Release v0.2.1

While the properties for a links node ids are not always set, they always are in the link info.

Also, the work done in this commit will easily allow to get the format of links and ports later,
so that we can get the format of them much more reliably,
and we can also get notified of changes to an existing global via the info callback.

.gitlab-ci.yml

@@ -0,0 +1,75 @@
+include:
+  - project: 'freedesktop/ci-templates'             # the project to include from
+    ref: '98f557799157ebb0395cf11d40f01f61fbbace20' # git ref of that project
+    file: '/templates/fedora.yml'                   # the actual file to include
+
+stages:
+  - prepare
+  - lint
+  - test
+  - extras
+
+variables:
+  FDO_UPSTREAM_REPO: 'ryuukyu/helvum'
+
+# Version and tag for our current container
+.fedora:
+  variables:
+    FDO_DISTRIBUTION_VERSION: '34'
+    # Update this to trigger a container rebuild
+    FDO_DISTRIBUTION_TAG: '2021-05-06.0'
+
+build-fedora-container:
+  extends:
+  - .fedora                            # our template job above
+  - .fdo.container-build@fedora@x86_64 # the CI template
+  stage: prepare
+  variables:
+    # clang-devel: required by rust bindgen
+    FDO_DISTRIBUTION_PACKAGES: >-
+      rust
+      cargo
+      rustfmt
+      clippy
+      pipewire-devel
+      gtk4-devel
+      clang-devel
+
+rustfmt:
+  extends:
+    - .fedora
+    - .fdo.distribution-image@fedora
+  stage: lint
+  script:
+    - cargo fmt --version
+    - cargo fmt -- --color=always --check
+
+test-stable:
+  extends:
+    - .fedora
+    - .fdo.distribution-image@fedora
+  stage: test
+  script:
+    - rustc --version
+    - cargo build --color=always --all-targets
+    - cargo test --color=always
+
+rustdoc:
+  extends:
+    - .fedora
+    - .fdo.distribution-image@fedora
+  stage: extras
+  variables:
+    RUSTDOCFLAGS: '-Dwarnings'
+  script:
+    - rustdoc --version
+    - cargo doc --no-deps
+
+clippy:
+  extends:
+    - .fedora
+    - .fdo.distribution-image@fedora
+  stage: extras
+  script:
+    - cargo clippy --version
+    - cargo clippy --color=always --all-targets -- -D warnings

Cargo.toml

@@ -1,14 +1,22 @@
 [package]
-name = "graphui"
+name = "helvum"
-version = "0.1.0"
+version = "0.2.1"
 authors = ["Tom A. Wagner <tom.a.wagner@protonmail.com>"]
 edition = "2018"
+license = "GPL-3.0-only"
+description = "A GTK patchbay for pipewire"
+repository = "https://gitlab.freedesktop.org/ryuukyu/helvum"
+readme = "README.md"
+keywords = ["pipewire", "gtk", "patchbay", "gui", "utility"]
+categories = ["gui", "multimedia"]
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-pipewire = { git = "https://gitlab.freedesktop.org/gdesmott/pipewire-rs", branch = "proxies"}
 gtk = { git = "https://github.com/gtk-rs/gtk4-rs/", package = "gtk4" }
+pipewire = { git = "https://gitlab.freedesktop.org/pipewire/pipewire-rs", branch = "main" }
 
 log = "0.4.11"
 env_logger = "0.8.2"
+
+once_cell = "1.7.2"

LICENSE

@@ -631,7 +631,7 @@ to attach them to the start of each source file to most effectively
 state the exclusion of warranty; and each file should have at least
 the "copyright" line and a pointer to where the full notice is found.
 
-    Pipewire Graphui
+    Helvum
     Copyright (C) 2020  Ryuukyu
 
     This program is free software: you can redistribute it and/or modify
@@ -652,7 +652,7 @@ Also add information on how to contact you by electronic and paper mail.
   If the program does terminal interaction, make it output a short
 notice like this when it starts in an interactive mode:
 
-    Pipewire Graphui  Copyright (C) 2020  Ryuukyu
+    Helvum  Copyright (C) 2020  Ryuukyu
     This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
     This is free software, and you are welcome to redistribute it
     under certain conditions; type `show c' for details.

README.md

@@ -1,23 +1,30 @@
-A graphical interface for viewing the current pipewire graph (name pending, suggestions welcome), inspired by the JACK tool [catia](https://kx.studio/Applications:Catia).
+Helvum is a GTK-based patchbay for pipewire, inspired by the JACK tool [catia](https://kx.studio/Applications:Catia).
 
 ![Screenshot](screenshot.png)
 
 # Features planned
 
-- Allow creation of links from one port to another.
+- Volume control
-- Color ports and links based on whether they carry audio, video or midi data.
+- "Debug mode" that lets you view advanced information for nodes and ports
 
 More suggestions are welcome!
 
+# Distribution packages
+
+- ArchLinux:
+  - [aur/helvum](https://aur.archlinux.org/packages/helvum)
+  - [aur/helvum-git](https://aur.archlinux.org/packages/helvum-git)
+
 # Building
 For compilation, you will need:
 
 - An up-to-date rust toolchain
-- gtk-4.0 and pipewire-0.3 development headers
+- `libclang-3.7` or higher
+- `gtk-4.0` and `pipewire-0.3` development headers
 
 To compile, run
 
     $ cargo build --release
 
 in the repository root.
-The resulting binary will be at `target/release/graphui`.
+The resulting binary will be at `target/release/helvum`.

docs/architecture.md

@@ -0,0 +1,51 @@
+# Architecture
+If you want to understand the high-level architecture of helvum,
+this document is the right place.
+
+It provides a birds-eye view of the general architecture, and also goes into details on some
+components like the view.
+
+# Top Level Architecture
+Helvum uses an architecture with the components laid out like this:
+
+```
+┌──────┐
+│ GTK  │
+│ View │
+└────┬─┘
+ Λ   ┆
+ │<───── updates view                               ┌───────┐
+ │   ┆                                              │ State │
+ │   ┆<─ notifies of user input                     └───────┘
+ │   ┆      (using signals)                             Λ
+ │   ┆                                                  │
+ │   ┆                                                  │<─── updates/reads state
+ │   V           notifies of remote changes             │
+┌┴────────────┐         via messages          ┌─────────┴─────────┐
+│ Application │<╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤     Seperate      │
+│   Object    ├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌>│  Pipewire Thread  │
+└─────────────┘   request changes to remote   └───────────────────┘
+                        via messages                    Λ
+                                                        ║
+                                                        ║
+                                                        V
+                                            [ Remote Pipewire Server ]
+```
+The program is split between two cooperating threads.
+The GTK thread (displayed on the left side) will sit in a GTK event processing loop, while the pipewire thread (displayed on the right side) will sit in a pipewire event processing loop.
+
+The `Application` object inside the GTK thread 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 on the remote pipewire server, the pipewire thread updates the state and notifies
+the `Application` in the GTK thread if changes are needed.
+The `Application` then updates the view to reflect those changes.
+
+Additionally, a user may also make changes using the view.
+For each change, the view notifies the `Application` by emitting a matching signal.
+The `Application` will then ask the pipewire thread to make those changes on the remote. \
+These changes will then be applied to the view like any other remote changes as explained above.
+
+# View Architecture
+TODO

