Modify architecture to run pipewire loop in second thread.

The pipewire loop now runs without interruption in a second thread and communicates with the GTK thread via a channel in each direction, instead of checking for events once a second and using callbacks. This allows changes to appear instantly in the view, instead of having to wait.
2026-03-15 03:26:10 +08:00 · 2021-05-05 21:43:52 +02:00
parent 75aa0a30d0
commit 076fec7eb4
9 changed files with 292 additions and 346 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -49,9 +49,9 @@ checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"

 [[package]]
 name = "bindgen"
-version = "0.57.0"
+version = "0.58.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fd4865004a46a0aafb2a0a5eb19d3c9fc46ee5f063a6cfc605c69ac9ecf5263d"
+checksum = "0f8523b410d7187a43085e7e064416ea32ded16bd0a4e6fc025e21616d01258f"
 dependencies = [
 "bitflags",
 "cexpr",
@@ -108,7 +108,7 @@ source = "git+https://github.com/gtk-rs/gtk-rs#51fea9aa4aff93a0322e87ea27c090465
 dependencies = [
 "glib-sys",
 "libc",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -342,7 +342,7 @@ dependencies = [
 "glib-sys",
 "gobject-sys",
 "libc",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -372,7 +372,7 @@ dependencies = [
 "gobject-sys",
 "libc",
 "pango-sys",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -399,7 +399,7 @@ dependencies = [
 "glib-sys",
 "gobject-sys",
 "libc",
- "system-deps 3.1.0",
+ "system-deps",
 "winapi",
 ]

@@ -441,7 +441,7 @@ version = "0.13.0"
 source = "git+https://github.com/gtk-rs/gtk-rs#51fea9aa4aff93a0322e87ea27c090465f43f1f4"
 dependencies = [
 "libc",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -457,7 +457,7 @@ source = "git+https://github.com/gtk-rs/gtk-rs#51fea9aa4aff93a0322e87ea27c090465
 dependencies = [
 "glib-sys",
 "libc",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -478,7 +478,7 @@ dependencies = [
 "glib-sys",
 "libc",
 "pkg-config",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -508,7 +508,7 @@ dependencies = [
 "graphene-sys",
 "libc",
 "pango-sys",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -563,7 +563,7 @@ dependencies = [
 "gsk4-sys",
 "libc",
 "pango-sys",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -581,7 +581,6 @@ version = "0.1.0"
 dependencies = [
 "env_logger",
 "gtk4",
- "libspa",
 "log",
 "once_cell",
 "pipewire",
@@ -664,8 +663,7 @@ dependencies = [
 [[package]]
 name = "libspa"
 version = "0.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "011074b4d7771195ec969f3053c5745d8cd22f4415e8348d3c574944b108b895"
+source = "git+https://gitlab.freedesktop.org/pipewire/pipewire-rs?branch=main#f8dc21b0f85f391201e7c6346b121fbd21c02836"
 dependencies = [
 "bitflags",
 "cc",
@@ -674,17 +672,16 @@ dependencies = [
 "libc",
 "libspa-sys",
 "nom 6.1.2",
- "system-deps 2.0.3",
+ "system-deps",
 ]

 [[package]]
 name = "libspa-sys"
 version = "0.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "19351566b3a5adc05e491dfaef725869a0d5e3f206662a29f6ba64381d674769"
+source = "git+https://gitlab.freedesktop.org/pipewire/pipewire-rs?branch=main#f8dc21b0f85f391201e7c6346b121fbd21c02836"
 dependencies = [
 "bindgen",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -773,7 +770,7 @@ dependencies = [
 "glib-sys",
 "gobject-sys",
 "libc",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -806,14 +803,15 @@ checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 [[package]]
 name = "pipewire"
 version = "0.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e678fc8a43e7e4d5a211c4ce16517cf0a4bca520d96d9f4df15f26193ef120aa"
+source = "git+https://gitlab.freedesktop.org/pipewire/pipewire-rs?branch=main#f8dc21b0f85f391201e7c6346b121fbd21c02836"
