Add registerProtocol method

Author: lijy91

example/lib/main.dart

@@ -12,6 +12,9 @@ bool _initialUriIsHandled = false;
 void main() {
   if (Platform.isMacOS || Platform.isWindows) {
     enableUniLinksDesktop();
+    if (Platform.isWindows) {
+      registerProtocol('unilinks');
+    }
   }
   runApp(MaterialApp(home: MyApp()));
 }
@@ -266,6 +269,8 @@ List<String>? getCmds() {
     cmdSuffix = "'";
   } else if (Platform.isMacOS) {
     cmd = 'open';
+  } else if (Platform.isWindows) {
+    cmd = 'start';
   } else {
     return null;
   }

example/windows/runner/main.cpp

@@ -5,8 +5,19 @@
 #include "flutter_window.h"
 #include "utils.h"
 
+#include <protocol_handler/protocol_handler_plugin.h>
+
 int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
                       _In_ wchar_t *command_line, _In_ int show_command) {
+  HWND hwnd = ::FindWindow(L"FLUTTER_RUNNER_WIN32_WINDOW", L"uni_links_desktop_example");
+  if (hwnd != NULL) {
+    DispatchToProtocolHandler(hwnd);
+
+    ::ShowWindow(hwnd, SW_NORMAL);
+    ::SetForegroundWindow(hwnd);
+    return EXIT_FAILURE;
+  }
+
   // Attach to console when present (e.g., 'flutter run') or create a
   // new console when running with a debugger.
   if (!::AttachConsole(ATTACH_PARENT_PROCESS) && ::IsDebuggerPresent()) {

lib/src/uni_links_desktop.dart

@@ -9,6 +9,10 @@ void enableUniLinksDesktop() {
   UniLinksPlatform.instance = UniLinksDesktop();
 }
 
+void registerProtocol(String scheme) {
+  protocolHandler.register(scheme);
+}
+
 class UniLinksDesktop extends UniLinksPlatform with ProtocolListener {
   /// Registers this class as the default instance of [UniLinksDesktop].
   static void registerWith() {