mask: u32,
    pub green_mask: u32,
    pub blue_mask: u32,
    pub pad0: [u8; 4],
}

impl From<Visualtype> for xcb_visualtype_t {
    fn from(value: Visualtype) -> xcb_visualtype_t {
        xcb_visualtype_t {
            visual_id: value.visual_id,
            class: value.class.into(),
            bits_per_rgb_value: value.bits_per_rgb_value,
            colormap_entries: value.colormap_entries,
            red_mask: value.red_mask,
            green_mask: value.green_mask,
            blue_mask: value.blue_mask,
            pad0: [0; 4],
        }
    }
}

pub(crate) struct WindowBuilder {
    app: Application,
    handler: Option<Box<dyn WinHandler>>,
    title: String,
    size: Size,
    min_size: Size,
}

impl WindowBuilder {
    pub fn new(app: Application) -> WindowBuilder {
        WindowBuilder {
            app,
            handler: None,
            title: String::new(),
            size: Size::new(500.0, 400.0),
            min_size: Size::new(0.0, 0.0),
        }
    }

    pub fn set_handler(&mut self, handler: Box<dyn WinHandler>) {
        self.handler = Some(handler);
    }

    pub fn set_size(&mut self, size: Size) {
        self.size = size;
    }

    pub fn set_min_size(&mut self, min_size: Size) {
        log::warn!("WindowBuilder::set_min_size is implemented, but the setting is currently unused for X11 platforms.");
        self.min_size = min_size;
    }

    pub fn resizable(&mut self, _resizable: bool) {
        log::warn!("WindowBuilder::resizable is currently unimplemented for X11 platforms.");
    }

    pub fn show_titlebar(&mut self, _show_titlebar: bool) {
        log::warn!("WindowBuilder::show_titlebar is currently unimplemented for X11 platforms.");
    }

    pub fn set_title<S: Into<String>>(&mut self, title: S) {
        self.title = title.into();
    }

    pub fn set_menu(&mut self, _menu: Menu) {
        // TODO(x11/menus): implement WindowBuilder::set_menu (currently a no-op)
    }

    /// Registers and returns all the atoms that the window will need.
    fn atoms(&self, window_id: u32) -> Result<WindowAtoms, Error> {
        let conn = self.app.connection();
        let atoms = WindowAtoms::new(conn.as_ref())?
            .reply()
            .context("get X11 atoms")?;

        // Replace the window's WM_PROTOCOLS with the following.
        let protocols = [atoms.WM_DELETE_WINDOW];
        conn.change_property32(
            PropMode::Replace,
            window_id,
            atoms.WM_PROTOCOLS,
            AtomEnum::ATOM,
            &protocols,
        )?
        .check()
        .context("set WM_PROTOCOLS")?;

        Ok(atoms)
    }

    fn create_cairo_surface(
        &self,
        window_id: u32,
        visual_type: &Visualtype,
    ) -> Result<XCBSurface, Error> {
        let conn = self.app.connection();
        let cairo_xcb_connection = unsafe {
            CairoXCBConnection::from_raw_none(
                conn.get_raw_xcb_connection() as *mut cairo_sys::xcb_connection_t
            )
        };
        let cairo_drawable = XCBDrawable(window_id);
        let mut xcb_visual = xcb_visualtype_t::from(*visual_type);
        let cairo_visual_type = unsafe {
            XCBVisualType::from_raw_none(
                &mut xcb_visual as *mut xcb_visualtype_t as *mut cairo_sys::xcb_visualtype_t,
            )
        };
        let cairo_surface = XCBSurface::create(
            &cairo_xcb_connection,
            &cairo_drawable,
            &cairo_visual_type,
            self.size.width as i32,
            self.size.height as i32,
        )
        .map_err(|status| anyhow!("Failed to create cairo surface: {}", status))?;
        Ok(cairo_surface)
    }

    // TODO(x11/menus): make menus if requested
    pub fn build(self) -> Result<WindowHandle, Error> {
        let conn = self.app.connection();
        let screen_num = self.app.screen_num();
        let id = conn.generate_id()?;
        let setup = conn.setup();
        let screen = setup
            .roots
            .get(screen_num as usize)
            .ok_or_else(|| anyhow!("Invalid screen num: {}", screen_num))?;
        let visual_type = util::get_visual_from_screen(&screen)
            .ok_or_else(|| anyhow!("Couldn't get visual from screen"))?;
        let visual_id = visual_type.visual_id;

        let cw_values = xproto::CreateWindowAux::new().event_mask(
            EventMask::Exposure
                | EventMask::StructureNotify
                | EventMask::KeyPress
                | EventMask::KeyRelease
                | EventMask::ButtonPress
                | EventMask::ButtonRelease
                | EventMask::PointerMotion,
        );

        // Create the actual window
        let (width, height) = (self.size.width as u16, self.size.height as u16);
        conn.create_window(
            // Window depth
            x11rb::COPY_FROM_PARENT.try_into().unwrap(),
            // The new window's ID
            id,
            // Parent window of this new window
            // TODO(#468): either `screen.root()` (no parent window) or pass parent here to attach
            screen.root,
            // X-coordinate of the new window
            0,
            // Y-coordinate of the new window
            0,
            // Width of the new window
            // TODO(x11/dpi_scaling): figure out DPI scaling
            width,
            // Height of the new window
            // TODO(x11/dpi_scaling): figure out DPI scaling
            height,
            // Border width
            0,
            // Window class type
            WindowClass::InputOutput,
            // Visual ID
            visual_id,
            // Window properties mask
            &cw_values,
        )?
        .check()
        .context("create window")?;

