Improve model selection in the assistant (#12472)

https://github.com/zed-industries/zed/assets/482957/3b017850-b7b6-457a-9b2f-324d5533442e


Release Notes:

- Improved the UX for selecting a model in the assistant panel. You can
now switch model using just the keyboard by pressing `alt-m`. Also, when
switching models via the UI, settings will now be updated automatically.

crates/ui/src/components/popover_menu.rs

@@ -13,6 +13,51 @@ pub trait PopoverTrigger: IntoElement + Clickable + Selectable + 'static {}
 
 impl<T: IntoElement + Clickable + Selectable + 'static> PopoverTrigger for T {}
 
+pub struct PopoverMenuHandle<M>(Rc<RefCell<Option<PopoverMenuHandleState<M>>>>);
+
+impl<M> Clone for PopoverMenuHandle<M> {
+    fn clone(&self) -> Self {
+        Self(self.0.clone())
+    }
+}
+
+impl<M> Default for PopoverMenuHandle<M> {
+    fn default() -> Self {
+        Self(Rc::default())
+    }
+}
+
+struct PopoverMenuHandleState<M> {
+    menu_builder: Rc<dyn Fn(&mut WindowContext) -> Option<View<M>>>,
+    menu: Rc<RefCell<Option<View<M>>>>,
+}
+
+impl<M: ManagedView> PopoverMenuHandle<M> {
+    pub fn show(&self, cx: &mut WindowContext) {
+        if let Some(state) = self.0.borrow().as_ref() {
+            show_menu(&state.menu_builder, &state.menu, cx);
+        }
+    }
+
+    pub fn hide(&self, cx: &mut WindowContext) {
+        if let Some(state) = self.0.borrow().as_ref() {
+            if let Some(menu) = state.menu.borrow().as_ref() {
+                menu.update(cx, |_, cx| cx.emit(DismissEvent));
+            }
+        }
+    }
+
+    pub fn toggle(&self, cx: &mut WindowContext) {
+        if let Some(state) = self.0.borrow().as_ref() {
+            if state.menu.borrow().is_some() {
+                self.hide(cx);
+            } else {
+                self.show(cx);
+            }
+        }
+    }
+}
+
 pub struct PopoverMenu<M: ManagedView> {
     id: ElementId,
     child_builder: Option<
@@ -28,6 +73,7 @@ pub struct PopoverMenu<M: ManagedView> {
     anchor: AnchorCorner,
     attach: Option<AnchorCorner>,
     offset: Option<Point<Pixels>>,
+    trigger_handle: Option<PopoverMenuHandle<M>>,
 }
 
 impl<M: ManagedView> PopoverMenu<M> {
@@ -36,35 +82,17 @@ impl<M: ManagedView> PopoverMenu<M> {
         self
     }
 
+    pub fn with_handle(mut self, handle: PopoverMenuHandle<M>) -> Self {
+        self.trigger_handle = Some(handle);
+        self
+    }
+
     pub fn trigger<T: PopoverTrigger>(mut self, t: T) -> Self {
         self.child_builder = Some(Box::new(|menu, builder| {
             let open = menu.borrow().is_some();
             t.selected(open)
                 .when_some(builder, |el, builder| {
-                    el.on_click({
-                        move |_, cx| {
-                            let Some(new_menu) = (builder)(cx) else {
-                                return;
-                            };
-                            let menu2 = menu.clone();
-                            let previous_focus_handle = cx.focused();
-
-                            cx.subscribe(&new_menu, move |modal, _: &DismissEvent, cx| {
-                                if modal.focus_handle(cx).contains_focused(cx) {
-                                    if let Some(previous_focus_handle) =
-                                        previous_focus_handle.as_ref()
-                                    {
-                                        cx.focus(previous_focus_handle);
-                                    }
-                                }
-                                *menu2.borrow_mut() = None;
-                                cx.refresh();
-                            })
-                            .detach();
-                            cx.focus_view(&new_menu);
-                            *menu.borrow_mut() = Some(new_menu);
-                        }
-                    })
+                    el.on_click(move |_, cx| show_menu(&builder, &menu, cx))
                 })
                 .into_any_element()
         }));
@@ -111,6 +139,32 @@ impl<M: ManagedView> PopoverMenu<M> {
     }
 }
 
+fn show_menu<M: ManagedView>(
+    builder: &Rc<dyn Fn(&mut WindowContext) -> Option<View<M>>>,
+    menu: &Rc<RefCell<Option<View<M>>>>,
+    cx: &mut WindowContext,
+) {
+    let Some(new_menu) = (builder)(cx) else {
+        return;
+    };
+    let menu2 = menu.clone();
+    let previous_focus_handle = cx.focused();
+
+    cx.subscribe(&new_menu, move |modal, _: &DismissEvent, cx| {
+        if modal.focus_handle(cx).contains_focused(cx) {
+            if let Some(previous_focus_handle) = previous_focus_handle.as_ref() {
+                cx.focus(previous_focus_handle);
+            }
+        }
+        *menu2.borrow_mut() = None;
+        cx.refresh();
+    })
+    .detach();
+    cx.focus_view(&new_menu);
+    *menu.borrow_mut() = Some(new_menu);
+    cx.refresh();
+}
+
 /// Creates a [`PopoverMenu`]
 pub fn popover_menu<M: ManagedView>(id: impl Into<ElementId>) -> PopoverMenu<M> {
     PopoverMenu {
@@ -120,6 +174,7 @@ pub fn popover_menu<M: ManagedView>(id: impl Into<ElementId>) -> PopoverMenu<M>
         anchor: AnchorCorner::TopLeft,
         attach: None,
         offset: None,
+        trigger_handle: None,
     }
 }
 
@@ -190,6 +245,15 @@ impl<M: ManagedView> Element for PopoverMenu<M> {
                     (child_builder)(element_state.menu.clone(), self.menu_builder.clone())
                 });
 
+                if let Some(trigger_handle) = self.trigger_handle.take() {
+                    if let Some(menu_builder) = self.menu_builder.clone() {
+                        *trigger_handle.0.borrow_mut() = Some(PopoverMenuHandleState {
+                            menu_builder,
+                            menu: element_state.menu.clone(),
+                        });
+                    }
+                }
+
                 let child_layout_id = child_element
                     .as_mut()
                     .map(|child_element| child_element.request_layout(cx));