gpui: Fix hide, activate method on Windows to hide/show application (#18164)

Release Notes:

- N/A

Continue #18161 to fix `cx.hide`, `cx.activate` method on Windows to
hide/show application.

## After


https://github.com/user-attachments/assets/fe0070f9-7844-4c2a-b859-3e22ee4b8d22

---------

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

crates/gpui/examples/window.rs

@@ -150,6 +150,18 @@ impl Render for WindowDemo {
                 )
                 .unwrap();
             }))
+            .child(button("Hide Application", |cx| {
+                cx.hide();
+
+                // Restore the application after 3 seconds
+                cx.spawn(|mut cx| async move {
+                    Timer::after(std::time::Duration::from_secs(3)).await;
+                    cx.update(|cx| {
+                        cx.activate(false);
+                    })
+                })
+                .detach();
+            }))
     }
 }
 

crates/gpui/src/platform/windows/platform.rs

@@ -33,6 +33,8 @@ use crate::*;
 pub(crate) struct WindowsPlatform {
     state: RefCell<WindowsPlatformState>,
     raw_window_handles: RwLock<SmallVec<[HWND; 4]>>,
+    // The window handles that are hided by `hide` method.
+    hidden_windows: RwLock<SmallVec<[HWND; 4]>>,
     // The below members will never change throughout the entire lifecycle of the app.
     icon: HICON,
     main_receiver: flume::Receiver<Runnable>,
@@ -100,6 +102,7 @@ impl WindowsPlatform {
         Self {
             state,
             raw_window_handles,
+            hidden_windows: RwLock::new(SmallVec::new()),
             icon,
             main_receiver,
             dispatch_event,
@@ -295,12 +298,25 @@ impl Platform for WindowsPlatform {
         }
     }
 
-    // todo(windows)
+    fn activate(&self, _ignoring_other_apps: bool) {
-    fn activate(&self, _ignoring_other_apps: bool) {}
+        let mut state = self.hidden_windows.write();
+        state.iter().for_each(|handle| unsafe {
+            ShowWindow(*handle, SW_SHOW).ok().log_err();
+        });
+        state.clear();
+    }
 
-    // todo(windows)
     fn hide(&self) {
-        unimplemented!()
+        let mut state = self.hidden_windows.write();
+        self.raw_window_handles
+            .read()
+            .iter()
+            .for_each(|handle| unsafe {
+                if IsWindowVisible(*handle).as_bool() {
+                    state.push(*handle);
+                    ShowWindow(*handle, SW_HIDE).ok().log_err();
+                }
+            });
     }
 
     // todo(windows)