        // Allocate a graphics context (currently used only for copying pixels when present is
        // unavailable).
        let gc = conn.generate_id()?;
        conn.create_gc(gc, id, &CreateGCAux::new())?
            .check()
            .context("create graphics context")?;

        // TODO(x11/errors): Should do proper cleanup (window destruction etc) in case of error
        let atoms = self.atoms(id)?;
        let cairo_surface = RefCell::new(self.create_cairo_surface(id, &visual_type)?);
        let state = RefCell::new(WindowState {
            size: self.size,
            invalid: Rect::ZERO,
        });
        let present_data = match self.initialize_present_data(id) {
            Ok(p) => Some(p),
            Err(e) => {
                log::info!("Failed to initialize present extension: {}", e);
                None
            }
        };
        let handler = RefCell::new(self.handler.unwrap());
        // When using present, we generally need two buffers (because after we present, we aren't
        // allowed to use that buffer for a little while, and so we might want to render to the
        // other one). Otherwise, we only need one.
        let buf_count = if present_data.is_some() { 2 } else { 1 };
        let buffers = RefCell::new(Buffers::new(
            conn,
            id,
            buf_count,
            width,
            height,
            screen.root_depth,
        )?);

        // Initialize some properties
        let pid = nix::unistd::Pid::this().as_raw();
        if let Ok(pid) = u32::try_from(pid) {
            conn.change_property32(
                xproto::PropMode::Replace,
                id,
                atoms._NET_WM_PID,
                AtomEnum::CARDINAL,
                &[pid],
            )?
            .check()
            .context("set _NET_WM_PID")?;
        }

        let window = Rc::new(Window {
            id,
            gc,
            app: self.app.clone(),
            handler,
            cairo_surface,
            atoms,
            state,
            timer_queue: Mutex::new(BinaryHeap::new()),
            idle_queue: Arc::new(Mutex::new(Vec::new())),
            idle_pipe: self.app.idle_pipe(),
            present_data: RefCell::new(present_data),
            buffers,
        });
        window.set_title(&self.title);

        let handle = WindowHandle::new(id, Rc::downgrade(&window));
        window.connect(handle.clone())?;

        self.app.add_window(id, window)?;

        Ok(handle)
    }

    fn initialize_present_data(&self, window_id: u32) -> Result<PresentData, Error> {
        if self.app.present_opcode().is_some() {
            let conn = self.app.connection();

            // We use the CompleteNotify events to schedule the next frame, and the IdleNotify
            // events to manage our buffers.
            let id = conn.generate_id()?;
            use x11rb::protocol::present::EventMask::*;
            conn.present_select_input(id, window_id, CompleteNotify | IdleNotify)?
                .check()
                .context("set present event mask")?;

            let region_id = conn.generate_id()?;
            conn.xfixes_create_region(region_id, &[])
                .context("create region")?;

            Ok(PresentData {
                serial: 0,
                region: region_id,
                waiting_on: None,
                needs_present: false,
                last_msc: None,
                last_ust: None,
            })
        } else {
            Err(anyhow!("no present opcode"))
        }
    }
}

/// An X11 window.
pub(crate) struct Window {
    id: u32,
    gc: Gcontext,
    app: Application,
    handler: RefCell<Box<dyn WinHandler>>,
    cairo_surface: RefCell<XCBSurface>,
    atoms: WindowAtoms,
    state: RefCell<WindowState>,
    /// Timers, sorted by "earliest deadline first"
    timer_queue: Mutex<BinaryHeap<Timer>>,
    idle_queue: Arc<Mutex<Vec<IdleKind>>>,
    // Writing to this wakes up the event loop, so that it can run idle handlers.
    idle_pipe: RawFd,

    /// When this is `Some(_)`, we use the X11 Present extension to present windows. This syncs all
    /// presentation to vblank and it appears to prevent tearing (subject to various caveats
    /// regarding broken video drivers).
    ///
    /// The Present extension works roughly like this: we submit a pixmap for presentation. It will
    /// get drawn at the next vblank, and some time shortly after that we'll get a notification
    /// that the drawing was completed.
    ///
    /// There are three ways that rendering can get triggered:
    /// 1) We render a frame, and it signals to us that an animation is requested. In this case, we
    ///     will render the next frame as soon as we get a notification that the just-presented
    ///     frame completed. In other words, we use `CompleteNotifyEvent` to schedule rendering.
    /// 2) We get an expose event telling us that a region got invalidated. In
    ///    this case, we will render the next frame immediately unless we're already waiting for a
    ///    completion notification. (If we are waiting for a completion notification, we just make
    ///    a note to schedule a new frame once we get it.)
    /// 3) Someone calls `invalidate` or `invalidate_rect` on us. We schedule ourselves to repaint
    ///    in the idle loop. This is better than rendering straight away, because for example they
    ///    might have called `invalidate` from their paint callback, and then we'd end up painting
    ///    re-entrantively.
    ///
    /// This is probably not the best (or at least, not the lowest-latency) scheme we can come up
    /// with, because invalidations that happen shortly after a vblank might need to wait 2 frames
    /// before they appear. If we're getting lots of invalidations, it might be better to render more
    /// than once per frame. Note that if we do, it will require some changes to part 1) above,
    /// because if we render twice in a frame then we will get two completion notifications in a
    /// row, so we don't want to present on both of them. The `msc` field of the completion
    /// notification might be useful here, because it allows us to check how many frames have
    /// actually been presented.
    present_data: RefCell<Option<PresentData>>,
    buffers: RefCell<Buffers>,
}

