Add drag and drop to work editor

src/editors/work.rs

@@ -74,6 +74,7 @@ impl WorkEditor {
         instrument_frame.set_child(Some(&instrument_list.widget));
 
         let part_list = List::new();
+        part_list.set_enable_dnd(true);
         structure_frame.set_child(Some(&part_list.widget));
 
         let (id, composer, instruments, structure) = match work {
@@ -208,18 +209,6 @@ impl WorkEditor {
         this.part_list.set_make_widget_cb(clone!(@strong this => move |index| {
             let pos = &this.structure.borrow()[index];
 
-            let drag_source = gtk::DragSource::new();
-            drag_source.set_content(Some(&gdk::ContentProvider::new_for_value(&(index as u32).to_value())));
-
-            let drop_target = gtk::DropTarget::new(glib::Type::U32, gdk::DragAction::MOVE);
-
-            drop_target.connect_property_value_notify(clone!(@strong this => move |drop_target| {
-                println!("{:?} -> {:?}", drop_target.get_value(), index);
-            }));
-
-            let handle = gtk::Image::from_icon_name(Some("open-menu-symbolic"));
-            handle.add_controller(&drag_source);
-
             let delete_button = gtk::Button::from_icon_name(Some("user-trash-symbolic"));
             delete_button.set_valign(gtk::Align::Center);
 
@@ -279,11 +268,9 @@ impl WorkEditor {
             let row = libhandy::ActionRow::new();
             row.set_activatable(true);
             row.set_title(Some(&pos.get_title()));
-            row.add_prefix(&handle);
             row.add_suffix(&delete_button);
             row.add_suffix(&edit_button);
             row.set_activatable_widget(Some(&edit_button));
-            row.add_controller(&drop_target);
 
             if let PartOrSection::Part(_) = pos {
                 // TODO: Replace with better solution to differentiate parts and sections.
@@ -293,6 +280,16 @@ impl WorkEditor {
             row.upcast()
         }));
 
+        this.part_list.set_move_cb(clone!(@strong this => move |old_index, new_index| {
+            let length = {
+                let mut structure = this.structure.borrow_mut();
+                structure.swap(old_index, new_index);
+                structure.len()
+            };
+
+            this.part_list.update(length);
+        }));
+
         add_part_button.connect_clicked(clone!(@strong this => move |_| {
             let navigator = this.navigator.borrow().clone();
             if let Some(navigator) = navigator {

src/widgets/list.rs

@@ -1,7 +1,7 @@
 use super::indexed_list_model::{IndexedListModel, ItemIndex};
 use glib::clone;
 use gtk::prelude::*;
-use std::cell::RefCell;
+use std::cell::{Cell, RefCell};
 use std::rc::Rc;
 
 /// A simple list of widgets.
@@ -9,8 +9,10 @@ pub struct List {
     pub widget: gtk::ListBox,
     model: IndexedListModel,
     filter: gtk::CustomFilter,
+    enable_dnd: Cell<bool>,
     make_widget_cb: RefCell<Option<Box<dyn Fn(usize) -> gtk::Widget>>>,
     filter_cb: RefCell<Option<Box<dyn Fn(usize) -> bool>>>,
+    move_cb: RefCell<Option<Box<dyn Fn(usize, usize)>>>,
 }
 
 impl List {
@@ -31,8 +33,10 @@ impl List {
             widget,
             model,
             filter,
+            enable_dnd: Cell::new(false),
             make_widget_cb: RefCell::new(None),
             filter_cb: RefCell::new(None),
+            move_cb: RefCell::new(None),
         });
 
         this.filter.set_filter_func(clone!(@strong this => move |index| {
@@ -47,8 +51,39 @@ impl List {
         this.widget.bind_model(Some(&filter_model), clone!(@strong this => move |index| {
             let index = index.downcast_ref::<ItemIndex>().unwrap().get() as usize;
             if let Some(cb) = &*this.make_widget_cb.borrow() {
-                cb(index)
+                let widget = cb(index);
+
+                if this.enable_dnd.get() {
+                    let drag_source = gtk::DragSource::new();
+
+                    drag_source.connect_drag_begin(clone!(@strong widget => move |_, drag| {
+                        // TODO: Replace with a better solution.
+                        let paintable = gtk::WidgetPaintable::new(Some(&widget));
+                        gtk::DragIcon::set_from_paintable(drag, &paintable, 0, 0);
+                    }));
+
+                    let drag_value = (index as u32).to_value();
+                    drag_source.set_content(Some(&gdk::ContentProvider::new_for_value(&drag_value)));
+
+                    let drop_target = gtk::DropTarget::new(glib::Type::U32, gdk::DragAction::COPY);
+
+                    drop_target.connect_drop(clone!(@strong this => move |_, value, _, _| {
+                        if let Some(cb) = &*this.move_cb.borrow() {
+                            let old_index: u32 = value.get_some().unwrap();
+                            cb(old_index as usize, index);
+                            true
                         } else {
+                            false
+                        }
+                    }));
+
+                    widget.add_controller(&drag_source);
+                    widget.add_controller(&drop_target);
+                }
+
+                widget
+            } else {
+                // This shouldn't be reachable under normal circumstances.
                 gtk::Label::new(None).upcast()
             }
         }));
@@ -56,6 +91,11 @@ impl List {
         this
     }
 
+    /// Whether the list should support drag and drop.
+    pub fn set_enable_dnd(&self, enable: bool) {
+        self.enable_dnd.set(enable);
+    }
+
     /// Set the closure to be called to construct widgets for the items.
     pub fn set_make_widget_cb<F: Fn(usize) -> gtk::Widget + 'static>(&self, cb: F) {
         self.make_widget_cb.replace(Some(Box::new(cb)));
@@ -67,6 +107,12 @@ impl List {
         self.filter_cb.replace(Some(Box::new(cb)));
     }
 
+    /// Set the closure to be called to when the use has dragged an item to a
+    /// new position.
+    pub fn set_move_cb<F: Fn(usize, usize) + 'static>(&self, cb: F) {
+        self.move_cb.replace(Some(Box::new(cb)));
+    }
+
     /// Select an item by its index. If the index is out of range, nothing will happen.
     pub fn select(&self, index: usize) {
         let row = self.widget.get_row_at_index(index as i32);