Incorporate ElementId as part of the Element::id trait method and expose GlobalId (#11101)

We're planning to associate "selection sources" with global element ids
to allow arbitrary UI text to be selected in GPUI. Previously, global
ids were not exposed outside the framework and we entangled management
of the element id stack with element state access. This was more
acceptable when element state was the only place we used global element
ids, but now that we're planning to use them more places, it makes sense
to deal with element identity as a first-class part of the element
system. We now ensure that the stack of element ids which forms the
current global element id is correctly managed in every phase of element
layout and paint and make the global id available to each element
method. In a subsequent PR, we'll use the global element id as part of
implementing arbitrary selection for UI text.

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>

crates/workspace/src/pane_group.rs

@@ -597,9 +597,9 @@ mod element {
     use std::{cell::RefCell, iter, rc::Rc, sync::Arc};
 
     use gpui::{
-        px, relative, Along, AnyElement, Axis, Bounds, Element, IntoElement, MouseDownEvent,
-        MouseMoveEvent, MouseUpEvent, ParentElement, Pixels, Point, Size, Style, WeakView,
-        WindowContext,
+        px, relative, Along, AnyElement, Axis, Bounds, Element, GlobalElementId, IntoElement,
+        MouseDownEvent, MouseMoveEvent, MouseUpEvent, ParentElement, Pixels, Point, Size, Style,
+        WeakView, WindowContext,
     };
     use gpui::{CursorStyle, Hitbox};
     use parking_lot::Mutex;
@@ -795,8 +795,13 @@ mod element {
         type RequestLayoutState = ();
         type PrepaintState = PaneAxisLayout;
 
+        fn id(&self) -> Option<ElementId> {
+            Some(self.basis.into())
+        }
+
         fn request_layout(
             &mut self,
+            _global_id: Option<&GlobalElementId>,
             cx: &mut ui::prelude::WindowContext,
         ) -> (gpui::LayoutId, Self::RequestLayoutState) {
             let mut style = Style::default();
@@ -810,17 +815,16 @@ mod element {
 
         fn prepaint(
             &mut self,
+            global_id: Option<&GlobalElementId>,
             bounds: Bounds<Pixels>,
             _state: &mut Self::RequestLayoutState,
             cx: &mut WindowContext,
         ) -> PaneAxisLayout {
             let dragged_handle = cx.with_element_state::<Rc<RefCell<Option<usize>>>, _>(
-                Some(self.basis.into()),
+                global_id.unwrap(),
                 |state, _cx| {
-                    let state = state
-                        .unwrap()
-                        .unwrap_or_else(|| Rc::new(RefCell::new(None)));
-                    (state.clone(), Some(state))
+                    let state = state.unwrap_or_else(|| Rc::new(RefCell::new(None)));
+                    (state.clone(), state)
                 },
             );
             let flexes = self.flexes.lock().clone();
@@ -897,6 +901,7 @@ mod element {
 
         fn paint(
             &mut self,
+            _id: Option<&GlobalElementId>,
             bounds: gpui::Bounds<ui::prelude::Pixels>,
             _: &mut Self::RequestLayoutState,
             layout: &mut Self::PrepaintState,

crates/workspace/src/toolbar.rs

@@ -158,8 +158,10 @@ impl Toolbar {
     {
         let location = item.set_active_pane_item(self.active_item.as_deref(), cx);
         cx.subscribe(&item, |this, item, event, cx| {
-            if let Some((_, current_location)) =
-                this.items.iter_mut().find(|(i, _)| i.id() == item.id())
+            if let Some((_, current_location)) = this
+                .items
+                .iter_mut()
+                .find(|(i, _)| i.id() == item.entity_id())
             {
                 match event {
                     ToolbarItemEvent::ChangeLocation(new_location) => {

crates/workspace/src/workspace.rs

@@ -28,9 +28,10 @@ use futures::{
 use gpui::{
     actions, canvas, impl_actions, point, relative, size, Action, AnyElement, AnyView, AnyWeakView,
     AppContext, AsyncAppContext, AsyncWindowContext, Bounds, DevicePixels, DragMoveEvent,
-    Entity as _, EntityId, EventEmitter, FocusHandle, FocusableView, Global, KeyContext, Keystroke,
-    LayoutId, ManagedView, Model, ModelContext, PathPromptOptions, Point, PromptLevel, Render,
-    Size, Subscription, Task, View, WeakView, WindowHandle, WindowOptions,
+    ElementId, Entity as _, EntityId, EventEmitter, FocusHandle, FocusableView, Global,
+    GlobalElementId, KeyContext, Keystroke, LayoutId, ManagedView, Model, ModelContext,
+    PathPromptOptions, Point, PromptLevel, Render, Size, Subscription, Task, View, WeakView,
+    WindowHandle, WindowOptions,
 };
 use item::{
     FollowableItem, FollowableItemHandle, Item, ItemHandle, ItemSettings, PreviewTabsSettings,
@@ -5060,7 +5061,15 @@ impl Element for DisconnectedOverlay {
     type RequestLayoutState = AnyElement;
     type PrepaintState = ();
 
-    fn request_layout(&mut self, cx: &mut WindowContext) -> (LayoutId, Self::RequestLayoutState) {
+    fn id(&self) -> Option<ElementId> {
+        None
+    }
+
+    fn request_layout(
+        &mut self,
+        _id: Option<&GlobalElementId>,
+        cx: &mut WindowContext,
+    ) -> (LayoutId, Self::RequestLayoutState) {
         let mut background = cx.theme().colors().elevated_surface_background;
         background.fade_out(0.2);
         let mut overlay = div()
@@ -5083,6 +5092,7 @@ impl Element for DisconnectedOverlay {
 
     fn prepaint(
         &mut self,
+        _id: Option<&GlobalElementId>,
         bounds: Bounds<Pixels>,
         overlay: &mut Self::RequestLayoutState,
         cx: &mut WindowContext,
@@ -5093,6 +5103,7 @@ impl Element for DisconnectedOverlay {
 
     fn paint(
         &mut self,
+        _id: Option<&GlobalElementId>,
         _: Bounds<Pixels>,
         overlay: &mut Self::RequestLayoutState,
         _: &mut Self::PrepaintState,