src/application.rs

@@ -0,0 +1,221 @@
+use std::cell::RefCell;
+
+use gtk::{
+    gio,
+    glib::{self, clone, Continue, Receiver},
+    prelude::*,
+    subclass::prelude::*,
+};
+use log::{info, warn};
+use pipewire::{channel::Sender, spa::Direction};
+
+use crate::{
+    view::{self},
+    GtkMessage, MediaType, PipewireLink, PipewireMessage,
+};
+
+static STYLE: &str = include_str!("style.css");
+
+mod imp {
+    use super::*;
+
+    use once_cell::unsync::OnceCell;
+
+    #[derive(Default)]
+    pub struct Application {
+        pub(super) graphview: view::GraphView,
+        pub(super) pw_sender: OnceCell<RefCell<Sender<GtkMessage>>>,
+    }
+
+    #[glib::object_subclass]
+    impl ObjectSubclass for Application {
+        const NAME: &'static str = "HelvumApplication";
+        type Type = super::Application;
+        type ParentType = gtk::Application;
+    }
+
+    impl ObjectImpl for Application {}
+    impl ApplicationImpl for Application {
+        fn activate(&self, app: &Self::Type) {
+            let scrollwindow = gtk::ScrolledWindowBuilder::new()
+                .child(&self.graphview)
+                .build();
+            let window = gtk::ApplicationWindowBuilder::new()
+                .application(app)
+                .default_width(1280)
+                .default_height(720)
+                .title("Helvum - Pipewire Patchbay")
+                .child(&scrollwindow)
+                .build();
+            window
+                .settings()
+                .set_gtk_application_prefer_dark_theme(true);
+            window.show();
+        }
+
+        fn startup(&self, app: &Self::Type) {
+            self.parent_startup(app);
+
+            // Load CSS from the STYLE variable.
+            let provider = gtk::CssProvider::new();
+            provider.load_from_data(STYLE.as_bytes());
+            gtk::StyleContext::add_provider_for_display(
+                &gtk::gdk::Display::default().expect("Error initializing gtk css provider."),
+                &provider,
+                gtk::STYLE_PROVIDER_PRIORITY_APPLICATION,
+            );
+        }
+    }
+    impl GtkApplicationImpl for Application {}
+}
+
+glib::wrapper! {
+    pub struct Application(ObjectSubclass<imp::Application>)
+        @extends gio::Application, gtk::Application,
+        @implements gio::ActionGroup, gio::ActionMap;
+}
+
+impl Application {
+    /// Create the view.
+    /// This will set up the entire user interface and prepare it for being run.
+    pub(super) fn new(
+        gtk_receiver: Receiver<PipewireMessage>,
+        pw_sender: Sender<GtkMessage>,
+    ) -> Self {
+        let app: Application =
+            glib::Object::new(&[("application-id", &"org.freedesktop.ryuukyu.helvum")])
+                .expect("Failed to create new Application");
+
+        let imp = imp::Application::from_instance(&app);
+        imp.pw_sender
+            .set(RefCell::new(pw_sender))
+            // Discard the returned sender, as it does not implement `Debug`.
+            .map_err(|_| ())
+            .expect("pw_sender field was already set");
+
+        // Add <Control-Q> shortcut for quitting the application.
+        let quit = gtk::gio::SimpleAction::new("quit", None);
+        quit.connect_activate(clone!(@weak app => move |_, _| {
+            app.quit();
+        }));
+        app.set_accels_for_action("app.quit", &["<Control>Q"]);
+        app.add_action(&quit);
+
+        // React to messages received from the pipewire thread.
+        gtk_receiver.attach(
+            None,
+            clone!(
+                @weak app => @default-return Continue(true),
+                move |msg| {
+                    match msg {
+                        PipewireMessage::NodeAdded{ id, name } => app.add_node(id,name),
+                        PipewireMessage::PortAdded{ id, node_id, name, direction, media_type} => app.add_port(id,name,node_id,direction,media_type),
+                        PipewireMessage::LinkAdded{ id, node_from, port_from, node_to, port_to} => app.add_link(id,node_from,port_from,node_to,port_to),
+                        PipewireMessage::NodeRemoved { id } => app.remove_node(id),
+                        PipewireMessage::PortRemoved { id, node_id } => app.remove_port(id, node_id),
+                        PipewireMessage::LinkRemoved { id } => app.remove_link(id)
+                    };
+                    Continue(true)
+                }
+            ),
+        );
+
+        app
+    }
+
+    /// Add a new node to the view.
+    pub fn add_node(&self, id: u32, name: String) {
+        info!("Adding node to graph: id {}", id);
+
+        imp::Application::from_instance(self)
+            .graphview
+            .add_node(id, view::Node::new(name.as_str()));
+    }
+
+    /// Add a new port to the view.
+    pub fn add_port(
+        &self,
+        id: u32,
+        name: String,
+        node_id: u32,
+        direction: Direction,
+        media_type: Option<MediaType>,
+    ) {
+        info!("Adding port to graph: id {}", id);
+
+        let imp = imp::Application::from_instance(self);
+
+        let port = view::Port::new(id, name.as_str(), direction, media_type);
+
+        // Create or delete a link if the widget emits the "port-toggled" signal.
+        if let Err(e) = port.connect_local(
+            "port_toggled",
+            false,
+            clone!(@weak self as app => @default-return None, move |args| {
+                // Args always look like this: &[widget, id_port_from, id_port_to]
+                let port_from = args[1].get::<u32>().unwrap();
+                let port_to = args[2].get::<u32>().unwrap();
+
+                app.toggle_link(port_from, port_to);
+
+                None
+            }),
+        ) {
+            warn!("Failed to connect to \"port-toggled\" signal: {}", e);
+        }
+
+        imp.graphview.add_port(node_id, id, port);
+    }
+
+    /// Add a new link to the view.
+    pub fn add_link(&self, id: u32, node_from: u32, port_from: u32, node_to: u32, port_to: u32) {
+        info!("Adding link to graph: id {}", id);
+
+        // FIXME: Links should be colored depending on the data they carry (video, audio, midi) like ports are.
+
+        // Update graph to contain the new link.
+        imp::Application::from_instance(self).graphview.add_link(
+            id,
+            PipewireLink {
+                node_from,
+                port_from,
+                node_to,
+                port_to,
+            },
+        );
+    }
+
+    // Toggle a link between the two specified ports on the remote pipewire server.
+    fn toggle_link(&self, port_from: u32, port_to: u32) {
+        let imp = imp::Application::from_instance(self);
+        let sender = imp.pw_sender.get().expect("pw_sender not set").borrow_mut();
+        sender
+            .send(GtkMessage::ToggleLink { port_from, port_to })
+            .expect("Failed to send message");
+    }
+
+    /// Remove the node with the specified id from the view.
+    fn remove_node(&self, id: u32) {
+        info!("Removing node from graph: id {}", id);
+
+        let imp = imp::Application::from_instance(self);
+        imp.graphview.remove_node(id);
+    }
+
+    /// Remove the port with the id `id` from the node with the id `node_id`
+    /// from the view.
+    fn remove_port(&self, id: u32, node_id: u32) {
+        info!("Removing port from graph: id {}, node_id: {}", id, node_id);
+
+        let imp = imp::Application::from_instance(self);
+        imp.graphview.remove_port(id, node_id);
+    }
+
+    /// Remove the link with the specified id from the view.
+    fn remove_link(&self, id: u32) {
+        info!("Removing link from graph: id {}", id);
+
+        let imp = imp::Application::from_instance(self);
+        imp.graphview.remove_link(id);
+    }
+}

src/main.rs

@@ -1,12 +1,63 @@
+mod application;
 mod pipewire_connection;
-mod pipewire_state;
 mod view;
 