// This creates a `struct WindowAtoms` containing the specified atoms as members (along with some
// convenience methods to intern and query those atoms). We use the following atoms:
//
// WM_PROTOCOLS
//
// List of atoms that identify the communications protocols between
// the client and window manager in which the client is willing to participate.
//
// https://www.x.org/releases/X11R7.6/doc/xorg-docs/specs/ICCCM/icccm.html#wm_protocols_property
//
// WM_DELETE_WINDOW
//
// Including this atom in the WM_PROTOCOLS property on each window makes sure that
// if the window manager respects WM_DELETE_WINDOW it will send us the event.
//
// The WM_DELETE_WINDOW event is sent when there is a request to close the window.
// Registering for but ignoring this event means that the window will remain open.
//
// https://www.x.org/releases/X11R7.6/doc/xorg-docs/specs/ICCCM/icccm.html#window_deletion
//
// _NET_WM_PID
//
// A property containing the PID of the process that created the window.
//
// https://specifications.freedesktop.org/wm-spec/wm-spec-1.3.html#idm45805407915360
//
// _NET_WM_NAME
//
// A version of WM_NAME supporting UTF8 text.
//
// https://specifications.freedesktop.org/wm-spec/wm-spec-1.3.html#idm45805407982336
//
// UTF8_STRING
//
// The type of _NET_WM_NAME
atom_manager! {
    WindowAtoms: WindowAtomsCookie {
        WM_PROTOCOLS,
        WM_DELETE_WINDOW,
        _NET_WM_PID,
        _NET_WM_NAME,
        UTF8_STRING,
    }
}

/// The mutable state of the window.
struct WindowState {
    size: Size,
    /// The region that was invalidated since the last time we rendered.
    invalid: Rect,
}

/// A collection of pixmaps for rendering to. This gets used in two different ways: if the present
/// extension is enabled, we render to a pixmap and then present it. If the present extension is
/// disabled, we render to a pixmap and then call `copy_area` on it (this probably isn't the best
/// way to imitate double buffering, but it's the fallback anyway).
struct Buffers {
    /// A list of idle pixmaps. We take a pixmap from here for rendering to.
    ///
    /// When we're not using the present extension, all pixmaps belong in here; as soon as we copy
    /// from one, we can use it again.
    ///
    /// When we submit a pixmap to present, we're not allowed to touch it again until we get a
    /// corresponding IDLE_NOTIFY event. In my limited experiments this happens shortly after
    /// vsync, meaning that we may want to start rendering the next pixmap before we get the old
    /// one back. Therefore, we keep a list of pixmaps. We pop one each time we render, and push
    /// one when we get IDLE_NOTIFY.
    ///
    /// Since the current code only renders at most once per vsync, two pixmaps seems to always be
    /// enough. Nevertheless, we will allocate more on the fly if we need them. Note that rendering
    /// more than once per vsync can only improve latency, because only the most recently-presented
    /// pixmap will get rendered.
    idle_pixmaps: Vec<Pixmap>,
    /// A list of all the allocated pixmaps (including the idle ones).
    all_pixmaps: Vec<Pixmap>,
    /// The sizes of the pixmaps (they all have the same size). In order to avoid repeatedly
    /// reallocating as the window size changes, we allow these to be bigger than the window.
    width: u16,
    height: u16,
    /// The depth of the currently allocated pixmaps.
    depth: u8,
}

/// The state involved in using X's [Present] extension.
///
/// [Present]: https://cgit.freedesktop.org/xorg/proto/presentproto/tree/presentproto.txt
#[derive(Debug)]
struct PresentData {
    /// A monotonically increasing present request counter.
    serial: u32,
    /// The region that we use for telling X what to present.
    region: Region,
    /// Did we submit a present that hasn't completed yet? If so, this is its serial number.
    waiting_on: Option<u32>,
    /// We need to render another frame as soon as the current one is done presenting.
    needs_present: bool,
    /// The last MSC (media stream counter) that was completed. This can be used to diagnose
    /// latency problems, because MSC is a frame counter: it increments once per frame. We should
    /// be presenting on every frame, and storing the last completed MSC lets us know if we missed
    /// one.
    last_msc: Option<u64>,
    /// The time at which the last frame was completed. The present protocol documentation doesn't
    /// define the units, but it appears to be in microseconds.
    last_ust: Option<u64>,
}

impl Window {
    fn connect(&self, handle: WindowHandle) -> Result<(), Error> {
        let mut handler = borrow_mut!(self.handler)?;
        let size = self.size()?;
        handler.connect(&handle.into());
        handler.scale(Scale::default());
        handler.size(size);
        Ok(())
    }

    /// Start the destruction of the window.
    pub fn destroy(&self) {
        log_x11!(self.app.connection().destroy_window(self.id));
    }

    fn size(&self) -> Result<Size, Error> {
        Ok(borrow!(self.state)?.size)
    }

    fn set_size(&self, size: Size) -> Result<(), Error> {
        // TODO(x11/dpi_scaling): detect DPI and scale size
        let new_size = {
            let mut state = borrow_mut!(self.state)?;
            if size != state.size {
                state.size = size;
                true
            } else {
                false
            }
        };
        if new_size {
            borrow_mut!(self.buffers)?.set_size(
                self.app.connection(),
                self.id,
                size.width as u16,
                size.height as u16,
            );
            borrow_mut!(self.cairo_surface)?
                .set_size(size.width as i32, size.height as i32)
                .map_err(|status| {
                    anyhow!(
                        "Failed to update cairo surface size to {:?}: {}",
                        size,
                        status
                    )
                })?;
            self.enlarge_invalid_rect(size.to_rect())?;
            borrow_mut!(self.handler)?.size(size);
        }
        Ok(())
    }

