fix(Windows): Send messages on main thread (workaround).

fixes #379

Author: llfbandit

record_windows/CHANGELOG.md

@@ -1,3 +1,6 @@
+## 1.0.5
+* fix: Send messages on main thread (workaround).
+
 ## 1.0.4
 * fix: Process path as wide string (UTF-16).
 

record_windows/pubspec.yaml

@@ -1,6 +1,6 @@
 name: record_windows
 description: Windows specific implementation for record package called by record_platform_interface.
-version: 1.0.4
+version: 1.0.5
 homepage: https://github.com/llfbandit/record/tree/master/record_windows
 
 environment:

record_windows/windows/record.cpp

@@ -1,29 +1,5 @@
-/*
-*
-* https://learn.microsoft.com/en-us/windows/uwp/audio-video-camera/codec-query
-* https://learn.microsoft.com/en-us/uwp/api/windows.media.core.codecsubtypes?view=winrt-22621
-*
-* https://github.com/microsoft/Windows-universal-samples/blob/main/Samples/CameraStarterKit/cpp/MainPage.xaml.h
-* https://github.com/microsoft/Windows-universal-samples/blob/main/Samples/CameraStarterKit/cpp/MainPage.xaml.cpp
-*
-* https://learn.microsoft.com/en-us/windows/win32/medfound/audio-video-capture
-* WMF FLAC https://stackoverflow.com/questions/48930499/how-do-i-encode-raw-48khz-32bits-pcm-to-flac-using-microsoft-media-foundation
-* WMF AAC https://learn.microsoft.com/en-us/windows/win32/medfound/aac-encoder
-* WMF https://learn.microsoft.com/en-us/windows/win32/medfound/audio-video-capture-in-media-foundation
-* https://learn.microsoft.com/en-us/windows/win32/medfound/tutorial--using-the-sink-writer-to-encode-video
-* https://learn.microsoft.com/en-us/windows/win32/medfound/audio-subtype-guids
-* https://github.com/microsoft/Windows-classic-samples/tree/main/Samples/Win7Samples/multimedia/mediafoundation/wavsink
-* https://learn.microsoft.com/fr-fr/windows/win32/api/_mf/
-* https://stackoverflow.com/questions/12917256/windows-media-foundation-recording-audio
-* https://github.com/sipsorcery/mediafoundationsamples/blob/master/MFAudioCaptureToSAR/MFAudioCaptureToSAR.cpp
-* https://chromium-review.googlesource.com/c/chromium/src/+/3293969
-*
-* https://learn.microsoft.com/en-us/windows/win32/medfound/uncompressed-audio-media-types
-*
-* https://learn.microsoft.com/en-us/windows/win32/medfound/tutorial--encoding-an-mp4-file-
-*/
-
 #include "record.h"
+#include "record_windows_plugin.h"
 
 namespace record_windows
 {
@@ -308,7 +284,9 @@ namespace record_windows
 		m_recordState = state;
 
 		if (m_stateEventHandler) {
-			m_stateEventHandler->Success(std::make_unique<flutter::EncodableValue>(state));
+			RecordWindowsPlugin::RunOnMainThread([this, state]() -> void {
+				m_stateEventHandler->Success(std::make_unique<flutter::EncodableValue>(state));
+			});
 		}
 	}
 

record_windows/windows/record_readercallback.cpp

@@ -1,4 +1,5 @@
 #include "record.h"
+#include "record_windows_plugin.h"
 
 namespace record_windows
 {
@@ -68,7 +69,10 @@ namespace record_windows
 							// Send data to stream when there's no writer
 							if (m_recordEventHandler && !m_pWriter) {
 								std::vector<uint8_t> bytes(pChunk, pChunk + size);
-								m_recordEventHandler->Success(std::make_unique<flutter::EncodableValue>(bytes));
+
+								RecordWindowsPlugin::RunOnMainThread([this, bytes]() -> void {
+									m_recordEventHandler->Success(std::make_unique<flutter::EncodableValue>(bytes));
+								});
 							}
 
 							GetAmplitude(pChunk, size, 2);

record_windows/windows/record_windows_plugin.cpp

@@ -21,17 +21,29 @@ namespace record_windows {
 		return hr;
 	}
 
-	void ErrorFromHR(HRESULT hr, MethodResult<EncodableValue>& result)
+	static void ErrorFromHR(HRESULT hr, MethodResult<EncodableValue>& result)
 	{
 		_com_error err(hr);
 		std::string errorText = Utf8FromUtf16(err.ErrorMessage());
 
 		result.Error("Record", "", EncodableValue(errorText));
 	}
 
+	static HWND GetRootWindow(flutter::FlutterView* view) {
+		return ::GetAncestor(view->GetNativeWindow(), GA_ROOT);
+	}
+
 	// static, Register the plugin
 	void RecordWindowsPlugin::RegisterWithRegistrar(flutter::PluginRegistrarWindows* registrar) {
-		auto plugin = std::make_unique<RecordWindowsPlugin>();
+		auto plugin = std::make_unique<RecordWindowsPlugin>(
+			[registrar](auto delegate) {
+				return registrar->RegisterTopLevelWindowProcDelegate(delegate);
+			},
+			[registrar](auto proc_id) {
+				registrar->UnregisterTopLevelWindowProcDelegate(proc_id);
+			},
+			[registrar] { return GetRootWindow(registrar->GetView()); }
+		);
 
 		m_binaryMessenger = registrar->messenger();
 