-use gtk::prelude::*;
+use gtk::{
+    glib::{self, PRIORITY_DEFAULT},
+    prelude::*,
+};
+use pipewire::spa::Direction;
 
-use std::{cell::RefCell, rc::Rc};
+/// Messages sent by the GTK thread to notify the pipewire thread.
+#[derive(Debug, Clone)]
+enum GtkMessage {
+    /// Toggle a link between the two specified ports.
+    ToggleLink { port_from: u32, port_to: u32 },
+    /// Quit the event loop and let the thread finish.
+    Terminate,
+}
 
-#[derive(Debug)]
+/// Messages sent by the pipewire thread to notify the GTK thread.
+#[derive(Debug, Clone)]
+enum PipewireMessage {
+    NodeAdded {
+        id: u32,
+        name: String,
+    },
+    PortAdded {
+        id: u32,
+        node_id: u32,
+        name: String,
+        direction: Direction,
+        media_type: Option<MediaType>,
+    },
+    LinkAdded {
+        id: u32,
+        node_from: u32,
+        port_from: u32,
+        node_to: u32,
+        port_to: u32,
+    },
+    NodeRemoved {
+        id: u32,
+    },
+    PortRemoved {
+        id: u32,
+        node_id: u32,
+    },
+    LinkRemoved {
+        id: u32,
+    },
+}
+
+#[derive(Debug, Copy, Clone)]
+pub enum MediaType {
+    Audio,
+    Video,
+    Midi,
+}
+
+#[derive(Debug, Clone)]
 pub struct PipewireLink {
     pub node_from: u32,
     pub port_from: u32,
@@ -18,42 +69,25 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     env_logger::init();
     gtk::init()?;
 
-    let graphview = Rc::new(RefCell::new(view::GraphView::new()));
+    // Aquire main context so that we can attach the gtk channel later.
+    let ctx = glib::MainContext::default();
+    let _guard = ctx.acquire().unwrap();
 
-    // Create the connection to the pipewire server and do an initial roundtrip before showing the view,
+    // Start the pipewire thread with channels in both directions.
-    // so that the graph is already populated when the window opens.
+    let (gtk_sender, gtk_receiver) = glib::MainContext::channel(PRIORITY_DEFAULT);
-    let pw_con = pipewire_connection::PipewireConnection::new(pipewire_state::PipewireState::new(
+    let (pw_sender, pw_receiver) = pipewire::channel::channel();
-        graphview.clone(),
+    let pw_thread =
-    ))
+        std::thread::spawn(move || pipewire_connection::thread_main(gtk_sender, pw_receiver));
-    .expect("Failed to initialize pipewire connection");
-    pw_con.roundtrip();
-    // From now on, call roundtrip() every second.
-    gtk::glib::timeout_add_seconds_local(1, move || {
-        pw_con.roundtrip();
-        Continue(true)
-    });
 
-    let app = gtk::Application::new(Some("org.freedesktop.pipewire.graphui"), Default::default())
+    let app = application::Application::new(gtk_receiver, pw_sender.clone());
-        .expect("Application creation failed");
 
-    app.connect_activate(move |app| {
+    app.run();
-        let scrollwindow = gtk::ScrolledWindowBuilder::new()
-            .child(&*graphview.borrow())
-            .build();
-        let window = gtk::ApplicationWindowBuilder::new()
-            .application(app)
-            .default_width(1280)
-            .default_height(720)
-            .title("Pipewire Graph Editor")
-            .child(&scrollwindow)
-            .build();
-        window
-            .get_settings()
-            .set_property_gtk_application_prefer_dark_theme(true);
-        window.show();
-    });
 
-    app.run(&std::env::args().collect::<Vec<_>>());
+    pw_sender
+        .send(GtkMessage::Terminate)
+        .expect("Failed to send message");
+
+    pw_thread.join().expect("Pipewire thread panicked");
 
     Ok(())
 }

src/pipewire_connection.rs

@@ -1,84 +1,273 @@
-use crate::pipewire_state::PipewireState;
+mod state;
+
+use std::{cell::RefCell, collections::HashMap, rc::Rc};
 
 use gtk::glib::{self, clone};
-use pipewire as pw;
+use log::{debug, info, warn};
-
+use pipewire::{
-use std::{
+    link::{Link, LinkListener},
-    cell::{Cell, RefCell},
+    prelude::*,
-    rc::Rc,
+    properties,
+    registry::{GlobalObject, Registry},
+    spa::{Direction, ForeignDict},
+    types::ObjectType,
+    Context, Core, MainLoop,
 };
 
-/// This struct is responsible for communication with the pipewire server.
+use crate::{GtkMessage, MediaType, PipewireMessage};
-/// It handles new globals appearing as well as globals being removed.
+use state::{Item, State};
-///
+
-/// It's `roundtrip` function must be called regularly to receive updates.
+enum ProxyItem {
-pub struct PipewireConnection {
+    Link {
-    mainloop: pw::MainLoop,
+        _proxy: Link,
-    _context: pw::Context<pw::MainLoop>,
+        _listener: LinkListener,
-    core: Rc<pw::Core>,
+    },
-    _registry: pw::registry::Registry,
-    _listeners: pw::registry::Listener,
-    _state: Rc<RefCell<PipewireState>>,
 }
 
-impl PipewireConnection {
+/// The "main" function of the pipewire thread.
-    pub fn new(state: PipewireState) -> Result<Self, String> {
+pub(super) fn thread_main(
-        // Initialize pipewire lib and obtain needed pipewire objects.
+    gtk_sender: glib::Sender<PipewireMessage>,
-        pw::init();
+    pw_receiver: pipewire::channel::Receiver<GtkMessage>,
-        let mainloop = pw::MainLoop::new().map_err(|_| "Failed to create pipewire mainloop!")?;
+) {
-        let context =
+    let mainloop = MainLoop::new().expect("Failed to create mainloop");
-            pw::Context::new(&mainloop).map_err(|_| "Failed to create pipewire context")?;
+    let context = Context::new(&mainloop).expect("Failed to create context");
-        let core = Rc::new(
+    let core = Rc::new(context.connect(None).expect("Failed to connect to remote"));
-            context
+    let registry = Rc::new(core.get_registry().expect("Failed to get registry"));
-                .connect()
-                .map_err(|_| "Failed to connect to pipewire core")?,
-        );
-        let registry = core.get_registry();
 
