focus_chain_provider/
lib.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

//! Provides a hanging-get implementation of the `fuchsia.ui.focus.FocusChainProvider` protocol.
//!
//! * Create a new publisher and request stream handler using [`make_publisher_and_stream_handler()`].
//! * Handle a new client's stream of watch requests using
//!   [`FocusChainProviderRequestStreamHandler::handle_request_stream`].
//! * Update the focus chain using [`FocusChainProviderPublisher::set_state_and_notify_if_changed`]
//!   or [`FocusChainProviderPublisher::set_state_and_notify_always`].

mod instance_counter;

use crate::instance_counter::InstanceCounter;
use async_utils::hanging_get::server as hanging_get;
use fidl_fuchsia_ui_focus::{
    self as focus, FocusChainProviderWatchFocusKoidChainResponder, FocusKoidChain,
};
use fidl_fuchsia_ui_focus_ext::FocusChainExt;
use fuchsia_async as fasync;
use futures::lock::Mutex;
use futures::stream::TryStreamExt;
use futures::TryFutureExt;
use std::sync::Arc;
use tracing::error;

// Local shorthand type aliases
type HangingGetNotifyFn =
    Box<dyn Fn(&FocusKoidChain, FocusChainProviderWatchFocusKoidChainResponder) -> bool + Send>;
type HangingGetBroker = hanging_get::HangingGet<
    FocusKoidChain,
    FocusChainProviderWatchFocusKoidChainResponder,
    HangingGetNotifyFn,
>;
type HangingGetPublisher = hanging_get::Publisher<
    FocusKoidChain,
    FocusChainProviderWatchFocusKoidChainResponder,
    HangingGetNotifyFn,
>;

/// Creates a new publisher and stream handler pair. Their initial focus chain value is always
/// `FocusKoidChain::default()`.
pub fn make_publisher_and_stream_handler(
) -> (FocusChainProviderPublisher, FocusChainProviderRequestStreamHandler) {
    let notify_fn: HangingGetNotifyFn =
        Box::new(|focus_koid_chain, responder| match responder.send(&focus_koid_chain) {
            Ok(()) => true,
            Err(e) => {
                error!("Failed to send focus chain to client: {e:?}");
                false
            }
        });

    let broker = hanging_get::HangingGet::new(FocusKoidChain::default(), notify_fn);
    let publisher = broker.new_publisher();
    let subscriber_counter = InstanceCounter::new();

    (
        FocusChainProviderPublisher { publisher },
        FocusChainProviderRequestStreamHandler {
            broker: Arc::new(Mutex::new(broker)),
            subscriber_counter,
        },
    )
}

/// Allows new focus chain values to be stored for transmission to watcher clients (through the
/// corresponding [`FocusChainProviderRequestStreamHandler`]).
///
/// Instantiate using [`make_publisher_and_stream_handler()`].
#[derive(Clone)]
pub struct FocusChainProviderPublisher {
    publisher: HangingGetPublisher,
}

impl FocusChainProviderPublisher {
    /// Updates the focus chain. If the new value is different from the previous value, sends an
    /// update to all listeners.
    ///
    /// Returns an error if there are any problems with duplicating the `FocusChain`.
    pub fn set_state_and_notify_if_changed<C: FocusChainExt>(
        &self,
        new_state: &C,
    ) -> Result<(), zx::Status> {
        let new_state = new_state.to_focus_koid_chain()?;
        let publisher = self.publisher.clone();
        publisher.update(|old_state| match old_state.as_ref().unwrap().equivalent(&new_state) {
            Ok(true) => false,
            Ok(false) => {
                *old_state = Some(new_state);
                true
            }
            Err(e) => unreachable!("Unexpected state {e:?}"),
        });
        Ok(())
    }

    /// Updates the focus chain. Sends an update to all listeners even if the value hasn't changed.
    ///
    /// Returns an error if there are any problems with duplicating the `FocusChain`.
    pub fn set_state_and_notify_always<C: FocusChainExt>(
        &self,
        new_state: &C,
    ) -> Result<(), zx::Status> {
        let publisher = self.publisher.clone();
        publisher.set(new_state.to_focus_koid_chain()?);
        Ok(())
    }
}