    // Ensure that our cairo context is targeting the right drawable, allocating one if necessary.
    fn update_cairo_surface(&self) -> Result<(), Error> {
        let mut buffers = borrow_mut!(self.buffers)?;
        let pixmap = if let Some(p) = buffers.idle_pixmaps.last() {
            *p
        } else {
            log::info!("ran out of idle pixmaps, creating a new one");
            buffers.create_pixmap(self.app.connection(), self.id)?
        };

        let drawable = XCBDrawable(pixmap);
        borrow_mut!(self.cairo_surface)?
            .set_drawable(&drawable, buffers.width as i32, buffers.height as i32)
            .map_err(|e| anyhow!("Failed to update cairo drawable: {}", e))?;
        Ok(())
    }

    fn render(&self) -> Result<(), Error> {
        let size = borrow!(self.state)?.size;
        let invalid_rect = borrow!(self.state)?.invalid;
        let mut anim = false;
        self.update_cairo_surface()?;
        {
            let surface = borrow!(self.cairo_surface)?;
            let mut cairo_ctx = cairo::Context::new(&surface);
            let mut piet_ctx = Piet::new(&mut cairo_ctx);
            piet_ctx.clip(invalid_rect);

            // We need to be careful with earlier returns here, because piet_ctx
            // can panic if it isn't finish()ed. Also, we want to reset cairo's clip
            // even on error.
            let err;
            match borrow_mut!(self.handler) {
                Ok(mut handler) => {
                    anim = handler.paint(&mut piet_ctx, invalid_rect);
                    err = piet_ctx
                        .finish()
                        .map_err(|e| anyhow!("Window::render - piet finish failed: {}", e));
                }
                Err(e) => {
                    err = Err(e);
                    if let Err(e) = piet_ctx.finish() {
                        // We can't return both errors, so just log this one.
                        log::error!("Window::render - piet finish failed in error branch: {}", e);
                    }
                }
            };
            cairo_ctx.reset_clip();

            err?;
        }

        borrow_mut!(self.state)?.invalid = Rect::ZERO;
        self.set_needs_present(false)?;

        let mut buffers = borrow_mut!(self.buffers)?;
        let pixmap = *buffers
            .idle_pixmaps
            .last()
            .ok_or_else(|| anyhow!("after rendering, no pixmap to present"))?;
        if let Some(present) = borrow_mut!(self.present_data)?.as_mut() {
            present.present(self.app.connection(), pixmap, self.id, invalid_rect)?;
            buffers.idle_pixmaps.pop();
            if anim {
                self.enlarge_invalid_rect(size.to_rect())?;
                present.needs_present = true;
            }
        } else {
            let (x, y) = (invalid_rect.x0 as i16, invalid_rect.y0 as i16);
            let (w, h) = (invalid_rect.width() as u16, invalid_rect.height() as u16);
            self.app
                .connection()
                .copy_area(pixmap, self.id, self.gc, x, y, x, y, w, h)?;
            // We aren't using the present extension, so use the idle loop to schedule redraws.
            // Note that the idle loop's wakeup times are roughly tied to the refresh rate, so this
            // shouldn't draw too often.
            if anim {
                self.invalidate();
            }
        }
        Ok(())
    }

    fn show(&self) {
        log_x11!(self.app.connection().map_window(self.id));
    }

    fn close(&self) {
        self.destroy();
    }

    /// Set whether the window should be resizable
    fn resizable(&self, _resizable: bool) {
        log::warn!("Window::resizeable is currently unimplemented for X11 platforms.");
    }

    /// Set whether the window should show titlebar
    fn show_titlebar(&self, _show_titlebar: bool) {
        log::warn!("Window::show_titlebar is currently unimplemented for X11 platforms.");
    }

    /// Bring this window to the front of the window stack and give it focus.
    fn bring_to_front_and_focus(&self) {
        // TODO(x11/misc): Unsure if this does exactly what the doc comment says; need a test case.
        let conn = self.app.connection();
        log_x11!(conn.configure_window(
            self.id,
            &xproto::ConfigureWindowAux::new().stack_mode(xproto::StackMode::Above),
        ));
        log_x11!(conn.set_input_focus(
            xproto::InputFocus::PointerRoot,
            self.id,
            xproto::Time::CurrentTime,
        ));
    }

    fn enlarge_invalid_rect(&self, rect: Rect) -> Result<(), Error> {
        let invalid = &mut borrow_mut!(self.state)?.invalid;
        // This is basically just a rectangle union, but we need to be careful because
        // `Rect::union` doesn't do what we want when one rect is empty.
        if invalid.area() == 0.0 {
            *invalid = rect;
        } else if rect.area() > 0.0 {
            *invalid = invalid.union(rect);
        }
        Ok(())
    }

    /// Redraw more-or-less now.
    ///
    /// "More-or-less" because if we're already waiting on a present, we defer the drawing until it
    /// completes.
    fn redraw_now(&self) -> Result<(), Error> {
        if self.waiting_on_present()? {
            self.set_needs_present(true)?;
        } else {
            self.render()?;
        }
        Ok(())
    }