-        let state = Rc::new(RefCell::new(state));
+    // Keep proxies and their listeners alive so that we can receive info events.
+    let proxies = Rc::new(RefCell::new(HashMap::new()));
 
-        // Notify state on globals added / removed
+    let state = Rc::new(RefCell::new(State::new()));
-        let _listeners = registry
-            .add_listener_local()
-            .global(clone!(@weak state => @default-panic, move |global| {
-                state.borrow_mut().global(global);
-            }))
-            .global_remove(clone!(@weak state => @default-panic, move |id| {
-                state.borrow_mut().global_remove(id);
-            }))
-            .register();
 
-        Ok(Self {
+    let _receiver = pw_receiver.attach(&mainloop, {
-            mainloop: mainloop,
+        clone!(@strong mainloop, @weak core, @weak registry, @strong state => move |msg| match msg {
-            _context: context,
+            GtkMessage::ToggleLink { port_from, port_to } => toggle_link(port_from, port_to, &core, &registry, &state),
-            core,
+            GtkMessage::Terminate => mainloop.quit(),
-            _registry: registry,
-            _listeners,
-            _state: state,
         })
-    }
+    });
 
-    /// Receive all events from the pipewire server, sending them to the `pipewire_state` struct for processing.
+    let _listener = registry
-    pub fn roundtrip(&self) {
+        .add_listener_local()
-        let done = Rc::new(Cell::new(false));
+        .global(clone!(@strong gtk_sender, @weak registry, @strong proxies, @strong state =>
-        let pending = self.core.sync(0);
+            move |global| match global.type_ {
-
+                ObjectType::Node => handle_node(global, &gtk_sender, &state),
-        let done_clone = done.clone();
+                ObjectType::Port => handle_port(global, &gtk_sender, &state),
-        let loop_clone = self.mainloop.clone();
+                ObjectType::Link => handle_link(global, &gtk_sender, &registry, &proxies, &state),
-
+                _ => {
-        let _listener = self
+                    // Other objects are not interesting to us
-            .core
-            .add_listener_local()
-            .done(move |id, seq| {
-                if id == pw::PW_ID_CORE && seq == pending {
-                    done_clone.set(true);
-                    loop_clone.quit();
                 }
-            })
+            }
-            .register();
+        ))
+        .global_remove(clone!(@strong proxies, @strong state => move |id| {
+            if let Some(item) = state.borrow_mut().remove(id) {
+                gtk_sender.send(match item {
+                    Item::Node { .. } => PipewireMessage::NodeRemoved {id},
+                    Item::Port { node_id } => PipewireMessage::PortRemoved {id, node_id},
+                    Item::Link { .. } => PipewireMessage::LinkRemoved {id},
+                }).expect("Failed to send message");
+            } else {
+                warn!(
+                    "Attempted to remove item with id {} that is not saved in state",
+                    id
+                );
+            }
 
-        while !done.get() {
+            proxies.borrow_mut().remove(&id);
-            self.mainloop.run();
+        }))
+        .register();
+
+    mainloop.run();
+}
+
+/// Handle a new node being added
+fn handle_node(
+    node: &GlobalObject<ForeignDict>,
+    sender: &glib::Sender<PipewireMessage>,
+    state: &Rc<RefCell<State>>,
+) {
+    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: Instead of checking these props, the "EnumFormat" parameter should be checked instead.
+    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();
+
+    state.borrow_mut().insert(
+        node.id,
+        Item::Node {
+            // widget: node_widget,
+            media_type,
+        },
+    );
+
+    sender
+        .send(PipewireMessage::NodeAdded { id: node.id, name })
+        .expect("Failed to send message");
+}
+
+/// Handle a new port being added
+fn handle_port(
+    port: &GlobalObject<ForeignDict>,
+    sender: &glib::Sender<PipewireMessage>,
+    state: &Rc<RefCell<State>>,
+) {
+    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
+    };
+
+    // Find out the nodes media type so that the port can be colored.
+    let media_type = if let Some(Item::Node { media_type, .. }) = state.borrow().get(node_id) {
+        media_type.to_owned()
+    } else {
+        warn!("Node not found for Port {}", port.id);
+        None
+    };
+
+    // Save node_id so we can delete this port easily.
+    state.borrow_mut().insert(port.id, Item::Port { node_id });
+
+    sender
+        .send(PipewireMessage::PortAdded {
+            id: port.id,
+            node_id,
+            name,
+            direction,
+            media_type,
+        })
+        .expect("Failed to send message");
+}
+
+/// Handle a new link being added
+fn handle_link(
+    link: &GlobalObject<ForeignDict>,
+    sender: &glib::Sender<PipewireMessage>,
+    registry: &Rc<Registry>,
+    proxies: &Rc<RefCell<HashMap<u32, ProxyItem>>>,
+    state: &Rc<RefCell<State>>,
+) {
+    debug!(
+        "New link (id:{}) appeared, setting up info listener.",
+        link.id
+    );
+
+    let proxy: Link = registry.bind(link).expect("Failed to bind to link proxy");
+    let listener = proxy
+        .add_listener_local()
+        .info(clone!(@strong state, @strong sender => move |info| {
+            debug!("Received link info: {:?}", info);
+
+            let id = info.id();
+
+            let mut state = state.borrow_mut();
+            if let Some(Item::Link { .. }) = state.get(id) {
+                // Info was an update - figure out if we should notify the gtk thread
+                // TODO
+            } else {
+                // First time we get info. We can now notify the gtk thread of a new link.
+                let node_from = info.output_node_id();
+                let port_from = info.output_port_id();
+                let node_to = info.input_node_id();
+                let port_to = info.input_port_id();
+
+                state.insert(id, Item::Link {
+                    port_from, port_to
+                });
+
+                sender.send(PipewireMessage::LinkAdded {
+                    id,
+                    node_from,
+                    port_from,
+                    node_to,
+                    port_to
+                }).expect(
+                    "Failed to send message"
+                );
+            }
+        }))
+        .register();
+
+    proxies.borrow_mut().insert(
+        link.id,
+        ProxyItem::Link {
+            _proxy: proxy,
+            _listener: listener,
+        },
+    );
+}
+
+/// Toggle a link between the two specified ports.
+fn toggle_link(
+    port_from: u32,
+    port_to: u32,
+    core: &Rc<Core>,
+    registry: &Rc<Registry>,
+    state: &Rc<RefCell<State>>,
+) {
+    let state = state.borrow_mut();
+    if let Some(id) = state.get_link_id(port_from, port_to) {
+        info!("Requesting removal of link with id {}", id);
+
+        // FIXME: Handle error
+        registry.destroy_global(id);
+    } else {
+        info!(
+            "Requesting creation of link from port id:{} to port id:{}",
+            port_from, port_to
+        );
+
+        let node_from = state
+            .get_node_of_port(port_from)
+            .expect("Requested port not in state");
+        let node_to = state
+            .get_node_of_port(port_to)
+            .expect("Requested port not in state");
+
+        if let Err(e) = core.create_object::<Link, _>(
+            "link-factory",
+            &properties! {
+                "link.output.node" => node_from.to_string(),
+                "link.output.port" => port_from.to_string(),
+                "link.input.node" => node_to.to_string(),
+                "link.input.port" => port_to.to_string(),
+                "object.linger" => "1"
+            },
+        ) {
+            warn!("Failed to create link: {}", e);
         }
     }
 }

