Add window tray example

new Win32pai:
* Shell_NotifyIcon
* GetSubMenu
* DestroyMenu
* TrackPopupMenuEx

new struct:
* NOTIFYICONDATA
* TPMPARAMS

new constants:
* Shell_NotifyIcon uFlags
* Shell_NotifyIcon WndProc callback msg
* NOTIFYICONDATA::uFlags
* NOTIFYICONDATA::dwState
* NOTIFYICONDATA::dwInfoFlags
* TrackPopupMenuEx uFlag
* LoadImage type, fuLoad

example/shell_notify_icon/_app.dart

@@ -0,0 +1,69 @@
+import 'dart:ffi';
+import 'dart:io';
+
+import 'package:win32/win32.dart';
+
+final hInst = GetModuleHandle(nullptr);
+
+const EVENT_QUIT = WM_APP + 2;
+const EVENT_TRAY_NOTIFY = WM_APP + 1;
+
+typedef LocalWndProc = bool Function(int hWnd,
+    int uMsg, int wParam, int lParam);
+
+final wndProc = Pointer.fromFunction<WindowProc>(_appWndProc, 0);
+
+void exec() {
+  final msg = MSG.allocate().addressOf;
+  while (GetMessage(msg, NULL, 0, 0) != 0) {
+    TranslateMessage(msg);
+    DispatchMessage(msg);
+  }
+}
+
+int loadDartIcon() {
+  final dartIconPath = _thisPath('dart.ico');
+  return LoadImage(
+      0,
+      TEXT(dartIconPath),
+      IMAGE_ICON,
+      0,
+      0,
+      LR_LOADFROMFILE | LR_DEFAULTSIZE | LR_SHARED
+  );
+}
+
+final _localWndProcs = <LocalWndProc>[];
+
+/// Use in iterateLocalWndProcs
+void registryWdnProc(LocalWndProc proc) => _localWndProcs.add(proc);
+
+void deregisterWndProc(LocalWndProc proc) {
+  _localWndProcs.remove(proc);
+}
+int _appWndProc(int hWnd, int uMsg, int wParam, int lParam) {
+  if (iterateLocalWndProcs(hWnd, uMsg, wParam, lParam)) {
+    return TRUE;
+  }
+
+  switch(uMsg) {
+    case WM_CLOSE:
+      ShowWindow(hWnd, SW_HIDE);
+      return TRUE;
+  }
+  return DefWindowProc(hWnd, uMsg, wParam, lParam);
+}
+
+bool iterateLocalWndProcs(int hWnd, int uMsg, int wParam, int lParam) {
+  for(final proc in _localWndProcs) {
+    final isProcProcessed = proc(hWnd, uMsg, wParam, lParam);
+    if (isProcProcessed) {
+      return true;
+    }
+  }
+  return false;
+}
+
+String _thisPath(String fileName) =>  Platform.script
+    .toFilePath()
+    .replaceFirst(RegExp(r'[^\\]+$'), fileName);

example/shell_notify_icon/_menu.dart

@@ -0,0 +1,63 @@
+import 'dart:ffi';
+import 'dart:math';
+
+import 'package:ffi/ffi.dart';
+import 'package:win32/win32.dart';
+
+import '_app.dart' as app;
+import '_tray.dart' as tray;
+
+void show({required int hWndParent}) {
+  final mousePos = _currentMousePos();
+  final hMenu = _buildMenu();
+
+  SetForegroundWindow(hWndParent);
+  TrackPopupMenuEx(hMenu,
+      _contextMenuFlags,
+      mousePos.x, mousePos.y,
+      hWndParent, nullptr);
+
+  DestroyMenu(hMenu);
+}
+
+bool wndProc(int hWnd, int uMsg, int wParam, int lParam) {
+  switch (uMsg) {
+    case WM_COMMAND:
+      final param = LOWORD(wParam);
+      switch (param) {
+        case app.EVENT_QUIT:
+          tray.removeIcon();
+          PostQuitMessage(0);
+          return true;
+      }
+  }
+  return false;
+}
+
+int _buildMenu() {
+  final hMenu = CreateMenu();
+  AppendMenu(hMenu, MF_STRING, app.EVENT_QUIT, TEXT("&Quit"));
+
+  final hMenubar = CreateMenu();
+  AppendMenu(hMenubar, MF_POPUP, hMenu, TEXT("_Parent"));
+
+  return GetSubMenu(hMenubar, 0);
+}
+
+Point<int> _currentMousePos() {
+  final point = POINT.allocate();
+  GetCursorPos(point.addressOf);
+  final result = Point(point.x, point.y);
+  free(point.addressOf);
+  return result;
+}
+
+int get _contextMenuFlags  {
+  var uFlags = TPM_RIGHTBUTTON;
+  if (GetSystemMetrics(SM_MENUDROPALIGNMENT) != 0) {
+    uFlags |= TPM_RIGHTALIGN;
+  } else {
+    uFlags |= TPM_LEFTALIGN;
+  }
+  return uFlags;
+}