    /// Schedule a redraw on the idle loop, or if we are waiting on present then schedule it for
    /// when the current present finishes.
    fn redraw_soon(&self) {
        if let Ok(true) = self.waiting_on_present() {
            if let Err(e) = self.set_needs_present(true) {
                log::error!("Window::redraw_soon - failed to schedule present: {}", e);
            }
        } else {
            let idle = IdleHandle {
                queue: Arc::clone(&self.idle_queue),
                pipe: self.idle_pipe,
            };
            idle.schedule_redraw();
        }
    }

    fn invalidate(&self) {
        match self.size() {
            Ok(size) => self.invalidate_rect(size.to_rect()),
            Err(err) => log::error!("Window::invalidate - failed to get size: {}", err),
        }
    }

    fn invalidate_rect(&self, rect: Rect) {
        if let Err(err) = self.enlarge_invalid_rect(rect) {
            log::error!("Window::invalidate_rect - failed to enlarge rect: {}", err);
        }

        self.redraw_soon();
    }

    fn set_title(&self, title: &str) {
        // This is technically incorrect. STRING encoding is *not* UTF8. However, I am not sure
        // what it really is. WM_LOCALE_NAME might be involved. Hopefully, nothing cares about this
        // as long as _NET_WM_NAME is also set (which uses UTF8).
        log_x11!(self.app.connection().change_property8(
            xproto::PropMode::Replace,
            self.id,
            AtomEnum::WM_NAME,
            AtomEnum::STRING,
            title.as_bytes(),
        ));
        log_x11!(self.app.connection().change_property8(
            xproto::PropMode::Replace,
            self.id,
            self.atoms._NET_WM_NAME,
            self.atoms.UTF8_STRING,
            title.as_bytes(),
        ));
    }

    fn set_menu(&self, _menu: Menu) {
        // TODO(x11/menus): implement Window::set_menu (currently a no-op)
    }

    fn get_scale(&self) -> Result<Scale, Error> {
        // TODO(x11/dpi_scaling): figure out DPI scaling
        Ok(Scale::new(1.0, 1.0))
    }

    pub fn handle_expose(&self, expose: &xproto::ExposeEvent) -> Result<(), Error> {
        // TODO(x11/dpi_scaling): when dpi scaling is
        // implemented, it needs to be used here too
        let rect = Rect::from_origin_size(
            (expose.x as f64, expose.y as f64),
            (expose.width as f64, expose.height as f64),
        );

        self.enlarge_invalid_rect(rect)?;
        if self.waiting_on_present()? {
            self.set_needs_present(true)?;
        } else if expose.count == 0 {
            self.redraw_soon();
        }
        Ok(())
    }

    pub fn handle_key_press(&self, key_press: &xproto::KeyPressEvent) -> Result<(), Error> {
        let hw_keycode = key_press.detail;
        let code = keycodes::hardware_keycode_to_code(hw_keycode);
        let mods = key_mods(key_press.state);
        let key = keycodes::code_to_key(code, mods);
        let location = keycodes::code_to_location(code);
        let state = KeyState::Down;
        let key_event = KeyEvent {
            code,
            key,
            mods,
            location,
            state,
            repeat: false,
            is_composing: false,
        };
        borrow_mut!(self.handler)?.key_down(key_event);
        Ok(())
    }

    pub fn handle_button_press(
        &self,
        button_press: &xproto::ButtonPressEvent,
    ) -> Result<(), Error> {
        let button = mouse_button(button_press.detail);
        let mouse_event = MouseEvent {
            pos: Point::new(button_press.event_x as f64, button_press.event_y as f64),
            // The xcb state field doesn't include the newly pressed button, but
            // druid wants it to be included.
            buttons: mouse_buttons(button_press.state).with(button),
            mods: key_mods(button_press.state),
            // TODO: detect the count
            count: 1,
            focus: false,
            button,
            wheel_delta: Vec2::ZERO,
        };
        borrow_mut!(self.handler)?.mouse_down(&mouse_event);
        Ok(())
    }

    pub fn handle_button_release(
        &self,
        button_release: &xproto::ButtonReleaseEvent,
    ) -> Result<(), Error> {
        let button = mouse_button(button_release.detail);
        let mouse_event = MouseEvent {
            pos: Point::new(button_release.event_x as f64, button_release.event_y as f64),
            // The xcb state includes the newly released button, but druid
            // doesn't want it.
            buttons: mouse_buttons(button_release.state).without(button),
            mods: key_mods(button_release.state),
            count: 0,
            focus: false,
            button,
            wheel_delta: Vec2::ZERO,
        };
        borrow_mut!(self.handler)?.mouse_up(&mouse_event);
        Ok(())
    }

    pub fn handle_wheel(&self, event: &xproto::ButtonPressEvent) -> Result<(), Error> {
        let button = event.detail;
        let mods = key_mods(event.state);

        // We use a delta of 120 per tick to match the behavior of Windows.
        let is_shift = mods.shift();
        let delta = match button {
            4 if is_shift => (-120.0, 0.0),
            4 => (0.0, -120.0),
            5 if is_shift => (120.0, 0.0),
            5 => (0.0, 120.0),
            6 => (-120.0, 0.0),
            7 => (120.0, 0.0),
            _ => return Err(anyhow!("unexpected mouse wheel button: {}", button)),
        };
        let mouse_event = MouseEvent {
            pos: Point::new(event.event_x as f64, event.event_y as f64),
            buttons: mouse_buttons(event.state),
            mods: key_mods(event.state),
            count: 0,
            focus: false,
            button: MouseButton::None,
            wheel_delta: delta.into(),
        };

        borrow_mut!(self.handler)?.wheel(&mouse_event);
        Ok(())
    }

    pub fn handle_motion_notify(
        &self,
        motion_notify: &xproto::MotionNotifyEvent,
    ) -> Result<(), Error> {
        let mouse_event = MouseEvent {
            pos: Point::new(motion_notify.event_x as f64, motion_notify.event_y as f64),
            buttons: mouse_buttons(motion_notify.state),
            mods: key_mods(motion_notify.state),
            count: 0,
            focus: false,
            button: MouseButton::None,
            wheel_delta: Vec2::ZERO,
        };
        borrow_mut!(self.handler)?.mouse_move(&mouse_event);
        Ok(())
    }