src/pipewire_connection/state.rs

@@ -0,0 +1,81 @@
+use std::collections::HashMap;
+
+use crate::MediaType;
+
+/// Any pipewire item we need to keep track of.
+/// These will be saved in the `State` struct associated with their id.
+pub(super) enum Item {
+    Node {
+        // Keep track of the nodes media type to color ports on it.
+        media_type: Option<MediaType>,
+    },
+    Port {
+        // Save the id of the node this is on so we can remove the port from it
+        // when it is deleted.
+        node_id: u32,
+    },
+    Link {
+        port_from: u32,
+        port_to: u32,
+    },
+}
+
+/// This struct keeps track of any relevant items and stores them under their IDs.
+///
+/// Given two port ids, it can also efficiently find the id of the link that connects them.
+#[derive(Default)]
+pub(super) struct State {
+    /// Map pipewire ids to items.
+    items: HashMap<u32, Item>,
+    /// Map `(output port id, input port id)` tuples to the id of the link that connects them.
+    links: HashMap<(u32, u32), u32>,
+}
+
+impl State {
+    /// Create a new, empty state.
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    /// Add a new item under the specified id.
+    pub fn insert(&mut self, id: u32, item: Item) {
+        if let Item::Link {
+            port_from, port_to, ..
+        } = item
+        {
+            self.links.insert((port_from, port_to), id);
+        }
+
+        self.items.insert(id, item);
+    }
+
+    /// Get the item that has the specified id.
+    pub fn get(&self, id: u32) -> Option<&Item> {
+        self.items.get(&id)
+    }
+
+    /// Get the id of the link that links the two specified ports.
+    pub fn get_link_id(&self, output_port: u32, input_port: u32) -> Option<u32> {
+        self.links.get(&(output_port, input_port)).copied()
+    }
+
+    /// Remove the item with the specified id, returning it if it exists.
+    pub fn remove(&mut self, id: u32) -> Option<Item> {
+        let removed = self.items.remove(&id);
+
+        if let Some(Item::Link { port_from, port_to }) = removed {
+            self.links.remove(&(port_from, port_to));
+        }
+
+        removed
+    }
+
+    /// Convenience function: Get the id of the node a port is on
+    pub fn get_node_of_port(&self, port: u32) -> Option<u32> {
+        if let Some(Item::Port { node_id }) = self.get(port) {
+            Some(*node_id)
+        } else {
+            None
+        }
+    }
+}

src/pipewire_state.rs

@@ -1,168 +0,0 @@
-use crate::{view, PipewireLink};
-
-use pipewire::{
-    port::Direction,
-    registry::{GlobalObject, ObjectType},
-};
-
-use std::{cell::RefCell, collections::HashMap, rc::Rc};
-
-enum Item {
-    Node(view::Node),
-    Port { node_id: u32 },
-    Link,
-}
-
-/// This struct stores the state of the pipewire graph.
-///
-/// It receives updates from the [`PipewireConnection`](crate::pipewire_connection::PipewireConnection)
-/// responsible for updating it and applies them to its internal state.
-///
-/// It also keeps the view updated to always reflect this internal state.
-pub struct PipewireState {
-    graphview: Rc<RefCell<view::GraphView>>,
-    items: HashMap<u32, Item>,
-}
-
-impl PipewireState {
-    pub fn new(graphview: Rc<RefCell<view::GraphView>>) -> Self {
-        let result = Self {
-            graphview,
-            items: HashMap::new(),
-        };
-
-        result
-    }
-
-    /// This function is called from the `PipewireConnection` struct responsible for updating this struct.
-    pub fn global(&mut self, global: GlobalObject) {
-        match global.type_ {
-            ObjectType::Node => {
-                self.add_node(global);
-            }
-            ObjectType::Port => {
-                self.add_port(global);
-            }
-            ObjectType::Link => {
-                self.add_link(global);
-            }
-            _ => {}
-        }
-    }
-
-    fn add_node(&mut self, node: GlobalObject) {
-        // Update graph to contain the new node.
-        let node_widget = crate::view::Node::new(&format!(
-            "{}",
-            node.props
-                .map(|dict| String::from(
-                    dict.get("node.nick")
-                        .or(dict.get("node.description"))
-                        .or(dict.get("node.name"))
-                        .unwrap_or_default()
-                ))
-                .unwrap_or_default()
-        ));
-        self.graphview
-            .borrow_mut()
-            .add_node(node.id, node_widget.clone());
-
-        // Save the created widget so we can delete ports easier.
-        self.items.insert(node.id, Item::Node(node_widget));
-    }
-
-    fn add_port(&mut self, port: GlobalObject) {
-        // Update graph to contain the new port.
-        let props = port.props.expect("Port object is missing properties");
-        let port_label = format!("{}", props.get("port.name").unwrap_or_default());
-        let node_id: u32 = props
-            .get("node.id")
-            .expect("Port has no node.id property!")
-            .parse()
-            .expect("Could not parse node.id property");
-        let new_port = crate::view::port::Port::new(
-            port.id,
-            &port_label,
-            if matches!(props.get("port.direction"), Some("in")) {
-                Direction::Input
-            } else {
-                Direction::Output
-            },
-        );
-
-        self.graphview
-            .borrow_mut()
-            .add_port_to_node(node_id, new_port.id, new_port);
-
-        // Save node_id so we can delete this port easily.
-        self.items.insert(port.id, Item::Port { node_id });
-    }
-
-    fn add_link(&mut self, link: GlobalObject) {
-        self.items.insert(link.id, Item::Link);
-
-        // Update graph to contain the new link.
-        let props = link.props.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.graphview.borrow_mut().add_link(
-            link.id,
-            PipewireLink {
-                node_from: output_node,
-                port_from: output_port,
-                node_to: input_node,
-                port_to: input_port,
-            },
-        );
-    }
-
-    /// This function is called from the `PipewireConnection` struct responsible for updating this struct.
-    pub fn global_remove(&mut self, id: u32) {
-        if let Some(item) = self.items.get(&id) {
-            match item {
-                Item::Node(_) => self.remove_node(id),
-                Item::Port { node_id } => self.remove_port(id, *node_id),
-                Item::Link => self.remove_link(id),
-            }
-
-            self.items.remove(&id);
-        } else {
-            log::warn!(
-                "Attempted to remove item with id {} that is not saved in state",
-                id
-            );
-        }
-    }
-
-    fn remove_node(&self, id: u32) {
-        self.graphview.borrow().remove_node(id);
-    }
-
-    fn remove_port(&self, id: u32, node_id: u32) {
-        if let Some(Item::Node(node)) = self.items.get(&node_id) {
-            node.remove_port(id);
-        }
-    }
-
-    fn remove_link(&self, id: u32) {
-        self.graphview.borrow().remove_link(id);
-    }
-}

src/style.css

@@ -0,0 +1,14 @@
+.audio {
+    background: rgb(50,100,240);
+    color: black;
+}
+
+.video {
+    background: rgb(200,200,0);
+    color: black;
+}
+
+.midi {
+    background: rgb(200,0,50);
+    color: black;
+}

src/view/graph_view.rs

@@ -1,71 +1,84 @@
-use super::Node;
+use super::{Node, Port};
 