 dependencies = [
 "anyhow",
 "bitflags",
+ "errno",
 "libc",
 "libspa",
 "libspa-sys",
+ "once_cell",
 "pipewire-sys",
 "signal",
 "thiserror",
@@ -822,12 +820,11 @@ dependencies = [
 [[package]]
 name = "pipewire-sys"
 version = "0.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3afc6fc22dcdb1e80c445725e7f95b610640a38f591783b38c3d58133d5e2135"
+source = "git+https://gitlab.freedesktop.org/pipewire/pipewire-rs?branch=main#f8dc21b0f85f391201e7c6346b121fbd21c02836"
 dependencies = [
 "bindgen",
 "libspa-sys",
- "system-deps 3.1.0",
+ "system-deps",
 ]

 [[package]]
@@ -957,9 +954,9 @@ checksum = "558dc50e1a5a5fa7112ca2ce4effcb321b0300c0d4ccf0776a9f60cd89031171"

 [[package]]
 name = "shlex"
-version = "0.1.1"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7fdf1b9db47230893d76faad238fd6097fd6d6a9245cd7a4d90dbd639536bbd2"
+checksum = "42a568c8f2cd051a4d283bd6eb0343ac214c1b0f1ac19f93e1175b2dee38c73d"

 [[package]]
 name = "signal"
@@ -1024,21 +1021,6 @@ dependencies = [
 "unicode-xid",
 ]

-[[package]]
-name = "system-deps"
-version = "2.0.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1b59b8aafd652f3c1469f16e6c223121e8a8dbe40c71475209c1401cff3a67ef"
-dependencies = [
- "heck",
- "pkg-config",
- "strum",
- "strum_macros",
- "thiserror",
- "toml",
- "version-compare",
-]
-
 [[package]]
 name = "system-deps"
 version = "3.1.0"
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,9 +14,7 @@ categories = ["gui", "multimedia"]

 [dependencies]
 gtk = { git = "https://github.com/gtk-rs/gtk4-rs/", package = "gtk4" }
-
-pipewire = "0.3.0"
-libspa = "0.3.0"
+pipewire = { git = "https://gitlab.freedesktop.org/pipewire/pipewire-rs", branch = "main" }

 log = "0.4.11"
 env_logger = "0.8.2"
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -15,45 +15,41 @@ Helvum uses an architecture with the components laid out like this:
 Λ   ┆
 │<───── updates view
 │   ┆
- │   ┆<─────────────── notifies of user input (using callbacks)
- │   ┆
+ │   ┆<─ notifies of user input
+ │   ┆    (using signals)
 │   ┆
 │   ┆
 │   V           notifies of remote changes
-┌┴───────────┐        (using callbacks)      ┌─────────────────────┐
-│            │<╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤                     │
-│ Controller │                               │ Pipewire Connection │
-│            ├──────────────────────────────>│                     │
+┌┴───────────┐         via messages          ┌─────────────────────┐
+│            │<╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤      Seperate       │
+│ Controller │                               │      Pipewire       │
+│            ├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌>│       Thread        │
 └┬───────────┘   Request changes to remote   └─────────────────────┘
- │                                                      Λ
+ │                      via messages                    Λ
 │                                                      ║
- │<─── updates/reads state            Communicates ───> ║
+ │<─── updates/reads state                              ║
 │                                                      ║
 V                                                      ║
 ┌───────┐                                               V
 │ State │                                   [ Remote Pipewire Server ]
 └───────┘
 ```
+The program is split between two threads, with most stuff happening inside the GTK thread.
+The GTK thread will sit in a GTK event processing loop, while the pipewire thread will sit in a
+pipewire event processing loop.

-The `Controller` struct is the centerpiece of this architecture.