@@ -48,14 +60,56 @@ namespace record_windows {
 		registrar->AddPlugin(std::move(plugin));
 	}
 
-	RecordWindowsPlugin::RecordWindowsPlugin() {
+	// static
+	std::queue<std::function<void()>> RecordWindowsPlugin::callbacks{};
+
+	// static
+	FlutterRootWindowProvider RecordWindowsPlugin::get_root_window{};
+
+	// static
+	void RecordWindowsPlugin::RunOnMainThread(std::function<void()> callback) {
+		callbacks.push(callback);
+		PostMessage(get_root_window(), WM_RUN_DELEGATE, 0, 0);
+	}
+
+	RecordWindowsPlugin::RecordWindowsPlugin(
+		WindowProcDelegateRegistrator registrator,
+		WindowProcDelegateUnregistrator unregistrator,
+		FlutterRootWindowProvider window_provider
+	):	m_win_proc_delegate_registrator(registrator),
+		m_win_proc_delegate_unregistrator(unregistrator) {
+
+		get_root_window = std::move(window_provider);
+
+		m_window_proc_id = m_win_proc_delegate_registrator(
+			[this](HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
+				return HandleWindowProc(hwnd, message, wparam, lparam);
+			}
+		);
 	}
 
 	RecordWindowsPlugin::~RecordWindowsPlugin() {
 		for (const auto& [recorderId, recorder] : m_recorders)
 		{
 			recorder->Dispose();
 		}
+
+		m_win_proc_delegate_unregistrator(m_window_proc_id);
+	}
+
+	std::optional<LRESULT> RecordWindowsPlugin::HandleWindowProc(HWND hwnd,
+		UINT message,
+		WPARAM wparam,
+		LPARAM lparam) {
+		std::optional<LRESULT> result;
+		switch (message) {
+		case WM_RUN_DELEGATE:
+			callbacks.front()();
+			callbacks.pop();
+			result = 0;
+			break;
+		}
+		return result;
 	}
 
 	// Called when a method is called on this plugin's channel from Dart.
@@ -190,7 +244,8 @@ namespace record_windows {
 				EncodableMap({
 					{EncodableValue("current"), EncodableValue(amp["current"])},
 					{EncodableValue("max"), EncodableValue(amp["max"])}
-					}))
+					}
+				))
 			);
 		}
 		else if (method_call.method_name().compare("isEncoderSupported") == 0)

record_windows/windows/record_windows_plugin.h

@@ -18,24 +18,45 @@
 
 #include "utils.h"
 #include "record.h"
+#include <queue>
 
 using namespace flutter;
 
+#define WM_RUN_DELEGATE (WM_USER + 101)
+
 namespace record_windows {
 	typedef flutter::EventSink<flutter::EncodableValue> FlEventSink;
 	typedef flutter::StreamHandlerError<flutter::EncodableValue> FlStreamHandlerError;
 
+	using FlutterRootWindowProvider = std::function<HWND()>;
+	using WindowProcDelegate = std::function<std::optional<LRESULT>(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam)>;
+	using WindowProcDelegateRegistrator = std::function<int(WindowProcDelegate delegate)>;
+	using WindowProcDelegateUnregistrator = std::function<void(int proc_id)>;
+
 	class RecordWindowsPlugin : public flutter::Plugin {
 	public:
 		static void RegisterWithRegistrar(flutter::PluginRegistrarWindows* registrar);
 
-		RecordWindowsPlugin();
+		RecordWindowsPlugin(
+			WindowProcDelegateRegistrator registrator,
+			WindowProcDelegateUnregistrator unregistrator,
+			FlutterRootWindowProvider window_provider
+		);
 		virtual ~RecordWindowsPlugin();
 
 		// Disallow copy and assign.
 		RecordWindowsPlugin(const RecordWindowsPlugin&) = delete;
 		RecordWindowsPlugin& operator=(const RecordWindowsPlugin&) = delete;
 
+		// The function to call to get the root window.
+		static FlutterRootWindowProvider get_root_window;
+
+		// A queue of callbacks to run on the main thread.
+		static std::queue<std::function<void()>> callbacks;
+
+		// Runs the given callback on the main thread.
+		static void RunOnMainThread(std::function<void()> callback);
+
 	private:
 		static inline BinaryMessenger* m_binaryMessenger;
 
@@ -50,6 +71,16 @@ namespace record_windows {
 		std::unique_ptr<RecordConfig> InitRecordConfig(const EncodableMap* args);
 
 		std::map<std::string, std::unique_ptr<Recorder>> m_recorders{};
+
+		// Called for top-level WindowProc delegation.
+		std::optional<LRESULT> HandleWindowProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
+
+		// The registrar for this plugin, for registering top-level WindowProc delegates.
+		WindowProcDelegateRegistrator m_win_proc_delegate_registrator;
+		WindowProcDelegateUnregistrator m_win_proc_delegate_unregistrator;
+
+		// The ID of the WindowProc delegate registration.
+		int m_window_proc_id = -1;
 	};
 
 }  // namespace record_windows