windows: TrayIcon SetTooltip + Readd (TaskbarCreated recovery)

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+- The Windows tray icon (`rivet::system::TrayIcon`) can update its tooltip
+  (`SetTooltip`) and re-register itself after an Explorer restart
+  (`Readd`, called from the host's `TaskbarCreated` broadcast handler) —
+  state-aware tray apps no longer re-allocate the icon to relabel it and no
+  longer lose it the first time the shell restarts. `TrayIcon` owns an icon
+  copy so recovery does not impose a new lifetime requirement on callers.
+
 - Bound and retry Ubuntu runner package-manager operations so a stalled mirror
   cannot consume an entire desktop validation job without a useful failure.
 - Removed the misleading `rivet-type` runtime descriptors from the pre-1.0

platform/windows/system/system_services.cpp

@@ -123,24 +123,60 @@ void Autostart::SetEnabled(std::wstring const& application_id,
 
 TrayIcon::TrayIcon(HWND window, UINT identifier, UINT callback_message,
                    std::wstring const& tooltip, HICON icon)
-    : window_(window), identifier_(identifier) {
+    : window_(window),
+      identifier_(identifier),
+      callback_message_(callback_message),
+      tooltip_(tooltip) {
+  icon_ = ::CopyIcon(icon);
+  if (icon_ == nullptr) ThrowLastError("CopyIcon");
+  try {
+    Add();
+  } catch (...) {
+    ::DestroyIcon(icon_);
+    icon_ = nullptr;
+    throw;
+  }
+}
+
+TrayIcon::~TrayIcon() {
+  NOTIFYICONDATAW data{};
+  data.cbSize = sizeof(data);
+  data.hWnd = window_;
+  data.uID = identifier_;
+  ::Shell_NotifyIconW(NIM_DELETE, &data);
+  if (icon_ != nullptr) ::DestroyIcon(icon_);
+}
+
+void TrayIcon::Add() {
   NOTIFYICONDATAW data{};
   data.cbSize = sizeof(data);
-  data.hWnd = window;
-  data.uID = identifier;
+  data.hWnd = window_;
+  data.uID = identifier_;
   data.uFlags = NIF_MESSAGE | NIF_TIP | NIF_ICON;
-  data.uCallbackMessage = callback_message;
-  data.hIcon = icon;
-  wcsncpy_s(data.szTip, tooltip.c_str(), _TRUNCATE);
+  data.uCallbackMessage = callback_message_;
+  data.hIcon = icon_;
+  wcsncpy_s(data.szTip, tooltip_.c_str(), _TRUNCATE);
   if (!::Shell_NotifyIconW(NIM_ADD, &data)) ThrowLastError("Shell_NotifyIconW");
 }
 
-TrayIcon::~TrayIcon() {
+void TrayIcon::SetTooltip(std::wstring const& tooltip) {
+  tooltip_ = tooltip;
+  NOTIFYICONDATAW data{};
+  data.cbSize = sizeof(data);
+  data.hWnd = window_;
+  data.uID = identifier_;
+  data.uFlags = NIF_TIP;
+  wcsncpy_s(data.szTip, tooltip_.c_str(), _TRUNCATE);
+  if (!::Shell_NotifyIconW(NIM_MODIFY, &data)) ThrowLastError("Shell_NotifyIconW");
+}
+
+void TrayIcon::Readd() {
   NOTIFYICONDATAW data{};
   data.cbSize = sizeof(data);
   data.hWnd = window_;
   data.uID = identifier_;
   ::Shell_NotifyIconW(NIM_DELETE, &data);
+  Add();
 }
 
 void TrayIcon::Notify(std::wstring const& title,

platform/windows/system/system_services.hpp

@@ -58,7 +58,10 @@ class Autostart final {
 };
 
 // Uses the first-party Shell_NotifyIcon surface. The owning HWND receives
-// callback_message for tray activation and must stay on the WinUI UI thread.
+// callback_message for tray activation and must stay on the WinUI UI thread;
+// the application intercepts callback_message (SetWindowSubclass) and also
+// forwards the TaskbarCreated broadcast to Readd() so the icon survives an
+// Explorer restart.
 class TrayIcon final {
  public:
   TrayIcon(HWND window, UINT identifier, UINT callback_message,
@@ -67,11 +70,24 @@ class TrayIcon final {
   TrayIcon(TrayIcon const&) = delete;
   TrayIcon& operator=(TrayIcon const&) = delete;
 
+  // The constructor copies `icon`; the caller retains ownership of its input
+  // handle and may release it immediately after construction.
+  // State labels change with the application (running/paused, today's
+  // totals); NIM_MODIFY with NIF_TIP, no re-add needed.
+  void SetTooltip(std::wstring const& tooltip);
+  // TaskbarCreated handler: NIM_DELETE + NIM_ADD with the stored payload.
+  // Cheap enough to call unconditionally from the broadcast path.
+  void Readd();
   void Notify(std::wstring const& title, std::wstring const& body) const;
 
  private:
+  void Add();
+
   HWND window_{};
   UINT identifier_{};
+  UINT callback_message_{};
+  std::wstring tooltip_;
+  HICON icon_{};
 };
 
 using CrashCallback = void (*)(EXCEPTION_POINTERS const*) noexcept;