    pub fn handle_client_message(
        &self,
        client_message: &xproto::ClientMessageEvent,
    ) -> Result<(), Error> {
        // https://www.x.org/releases/X11R7.7/doc/libX11/libX11/libX11.html#id2745388
        // https://www.x.org/releases/X11R7.6/doc/xorg-docs/specs/ICCCM/icccm.html#window_deletion
        if client_message.type_ == self.atoms.WM_PROTOCOLS && client_message.format == 32 {
            let protocol = client_message.data.as_data32()[0];
            if protocol == self.atoms.WM_DELETE_WINDOW {
                self.close();
            }
        }
        Ok(())
    }

    #[allow(clippy::trivially_copy_pass_by_ref)]
    pub fn handle_destroy_notify(
        &self,
        _destroy_notify: &xproto::DestroyNotifyEvent,
    ) -> Result<(), Error> {
        borrow_mut!(self.handler)?.destroy();
        Ok(())
    }

    pub fn handle_configure_notify(&self, event: &ConfigureNotifyEvent) -> Result<(), Error> {
        self.set_size(Size::new(event.width as f64, event.height as f64))
    }

    pub fn handle_complete_notify(&self, event: &CompleteNotifyEvent) -> Result<(), Error> {
        if let Some(present) = borrow_mut!(self.present_data)?.as_mut() {
            // A little sanity check (which isn't worth an early return): we should only have
            // one present request in flight, so we should only get notified about the request
            // that we're waiting for.
            if present.waiting_on != Some(event.serial) {
                log::warn!(
                    "Got a notify for serial {}, but waiting on {:?}",
                    event.serial,
                    present.waiting_on
                );
            }

            // Check whether we missed presenting on any frames.
            if let Some(last_msc) = present.last_msc {
                if last_msc.wrapping_add(1) != event.msc {
                    log::debug!(
                        "missed a present: msc went from {} to {}",
                        last_msc,
                        event.msc
                    );
                    if let Some(last_ust) = present.last_ust {
                        log::debug!("ust went from {} to {}", last_ust, event.ust);
                    }
                }
            }

            // Only store the last MSC if we're animating (if we aren't animating, missed MSCs
            // aren't interesting).
            present.last_msc = if present.needs_present {
                Some(event.msc)
            } else {
                None
            };
            present.last_ust = Some(event.ust);
            present.waiting_on = None;
        }

        if self.needs_present()? {
            self.render()?;
        }
        Ok(())
    }

    pub fn handle_idle_notify(&self, event: &IdleNotifyEvent) -> Result<(), Error> {
        let mut buffers = borrow_mut!(self.buffers)?;
        if buffers.all_pixmaps.contains(&event.pixmap) {
            buffers.idle_pixmaps.push(event.pixmap);
        } else {
            // We must have reallocated the buffers while this pixmap was busy, so free it now.
            // Regular freeing happens in `Buffers::free_pixmaps`.
            self.app.connection().free_pixmap(event.pixmap)?;
        }
        Ok(())
    }

    fn waiting_on_present(&self) -> Result<bool, Error> {
        Ok(borrow!(self.present_data)?
            .as_ref()
            .map(|p| p.waiting_on.is_some())
            .unwrap_or(false))
    }

    fn set_needs_present(&self, val: bool) -> Result<(), Error> {
        if let Some(present) = borrow_mut!(self.present_data)?.as_mut() {
            present.needs_present = val;
        }
        Ok(())
    }

    fn needs_present(&self) -> Result<bool, Error> {
        Ok(borrow!(self.present_data)?
            .as_ref()
            .map(|p| p.needs_present)
            .unwrap_or(false))
    }

    pub(crate) fn run_idle(&self) {
        let mut queue = Vec::new();
        std::mem::swap(&mut *self.idle_queue.lock().unwrap(), &mut queue);

        let mut needs_redraw = false;
        if let Ok(mut handler) = self.handler.try_borrow_mut() {
            for callback in queue {
                match callback {
                    IdleKind::Callback(f) => {
                        f.call(handler.as_any());
                    }
                    IdleKind::Token(tok) => {
                        handler.idle(tok);
                    }
                    IdleKind::Redraw => {
                        needs_redraw = true;
                    }
                }
            }
        } else {
            log::error!("Not running idle callbacks because the handler is borrowed");
        }

        if needs_redraw {
            if let Err(e) = self.redraw_now() {
                log::error!("Error redrawing: {}", e);
            }
        }
    }

    pub(crate) fn next_timeout(&self) -> Option<Instant> {
        if let Some(timer) = self.timer_queue.lock().unwrap().peek() {
            Some(timer.deadline())
        } else {
            None
        }
    }

    pub(crate) fn run_timers(&self, now: Instant) {
        while let Some(deadline) = self.next_timeout() {
            if deadline > now {
                break;
            }
            // Remove the timer and get the token
            let token = self.timer_queue.lock().unwrap().pop().unwrap().token();
            if let Ok(mut handler_borrow) = self.handler.try_borrow_mut() {
                handler_borrow.timer(token);
            }
        }
    }
}

impl Buffers {
    fn new(
        conn: &Rc<XCBConnection>,
        window_id: u32,
        buf_count: usize,
        width: u16,
        height: u16,
        depth: u8,
    ) -> Result<Buffers, Error> {
        let mut ret = Buffers {
            width,
            height,
            depth,
            idle_pixmaps: Vec::new(),
            all_pixmaps: Vec::new(),
        };
        ret.create_pixmaps(conn, window_id, buf_count)?;
        Ok(ret)
    }

