gpui: Keep drag cursor style when dragging (#24797)

Release Notes:

- Improve to keep drag cursor style on dragging resize handles.

---

### Before


https://github.com/user-attachments/assets/d4100d01-ac02-42b8-b923-9f2b4633c458

### After


https://github.com/user-attachments/assets/b5a450cd-c6de-4b39-a79c-2d73fcbad209

With example:

```
cargo run -p gpui --example drag_drop
```


https://github.com/user-attachments/assets/4cba1966-1578-40ce-a435-64ec11bcace5

crates/gpui/src/app.rs

@@ -31,10 +31,10 @@ use util::ResultExt;
 
 use crate::{
     Action, ActionBuildError, ActionRegistry, Any, AnyView, AnyWindowHandle, AppContext, Asset,
-    AssetSource, BackgroundExecutor, Bounds, ClipboardItem, DispatchPhase, DisplayId, EventEmitter,
-    FocusHandle, FocusMap, ForegroundExecutor, Global, KeyBinding, Keymap, Keystroke, LayoutId,
-    Menu, MenuItem, OwnedMenu, PathPromptOptions, Pixels, Platform, PlatformDisplay, Point,
-    PromptBuilder, PromptHandle, PromptLevel, Render, RenderablePromptHandle, Reservation,
+    AssetSource, BackgroundExecutor, Bounds, ClipboardItem, CursorStyle, DispatchPhase, DisplayId,
+    EventEmitter, FocusHandle, FocusMap, ForegroundExecutor, Global, KeyBinding, Keymap, Keystroke,
+    LayoutId, Menu, MenuItem, OwnedMenu, PathPromptOptions, Pixels, Platform, PlatformDisplay,
+    Point, PromptBuilder, PromptHandle, PromptLevel, Render, RenderablePromptHandle, Reservation,
     ScreenCaptureSource, SharedString, SubscriberSet, Subscription, SvgRenderer, Task, TextSystem,
     Window, WindowAppearance, WindowHandle, WindowId, WindowInvalidator, current_platform, hash,
     init_app_menus,
@@ -1803,6 +1803,9 @@ pub struct AnyDrag {
     /// This is used to render the dragged item in the same place
     /// on the original element that the drag was initiated
     pub cursor_offset: Point<Pixels>,
+
+    /// The cursor style to use while dragging
+    pub cursor_style: Option<CursorStyle>,
 }
 
 /// Contains state associated with a tooltip. You'll only need this struct if you're implementing

crates/gpui/src/elements/div.rs

@@ -1615,7 +1615,11 @@ impl Interactivity {
                                             global_id, hitbox, &style, window, cx,
                                         );
 
-                                        if !cx.has_active_drag() {
+                                        if let Some(drag) = cx.active_drag.as_ref() {
+                                            if let Some(mouse_cursor) = drag.cursor_style {
+                                                window.set_cursor_style(mouse_cursor, None);
+                                            }
+                                        } else {
                                             if let Some(mouse_cursor) = style.mouse_cursor {
                                                 window.set_cursor_style(mouse_cursor, Some(hitbox));
                                             }
@@ -1838,6 +1842,7 @@ impl Interactivity {
                 }
             });
         }
+        let drag_cursor_style = self.base_style.as_ref().mouse_cursor;
 
         let mut drag_listener = mem::take(&mut self.drag_listener);
         let drop_listeners = mem::take(&mut self.drop_listeners);
@@ -1929,6 +1934,7 @@ impl Interactivity {
                                         view: drag,
                                         value: drag_value,
                                         cursor_offset,
+                                        cursor_style: drag_cursor_style,
                                     });
                                     pending_mouse_down.take();
                                     window.refresh();
@@ -2269,6 +2275,7 @@ impl Interactivity {
                     }
                 }
 
+                style.mouse_cursor = drag.cursor_style;
                 cx.active_drag = Some(drag);
             }
         }

crates/gpui/src/window.rs

@@ -3093,6 +3093,7 @@ impl Window {
                             value: Arc::new(paths.clone()),
                             view: cx.new(|_| paths).into(),
                             cursor_offset: position,
+                            cursor_style: None,
                         });
                     }
                     PlatformInput::MouseMove(MouseMoveEvent {