-use gtk::{glib, graphene, gsk, prelude::*, subclass::prelude::*, WidgetExt};
+use gtk::{
+    glib::{self, clone},
+    graphene, gsk,
+    prelude::*,
+    subclass::prelude::*,
+};
 
 use std::collections::HashMap;
 
 mod imp {
     use super::*;
 
-    use gtk::{gdk, WidgetExt};
-
     use std::{cell::RefCell, rc::Rc};
 
+    use log::warn;
+
+    #[derive(Default)]
     pub struct GraphView {
         pub(super) nodes: RefCell<HashMap<u32, Node>>,
         pub(super) links: RefCell<HashMap<u32, crate::PipewireLink>>,
-        pub(super) dragged: Rc<RefCell<Option<gtk::Widget>>>,
     }
 
+    #[glib::object_subclass]
     impl ObjectSubclass for GraphView {
         const NAME: &'static str = "GraphView";
         type Type = super::GraphView;
         type ParentType = gtk::Widget;
-        type Instance = glib::subclass::simple::InstanceStruct<Self>;
-        type Class = glib::subclass::simple::ClassStruct<Self>;
-
-        glib::object_subclass!();
 
         fn class_init(klass: &mut Self::Class) {
             // The layout manager determines how child widgets are laid out.
             klass.set_layout_manager_type::<gtk::FixedLayout>();
         }
-
-        fn new() -> Self {
-            Self {
-                nodes: RefCell::new(HashMap::new()),
-                links: RefCell::new(HashMap::new()),
-                dragged: Rc::new(RefCell::new(None)),
-            }
-        }
     }
 
     impl ObjectImpl for GraphView {
         fn constructed(&self, obj: &Self::Type) {
             self.parent_constructed(obj);
 
-            // Move the Node that is currently being dragged to the cursor position as long as Mouse Button 1 is held.
+            let drag_state = Rc::new(RefCell::new(None));
-            let motion_controller = gtk::EventControllerMotion::new();
+            let drag_controller = gtk::GestureDrag::new();
-            motion_controller.connect_motion(|controller, x, y| {
-                let instance = controller
-                    .get_widget()
-                    .unwrap()
-                    .dynamic_cast::<Self::Type>()
-                    .unwrap();
-                let this = imp::GraphView::from_instance(&instance);
 
-                if let Some(ref widget) = *this.dragged.borrow() {
+            drag_controller.connect_drag_begin(
-                    if controller
+                clone!(@strong drag_state => move |drag_controller, x, y| {
-                        .get_current_event()
+                let mut drag_state = drag_state.borrow_mut();
-                        .unwrap()
+                let widget = drag_controller
-                        .get_modifier_state()
+                    .widget()
-                        .contains(gdk::ModifierType::BUTTON1_MASK)
+                    .expect("drag-begin event has no widget")
-                    {
+                    .dynamic_cast::<Self::Type>()
-                        instance.move_node(&widget, x as f32, y as f32);
+                    .expect("drag-begin event is not on the GraphView");
+                // pick() should at least return the widget itself.
+                let target = widget.pick(x, y, gtk::PickFlags::DEFAULT).expect("drag-begin pick() did not return a widget");
+                *drag_state = if target.ancestor(Port::static_type()).is_some() {
+                    // The user targeted a port, so the dragging should be handled by the Port
+                    // component instead of here.
+                    None
+                } else if let Some(target) = target.ancestor(Node::static_type()) {
+                    // The user targeted a Node without targeting a specific Port.
+                    // Drag the Node around the screen.
+                    let (x, y) = widget.get_node_position(&target);
+                    Some((target, x, y))
+                } else {
+                    None
+                }
+            }));
+            drag_controller.connect_drag_update(
+                clone!(@strong drag_state => move |drag_controller, x, y| {
+                    let widget = drag_controller
+                        .widget()
+                        .expect("drag-update event has no widget")
+                        .dynamic_cast::<Self::Type>()
+                        .expect("drag-update event is not on the GraphView");
+                    let drag_state = drag_state.borrow();
+                    if let Some((ref node, x1, y1)) = *drag_state {
+                        widget.move_node(node, x1 + x as f32, y1 + y as f32);
                     }
-                };
+                }
-            });
+                ),
-            obj.add_controller(&motion_controller);
+            );
+            obj.add_controller(&drag_controller);
         }
 
         fn dispose(&self, _obj: &Self::Type) {
@@ -81,7 +94,7 @@ mod imp {
             /* FIXME: A lot of hardcoded values in here.
             Try to use relative units (em) and colours from the theme as much as possible. */
 
-            let alloc = widget.get_allocation();
+            let alloc = widget.allocation();
 
             let cr = snapshot
                 .append_cairo(&graphene::Rect::new(
@@ -93,9 +106,11 @@ mod imp {
                 .expect("Failed to get cairo context");
 
             // Try to replace the background color with a darker one from the theme.
-            if let Some(rgba) = widget.get_style_context().lookup_color("text_view_bg") {
+            if let Some(rgba) = widget.style_context().lookup_color("text_view_bg") {
                 cr.set_source_rgb(rgba.red.into(), rgba.green.into(), rgba.blue.into());
-                cr.paint();
+                if let Err(e) = cr.paint() {
+                    warn!("Failed to paint graphview background: {}", e);
+                };
             } // TODO: else log colour not found
 
             // Draw a nice grid on the background.
@@ -113,7 +128,9 @@ mod imp {
                 cr.line_to(x, alloc.height as f64);
                 x += 20.0; // TODO: Change to em;
             }
-            cr.stroke();
+            if let Err(e) = cr.stroke() {
+                warn!("Failed to draw graphview grid: {}", e);
+            };
 
             // Draw all links
             cr.set_line_width(2.0);
@@ -122,7 +139,9 @@ mod imp {
                 if let Some((from_x, from_y, to_x, to_y)) = self.get_link_coordinates(link) {
                     cr.move_to(from_x, from_y);
                     cr.curve_to(from_x + 75.0, from_y, to_x - 75.0, to_y, to_x, to_y);
-                    cr.stroke();
+                    if let Err(e) = cr.stroke() {
+                        warn!("Failed to draw graphview links: {}", e);
+                    };
                 } else {
                     log::warn!("Could not get allocation of ports of link: {:?}", link);
                 }
@@ -132,7 +151,7 @@ mod imp {
             self.nodes
                 .borrow()
                 .values()
-                .for_each(|node| self.get_instance().snapshot_child(node, snapshot));
+                .for_each(|node| self.instance().snapshot_child(node, snapshot));
         }
     }
 
@@ -147,31 +166,31 @@ mod imp {
             // For some reason, gtk4::WidgetExt::translate_coordinates gives me incorrect values,
             // so we manually calculate the needed offsets here.
 
