editor: Implement drag and drop where it makes sense

src/util/activatable_row.rs

@@ -0,0 +1,109 @@
+use std::cell::RefCell;
+
+use gtk::{
+    glib::{self, clone, subclass::Signal},
+    prelude::*,
+    subclass::prelude::*,
+};
+use once_cell::sync::Lazy;
+
+mod imp {
+    use super::*;
+
+    #[derive(Default)]
+    pub struct ActivatableRow {
+        pub previous_parent: RefCell<Option<gtk::ListBox>>,
+        pub previous_signal_handler_id: RefCell<Option<glib::SignalHandlerId>>,
+    }
+
+    #[glib::object_subclass]
+    impl ObjectSubclass for ActivatableRow {
+        const NAME: &'static str = "MusicusActivatableRow";
+        type Type = super::ActivatableRow;
+        type ParentType = gtk::ListBoxRow;
+    }
+
+    impl ObjectImpl for ActivatableRow {
+        fn constructed(&self) {
+            self.parent_constructed();
+
+            let obj = self.obj();
+            obj.connect_parent_notify(clone!(
+                #[weak]
+                obj,
+                move |_: &super::ActivatableRow| {
+                    let previous_parent = obj.imp().previous_parent.borrow_mut().take();
+                    let previous_signal_handler_id =
+                        obj.imp().previous_signal_handler_id.borrow_mut().take();
+                    if let (Some(previous_parent), Some(previous_signal_handler_id)) =
+                        (previous_parent, previous_signal_handler_id)
+                    {
+                        previous_parent.disconnect(previous_signal_handler_id);
+                    }
+
+                    if let Some(parent) = obj.parent().and_downcast::<gtk::ListBox>() {
+                        let signal_handler_id = parent.connect_row_activated(clone!(
+                            #[weak]
+                            obj,
+                            move |_: &gtk::ListBox, row: &gtk::ListBoxRow| {
+                                if *row == obj {
+                                    obj.activate();
+                                }
+                            }
+                        ));
+
+                        obj.imp().previous_parent.replace(Some(parent));
+                        obj.imp()
+                            .previous_signal_handler_id
+                            .replace(Some(signal_handler_id));
+                    }
+                }
+            ));
+        }
+
+        fn signals() -> &'static [Signal] {
+            static SIGNALS: Lazy<Vec<Signal>> =
+                Lazy::new(|| vec![Signal::builder("activated").build()]);
+
+            SIGNALS.as_ref()
+        }
+    }
+
+    impl WidgetImpl for ActivatableRow {}
+
+    impl ListBoxRowImpl for ActivatableRow {
+        fn activate(&self) {
+            self.obj().emit_by_name::<()>("activated", &[]);
+        }
+    }
+}
+
+glib::wrapper! {
+    /// A simple helper widget for connecting a signal handler to a single [`gtk::ListBoxRow`] for
+    /// handling activation.
+    pub struct ActivatableRow(ObjectSubclass<imp::ActivatableRow>)
+        @extends gtk::Widget, gtk::ListBoxRow;
+}
+
+impl ActivatableRow {
+    pub fn new<W>(child: &W) -> Self
+    where
+        W: IsA<gtk::Widget>,
+    {
+        let obj: Self = glib::Object::builder()
+            .property("activatable", true)
+            .property("selectable", false)
+            .build();
+
+        obj.set_child(Some(child));
+        obj
+    }
+
+    pub fn connect_activated<F: Fn(&Self) + 'static>(&self, f: F) -> glib::SignalHandlerId {
+        self.connect_local("activated", true, move |values| {
+            let obj = values[0].get::<Self>().unwrap();
+            f(&obj);
+            None
+        })
+    }
+}

src/util/drag_widget.rs

@@ -0,0 +1,41 @@
+use adw::{prelude::*, subclass::prelude::*};
+
+mod imp {
+    use super::*;
+
+    #[derive(Default)]
+    pub struct DragWidget {}
+
+    #[glib::object_subclass]
+    impl ObjectSubclass for DragWidget {
+        const NAME: &'static str = "MusicusDragWidget";
+        type Type = super::DragWidget;
+        type ParentType = adw::Bin;
+
+        fn class_init(klass: &mut Self::Class) {
+            klass.set_css_name("dragwidget");
+        }
+    }
+
+    impl ObjectImpl for DragWidget {}
+    impl WidgetImpl for DragWidget {}
+    impl BinImpl for DragWidget {}
+}
+
+glib::wrapper! {
+    /// A simple helper widget for displaying a drag icon for a widget.
+    pub struct DragWidget(ObjectSubclass<imp::DragWidget>)
+        @extends gtk::Widget, adw::Bin;
+}
+
+impl DragWidget {
+    pub fn new<W>(widget: &W) -> Self
+    where
+        W: IsA<gtk::Widget>,
+    {
+        let obj: Self = glib::Object::new();
+        let picture = gtk::Picture::for_paintable(&gtk::WidgetPaintable::new(Some(widget)));
+        obj.set_child(Some(&picture));
+        obj
+    }
+}