-It registers callbacks with the `PipewireConnection` struct to get notified of any changes
-on the remote.
+The `Controller` struct inside the GTK thread is the centerpiece of this architecture.
+It communicates with the pipewire thread using two channels,
+where each message sent by one thread will trigger the loop of the other thread to invoke a callback
+with the received message.

-For each change it is notified of, it updates the view to reflect those changes, and additionally memorizes anything it might need later in the state.
+For each change on the remote pipewire server, the GTK thread is notified by the pipewire thread
+and updates the view to reflect those changes, and additionally memorizes anything it might need later in the state.

 Additionally, a user may also make changes using the view.
-For each change, the view notifies the controller by invoking callbacks registered on it.
+For each change, the view notifies the controller by emitting a matching signal.
 The controller will then request the pipewire connection to make those changes on the remote. \
 These changes will then be applied to the view like any other remote changes as explained above.

-## Control flow
-Most of the time, the program will sit idle in a gtk event processing loop.
-
-For any changes made using the view, gtk will emit an event on some widget, which will result in a closure on that widget being called, and in turn the controller being updated.
-
-On the other hand, we may receive updates from the remote pipewire server at any moment. \
-To process these changes, the gtk event loop is set up to trigger a roundtrip on the pipewire
-connection on an interval. During this roundtrip, we process all events sent to us by the pipewire server and notify the controller of them.
-
 # View Architecture
 TODO
--- a/src/controller.rs
+++ b/src/controller.rs
@@ -1,13 +1,12 @@
 use std::{cell::RefCell, collections::HashMap, rc::Rc};

-use gtk::glib::{self, clone};
-use libspa::{ForeignDict, ReadableDict};
+use gtk::glib::{self, clone, Continue, Receiver};
 use log::{info, warn};
-use pipewire::{port::Direction, registry::GlobalObject, types::ObjectType};
+use pipewire::spa::Direction;

-use crate::{pipewire_connection::PipewireConnection, view};
+use crate::{view, PipewireLink, PipewireMessage};

-#[derive(Copy, Clone)]
+#[derive(Debug, Copy, Clone)]
 pub enum MediaType {
    Audio,
    Video,
@@ -41,7 +40,6 @@ enum Item {
 ///
 /// It also keeps and manages a state object that contains the current state of objects present on the remote.
 pub struct Controller {
-    con: Rc<RefCell<PipewireConnection>>,
    state: HashMap<u32, Item>,
    view: Rc<view::View>,
 }
@@ -56,95 +54,52 @@ impl Controller {
    /// will also drop the controller, unless the `Rc` is cloned outside of this function.
    pub(super) fn new(
        view: Rc<view::View>,
-        con: Rc<RefCell<PipewireConnection>>,
+        gtk_receiver: Receiver<PipewireMessage>,
    ) -> Rc<RefCell<Controller>> {
        let result = Rc::new(RefCell::new(Controller {
-            con,
            view,
            state: HashMap::new(),
        }));

-        result
-            .borrow()
-            .con
+        // React to messages received from the pipewire thread.
+        gtk_receiver.attach(
+            None,
+            clone!(
+                @weak result as controller => @default-return Continue(true),
+                move |msg| {
+                    match msg {
+                        PipewireMessage::NodeAdded {
+                            id,
+                            name,
+                            media_type,
+                        } => controller.borrow_mut().add_node(id, name, media_type),
+                        PipewireMessage::PortAdded {
+                            id,
+                            node_id,
+                            name,
+                            direction,
+                        } => controller
                            .borrow_mut()
-            .on_global_add(Some(Box::new(
-                clone!(@weak result as this => move |global| {
-                    this.borrow_mut().global_add(global);
-                }),
-            )));
-        result
-            .borrow()
-            .con
-            .borrow_mut()
-            .on_global_remove(Some(Box::new(clone!(@weak result as this => move |id| {
-                    this.borrow_mut().global_remove(id);
-            }))));
+                            .add_port(id, node_id, name, direction),
+                        PipewireMessage::LinkAdded { id, link } => controller.borrow_mut().add_link(id, link),
+                        PipewireMessage::ObjectRemoved { id } => controller.borrow_mut().remove_global(id),
+                    };
+                    Continue(true)
+                }
+            )
+        );

        result
    }

-    /// Handle a new global object being added.