    /// Frees all the X pixmaps that we hold.
    fn free_pixmaps(&mut self, conn: &Rc<XCBConnection>) {
        // We can't touch pixmaps if the present extension is waiting on them, so only free the
        // idle ones. We'll free the busy ones when we get notified that they're idle in `Window::handle_idle_notify`.
        for &p in &self.idle_pixmaps {
            log_x11!(conn.free_pixmap(p));
        }
        self.all_pixmaps.clear();
        self.idle_pixmaps.clear();
    }

    fn set_size(&mut self, conn: &Rc<XCBConnection>, window_id: u32, width: u16, height: u16) {
        // How big should the buffer be if we want at least x pixels? Rounding up to the next power
        // of 2 has the potential to waste 75% of our memory (factor 2 in both directions), so
        // instead we round up to the nearest number of the form 2^k or 3 * 2^k.
        fn next_size(x: u16) -> u16 {
            // We round up to the nearest multiple of `accuracy`, which is between x/2 and x/4.
            // Don't bother rounding to anything smaller than 32 = 2^(7-1).
            let accuracy = 1 << ((16 - x.leading_zeros()).max(7) - 2);
            let mask = accuracy - 1;
            (x + mask) & !mask
        }

        let width = next_size(width);
        let height = next_size(height);
        if (width, height) != (self.width, self.height) {
            let count = self.all_pixmaps.len();
            self.free_pixmaps(conn);
            self.width = width;
            self.height = height;
            log_x11!(self.create_pixmaps(conn, window_id, count));
        }
    }

    /// Creates a new pixmap for rendering to. The new pixmap will be first in line for rendering.
    fn create_pixmap(&mut self, conn: &Rc<XCBConnection>, window_id: u32) -> Result<Pixmap, Error> {
        let pixmap_id = conn.generate_id()?;
        conn.create_pixmap(self.depth, pixmap_id, window_id, self.width, self.height)?;
        self.all_pixmaps.push(pixmap_id);
        self.idle_pixmaps.push(pixmap_id);
        Ok(pixmap_id)
    }

    fn create_pixmaps(
        &mut self,
        conn: &Rc<XCBConnection>,
        window_id: u32,
        count: usize,
    ) -> Result<(), Error> {
        if !self.all_pixmaps.is_empty() {
            self.free_pixmaps(conn);
        }

        for _ in 0..count {
            self.create_pixmap(conn, window_id)?;
        }
        Ok(())
    }
}

impl PresentData {
    // We have already rendered into the active pixmap buffer. Present it to the
    // X server, and then rotate the buffers.
    fn present(
        &mut self,
        conn: &Rc<XCBConnection>,
        pixmap: Pixmap,
        window_id: u32,
        rect: Rect,
    ) -> Result<(), Error> {
        let x_rect = Rectangle {
            x: rect.x0 as i16,
            y: rect.y0 as i16,
            width: rect.width() as u16,
            height: rect.height() as u16,
        };

        conn.xfixes_set_region(self.region, &[x_rect])?;
        conn.present_pixmap(
            window_id,
            pixmap,
            self.serial,
            // valid region of the pixmap
            self.region,
            // region of the window that must get updated
            self.region,
            // window-relative x-offset of the pixmap
            0,
            // window-relative y-offset of the pixmap
            0,
            // target CRTC
            x11rb::NONE,
            // wait fence
            x11rb::NONE,
            // idle fence
            x11rb::NONE,
            // present options
            x11rb::protocol::present::Option::None.into(),
            // target msc (0 means present at the next time that msc % divisor == remainder)
            0,
            // divisor
            1,
            // remainder
            0,
            // notifies
            &[],
        )?;
        self.waiting_on = Some(self.serial);
        self.serial += 1;
        Ok(())
    }
}

// Converts from, e.g., the `details` field of `xcb::xproto::ButtonPressEvent`
fn mouse_button(button: u8) -> MouseButton {
    match button {
        1 => MouseButton::Left,
        2 => MouseButton::Middle,
        3 => MouseButton::Right,
        // buttons 4 through 7 are for scrolling.
        4..=7 => MouseButton::None,
        8 => MouseButton::X1,
        9 => MouseButton::X2,
        _ => {
            log::warn!("unknown mouse button code {}", button);
            MouseButton::None
        }
    }
}

// Extracts the mouse buttons from, e.g., the `state` field of
// `xcb::xproto::ButtonPressEvent`
fn mouse_buttons(mods: u16) -> MouseButtons {
    let mut buttons = MouseButtons::new();
    let button_masks = &[
        (xproto::ButtonMask::M1, MouseButton::Left),
        (xproto::ButtonMask::M2, MouseButton::Middle),
        (xproto::ButtonMask::M3, MouseButton::Right),
        // TODO: determine the X1/X2 state, using our own caching if necessary.
        // BUTTON_MASK_4/5 do not work: they are for scroll events.
    ];
    for (mask, button) in button_masks {
        if mods & (*mask as u16) != 0 {
            buttons.insert(*button);
        }
    }
    buttons
}

