dnd_source: Add suppport for surface offset

The `drag_icon` callback is passed the offset of the cursor within the
widget at the start of the drag, and can return an offset the drag
surface should be placed relative to the cursor.

iced

@@ -1 +1 @@
-Subproject commit 2cc6865c908d025e43d7fc937f6b67defd51ea18
+Subproject commit 9ad04dadde75ac4b445602fc6f31e05d7b7003c3

src/widget/dnd_source.rs

@@ -32,7 +32,7 @@ pub struct DndSource<'a, Message, D> {
     container: Element<'a, Message>,
     window: Option<window::Id>,
     drag_content: Option<Box<dyn Fn() -> D>>,
-    drag_icon: Option<Box<dyn Fn() -> (Element<'static, ()>, tree::State)>>,
+    drag_icon: Option<Box<dyn Fn(Vector) -> (Element<'static, ()>, tree::State, Vector)>>,
     on_start: Option<Message>,
     on_cancelled: Option<Message>,
     on_finish: Option<Message>,
@@ -90,7 +90,7 @@ impl<
     #[must_use]
     pub fn drag_icon(
         mut self,
-        f: impl Fn() -> (Element<'static, ()>, tree::State) + 'static,
+        f: impl Fn(Vector) -> (Element<'static, ()>, tree::State, Vector) + 'static,
     ) -> Self {
         self.drag_icon = Some(Box::new(f));
         self
@@ -102,7 +102,7 @@ impl<
         self
     }
 
-    pub fn start_dnd(&self, clipboard: &mut dyn Clipboard, bounds: Rectangle) {
+    pub fn start_dnd(&self, clipboard: &mut dyn Clipboard, bounds: Rectangle, offset: Vector) {
         let Some(content) = self.drag_content.as_ref().map(|f| f()) else {
             return;
         };
@@ -116,13 +116,14 @@ impl<
                 Some(iced_core::clipboard::DndSource::Widget(self.id.clone()))
             },
             self.drag_icon.as_ref().map(|f| {
-                let (icon, state) = f();
-                (
+                let (icon, state, offset) = f(offset);
+                iced_core::clipboard::IconSurface::new(
                     container(icon)
                         .width(Length::Fixed(bounds.width))
                         .height(Length::Fixed(bounds.height))
                         .into(),
                     state,
+                    offset,
                 )
             }),
             Box::new(content),
@@ -262,7 +263,11 @@ impl<
                                     if let Some(on_start) = self.on_start.as_ref() {
                                         shell.publish(on_start.clone())
                                     }
-                                    self.start_dnd(clipboard, state.cached_bounds);
+                                    let offset = Vector::new(
+                                        left_pressed_position.x - layout.bounds().x,
+                                        left_pressed_position.y - layout.bounds().y,
+                                    );
+                                    self.start_dnd(clipboard, state.cached_bounds, offset);
                                     state.is_dragging = true;
                                     state.left_pressed_position = None;
                                 }

src/widget/text_input/input.rs

@@ -1350,12 +1350,13 @@ where
                                     clipboard,
                                     false,
                                     id.map(|id| iced_core::clipboard::DndSource::Widget(id)),
-                                    Some((
+                                    Some(iced_core::clipboard::IconSurface::new(
                                         Element::from(
                                             TextInput::<'static, ()>::new("", input_text.clone())
                                                 .dnd_icon(true),
                                         ),
                                         iced_core::widget::tree::State::new(state_clone),
+                                        Vector::ZERO,
                                     )),
                                     Box::new(TextInputString(input_text)),
                                     DndAction::Move,