-    /// Relevant objects are displayed to the user and/or stored to the state.
-    ///
-    /// It is called from the `PipewireConnection` via callback.
-    fn global_add(&mut self, global: &GlobalObject<ForeignDict>) {
-        match global.type_ {
-            ObjectType::Node => {
-                self.add_node(global);
-            }
-            ObjectType::Port => {
-                self.add_port(global);
-            }
-            ObjectType::Link => {
-                self.add_link(global);
-            }
-            _ => {}
-        }
-    }
-
    /// Handle a node object being added.
-    fn add_node(&mut self, node: &GlobalObject<ForeignDict>) {
-        info!("Adding node to graph: id {}", node.id);
+    pub(super) fn add_node(&mut self, id: u32, name: String, media_type: Option<MediaType>) {
+        info!("Adding node to graph: id {}", id);

-        // Get the nicest possible name for the node, using a fallback chain of possible name attributes.
-        let node_name = &node
-            .props
-            .as_ref()
-            .map(|dict| {
-                String::from(
-                    dict.get("node.nick")
-                        .or_else(|| dict.get("node.description"))
-                        .or_else(|| dict.get("node.name"))
-                        .unwrap_or_default(),
-                )
-            })
-            .unwrap_or_default();
-
-        // FIXME: This relies on the node being passed to us by the pipwire server before its port.
-        let media_type = node
-            .props
-            .as_ref()
-            .map(|props| {
-                props.get("media.class").map(|class| {
-                    if class.contains("Audio") {
-                        Some(MediaType::Audio)
-                    } else if class.contains("Video") {
-                        Some(MediaType::Video)
-                    } else if class.contains("Midi") {
-                        Some(MediaType::Midi)
-                    } else {
-                        None
-                    }
-                })
-            })
-            .flatten()
-            .flatten();
-
-        self.view.add_node(node.id, node_name);
+        self.view.add_node(id, name.as_str());

        self.state.insert(
-            node.id,
+            id,
            Item::Node {
                // widget: node_widget,
                media_type,
@@ -153,94 +108,43 @@ impl Controller {
    }

    /// Handle a port object being added.
-    fn add_port(&mut self, port: &GlobalObject<ForeignDict>) {
-        info!("Adding port to graph: id {}", port.id);
+    pub(super) fn add_port(&mut self, id: u32, node_id: u32, name: String, direction: Direction) {
+        info!("Adding port to graph: id {}", id);

        // Update graph to contain the new port.
-        let props = port
-            .props
-            .as_ref()
-            .expect("Port object is missing properties");
-        let port_label = props.get("port.name").unwrap_or_default().to_string();
-        let node_id: u32 = props
-            .get("node.id")
-            .expect("Port has no node.id property!")
-            .parse()
-            .expect("Could not parse node.id property");

        // Find out the nodes media type so that the port can be colored.
        let media_type = if let Some(Item::Node { media_type, .. }) = self.state.get(&node_id) {
            media_type.to_owned()
        } else {
-            warn!("Node not found for Port {}", port.id);
+            warn!("Node not found for Port {}", id);
            None
        };

-        self.view.add_port(
-            node_id,
-            port.id,
-            &port_label,
-            if matches!(props.get("port.direction"), Some("in")) {
-                Direction::Input
-            } else {
-                Direction::Output
-            },
-            media_type,
-        );
+        self.view
+            .add_port(node_id, id, &name, direction, media_type);

        // Save node_id so we can delete this port easily.