-            let from_port = &nodes.get(&link.node_from)?.get_port(link.port_from)?.widget;
+            let from_port = &nodes.get(&link.node_from)?.get_port(link.port_from)?;
             let gtk::Allocation {
                 x: mut fx,
                 y: mut fy,
                 width: fw,
                 height: fh,
-            } = from_port.get_allocation();
+            } = from_port.allocation();
             let from_node = from_port
-                .get_ancestor(Node::static_type())
+                .ancestor(Node::static_type())
                 .expect("Port is not a child of a node");
-            let gtk::Allocation { x: fnx, y: fny, .. } = from_node.get_allocation();
+            let gtk::Allocation { x: fnx, y: fny, .. } = from_node.allocation();
             fx += fnx + fw;
             fy += fny + (fh / 2);
 
-            let to_port = &nodes.get(&link.node_to)?.get_port(link.port_to)?.widget;
+            let to_port = &nodes.get(&link.node_to)?.get_port(link.port_to)?;
             let gtk::Allocation {
                 x: mut tx,
                 y: mut ty,
                 height: th,
                 ..
-            } = to_port.get_allocation();
+            } = to_port.allocation();
             let to_node = to_port
-                .get_ancestor(Node::static_type())
+                .ancestor(Node::static_type())
                 .expect("Port is not a child of a node");
-            let gtk::Allocation { x: tnx, y: tny, .. } = to_node.get_allocation();
+            let gtk::Allocation { x: tnx, y: tny, .. } = to_node.allocation();
             tx += tnx;
             ty += tny + (th / 2);
 
@@ -212,7 +231,7 @@ impl GraphView {
         }
     }
 
-    pub fn add_port_to_node(&self, node_id: u32, port_id: u32, port: crate::view::port::Port) {
+    pub fn add_port(&self, node_id: u32, port_id: u32, port: crate::view::port::Port) {
         let private = imp::GraphView::from_instance(self);
 
         if let Some(node) = private.nodes.borrow_mut().get_mut(&node_id) {
@@ -227,6 +246,14 @@ impl GraphView {
         }
     }
 
+    pub fn remove_port(&self, id: u32, node_id: u32) {
+        let private = imp::GraphView::from_instance(self);
+        let nodes = private.nodes.borrow();
+        if let Some(node) = nodes.get(&node_id) {
+            node.remove_port(id);
+        }
+    }
+
     /// Add a link to the graph.
     ///
     /// `add_link` takes three arguments: `link_id` is the id of the link as assigned by the pipewire server,
@@ -245,23 +272,36 @@ impl GraphView {
         self.queue_draw();
     }
 
-    pub fn set_dragged(&self, widget: Option<gtk::Widget>) {
+    pub(super) fn get_node_position(&self, node: &gtk::Widget) -> (f32, f32) {
-        *imp::GraphView::from_instance(self).dragged.borrow_mut() = widget;
+        let layout_manager = self
+            .layout_manager()
+            .expect("Failed to get layout manager")
+            .dynamic_cast::<gtk::FixedLayout>()
+            .expect("Failed to cast to FixedLayout");
+
+        let node = layout_manager
+            .layout_child(node)
+            .expect("Could not get layout child")
+            .dynamic_cast::<gtk::FixedLayoutChild>()
+            .expect("Could not cast to FixedLayoutChild");
+        let transform = node.transform().unwrap_or_default();
+        transform.to_translate()
     }
 
-    pub fn move_node(&self, node: &gtk::Widget, x: f32, y: f32) {
+    pub(super) fn move_node(&self, node: &gtk::Widget, x: f32, y: f32) {
         let layout_manager = self
-            .get_layout_manager()
+            .layout_manager()
             .expect("Failed to get layout manager")
             .dynamic_cast::<gtk::FixedLayout>()
             .expect("Failed to cast to FixedLayout");
 
         let transform = gsk::Transform::new()
-            .translate(&graphene::Point::new(x, y))
+            // Nodes should not be able to be dragged out of the view, so we use `max(coordinate, 0.0)` to prevent that.
+            .translate(&graphene::Point::new(f32::max(x, 0.0), f32::max(y, 0.0)))
             .unwrap();
 
         layout_manager
-            .get_layout_child(node)
+            .layout_child(node)
             .expect("Could not get layout child")
             .dynamic_cast::<gtk::FixedLayoutChild>()
             .expect("Could not cast to FixedLayoutChild")
@@ -272,3 +312,9 @@ impl GraphView {
         self.queue_draw();
     }
 }
+
+impl Default for GraphView {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/view/mod.rs

@@ -1,6 +1,11 @@
+//! The view presented to the user.
+//!
+//! This module contains gtk widgets needed to present the graphical user interface.
+
 mod graph_view;
 mod node;
-pub mod port;
+mod port;
 
 pub use graph_view::GraphView;
 pub use node::Node;
+pub use port::Port;

src/view/node.rs

@@ -1,7 +1,5 @@
-use super::graph_view::GraphView;
+use gtk::{glib, prelude::*, subclass::prelude::*};
-
+use pipewire::spa::Direction;
-use gtk::{glib, prelude::*, subclass::prelude::*, WidgetExt};
-use pipewire::port::Direction;
 
 use std::{collections::HashMap, rc::Rc};
 
@@ -18,14 +16,11 @@ mod imp {
         pub(super) num_ports_out: Cell<u32>,
     }
 
+    #[glib::object_subclass]
     impl ObjectSubclass for Node {
         const NAME: &'static str = "Node";
         type Type = super::Node;
         type ParentType = gtk::Widget;
-        type Instance = glib::subclass::simple::InstanceStruct<Self>;
-        type Class = glib::subclass::simple::ClassStruct<Self>;
-
-        glib::object_subclass!();
 
         fn class_init(klass: &mut Self::Class) {
             klass.set_layout_manager_type::<gtk::BinLayout>();
@@ -37,35 +32,6 @@ mod imp {
 
             grid.attach(&label, 0, 0, 2, 1);
 
-            let motion_controller = gtk::EventControllerMotion::new();
-            motion_controller.connect_enter(|controller, _, _| {
-                // Tell the graphview that the Node is the target of a drag when the mouse enters its label
-                let widget = controller
-                    .get_widget()
-                    .expect("Controller with enter event has no widget")
-                    .get_ancestor(super::Node::static_type())
-                    .expect("Node label does not have a node ancestor widget");
-                widget
-                    .get_ancestor(GraphView::static_type())
-                    .expect("Node with enter event is not on graph")
-                    .dynamic_cast::<GraphView>()
-                    .unwrap()
-                    .set_dragged(Some(widget));
-            });
-            motion_controller.connect_leave(|controller| {
-                // Tell the graphview that the Node is no longer the target of a drag when the mouse leaves.
-                // FIXME: Check that we are the current target before setting none.
-                controller
-                    .get_widget()
-                    .expect("Controller with leave event has no widget")
-                    .get_ancestor(GraphView::static_type())
-                    .expect("Node with leave event is not on graph")
-                    .dynamic_cast::<GraphView>()
-                    .unwrap()
-                    .set_dragged(None);
-            });
-            label.add_controller(&motion_controller);
-
             // Display a grab cursor when the mouse is over the label so the user knows the node can be dragged.
             label.set_cursor(gtk::gdk::Cursor::from_name("grab", None).as_ref());
 
