diff options
Diffstat (limited to 'src/corelib/kernel/qeventdispatcher_wasm.cpp')
| -rw-r--r-- | src/corelib/kernel/qeventdispatcher_wasm.cpp | 1000 |
1 files changed, 1000 insertions, 0 deletions
diff --git a/src/corelib/kernel/qeventdispatcher_wasm.cpp b/src/corelib/kernel/qeventdispatcher_wasm.cpp new file mode 100644 index 0000000000..4aa435b64b --- /dev/null +++ b/src/corelib/kernel/qeventdispatcher_wasm.cpp @@ -0,0 +1,1000 @@ +// Copyright (C) 2021 The Qt Company Ltd. +// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only + +#include "qeventdispatcher_wasm_p.h" + +#include <QtCore/private/qabstracteventdispatcher_p.h> // for qGlobalPostedEventsCount() +#include <QtCore/qcoreapplication.h> +#include <QtCore/qthread.h> +#include <QtCore/qsocketnotifier.h> +#include <QtCore/private/qstdweb_p.h> + +#include "emscripten.h" +#include <emscripten/html5.h> +#include <emscripten/threading.h> +#include <emscripten/val.h> + +using namespace std::chrono; +using namespace std::chrono_literals; + +QT_BEGIN_NAMESPACE + +// using namespace emscripten; + +Q_LOGGING_CATEGORY(lcEventDispatcher, "qt.eventdispatcher"); +Q_LOGGING_CATEGORY(lcEventDispatcherTimers, "qt.eventdispatcher.timers"); + +#if QT_CONFIG(thread) +#define LOCK_GUARD(M) std::lock_guard<std::mutex> lock(M) +#else +#define LOCK_GUARD(M) +#endif + +// Emscripten asyncify currently supports one level of suspend - +// recursion is not permitted. We track the suspend state here +// on order to fail (more) gracefully, but we can of course only +// track Qts own usage of asyncify. +static bool g_is_asyncify_suspended = false; + +#if defined(QT_STATIC) + +static bool useAsyncify() +{ + return qstdweb::haveAsyncify(); +} + +static bool useJspi() +{ + return qstdweb::haveJspi(); +} + +// clang-format off +EM_ASYNC_JS(void, qt_jspi_suspend_js, (), { + ++Module.qtJspiSuspensionCounter; + + await new Promise(resolve => { + Module.qtAsyncifyWakeUp.push(resolve); + }); +}); + +EM_JS(bool, qt_jspi_resume_js, (), { + if (!Module.qtJspiSuspensionCounter) + return false; + + --Module.qtJspiSuspensionCounter; + + setTimeout(() => { + const wakeUp = (Module.qtAsyncifyWakeUp ?? []).pop(); + if (wakeUp) wakeUp(); + }); + return true; +}); + +EM_JS(bool, qt_jspi_can_resume_js, (), { + return Module.qtJspiSuspensionCounter > 0; +}); + +EM_JS(void, init_jspi_support_js, (), { + Module.qtAsyncifyWakeUp = []; + Module.qtJspiSuspensionCounter = 0; +}); +// clang-format on + +void initJspiSupport() { + init_jspi_support_js(); +} + +Q_CONSTRUCTOR_FUNCTION(initJspiSupport); + +// clang-format off +EM_JS(void, qt_asyncify_suspend_js, (), { + if (Module.qtSuspendId === undefined) + Module.qtSuspendId = 0; + let sleepFn = (wakeUp) => { + Module.qtAsyncifyWakeUp = wakeUp; + }; + ++Module.qtSuspendId; + return Asyncify.handleSleep(sleepFn); +}); + +EM_JS(void, qt_asyncify_resume_js, (), { + let wakeUp = Module.qtAsyncifyWakeUp; + if (wakeUp == undefined) + return; + Module.qtAsyncifyWakeUp = undefined; + const suspendId = Module.qtSuspendId; + + // Delayed wakeup with zero-timer. Workaround/fix for + // https://github.com/emscripten-core/emscripten/issues/10515 + setTimeout(() => { + // Another suspend occurred while the timeout was in queue. + if (Module.qtSuspendId !== suspendId) + return; + wakeUp(); + }); +}); +// clang-format on + +#else + +// EM_JS is not supported for side modules; disable asyncify + +static bool useAsyncify() +{ + return false; +} + +static bool useJspi() +{ + return false; +} + +void qt_jspi_suspend_js() +{ + Q_UNREACHABLE(); +} + +bool qt_jspi_resume_js() +{ + Q_UNREACHABLE(); + return false; +} + +bool qt_jspi_can_resume_js() +{ + Q_UNREACHABLE(); + return false; +} + +void qt_asyncify_suspend_js() +{ + Q_UNREACHABLE(); +} + +void qt_asyncify_resume_js() +{ + Q_UNREACHABLE(); +} + +#endif // defined(QT_STATIC) + +// Suspends the main thread until qt_asyncify_resume() is called. Returns +// false immediately if Qt has already suspended the main thread (recursive +// suspend is not supported by Emscripten). Returns true (after resuming), +// if the thread was suspended. +bool qt_asyncify_suspend() +{ + if (g_is_asyncify_suspended) + return false; + g_is_asyncify_suspended = true; + qt_asyncify_suspend_js(); + return