Add example on how to use egui_dnd without storing unique ids, by usi…

…ng the items index as id

crates/egui_dnd/examples/index_as_id.rs

@@ -0,0 +1,74 @@
+use eframe::egui;
+use egui::{CentralPanel, Id};
+use egui_dnd::{dnd, DragDropItem};
+
+#[derive(Clone, Hash)]
+struct Item {
+    name: String,
+}
+
+impl Item {
+    fn new(name: &str) -> Self {
+        Self {
+            name: name.to_string(),
+        }
+    }
+}
+
+// In order to use the index as id we need to implement DragDropItem for a wrapper struct
+struct EnumeratedItem<T> {
+    item: T,
+    index: usize,
+}
+
+impl<T> DragDropItem for EnumeratedItem<T> {
+    fn id(&self) -> Id {
+        Id::new(self.index)
+    }
+}
+
+pub fn main() -> eframe::Result<()> {
+    let mut items = vec![
+        Item::new("alfred"),
+        Item::new("bernhard"),
+        Item::new("christian"),
+        Item::new("alfred"),
+    ];
+
+    eframe::run_simple_native(
+        "DnD Simple Example",
+        Default::default(),
+        move |ctx, _frame| {
+            CentralPanel::default().show(ctx, |ui| {
+                let response = dnd(ui, "dnd_example")
+                    // Since egui_dnd's animations rely on the ids not
+                    // changing after the drag finished we need to disable animations
+                    .with_animation_time(0.0)
+                    .show(
+                        items
+                            .iter_mut()
+                            .enumerate()
+                            .map(|(i, item)| EnumeratedItem { item, index: i }),
+                        |ui, item, handle, state| {
+                            ui.horizontal(|ui| {
+                                handle.ui(ui, |ui| {
+                                    if state.dragged {
+                                        ui.label("dragging");
+                                    } else {
+                                        ui.label("drag");
+                                    }
+                                });
+                                ui.label(&item.item.name);
+                            });
+                        },
+                    );
+
+                // Since the item id may not change while a drag is ongoing we need to wait
+                // until the drag is finished before updating the items
+                if response.is_drag_finished() {
+                    response.update_vec(&mut items);
+                }
+            });
+        },
+    )
+}

crates/egui_dnd/src/lib.rs

@@ -114,10 +114,10 @@ impl<'a> Dnd<'a> {
     }
 
     /// Display the drag and drop UI.
-    /// `items` should be an iterator over items that should be sorted.
+    /// `items` should be an iterator over items that should be sortable.
     ///
-    /// The items won't be sorted automatically, but you can use [Dnd::show_vec] or [DragDropResponse::update_vec] to do so.
-    /// If your items aren't in a vec, you have to sort them yourself.
+    /// The items won't be updated automatically, but you can use [Dnd::show_vec] or [DragDropResponse::update_vec] to do so.
+    /// If your items aren't in a vec, you have to update the order yourself.
     ///
     /// `item_ui` is called for each item. Display your item there.
     /// `item_ui` gets a [Handle] that can be used to display the drag handle.