Protocol 11: sit out replaces kicking; nudge

Anyone can sit anyone out (host included); only you bring yourself back.
Out members stay in chat and the party, never block or count, and load no
media; a card with the live position and Join back (Space) replaces the
video. The mini player's x sits you out; optionally idle does too. Nudge:
the server forwards it to the target only (3/s, 20/min per sender); the
target hears the nudge sound, gets a toast and a taskbar attention
request. Kick, its messages, errors and dialog are gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/windows/runner/flutter_window.cpp

@@ -2,6 +2,8 @@
 
 #include <optional>
 
+#include <flutter/standard_method_codec.h>
+
 #include "flutter/generated_plugin_registrant.h"
 
 FlutterWindow::FlutterWindow(const flutter::DartProject& project)
@@ -25,6 +27,24 @@ bool FlutterWindow::OnCreate() {
     return false;
   }
   RegisterPlugins(flutter_controller_->engine());
+  window_channel_ = std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
+      flutter_controller_->engine()->messenger(), "starsync/window",
+      &flutter::StandardMethodCodec::GetInstance());
+  window_channel_->SetMethodCallHandler(
+      [this](const flutter::MethodCall<flutter::EncodableValue>& call,
+             std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>> result) {
+        if (call.method_name() != "attention") {
+          result->NotImplemented();
+          return;
+        }
+        HWND hwnd = GetHandle();
+        if (hwnd != nullptr && GetForegroundWindow() != hwnd) {
+          // Flashes until the window comes to the front.
+          FLASHWINFO info{sizeof(FLASHWINFO), hwnd, FLASHW_ALL | FLASHW_TIMERNOFG, 0, 0};
+          FlashWindowEx(&info);
+        }
+        result->Success();
+      });
   SetChildContent(flutter_controller_->view()->GetNativeWindow());
 
   flutter_controller_->engine()->SetNextFrameCallback([&]() {
@@ -40,6 +60,7 @@ bool FlutterWindow::OnCreate() {
 }
 
 void FlutterWindow::OnDestroy() {
+  window_channel_ = nullptr;
   if (flutter_controller_) {
     flutter_controller_ = nullptr;
   }

apps/desktop/windows/runner/flutter_window.h

@@ -3,6 +3,8 @@
 
 #include <flutter/dart_project.h>
 #include <flutter/flutter_view_controller.h>
+#include <flutter/method_channel.h>
+#include <flutter/encodable_value.h>
 
 #include <memory>
 
@@ -28,6 +30,10 @@ class FlutterWindow : public Win32Window {
 
   // The Flutter instance hosted by this window.
   std::unique_ptr<flutter::FlutterViewController> flutter_controller_;
+
+  // "starsync/window": `attention` flashes the taskbar entry while the
+  // window is not in front (lib/src/platform/attention.dart).
+  std::unique_ptr<flutter::MethodChannel<flutter::EncodableValue>> window_channel_;
 };
 
 #endif  // RUNNER_FLUTTER_WINDOW_H_