-        self.state.insert(port.id, Item::Port { node_id });
+        self.state.insert(id, Item::Port { node_id });
    }

    /// Handle a link object being added.
-    fn add_link(&mut self, link: &GlobalObject<ForeignDict>) {
-        info!("Adding link to graph: id {}", link.id);
+    pub(super) fn add_link(&mut self, id: u32, link: PipewireLink) {
+        info!("Adding link to graph: id {}", id);

        // FIXME: Links should be colored depending on the data they carry (video, audio, midi) like ports are.

-        self.state.insert(link.id, Item::Link);
+        self.state.insert(id, Item::Link);

        // Update graph to contain the new link.
-        let props = link
-            .props
-            .as_ref()
-            .expect("Link object is missing properties");
-        let input_node: u32 = props
-            .get("link.input.node")
-            .expect("Link has no link.input.node property")
-            .parse()
-            .expect("Could not parse link.input.node property");
-        let input_port: u32 = props
-            .get("link.input.port")
-            .expect("Link has no link.input.port property")
-            .parse()
-            .expect("Could not parse link.input.port property");
-        let output_node: u32 = props
-            .get("link.output.node")
-            .expect("Link has no link.input.node property")
-            .parse()
-            .expect("Could not parse link.input.node property");
-        let output_port: u32 = props
-            .get("link.output.port")
-            .expect("Link has no link.output.port property")
-            .parse()
-            .expect("Could not parse link.output.port property");
-        self.view.add_link(
-            link.id,
-            crate::PipewireLink {
-                node_from: output_node,
-                port_from: output_port,
-                node_to: input_node,
-                port_to: input_port,
-            },
-        );
+        self.view.add_link(id, link);
    }

    /// Handle a globalobject being removed.
    /// Relevant objects are removed from the view and/or the state.
    ///
    /// This is called from the `PipewireConnection` via callback.
-    fn global_remove(&mut self, id: u32) {
+    pub(super) fn remove_global(&mut self, id: u32) {
        if let Some(item) = self.state.remove(&id) {
            match item {
                Item::Node { .. } => {
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,7 +4,38 @@ mod view;

 use std::rc::Rc;

-use gtk::{glib, prelude::*};
+use controller::MediaType;
+use gtk::glib::{self, PRIORITY_DEFAULT};
+use pipewire::spa::Direction;
+
+/// Messages used GTK thread to command the pipewire thread.
+#[derive(Debug)]
+enum GtkMessage {
+    /// Quit the event loop and let the thread finish.
+    Terminate,
+}
+
+/// Messages used pipewire thread to notify the GTK thread.
+#[derive(Debug)]
+enum PipewireMessage {
+    /// A new node has appeared.
+    NodeAdded {
+        id: u32,
+        name: String,
+        media_type: Option<MediaType>,
+    },
+    /// A new port has appeared.
+    PortAdded {
+        id: u32,
+        node_id: u32,
+        name: String,
+        direction: Direction,
+    },
+    /// A new link has appeared.
+    LinkAdded { id: u32, link: PipewireLink },
+    /// An object was removed
+    ObjectRemoved { id: u32 },
+}

 #[derive(Debug)]
 pub struct PipewireLink {
@@ -18,20 +49,22 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
    env_logger::init();
    gtk::init()?;

-    let view = Rc::new(view::View::new());
-    let pw_con = pipewire_connection::PipewireConnection::new()?;
-    let _controller = controller::Controller::new(view.clone(), pw_con.clone());
+    // Start the pipewire thread with channels in both directions.
+    let (gtk_sender, gtk_receiver) = glib::MainContext::channel(PRIORITY_DEFAULT);
+    let (pw_sender, pw_receiver) = pipewire::channel::channel();
+    let pw_thread =
+        std::thread::spawn(move || pipewire_connection::thread_main(gtk_sender, pw_receiver));

-    // Do an initial roundtrip before showing the view,
-    // so that the graph is already populated when the window opens.
