From 8ab04bd586b1d4ee9b698453a2be1ddb8b6068a4 Mon Sep 17 00:00:00 2001
From: Lucas Meurer <lucasmeurer96@gmail.com>
Date: Thu, 3 Aug 2023 19:11:45 +0200
Subject: [PATCH] Add index property to ItemState

---
 examples/simple.rs |  8 ++++++--
 src/lib.rs         |  9 +++++++--
 src/state.rs       | 13 +++++++++++--
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/examples/simple.rs b/examples/simple.rs
index a7d1287..21723a8 100644
--- a/examples/simple.rs
+++ b/examples/simple.rs
@@ -10,9 +10,13 @@ pub fn main() -> eframe::Result<()> {
         Default::default(),
         move |ctx, _frame| {
             CentralPanel::default().show(ctx, |ui| {
-                dnd(ui, "dnd_example").show_vec(&mut items, |ui, item, handle, _state| {
+                dnd(ui, "dnd_example").show_vec(&mut items, |ui, item, handle, state| {
                     handle.ui(ui, |ui| {
-                        ui.label("drag");
+                        if state.dragged {
+                            ui.label("dragging");
+                        } else {
+                            ui.label("drag");
+                        }
                     });
                     ui.label(*item);
                 });
diff --git a/src/lib.rs b/src/lib.rs
index 28de902..140b959 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -146,8 +146,8 @@ impl<'a> Dnd<'a> {
             mut drag_drop_ui,
         } = self;
 
-        let response = drag_drop_ui.ui(ui, items, |item, ui, handle, dragged| {
-            item_ui(ui, item, handle, ItemState { dragged });
+        let response = drag_drop_ui.ui(ui, items, |item, ui, handle, item_state| {
+            item_ui(ui, item, handle, item_state);
         });
 
         ui.ctx().data_mut(|data| data.insert_temp(id, drag_drop_ui));
@@ -175,4 +175,9 @@ impl<'a> Dnd<'a> {
 pub struct ItemState {
     /// True if the item is currently being dragged.
     pub dragged: bool,
+    /// Index of the item in the list.
+    /// Note that when you sort the source list while the drag is still ongoing (default behaviour
+    /// of [Dnd::show_vec]), this index will updated while the item is being dragged.
+    /// If you sort once after the item is dropped, the index will be stable during the drag.
+    pub index: usize,
 }
diff --git a/src/state.rs b/src/state.rs
index e4bf5a2..f8fbde9 100644
--- a/src/state.rs
+++ b/src/state.rs
@@ -4,6 +4,7 @@ use std::time::{Duration, SystemTime};
 
 use egui::{CursorIcon, Id, InnerResponse, LayerId, Order, Pos2, Rect, Sense, Ui, Vec2};
 
+use crate::ItemState;
 #[cfg(target_arch = "wasm32")]
 use web_time::{Duration, SystemTime};
 
@@ -490,7 +491,7 @@ impl DragDropUi {
         &mut self,
         ui: &mut Ui,
         values: impl Iterator<Item = T>,
-        mut item_ui: impl FnMut(T, &mut Ui, Handle, bool),
+        mut item_ui: impl FnMut(T, &mut Ui, Handle, ItemState),
     ) -> DragDropResponse {
         // During the first frame, we check if the pointer is actually over any of the item handles and cancel the drag if it isn't
         let mut first_frame = false;
@@ -626,7 +627,15 @@ impl DragDropUi {
                                 item_id,
                                 &mut hovering_over_any_handle,
                                 |ui, handle| {
-                                    item_ui(item, ui, handle, is_dragged_item);
+                                    item_ui(
+                                        item,
+                                        ui,
+                                        handle,
+                                        ItemState {
+                                            dragged: is_dragged_item,
+                                            index: idx,
+                                        },
+                                    );
                                 },
                             )
                         })