Invalidate view when entering/exiting fullscreen

This is required for `render_titlebar` to eventually adapt to
fullscreen status to affect the size of left padding on workspace
name to account for the traffic lights presence/absence

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/gpui/src/app.rs

@@ -959,6 +959,7 @@ type GlobalObservationCallback = Box<dyn FnMut(&mut MutableAppContext)>;
 type ReleaseObservationCallback = Box<dyn FnOnce(&dyn Any, &mut MutableAppContext)>;
 type ActionObservationCallback = Box<dyn FnMut(TypeId, &mut MutableAppContext)>;
 type WindowActivationCallback = Box<dyn FnMut(bool, &mut MutableAppContext) -> bool>;
+type WindowFullscreenCallback = Box<dyn FnMut(bool, &mut MutableAppContext) -> bool>;
 type DeserializeActionCallback = fn(json: &str) -> anyhow::Result<Box<dyn Action>>;
 type WindowShouldCloseSubscriptionCallback = Box<dyn FnMut(&mut MutableAppContext) -> bool>;
 
@@ -1069,6 +1070,7 @@ pub struct MutableAppContext {
     subscriptions: SubscriptionMappings<usize, SubscriptionCallback>,
     observations: SubscriptionMappings<usize, ObservationCallback>,
     window_activation_observations: SubscriptionMappings<usize, WindowActivationCallback>,
+    window_fullscreen_observations: SubscriptionMappings<usize, WindowFullscreenCallback>,
 
     release_observations: Arc<Mutex<HashMap<usize, BTreeMap<usize, ReleaseObservationCallback>>>>,
     action_dispatch_observations: Arc<Mutex<BTreeMap<usize, ActionObservationCallback>>>,
@@ -1126,6 +1128,7 @@ impl MutableAppContext {
             release_observations: Default::default(),
             global_observations: Default::default(),
             window_activation_observations: Default::default(),
+            window_fullscreen_observations: Default::default(),
             action_dispatch_observations: Default::default(),
             presenters_and_platform_windows: HashMap::new(),
             foreground,
@@ -1662,6 +1665,26 @@ impl MutableAppContext {
         }
     }
 
+    fn observe_fullscreen<F>(&mut self, window_id: usize, callback: F) -> Subscription
+    where
+        F: 'static + FnMut(bool, &mut MutableAppContext) -> bool,
+    {
+        let subscription_id = post_inc(&mut self.next_subscription_id);
+        self.pending_effects
+            .push_back(Effect::WindowFullscreenObservation {
+                window_id,
+                subscription_id,
+                callback: Box::new(callback),
+            });
+        Subscription::WindowFullscreenObservation {
+            id: subscription_id,
+            window_id,
+            observations: Some(Arc::downgrade(
+                &self.window_activation_observations.internal,
+            )),
+        }
+    }
+
     pub fn defer(&mut self, callback: impl 'static + FnOnce(&mut MutableAppContext)) {
         self.pending_effects.push_back(Effect::Deferred {
             callback: Box::new(callback),
@@ -2361,6 +2384,16 @@ impl MutableAppContext {
                             is_active,
                         } => self.handle_window_activation_effect(window_id, is_active),
 
+                        Effect::WindowFullscreenObservation {
+                            window_id,
+                            subscription_id,
+                            callback,
+                        } => self.window_fullscreen_observations.add_or_remove_callback(
+                            window_id,
+                            subscription_id,
+                            callback,
+                        ),
+
                         Effect::FullscreenWindow {
                             window_id,
                             is_fullscreen,
@@ -2535,6 +2568,11 @@ impl MutableAppContext {
             let window = this.cx.windows.get_mut(&window_id)?;
             window.is_fullscreen = is_fullscreen;
 