true; +} + +// Wakes any currently suspended main thread. Returns true if the main +// thread was suspended, in which case it will now be asynchronously woken. +void qt_asyncify_resume() +{ + if (!g_is_asyncify_suspended) + return; + g_is_asyncify_suspended = false; + qt_asyncify_resume_js(); +} + + +Q_CONSTINIT QEventDispatcherWasm *QEventDispatcherWasm::g_mainThreadEventDispatcher = nullptr; +#if QT_CONFIG(thread) +Q_CONSTINIT QVector<QEventDispatcherWasm *> QEventDispatcherWasm::g_secondaryThreadEventDispatchers; +Q_CONSTINIT std::mutex QEventDispatcherWasm::g_staticDataMutex; +emscripten::ProxyingQueue QEventDispatcherWasm::g_proxyingQueue; +pthread_t QEventDispatcherWasm::g_mainThread; +#endif +// ### dynamic initialization: +std::multimap<int, QSocketNotifier *> QEventDispatcherWasm::g_socketNotifiers; +std::map<int, QEventDispatcherWasm::SocketReadyState> QEventDispatcherWasm::g_socketState; + +QEventDispatcherWasm::QEventDispatcherWasm() +{ + // QEventDispatcherWasm operates in two main modes: + // - On the main thread: + // The event dispatcher can process native events but can't + // block and wait for new events, unless asyncify is used. + // - On a secondary thread: + // The event dispatcher can't process native events but can + // block and wait for new events. + // + // Which mode is determined by the calling thread: construct + // the event dispatcher object on the thread where it will live. + + qCDebug(lcEventDispatcher) << "Creating QEventDispatcherWasm instance" << this + << "is main thread" << emscripten_is_main_runtime_thread(); + + if (emscripten_is_main_runtime_thread()) { + // There can be only one main thread event dispatcher at a time; in + // addition the main instance is used by the secondary thread event + // dispatchers so we set a global pointer to it. + Q_ASSERT(g_mainThreadEventDispatcher == nullptr); + g_mainThreadEventDispatcher = this; +#if QT_CONFIG(thread) + g_mainThread = pthread_self(); +#endif + + // Call the "onLoaded" JavaScript callback, unless startup tasks + // have been registered which should complete first. Run async + // to make sure event dispatcher construction (in particular any + // subclass construction) has completed first. + runAsync(callOnLoadedIfRequired); + } else { +#if QT_CONFIG(thread) + std::lock_guard<std::mutex> lock(g_staticDataMutex); + g_secondaryThreadEventDispatchers.append(this); +#endif + } +} + +QEventDispatcherWasm::~QEventDispatcherWasm() +{ + qCDebug(lcEventDispatcher) << "Destroying QEventDispatcherWasm instance" << this; + + delete m_timerInfo; + +#if QT_CONFIG(thread) + if (isSecondaryThreadEventDispatcher()) { + std::lock_guard<std::mutex> lock(g_staticDataMutex); + g_secondaryThreadEventDispatchers.remove(g_secondaryThreadEventDispatchers.indexOf(this)); + } else +#endif + { + if (m_timerId > 0) + emscripten_clear_timeout(m_timerId); + if (!g_socketNotifiers.empty()) { + qWarning("QEventDispatcherWasm: main thread event dispatcher deleted with active socket notifiers"); + clearEmscriptenSocketCallbacks(); + g_socketNotifiers.clear(); + } + g_mainThreadEventDispatcher = nullptr; + if (!g_socketNotifiers.empty()) { + qWarning("QEventDispatcherWasm: main thread event dispatcher deleted with active socket notifiers"); + clearEmscriptenSocketCallbacks(); + g_socketNotifiers.clear(); + } + + g_socketState.clear(); + } +} + +bool QEventDispatcherWasm::isMainThreadEventDispatcher() +{ + return this == g_mainThreadEventDispatcher; +} + +bool QEventDispatcherWasm::isSecondaryThreadEventDispatcher() +{ + return this != g_mainThreadEventDispatcher; +} + +bool QEventDispatcherWasm::isValidEventDispatcherPointer(QEventDispatcherWasm *eventDispatcher) +{ + if (eventDispatcher == g_mainThreadEventDispatcher) + return true; +#if QT_CONFIG(thread) + if (g_secondaryThreadEventDispatchers.contains(eventDispatcher)) + return true; +#endif + return false; +} + +bool QEventDispatcherWasm::processEvents(QEventLoop::ProcessEventsFlags flags) +{ + qCDebug(lcEventDispatcher) << "QEventDispatcherWasm::processEvents flags" << flags; + + emit awake(); + + if (isMainThreadEventDispatcher()) { + if (flags & QEventLoop::DialogExec) + handleDialogExec(); + else if (flags & QEventLoop::ApplicationExec) + handleApplicationExec(); + } + +#if