-    pw_con.borrow().roundtrip();
-    // From now on, call roundtrip() every second.
-    glib::timeout_add_seconds_local(1, move || {
-        pw_con.borrow().roundtrip();
-        Continue(true)
-    });
+    let view = Rc::new(view::View::new());
+    let _controller = controller::Controller::new(view.clone(), gtk_receiver);

    view.run();

+    pw_sender
+        .send(GtkMessage::Terminate)
+        .expect("Failed to send message");
+
+    pw_thread.join().expect("Pipewire thread panicked");
+
    Ok(())
 }
--- a/src/pipewire_connection.rs
+++ b/src/pipewire_connection.rs
@@ -1,123 +1,159 @@
-use gtk::glib::{self, clone};
-use libspa::ForeignDict;
-use log::trace;
-use once_cell::unsync::OnceCell;
-use pipewire as pw;
-use pw::registry::GlobalObject;
-
-use std::{
-    cell::{Cell, RefCell},
-    rc::Rc,
+use gtk::glib;
+use pipewire::{
+    prelude::*,
+    registry::GlobalObject,
+    spa::{Direction, ForeignDict},
+    types::ObjectType,
+    Context, MainLoop,
 };

-/// This struct is responsible for communication with the pipewire server.
-/// The owner of this struct can subscribe to notifications for globals added or removed.
-///
-/// It's `roundtrip` function must be called regularly to receive updates.
-pub struct PipewireConnection {
-    mainloop: pw::MainLoop,
-    _context: pw::Context<pw::MainLoop>,
-    core: pw::Core,
-    registry: pw::registry::Registry,
-    listeners: OnceCell<pw::registry::Listener>,
-    on_global_add: Option<Box<dyn Fn(&GlobalObject<ForeignDict>)>>,
-    on_global_remove: Option<Box<dyn Fn(u32)>>,
+use crate::{controller::MediaType, GtkMessage, PipewireMessage};
+
+/// The "main" function of the pipewire thread.
+pub(super) fn thread_main(
+    gtk_sender: glib::Sender<PipewireMessage>,
+    pw_receiver: pipewire::channel::Receiver<GtkMessage>,
+) {
+    let mainloop = MainLoop::new().expect("Failed to create mainloop");
+    let context = Context::new(&mainloop).expect("Failed to create context");
+    let core = context.connect(None).expect("Failed to connect to remote");
+    let registry = core.get_registry().expect("Failed to get registry");
+
+    let _receiver = pw_receiver.attach(&mainloop, {
+        let mainloop = mainloop.clone();
+        move |msg| match msg {
+            GtkMessage::Terminate => mainloop.quit(),
        }
+    });

-impl PipewireConnection {
-    /// Create a new Pipewire Connection.
-    ///
-    /// This returns an `Rc`, because weak references to the result are needed inside closures set up during creation.
-    pub fn new() -> Result<Rc<RefCell<Self>>, pw::Error> {
-        // Initialize pipewire lib and obtain needed pipewire objects.
-        pw::init();
-        let mainloop = pw::MainLoop::new()?;
-        let context = pw::Context::new(&mainloop)?;
-        let core = context.connect(None)?;
-        let registry = core.get_registry()?;
-
-        let result = Rc::new(RefCell::new(Self {
-            mainloop,
-            _context: context,
-            core,
-            registry,
-            listeners: OnceCell::new(),
-            on_global_add: None,
-            on_global_remove: None,
-        }));
-
-        // Notify state on globals added / removed
-        let listeners = result
-            .borrow()
-            .registry
+    let _listener = registry
        .add_listener_local()
-            .global(clone!(@weak result as this => move |global| {
-                trace!("Global is added: {}", global.id);
-                let con = this.borrow();
-                if let Some(callback) = con.on_global_add.as_ref() {
-                    callback(global)
-                } else {
-                    trace!("No on_global_add callback registered");
+        .global({
+            let sender = gtk_sender.clone();
+            move |global| match global.type_ {
+                ObjectType::Node => handle_node(global, &sender),
+                ObjectType::Port => handle_port(global, &sender),
+                ObjectType::Link => handle_link(global, &sender),
+                _ => {
+                    // Other objects are not interesting to us
                }
-            }))
-            .global_remove(clone!(@weak result as this => move |id| {
-                trace!("Global is removed: {}", id);
-                let con = this.borrow();
-                if let Some(callback) = con.on_global_remove.as_ref() {
-                    callback(id)
-                } else {
-                    trace!("No on_global_remove callback registered");
-                }
-            }))
-            .register();
-
-        // Makeshift `expect()`: listeners does not implement `Debug`, so we can not use `expect`.