+            let mut observations = this.window_fullscreen_observations.clone_ref();
+            observations.emit_and_cleanup(window_id, this, |callback, this| {
+                callback(is_fullscreen, this)
+            });
+
             Some(())
         });
     }
@@ -3019,6 +3057,11 @@ pub enum Effect {
         subscription_id: usize,
         callback: WindowActivationCallback,
     },
+    WindowFullscreenObservation {
+        window_id: usize,
+        subscription_id: usize,
+        callback: WindowFullscreenCallback,
+    },
     RefreshWindows,
     ActionDispatchNotification {
         action_id: TypeId,
@@ -3136,6 +3179,15 @@ impl Debug for Effect {
                 .field("window_id", window_id)
                 .field("is_fullscreen", is_fullscreen)
                 .finish(),
+            Effect::WindowFullscreenObservation {
+                window_id,
+                subscription_id,
+                callback: _,
+            } => f
+                .debug_struct("Effect::WindowFullscreenObservation")
+                .field("window_id", window_id)
+                .field("subscription_id", subscription_id)
+                .finish(),
             Effect::RefreshWindows => f.debug_struct("Effect::FullViewRefresh").finish(),
             Effect::WindowShouldCloseSubscription { window_id, .. } => f
                 .debug_struct("Effect::WindowShouldCloseSubscription")
@@ -3807,6 +3859,24 @@ impl<'a, T: View> ViewContext<'a, T> {
             })
     }
 
+    pub fn observe_fullscreen<F>(&mut self, mut callback: F) -> Subscription
+    where
+        F: 'static + FnMut(&mut T, bool, &mut ViewContext<T>),
+    {
+        let observer = self.weak_handle();
+        self.app
+            .observe_fullscreen(self.window_id(), move |active, cx| {
+                if let Some(observer) = observer.upgrade(cx) {
+                    observer.update(cx, |observer, cx| {
+                        callback(observer, active, cx);
+                    });
+                    true
+                } else {
+                    false
+                }
+            })
+    }
+
     pub fn emit(&mut self, payload: T::Event) {
         self.app.pending_effects.push_back(Effect::Event {
             entity_id: self.view_id,
@@ -5128,6 +5198,12 @@ pub enum Subscription {
         observations:
             Option<Weak<Mutex<HashMap<usize, BTreeMap<usize, Option<WindowActivationCallback>>>>>>,
     },
+    WindowFullscreenObservation {
+        id: usize,
+        window_id: usize,
+        observations:
+            Option<Weak<Mutex<HashMap<usize, BTreeMap<usize, Option<WindowActivationCallback>>>>>>,
+    },
 }
 
 impl Subscription {
@@ -5157,6 +5233,9 @@ impl Subscription {
             Subscription::WindowActivationObservation { observations, .. } => {
                 observations.take();
             }
+            Subscription::WindowFullscreenObservation { observations, .. } => {
+                observations.take();
+            }
         }
     }
 }
@@ -5291,6 +5370,27 @@ impl Drop for Subscription {
                     }
                 }
             }
+            Subscription::WindowFullscreenObservation {
+                id,
+                window_id,
+                observations,
+            } => {
+                if let Some(observations) = observations.as_ref().and_then(Weak::upgrade) {
+                    match observations
+                        .lock()
+                        .entry(*window_id)
+                        .or_default()
+                        .entry(*id)
+                    {
+                        btree_map::Entry::Vacant(entry) => {
+                            entry.insert(None);
+                        }
+                        btree_map::Entry::Occupied(entry) => {
+                            entry.remove();
+                        }
+                    }
+                }
+            }
         }
     }
 }

crates/workspace/src/workspace.rs

@@ -823,6 +823,8 @@ enum FollowerItem {
 
 impl Workspace {
     pub fn new(project: ModelHandle<Project>, cx: &mut ViewContext<Self>) -> Self {
+        cx.observe_fullscreen(|_, _, cx| cx.notify()).detach();
+
         cx.observe_window_activation(Self::on_window_activation_changed)
             .detach();
         cx.observe(&project, |_, _, cx| cx.notify()).detach();