example/shell_notify_icon/_tray.dart

@@ -0,0 +1,65 @@
+import 'dart:ffi';
+import 'package:ffi/ffi.dart';
+import 'package:win32/win32.dart';
+
+import '_app.dart' as app;
+import '_menu.dart' as menu;
+
+NOTIFYICONDATA _nid = NOTIFYICONDATA.allocate();
+
+bool _trayWndProc(int hWnd, int msg, int wParam, int lParam)  {
+  switch (msg) {
+    case app.EVENT_TRAY_NOTIFY:
+      final trayMsg = _fixNotifyDataToVersion4(LOWORD(lParam));
+      switch (trayMsg) {
+        case NIN_SELECT:
+          ShowWindow(_nid.hWnd, IsWindowVisible(_nid.hWnd) == 1
+              ? SW_HIDE
+              : SW_SHOW);
+          SetForegroundWindow(_nid.hWnd);
+          return true;
+
+        case WM_CONTEXTMENU:
+          menu.show(hWndParent: hWnd);
+          return true;
+      }
+  }
+  return false;
+}
+
+void addIcon({required int hWndParent}) {
+  _nid.hWnd = hWndParent;
+  _nid.uFlags = NIF_ICON | NIF_TIP | NIF_MESSAGE | NIF_SHOWTIP | NIF_GUID;
+  _nid.szTip = 'Dart tray';
+  _nid.uCallbackMessage = app.EVENT_TRAY_NOTIFY;
+  _nid.hIcon = app.loadDartIcon();
+
+  Shell_NotifyIcon(NIM_ADD, _nid.addressOf);
+
+  // TODO: uVersion does not yet support. See NOTIFYICONDATA declaration
+  // nid.uVersion = 4;
+  // Shell_NotifyIcon(NIM_SETVERSION, nid.addressOf);
+
+  app.registryWdnProc(_trayWndProc);
+}
+
+void removeIcon() {
+  Shell_NotifyIcon(NIM_DELETE, _nid.addressOf);
+  free(_nid.addressOf);
+  app.deregisterWndProc(_trayWndProc);
+}
+
+int _fixNotifyDataToVersion4(int msg) {
+  switch(msg) {
+    case 521: return WM_MBUTTONDBLCLK;
+    case 520: return WM_MBUTTONUP;
+    case 519: return WM_MBUTTONDOWN;
+    case 517: return WM_CONTEXTMENU;
+    case 516: return WM_RBUTTONDOWN;
+    case 515: return WM_LBUTTONDBLCLK;
+    case 514: return NIN_SELECT;
+    case 513: return WM_LBUTTONDOWN;
+    case 512: return WM_MOUSEMOVE;
+  }
+  return msg;
+}

example/shell_notify_icon/_window.dart

@@ -0,0 +1,60 @@
+import 'dart:ffi';
+import 'dart:math' as math;
+
+import 'package:win32/win32.dart';
+
+import '_app.dart' as app;
+
+bool _windowWndProc(int hWnd, int uMsg, int wParam, int lParam) {
+  switch(uMsg) {
+    case WM_CLOSE:
+      ShowWindow(hWnd, SW_HIDE);
+      return true;
+  }
+  return false;
+}
+
+int createHidden() {
+  final windowClassNme = _regWinClass();
+  final rect = _getWindowCenterRect();
+  final hWnd = CreateWindowEx(
+      0,
+      TEXT(windowClassNme),
+      TEXT('Tray Callback Window'),
+      WS_OVERLAPPEDWINDOW,
+      rect.left,
+      rect.top,
+      rect.width,
+      rect.height,
+      NULL,
+      NULL,
+      app.hInst,
+      nullptr);
+  app.registryWdnProc(_windowWndProc);
+  return hWnd;
+}
+
+String _regWinClass() {
+  const windowClass = 'Tray_Callback_Window';
+  final wc = WNDCLASS.allocate();
+  wc.style = CS_HREDRAW | CS_VREDRAW;
+  wc.lpfnWndProc = app.wndProc;
+  wc.hInstance = app.hInst;
+  wc.hIcon = app.loadDartIcon();
+  wc.hCursor = LoadCursor(NULL, IDC_ARROW);
+  wc.lpszClassName = TEXT(windowClass);
+  RegisterClass(wc.addressOf);
+  return windowClass;
+}
+
+math.Rectangle<int> _getWindowCenterRect() {
+  const windowWidth = 500;
+  const windowHeight = 250;
+
+  final screenWidth = GetSystemMetrics(SM_CXFULLSCREEN);
+  final screenHeight = GetSystemMetrics(SM_CYFULLSCREEN);
+
+  final x = (screenWidth - windowWidth) ~/ 2;
+  final y = (screenHeight - windowHeight) ~/ 2;
+  return math.Rectangle(x, y, windowWidth, windowHeight);
+}

example/shell_notify_icon/main.dart

@@ -0,0 +1,12 @@
+import '_app.dart' as app;
+import '_menu.dart' as menu;
+import '_tray.dart' as tray;
+import '_window.dart' as window;
+
+void main() {
+  final hWnd = window.createHidden();
+  tray.addIcon(hWndParent: hWnd);
+  app.registryWdnProc(menu.wndProc);
+  app.exec();
+}
+