Fix dock resizing (#3663)

This fixes some bugs in the display and tracking of dock resizes

Release Notes:

-

crates/gpui2/src/elements/canvas.rs

@@ -27,7 +27,7 @@ impl IntoElement for Canvas {
 }
 
 impl Element for Canvas {
-    type State = ();
+    type State = Style;
 
     fn layout(
         &mut self,
@@ -37,11 +37,11 @@ impl Element for Canvas {
         let mut style = Style::default();
         style.refine(&self.style);
         let layout_id = cx.request_layout(&style, []);
-        (layout_id, ())
+        (layout_id, style)
     }
 
-    fn paint(self, bounds: Bounds<Pixels>, _: &mut (), cx: &mut WindowContext) {
-        (self.paint_callback)(&bounds, cx)
+    fn paint(self, bounds: Bounds<Pixels>, style: &mut Style, cx: &mut WindowContext) {
+        style.paint(bounds, cx, |cx| (self.paint_callback)(&bounds, cx));
     }
 }
 

crates/gpui2/src/elements/div.rs

@@ -213,7 +213,7 @@ pub trait InteractiveElement: Sized {
         listener: impl Fn(&DragMoveEvent<T>, &mut WindowContext) + 'static,
     ) -> Self
     where
-        T: Render,
+        T: 'static,
     {
         self.interactivity().mouse_move_listeners.push(Box::new(
             move |event, bounds, phase, cx| {
@@ -223,7 +223,7 @@ pub trait InteractiveElement: Sized {
                     if cx
                         .active_drag
                         .as_ref()
-                        .is_some_and(|drag| drag.value.type_id() == TypeId::of::<T>())
+                        .is_some_and(|drag| (*drag.value).type_id() == TypeId::of::<T>())
                     {
                         (listener)(
                             &DragMoveEvent {