-        assert!(
-            result.borrow_mut().listeners.set(listeners).is_ok(),
-            "PipewireConnection.listeners field already set"
-        );
-
-        Ok(result)
-    }
-
-    /// Receive all events from the pipewire server, sending them to the `pipewire_state` struct for processing.
-    pub fn roundtrip(&self) {
-        trace!("Starting roundtrip");
-
-        let done = Rc::new(Cell::new(false));
-        let pending = self
-            .core
-            .sync(0)
-            .expect("Failed to trigger core sync event");
-
-        let done_clone = done.clone();
-        let loop_clone = self.mainloop.clone();
-
-        let _listener = self
-            .core
-            .add_listener_local()
-            .done(move |id, seq| {
-                if id == pw::PW_ID_CORE && seq == pending {
-                    done_clone.set(true);
-                    loop_clone.quit();
            }
        })
+        .global_remove(move |id| {
+            gtk_sender
+                .send(PipewireMessage::ObjectRemoved { id })
+                .expect("Failed to send message")
+        })
        .register();

-        while !done.get() {
-            self.mainloop.run();
+    mainloop.run();
 }

-        trace!("Roundtrip finished");
+/// Handle a new node being added
+fn handle_node(node: &GlobalObject<ForeignDict>, sender: &glib::Sender<PipewireMessage>) {
+    let props = node
+        .props
+        .as_ref()
+        .expect("Node object is missing properties");
+
+    // Get the nicest possible name for the node, using a fallback chain of possible name attributes.
+    let name = String::from(
+        props
+            .get("node.nick")
+            .or_else(|| props.get("node.description"))
+            .or_else(|| props.get("node.name"))
+            .unwrap_or_default(),
+    );
+
+    // FIXME: This relies on the node being passed to us by the pipwire server before its port.
+    let media_type = props
+        .get("media.class")
+        .map(|class| {
+            if class.contains("Audio") {
+                Some(MediaType::Audio)
+            } else if class.contains("Video") {
+                Some(MediaType::Video)
+            } else if class.contains("Midi") {
+                Some(MediaType::Midi)
+            } else {
+                None
+            }
+        })
+        .flatten();
+
+    sender
+        .send(PipewireMessage::NodeAdded {
+            id: node.id,
+            name,
+            media_type,
+        })
+        .expect("Failed to send message");
 }

-    /// Set or unset a callback that gets called when a new global is added.
-    pub fn on_global_add(&mut self, callback: Option<Box<dyn Fn(&GlobalObject<ForeignDict>)>>) {
-        self.on_global_add = callback;
+/// Handle a new port being added
+fn handle_port(port: &GlobalObject<ForeignDict>, sender: &glib::Sender<PipewireMessage>) {
+    let props = port
+        .props
+        .as_ref()
+        .expect("Port object is missing properties");
+    let name = props.get("port.name").unwrap_or_default().to_string();
+    let node_id: u32 = props
+        .get("node.id")
+        .expect("Port has no node.id property!")