/// Handles streams of requests from `FocusChainProvider` clients, responding to them with the
/// latest value from the corresponding [`FocusChainProviderPublisher`].
///
/// Instantiate using [`make_publisher_and_stream_handler()`].
#[derive(Clone)]
pub struct FocusChainProviderRequestStreamHandler {
    broker: Arc<Mutex<HangingGetBroker>>,
    subscriber_counter: InstanceCounter,
}

impl FocusChainProviderRequestStreamHandler {
    /// Handles a [`fidl_fuchsia_ui_focus::FocusChainProviderRequestStream`] for a single client,
    /// spawning a new local `Task`.
    #[must_use = "The Task must be retained or `.detach()`ed."]
    pub fn handle_request_stream(
        &self,
        mut stream: focus::FocusChainProviderRequestStream,
    ) -> fasync::Task<()> {
        let broker = self.broker.clone();
        let counter = self.subscriber_counter.clone();
        fasync::Task::local(
            async move {
                let subscriber = broker.lock().await.new_subscriber();
                // Will be dropped when the task is being dropped.
                let _count_token = counter.make_token();
                while let Some(req) = stream.try_next().await? {
                    match req {
                        focus::FocusChainProviderRequest::WatchFocusKoidChain {
                            payload: _payload,
                            responder,
                        } => {
                            subscriber.register(responder)?;
                        }
                    }
                }
                Ok(())
            }
            .unwrap_or_else(|e: anyhow::Error| error!("{e:#?}")),
        )
    }

    /// Returns the number of active subscribers. Mostly useful for tests.
    pub fn subscriber_count(&self) -> usize {
        self.subscriber_counter.count()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use fidl_fuchsia_ui_focus_test_helpers::make_focus_chain;

    // Most of the testing happens in `async_utils::hanging_get`.
    #[fuchsia::test]
    async fn smoke_test() {
        let (publisher, stream_handler) = super::make_publisher_and_stream_handler();
        let (client, stream) =
            fidl::endpoints::create_proxy_and_stream::<focus::FocusChainProviderMarker>();
        stream_handler.handle_request_stream(stream).detach();
        assert_eq!(stream_handler.subscriber_count(), 0);

        let received_focus_koid_chain = client
            .watch_focus_koid_chain(&focus::FocusChainProviderWatchFocusKoidChainRequest::default())
            .await
            .expect("watch_focus_koid_chain");
        assert!(received_focus_koid_chain.equivalent(&FocusKoidChain::default()).unwrap());
        assert_eq!(stream_handler.subscriber_count(), 1);

        let (served_focus_chain, _view_ref_controls) = make_focus_chain(2);
        publisher.set_state_and_notify_if_changed(&served_focus_chain).expect("set_state");
        let received_focus_koid_chain = client
            .watch_focus_koid_chain(&focus::FocusChainProviderWatchFocusKoidChainRequest::default())
            .await
            .expect("watch_focus_chain");
        assert!(received_focus_koid_chain.equivalent(&served_focus_chain).unwrap());
        assert_eq!(stream_handler.subscriber_count(), 1);
    }

    #[fuchsia::test]
    async fn only_newest_value_is_sent() {
        let (publisher, stream_handler) = super::make_publisher_and_stream_handler();
        let (client, stream) =
            fidl::endpoints::create_proxy_and_stream::<focus::FocusChainProviderMarker>();
        stream_handler.handle_request_stream(stream).detach();

        let received_focus_koid_chain = client
            .watch_focus_koid_chain(&focus::FocusChainProviderWatchFocusKoidChainRequest::default())
            .await
            .expect("watch_focus_koid_chain");
        assert!(received_focus_koid_chain.equivalent(&FocusKoidChain::default()).unwrap());

        let (served_focus_chain, _view_ref_controls) = make_focus_chain(2);
        publisher.set_state_and_notify_if_changed(&served_focus_chain).expect("set_state");

        let (served_focus_chain, _view_ref_controls) = make_focus_chain(3);
        publisher.set_state_and_notify_if_changed(&served_focus_chain).expect("set_state");

        let received_focus_koid_chain = client
            .watch_focus_koid_chain(&focus::FocusChainProviderWatchFocusKoidChainRequest::default())
            .await
            .expect("watch_focus_chain");
        assert_eq!(received_focus_koid_chain.len(), 3);
        assert!(received_focus_koid_chain.equivalent(&served_focus_chain).unwrap());
    }
}