// Extracts the keyboard modifiers from, e.g., the `state` field of
// `xcb::xproto::ButtonPressEvent`
fn key_mods(mods: u16) -> Modifiers {
    let mut ret = Modifiers::default();
    let mut key_masks = [
        (xproto::ModMask::Shift, Modifiers::SHIFT),
        (xproto::ModMask::Control, Modifiers::CONTROL),
        // X11's mod keys are configurable, but this seems
        // like a reasonable default for US keyboards, at least,
        // where the "windows" key seems to be MOD_MASK_4.
        (xproto::ModMask::M1, Modifiers::ALT),
        (xproto::ModMask::M2, Modifiers::NUM_LOCK),
        (xproto::ModMask::M4, Modifiers::META),
        (xproto::ModMask::Lock, Modifiers::CAPS_LOCK),
    ];
    for (mask, modifiers) in &mut key_masks {
        if mods & (*mask as u16) != 0 {
            ret |= *modifiers;
        }
    }
    ret
}

/// A handle that can get used to schedule an idle handler. Note that
/// this handle can be cloned and sent between threads.
#[derive(Clone)]
pub struct IdleHandle {
    queue: Arc<Mutex<Vec<IdleKind>>>,
    pipe: RawFd,
}

pub(crate) enum IdleKind {
    Callback(Box<dyn IdleCallback>),
    Token(IdleToken),
    Redraw,
}

impl IdleHandle {
    fn wake(&self) {
        loop {
            match nix::unistd::write(self.pipe, &[0]) {
                Err(nix::Error::Sys(nix::errno::Errno::EINTR)) => {}
                Err(nix::Error::Sys(nix::errno::Errno::EAGAIN)) => {}
                Err(e) => {
                    log::error!("Failed to write to idle pipe: {}", e);
                    break;
                }
                Ok(_) => {
                    break;
                }
            }
        }
    }

    pub(crate) fn schedule_redraw(&self) {
        self.queue.lock().unwrap().push(IdleKind::Redraw);
        self.wake();
    }

    pub fn add_idle_callback<F>(&self, callback: F)
    where
        F: FnOnce(&dyn Any) + Send + 'static,
    {
        self.queue
            .lock()
            .unwrap()
            .push(IdleKind::Callback(Box::new(callback)));
        self.wake();
    }

    pub fn add_idle_token(&self, token: IdleToken) {
        self.queue.lock().unwrap().push(IdleKind::Token(token));
        self.wake();
    }
}

#[derive(Clone, Default)]
pub(crate) struct WindowHandle {
    id: u32,
    window: Weak<Window>,
}

impl WindowHandle {
    fn new(id: u32, window: Weak<Window>) -> WindowHandle {
        WindowHandle { id, window }
    }

    pub fn show(&self) {
        if let Some(w) = self.window.upgrade() {
            w.show();
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn close(&self) {
        if let Some(w) = self.window.upgrade() {
            w.close();
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn resizable(&self, resizable: bool) {
        if let Some(w) = self.window.upgrade() {
            w.resizable(resizable);
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn show_titlebar(&self, show_titlebar: bool) {
        if let Some(w) = self.window.upgrade() {
            w.show_titlebar(show_titlebar);
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn bring_to_front_and_focus(&self) {
        if let Some(w) = self.window.upgrade() {
            w.bring_to_front_and_focus();
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn invalidate(&self) {
        if let Some(w) = self.window.upgrade() {
            w.invalidate();
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn invalidate_rect(&self, rect: Rect) {
        if let Some(w) = self.window.upgrade() {
            w.invalidate_rect(rect);
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn set_title(&self, title: &str) {
        if let Some(w) = self.window.upgrade() {
            w.set_title(title);
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn set_menu(&self, menu: Menu) {
        if let Some(w) = self.window.upgrade() {
            w.set_menu(menu);
        } else {
            log::error!("Window {} has already been dropped", self.id);
        }
    }

    pub fn text(&self) -> Text {
        // I'm not entirely sure what this method is doing here, so here's a Text.
        Text::new()
    }

    pub fn request_timer(&self, deadline: Instant) -> TimerToken {
        if let Some(w) = self.window.upgrade() {
            let timer = Timer::new(deadline);
            w.timer_queue.lock().unwrap().push(timer);
            timer.token()
        } else {
            TimerToken::INVALID
        }
    }

    pub fn set_cursor(&mut self, _cursor: &Cursor) {
        // TODO(x11/cursors): implement WindowHandle::set_cursor
    }

    pub fn open_file_sync(&mut self, _options: FileDialogOptions) -> Option<FileInfo> {
        // TODO(x11/file_dialogs): implement WindowHandle::open_file_sync
        log::warn!("WindowHandle::open_file_sync is currently unimplemented for X11 platforms.");
        None
    }

    pub fn save_as_sync(&mut self, _options: FileDialogOptions) -> Option<FileInfo> {
        // TODO(x11/file_dialogs): implement WindowHandle::save_as_sync
        log::warn!("WindowHandle::save_as_sync is currently unimplemented for X11 platforms.");
        None
    }

    pub fn show_context_menu(&self, _menu: Menu, _pos: Point) {
        // TODO(x11/menus): implement WindowHandle::show_context_menu
        log::warn!("WindowHandle::show_context_menu is currently unimplemented for X11 platforms.");
    }

    pub fn get_idle_handle(&self) -> Option<IdleHandle> {
        if let Some(w) = self.window.upgrade() {
            Some(IdleHandle {
                queue: Arc::clone(&w.idle_queue),
                pipe: w.idle_pipe,
            })
        } else {
            None
        }
    }

    pub fn get_scale(&self) -> Result<Scale, ShellError> {
        if let Some(w) = self.window.upgrade() {
            Ok(w.get_scale()?)
        } else {
            log::error!("Window {} has already been dropped", self.id);
            Ok(Scale::new(1.0, 1.0))
        }
    }
}