Avoid panic by accessing view handle by global in wrong window

View handles are window specific but this global will be doing things
in all windows, that would cause a panic when it attempted to update
a status bar mode indicator in a background window

Co-Authored-By: Mikayla Maki <mikayla@zed.dev>

crates/vim/src/mode_indicator.rs

@@ -1,20 +1,60 @@
-use gpui::{elements::Label, AnyElement, Element, Entity, View, ViewContext};
+use gpui::{
+    elements::{Empty, Label},
+    AnyElement, Element, Entity, Subscription, View, ViewContext,
+};
+use settings::SettingsStore;
 use workspace::{item::ItemHandle, StatusItemView};
 
-use crate::state::Mode;
+use crate::{state::Mode, Vim, VimEvent, VimModeSetting};
 
 pub struct ModeIndicator {
-    pub mode: Mode,
+    pub mode: Option<Mode>,
+    _subscription: Subscription,
 }
 
 impl ModeIndicator {
-    pub fn new(mode: Mode) -> Self {
-        Self { mode }
+    pub fn new(cx: &mut ViewContext<Self>) -> Self {
+        let handle = cx.handle().downgrade();
+
+        let _subscription = cx.subscribe_global::<VimEvent, _>(move |&event, cx| {
+            if let Some(mode_indicator) = handle.upgrade(cx) {
+                match event {
+                    VimEvent::ModeChanged { mode } => {
+                        cx.update_window(mode_indicator.window_id(), |cx| {
+                            mode_indicator.update(cx, move |mode_indicator, cx| {
+                                mode_indicator.set_mode(mode, cx);
+                            })
+                        });
+                    }
+                }
+            }
+        });
+
+        cx.observe_global::<SettingsStore, _>(move |mode_indicator, cx| {
+            if settings::get::<VimModeSetting>(cx).0 {
+                mode_indicator.mode = cx
+                    .has_global::<Vim>()
+                    .then(|| cx.global::<Vim>().state.mode);
+            } else {
+                mode_indicator.mode.take();
+            }
+        })
+        .detach();
+
+        // Vim doesn't exist in some tests
+        let mode = cx
+            .has_global::<Vim>()
+            .then(|| cx.global::<Vim>().state.mode);
+
+        Self {
+            mode,
+            _subscription,
+        }
     }
 
     pub fn set_mode(&mut self, mode: Mode, cx: &mut ViewContext<Self>) {
-        if mode != self.mode {
-            self.mode = mode;
+        if self.mode != Some(mode) {
+            self.mode = Some(mode);
             cx.notify();
         }
     }
@@ -30,11 +70,16 @@ impl View for ModeIndicator {
     }
 
     fn render(&mut self, cx: &mut ViewContext<Self>) -> AnyElement<Self> {
+        let Some(mode) = self.mode.as_ref() else {
+            return Empty::new().into_any();
+        };
+
         let theme = &theme::current(cx).workspace.status_bar;
+
         // we always choose text to be 12 monospace characters
         // so that as the mode indicator changes, the rest of the
         // UI stays still.
-        let text = match self.mode {
+        let text = match mode {
             Mode::Normal => "-- NORMAL --",
             Mode::Insert => "-- INSERT --",
             Mode::Visual { line: false } => "-- VISUAL --",