+        .parse()
+        .expect("Could not parse node.id property");
+    let direction = if matches!(props.get("port.direction"), Some("in")) {
+        Direction::Input
+    } else {
+        Direction::Output
+    };
+
+    sender
+        .send(PipewireMessage::PortAdded {
+            id: port.id,
+            node_id,
+            name,
+            direction,
+        })
+        .expect("Failed to send message");
 }

-    /// Set or unset a callback that gets called when a global is removed.
-    pub fn on_global_remove(&mut self, callback: Option<Box<dyn Fn(u32)>>) {
-        self.on_global_remove = callback;
-    }
+/// Handle a new link being added
+fn handle_link(link: &GlobalObject<ForeignDict>, sender: &glib::Sender<PipewireMessage>) {
+    let props = link
+        .props
+        .as_ref()
+        .expect("Link object is missing properties");
+    let node_from: u32 = props
+        .get("link.output.node")
+        .expect("Link has no link.input.node property")
+        .parse()
+        .expect("Could not parse link.input.node property");
+    let port_from: u32 = props
+        .get("link.output.port")
+        .expect("Link has no link.output.port property")
+        .parse()
+        .expect("Could not parse link.output.port property");
+    let node_to: u32 = props
+        .get("link.input.node")
+        .expect("Link has no link.input.node property")
+        .parse()
+        .expect("Could not parse link.input.node property");
+    let port_to: u32 = props
+        .get("link.input.port")
+        .expect("Link has no link.input.port property")
+        .parse()
+        .expect("Could not parse link.input.port property");
+
+    sender
+        .send(PipewireMessage::LinkAdded {
+            id: link.id,
+            link: crate::PipewireLink {
+                node_from,
+                port_from,
+                node_to,
+                port_to,
+            },
+        })
+        .expect("Failed to send message");
 }
--- a/src/view/mod.rs
+++ b/src/view/mod.rs
@@ -13,7 +13,7 @@ use gtk::{
    glib::{self, clone},
    prelude::*,
 };
-use pipewire::port::Direction;
+use pipewire::spa::Direction;

 use crate::controller::MediaType;

--- a/src/view/node.rs
+++ b/src/view/node.rs
@@ -1,7 +1,7 @@
 use super::graph_view::GraphView;

 use gtk::{glib, prelude::*, subclass::prelude::*, WidgetExt};
-use pipewire::port::Direction;
+use pipewire::spa::Direction;

 use std::{collections::HashMap, rc::Rc};

--- a/src/view/port.rs
+++ b/src/view/port.rs
@@ -1,9 +1,11 @@
 use gtk::{glib, prelude::*, subclass::prelude::*};
+use pipewire::spa::Direction;

 use crate::controller::MediaType;

 mod imp {
    use once_cell::unsync::OnceCell;
+    use pipewire::spa::Direction;

    use super::*;

@@ -11,7 +13,7 @@ mod imp {
    #[derive(Default)]
    pub struct Port {
        pub(super) id: OnceCell<u32>,
-        pub(super) direction: OnceCell<pipewire::port::Direction>,
+        pub(super) direction: OnceCell<Direction>,
    }

    #[glib::object_subclass]
@@ -32,12 +34,7 @@ glib::wrapper! {
 }

 impl Port {
-    pub fn new(
-        id: u32,
-        name: &str,
-        direction: pipewire::port::Direction,
-        media_type: Option<MediaType>,
-    ) -> Self {
+    pub fn new(id: u32, name: &str, direction: Direction, media_type: Option<MediaType>) -> Self {
        // Create the widget and initialize needed fields
        let res: Self = glib::Object::new(&[]).expect("Failed to create Port");
        let private = imp::Port::from_instance(&res);
@@ -60,7 +57,7 @@ impl Port {
        res
    }

-    pub fn direction(&self) -> &pipewire::port::Direction {
+    pub fn direction(&self) -> &Direction {
        let private = imp::Port::from_instance(self);
        private.direction.get().expect("Port direction is not set")
    }