@@ -111,21 +77,17 @@ impl Node {
     pub fn add_port(&mut self, id: u32, port: super::port::Port) {
         let private = imp::Node::from_instance(self);
 
-        match port.direction {
+        match port.direction() {
             Direction::Input => {
                 private
                     .grid
-                    .attach(&port.widget, 0, private.num_ports_in.get() as i32 + 1, 1, 1);
+                    .attach(&port, 0, private.num_ports_in.get() as i32 + 1, 1, 1);
                 private.num_ports_in.set(private.num_ports_in.get() + 1);
             }
             Direction::Output => {
-                private.grid.attach(
+                private
-                    &port.widget,
+                    .grid
-                    1,
+                    .attach(&port, 1, private.num_ports_out.get() as i32 + 1, 1, 1);
-                    private.num_ports_out.get() as i32 + 1,
-                    1,
-                    1,
-                );
                 private.num_ports_out.set(private.num_ports_out.get() + 1);
             }
         }
@@ -135,22 +97,18 @@ impl Node {
 
     pub fn get_port(&self, id: u32) -> Option<Rc<super::port::Port>> {
         let private = imp::Node::from_instance(self);
-        private
+        private.ports.borrow_mut().get(&id).cloned()
-            .ports
-            .borrow_mut()
-            .get(&id)
-            .map(|port_rc| port_rc.clone())
     }
 
     pub fn remove_port(&self, id: u32) {
         let private = imp::Node::from_instance(self);
         if let Some(port) = private.ports.borrow_mut().remove(&id) {
-            match port.direction {
+            match port.direction() {
                 Direction::Input => private.num_ports_in.set(private.num_ports_in.get() - 1),
                 Direction::Output => private.num_ports_in.set(private.num_ports_out.get() - 1),
             }
 
-            port.widget.unparent();
+            port.unparent();
         }
     }
 }

src/view/port.rs

@@ -1,16 +1,130 @@
-/// Graphical representation of a pipewire port.
+use gtk::{
-pub struct Port {
+    gdk,
-    pub(super) widget: gtk::Button,
+    glib::{self, subclass::Signal},
-    pub id: u32,
+    prelude::*,
-    pub direction: pipewire::port::Direction,
+    subclass::prelude::*,
+};
+use log::warn;
+use pipewire::spa::Direction;
+
+use crate::MediaType;
+
+mod imp {
+    use once_cell::{sync::Lazy, unsync::OnceCell};
+    use pipewire::spa::Direction;
+
+    use super::*;
+
+    /// Graphical representation of a pipewire port.
+    #[derive(Default)]
+    pub struct Port {
+        pub(super) id: OnceCell<u32>,
+        pub(super) direction: OnceCell<Direction>,
+    }
+
+    #[glib::object_subclass]
+    impl ObjectSubclass for Port {
+        const NAME: &'static str = "Port";
+        type Type = super::Port;
+        type ParentType = gtk::Button;
+    }
+
+    impl ObjectImpl for Port {
+        fn signals() -> &'static [Signal] {
+            static SIGNALS: Lazy<Vec<Signal>> = Lazy::new(|| {
+                vec![Signal::builder(
+                    "port-toggled",
+                    // Provide id of output port and input port to signal handler.
+                    &[<u32>::static_type().into(), <u32>::static_type().into()],
+                    // signal handler sends back nothing.
+                    <()>::static_type().into(),
+                )
+                .build()]
+            });
+
+            SIGNALS.as_ref()
+        }
+    }
+    impl WidgetImpl for Port {}
+    impl ButtonImpl for Port {}
+}
+
+glib::wrapper! {
+    pub struct Port(ObjectSubclass<imp::Port>)
+        @extends gtk::Button, gtk::Widget;
 }
 
 impl Port {
-    pub fn new(id: u32, name: &str, direction: pipewire::port::Direction) -> Self {
+    pub fn new(id: u32, name: &str, direction: Direction, media_type: Option<MediaType>) -> Self {
-        Self {
+        // Create the widget and initialize needed fields
-            widget: gtk::Button::with_label(name),
+        let res: Self = glib::Object::new(&[]).expect("Failed to create Port");
-            id,
+        let private = imp::Port::from_instance(&res);
-            direction,
+        private.id.set(id).expect("Port id already set");
+        private
+            .direction
+            .set(direction)
+            .expect("Port direction already set");
+
+        res.set_child(Some(&gtk::Label::new(Some(name))));
+
+        // Add either a drag source or drop target controller depending on direction,
+        // they will be responsible for link creation by dragging an output port onto an input port.
+        //
+        // FIXME: The type used for dragging is simply a u32.
+        //   This means that anything that provides a u32 could be dragged onto a input port,
+        //   leading to that port trying to create a link to an invalid output port.
+        //   We should use a newtype instead of a plain u32.
+        //   Additionally, this does not protect against e.g. dropping an outgoing audio port on an ingoing video port.
+        match direction {
+            Direction::Input => {
+                let drop_target = gtk::DropTarget::new(u32::static_type(), gdk::DragAction::COPY);
+                let this = res.clone();
+                drop_target.connect_drop(move |drop_target, val, _, _| {
+                    if let Ok(source_id) = val.get::<u32>() {
+                        // Get the callback registered in the widget and call it
+                        drop_target
+                            .widget()
+                            .expect("Drop target has no widget")
+                            .emit_by_name("port-toggled", &[&source_id, &this.id()])
+                            .expect("Failed to send signal");
+                    } else {
+                        warn!("Invalid type dropped on ingoing port");
+                    }
+
+                    true
+                });
+                res.add_controller(&drop_target);
+            }
+            Direction::Output => {
+                // The port will simply provide its pipewire id to the drag target.
+                let drag_src = gtk::DragSourceBuilder::new()
+                    .content(&gdk::ContentProvider::for_value(&(id.to_value())))
+                    .build();
+                res.add_controller(&drag_src);
+
+                // Display a grab cursor when the mouse is over the port so the user knows it can be dragged to another port.
+                res.set_cursor(gtk::gdk::Cursor::from_name("grab", None).as_ref());
+            }
         }
+
+        // Color the port according to its media type.
+        match media_type {
+            Some(MediaType::Video) => res.add_css_class("video"),
+            Some(MediaType::Audio) => res.add_css_class("audio"),
+            Some(MediaType::Midi) => res.add_css_class("midi"),
+            None => {}
+        }
+
+        res
+    }
+
+    pub fn id(&self) -> u32 {
+        let private = imp::Port::from_instance(self);
+        private.id.get().copied().expect("Port id is not set")
+    }
+
+    pub fn direction(&self) -> &Direction {
+        let private = imp::Port::from_instance(self);
+        private.direction.get().expect("Port direction is not set")
     }
 }