Add hook system.

src/Terminal.zig

@@ -52,11 +52,18 @@ on_exit: *const fn (ctx: ?*anyopaque) void,
 /// Called when this terminal takes keyboard focus.
 on_focus: *const fn (ctx: ?*anyopaque) void,
 
+/// Called when the child reports a change of state, so the owner can show
+/// it in the tab strip.
+on_status: *const fn (ctx: ?*anyopaque, status: Status) void,
+
 ctx: ?*anyopaque = null,
 
 /// What a layout can specify for a terminal pane.
 pub const Options = Session.Options;
 
+/// What the child is doing. Reported by the session; passed straight through.
+pub const Status = Session.Status;
+
 pub fn create(
     alloc: std.mem.Allocator,
     opts: Options,
@@ -76,6 +83,7 @@ pub fn create(
         .on_title = cbs.on_title,
         .on_exit = cbs.on_exit,
         .on_focus = cbs.on_focus,
+        .on_status = cbs.on_status,
         .ctx = cbs.ctx,
     };
 
@@ -87,6 +95,7 @@ pub fn create(
         .on_damage = &onDamage,
         .on_title = &onSessionTitle,
         .on_exit = &onSessionExit,
+        .on_status = &onSessionStatus,
         .ctx = self,
     });
     errdefer self.session.destroy();
@@ -189,6 +198,11 @@ fn onSessionTitle(ctx: ?*anyopaque, title: []const u8) void {
     self.on_title(self.ctx, title);
 }
 
+fn onSessionStatus(ctx: ?*anyopaque, status: Status) void {
+    const self: *Terminal = @ptrCast(@alignCast(ctx.?));
+    self.on_status(self.ctx, status);
+}
+
 fn onNotifyHasFocus(
     _: *gtk.DrawingArea,
     _: *gobject.ParamSpec,