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tutorials: Use async-channel instead of the glib MainContext channel

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The latter will be removed in favour of using async code in the future,
and async code generally allows for more flexible message handling than the
callback based MainContext channel.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1333>
This commit is contained in:
Sebastian Dröge 2023-10-30 10:56:39 +02:00
parent 130dc49b22
commit fc4a0d29c6
3 changed files with 94 additions and 87 deletions
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2
tutorials/Cargo.toml
View file

@ -16,6 +16,8 @@ gst-pbutils = { package = "gstreamer-pbutils", path = "../gstreamer-pbutils" }
byte-slice-cast = "1"
anyhow = "1"
termion = { version = "2", optional = true }
async-channel = "2.0.0"
futures = "0.3"
[target.'cfg(target_os = "macos")'.dependencies]
cocoa = "0.25"

85
tutorials/src/bin/basic-tutorial-13.rs
View file

@ -65,7 +65,7 @@ fn send_seek_event(pipeline: &Element, rate: f64) -> bool {
}
// This is where we get the user input from the terminal.
fn handle_keyboard(ready_tx: glib::Sender<Command>) {
fn handle_keyboard(ready_tx: async_channel::Sender<Command>) {
// We set the terminal in "raw mode" so that we can get the keys without waiting for the user
// to press return.
let _stdout = io::stdout().into_raw_mode().unwrap();
@ -84,7 +84,7 @@ fn handle_keyboard(ready_tx: glib::Sender<Command>) {
_ => continue,
};
ready_tx
.send(command)
.send_blocking(command)
.expect("failed to send data through channel");
if command == Command::Quit {
break;
@ -116,7 +116,7 @@ USAGE: Choose one of the following options, then press enter:
let _guard = main_context.acquire().unwrap();
// Build the channel to get the terminal inputs from a different thread.
let (ready_tx, ready_rx) = glib::MainContext::channel(glib::Priority::DEFAULT);
let (ready_tx, ready_rx) = async_channel::bounded(5);
thread::spawn(move || handle_keyboard(ready_tx));
@ -135,51 +135,52 @@ USAGE: Choose one of the following options, then press enter:
let mut playing = true;
let mut rate = 1.;
ready_rx.attach(Some(&main_loop.context()), move |command: Command| {
let pipeline = match pipeline_weak.upgrade() {
Some(pipeline) => pipeline,
None => return glib::ControlFlow::Continue,
};
match command {
Command::PlayPause => {
let status = if playing {
let _ = pipeline.set_state(State::Paused);
"PAUSE"
} else {
let _ = pipeline.set_state(State::Playing);
"PLAYING"
};
playing = !playing;
println!("Setting state to {status}\r");
}
Command::DataRateUp => {
if send_seek_event(&pipeline, rate * 2.) {
rate *= 2.;
main_context.spawn_local(async move {
while let Ok(command) = ready_rx.recv().await {
let Some(pipeline) = pipeline_weak.upgrade() else {
break;
};
match command {
Command::PlayPause => {
let status = if playing {
let _ = pipeline.set_state(State::Paused);
"PAUSE"
} else {
let _ = pipeline.set_state(State::Playing);
"PLAYING"
};
playing = !playing;
println!("Setting state to {status}\r");
}
}
Command::DataRateDown => {
if send_seek_event(&pipeline, rate / 2.) {
rate /= 2.;
Command::DataRateUp => {
if send_seek_event(&pipeline, rate * 2.) {
rate *= 2.;
}
}
}
Command::ReverseRate => {
if send_seek_event(&pipeline, rate * -1.) {
rate *= -1.;
Command::DataRateDown => {
if send_seek_event(&pipeline, rate / 2.) {
rate /= 2.;
}
}
}
Command::NextFrame => {
if let Some(video_sink) = pipeline.property::<Option<Element>>("video-sink") {
// Send the event
let step = Step::new(gst::format::Buffers::ONE, rate.abs(), true, false);
video_sink.send_event(step);
println!("Stepping one frame\r");
Command::ReverseRate => {
if send_seek_event(&pipeline, rate * -1.) {
rate *= -1.;
}
}
Command::NextFrame => {
if let Some(video_sink) = pipeline.property::<Option<Element>>("video-sink") {
// Send the event
let step = Step::new(gst::format::Buffers::ONE, rate.abs(), true, false);
video_sink.send_event(step);
println!("Stepping one frame\r");
}
}
Command::Quit => {
main_loop_clone.quit();
}
}
Command::Quit => {
main_loop_clone.quit();
}
}
glib::ControlFlow::Continue
});
main_loop.run();

