macos: hook up change title events

include/ghostty.h

@@ -26,10 +26,12 @@ extern "C" {
 // structs. To find the Zig struct, grep for this type name. The documentation
 // for all of these types is available in the Zig source.
 typedef void (*ghostty_runtime_wakeup_cb)(void *);
+typedef void (*ghostty_runtime_set_title_cb)(void *, const char *);
 
 typedef struct {
     void *userdata;
     ghostty_runtime_wakeup_cb wakeup_cb;
+    ghostty_runtime_set_title_cb set_title_cb;
 } ghostty_runtime_config_s;
 
 typedef struct {

macos/Sources/GhosttyApp.swift

@@ -22,6 +22,7 @@ struct GhosttyApp: App {
             case .ready:
                 TerminalView(app: ghostty.app!)
                     .modifier(WindowObservationModifier())
+                    .navigationTitle(ghostty.title)
             }
         }
     }
@@ -35,6 +36,9 @@ class GhosttyState: ObservableObject {
     /// The readiness value of the state.
     @Published var readiness: Readiness = .loading
     
+    /// The title of the window as requested by the underlying terminal.
+    @Published var title: String = "Ghostty";
+    
     /// The ghostty global configuration.
     var config: ghostty_config_t? = nil
     
@@ -69,7 +73,8 @@ class GhosttyState: ObservableObject {
         // uses to interface with the application runtime environment.
         var runtime_cfg = ghostty_runtime_config_s(
             userdata: Unmanaged.passUnretained(self).toOpaque(),
-            wakeup_cb: { userdata in GhosttyState.wakeup(userdata) })
+            wakeup_cb: { userdata in GhosttyState.wakeup(userdata) },
+            set_title_cb: { userdata, title in GhosttyState.setTitle(userdata, title: title) })
 
         // Create the ghostty app.
         guard let app = ghostty_app_new(&runtime_cfg, cfg) else {
@@ -97,6 +102,14 @@ class GhosttyState: ObservableObject {
         DispatchQueue.main.async { state.appTick() }
     }
     
+    static func setTitle(_ userdata: UnsafeMutableRawPointer?, title: UnsafePointer<CChar>?) {
+        let state = Unmanaged<GhosttyState>.fromOpaque(userdata!).takeUnretainedValue()
+        guard let titleStr = String(cString: title!, encoding: .utf8) else { return }
+        DispatchQueue.main.async {
+            state.title = titleStr
+        }
+    }
+    
     deinit {
         ghostty_app_free(app)
         ghostty_config_free(config)

src/apprt/embedded.zig

@@ -29,6 +29,9 @@ pub const App = struct {
         /// Callback called to wakeup the event loop. This should trigger
         /// a full tick of the app loop.
         wakeup: *const fn (?*anyopaque) callconv(.C) void,
+
+        /// Called to set the title of the window.
+        set_title: *const fn (?*anyopaque, [*]const u8) callconv(.C) void,
     };
 
     opts: Options,
@@ -97,8 +100,10 @@ pub const Window = struct {
     }
 
     pub fn setTitle(self: *Window, slice: [:0]const u8) !void {
-        _ = self;
-        _ = slice;
+        self.core_win.app.runtime.opts.set_title(
+            self.core_win.app.runtime.opts.userdata,
+            slice.ptr,
+        );
     }
 
     pub fn getClipboardString(self: *const Window) ![:0]const u8 {