94
tutorials/src/bin/playback-tutorial-5.rs
View file

@ -15,7 +15,7 @@ enum Command {
Quit,
}
fn handle_keyboard(ready_tx: glib::Sender<Command>) {
fn handle_keyboard(ready_tx: async_channel::Sender<Command>) {
let mut stdin = termion::async_stdin().keys();
loop {
@ -36,7 +36,7 @@ fn handle_keyboard(ready_tx: glib::Sender<Command>) {
_ => continue,
};
ready_tx
.send(command.clone())
.send_blocking(command.clone())
.expect("Failed to send command to the main thread.");
if command == Command::Quit {
break;
@ -104,7 +104,7 @@ fn tutorial_main() -> Result<(), Error> {
let _guard = main_context.acquire().unwrap();
// Build the channel to get the terminal inputs from a different thread.
let (ready_tx, ready_rx) = glib::MainContext::channel(glib::Priority::DEFAULT);
let (ready_tx, ready_rx) = async_channel::bounded(5);
// Start the keyboard handling thread
thread::spawn(move || handle_keyboard(ready_tx));
@ -121,61 +121,65 @@ fn tutorial_main() -> Result<(), Error> {
// Start playing
pipeline.set_state(gst::State::Playing)?;
ready_rx.attach(Some(&main_loop.context()), move |command: Command| {
let pipeline = match pipeline_weak.upgrade() {
Some(pipeline) => pipeline,
None => return glib::ControlFlow::Continue,
};
main_context.spawn_local(async move {
while let Ok(command) = ready_rx.recv().await {
let Some(pipeline) = pipeline_weak.upgrade() else {
break;
};
match command {
Command::UpdateChannel(ref name, increase) => {
let balance = pipeline
.dynamic_cast_ref::<gst_video::ColorBalance>()
.unwrap();
update_color_channel(name, increase, balance);
print_current_values(&pipeline);
}
Command::Quit => {
main_loop_clone.quit();
match command {
Command::UpdateChannel(ref name, increase) => {
let balance = pipeline
.dynamic_cast_ref::<gst_video::ColorBalance>()
.unwrap();
update_color_channel(name, increase, balance);
print_current_values(&pipeline);
}
Command::Quit => {
main_loop_clone.quit();
}
}
}
glib::ControlFlow::Continue
});
// Handle bus errors / EOS correctly
let main_loop_clone = main_loop.clone();
let bus = pipeline.bus().unwrap();
let mut bus_stream = bus.stream();
let pipeline_weak = pipeline.downgrade();
let _bus_watch = bus.add_watch(move |_bus, message| {
use gst::MessageView;
main_context.spawn_local(async move {
use futures::prelude::*;
let pipeline = match pipeline_weak.upgrade() {
Some(pipeline) => pipeline,
None => return glib::ControlFlow::Continue,
};
while let Some(message) = bus_stream.next().await {
use gst::MessageView;
match message.view() {
MessageView::Error(err) => {
eprintln!(
"Error received from element {:?} {}",
err.src().map(|s| s.path_string()),
err.error()
);
eprintln!("Debugging information: {:?}", err.debug());
main_loop_clone.quit();
glib::ControlFlow::Break
let Some(pipeline) = pipeline_weak.upgrade() else {
break;
};
match message.view() {
MessageView::Error(err) => {
eprintln!(
"Error received from element {:?} {}",
err.src().map(|s| s.path_string()),
err.error()
);
eprintln!("Debugging information: {:?}", err.debug());
main_loop_clone.quit();
break;
}
MessageView::Eos(..) => {
println!("Reached end of stream");
pipeline
.set_state(gst::State::Ready)
.expect("Unable to set the pipeline to the `Ready` state");
main_loop_clone.quit();
break;
}
_ => (),
}
MessageView::Eos(..) => {
println!("Reached end of stream");
pipeline
.set_state(gst::State::Ready)
.expect("Unable to set the pipeline to the `Ready` state");
main_loop_clone.quit();
glib::ControlFlow::Break
}
_ => glib::ControlFlow::Continue,
}
})?;
});
// Print initial values for all channels
print_current_values(&pipeline);