QT_CONFIG(thread) + { + // Reset wakeUp state: if wakeUp() was called at some point before + // this then processPostedEvents() below will service that call. + std::unique_lock<std::mutex> lock(m_mutex); + m_wakeUpCalled = false; + } +#endif + + processPostedEvents(); + + // The processPostedEvents() call above may process an event which deletes the + // application object and the event dispatcher; stop event processing in that case. + if (!isValidEventDispatcherPointer(this)) + return false; + + if (m_interrupted) { + m_interrupted = false; + return false; + } + + if (flags & QEventLoop::WaitForMoreEvents) + wait(); + + if (m_processTimers) { + m_processTimers = false; + processTimers(); + } + + return false; +} + +void QEventDispatcherWasm::registerSocketNotifier(QSocketNotifier *notifier) +{ + LOCK_GUARD(g_staticDataMutex); + + bool wasEmpty = g_socketNotifiers.empty(); + g_socketNotifiers.insert({notifier->socket(), notifier}); + if (wasEmpty) + runOnMainThread([] { setEmscriptenSocketCallbacks(); }); +} + +void QEventDispatcherWasm::unregisterSocketNotifier(QSocketNotifier *notifier) +{ + LOCK_GUARD(g_staticDataMutex); + + auto notifiers = g_socketNotifiers.equal_range(notifier->socket()); + for (auto it = notifiers.first; it != notifiers.second; ++it) { + if (it->second == notifier) { + g_socketNotifiers.erase(it); + break; + } + } + + if (g_socketNotifiers.empty()) + runOnMainThread([] { clearEmscriptenSocketCallbacks(); }); +} + +void QEventDispatcherWasm::registerTimer(Qt::TimerId timerId, Duration interval, Qt::TimerType timerType, QObject *object) +{ +#ifndef QT_NO_DEBUG + if (qToUnderlying(timerId) < 1 || interval < 0ns || !object) { + qWarning("QEventDispatcherWasm::registerTimer: invalid arguments"); + return; + } else if (object->thread() != thread() || thread() != QThread::currentThread()) { + qWarning("QEventDispatcherWasm::registerTimer: timers cannot be started from another " + "thread"); + return; + } +#endif + qCDebug(lcEventDispatcherTimers) << "registerTimer" << int(timerId) << interval << timerType << object; + + m_timerInfo->registerTimer(timerId, interval, timerType, object); + updateNativeTimer(); +} + +bool QEventDispatcherWasm::unregisterTimer(Qt::TimerId timerId) +{ +#ifndef QT_NO_DEBUG + if (qToUnderlying(timerId) < 1) { + qWarning("QEventDispatcherWasm::unregisterTimer: invalid argument"); + return false; + } else if (thread() != QThread::currentThread()) { + qWarning("QEventDispatcherWasm::unregisterTimer: timers cannot be stopped from another " + "thread"); + return false; + } +#endif + + qCDebug(lcEventDispatcherTimers) << "unregisterTimer" << int(timerId); + + bool ans = m_timerInfo->unregisterTimer(timerId); + updateNativeTimer(); + return ans; +} + +bool QEventDispatcherWasm::unregisterTimers(QObject *object) +{ +#ifndef QT_NO_DEBUG + if (!object) { + qWarning("QEventDispatcherWasm::unregisterTimers: invalid argument"); + return false; + } else if (object->thread() != thread() || thread() != QThread::currentThread()) { + qWarning("QEventDispatcherWasm::unregisterTimers: timers cannot be stopped from another " + "thread"); + return false; + } +#endif + + qCDebug(lcEventDispatcherTimers) << "registerTimer" << object; + + bool ans = m_timerInfo->unregisterTimers(object); + updateNativeTimer(); + return ans; +} + +QList<QAbstractEventDispatcher::TimerInfoV2> +QEventDispatcherWasm::timersForObject(QObject *object) const +{ +#ifndef QT_NO_DEBUG + if (!object) { + qWarning("QEventDispatcherWasm:registeredTimers: invalid argument"); + return {}; + } +#endif + + return m_timerInfo->registeredTimers(object); +} + +QEventDispatcherWasm::Duration QEventDispatcherWasm::remainingTime(Qt::TimerId timerId) const +{ + return m_timerInfo->remainingDuration(timerId); +} + +void QEventDispatcherWasm::interrupt() +{ + m_interrupted = true; + wakeUp(); +} + +void QEventDispatcherWasm::wakeUp() +{ + // The event dispatcher thread may be blocked or suspended by + // wait(), or control may have been returned to the browser's + // event loop. Make sure the thread is unblocked or make it + // process events. + bool wasBlocked = wakeEventDispatcherThread(); + // JSPI does not need a scheduled call to processPostedEvents, as the stack is not unwound + // at startup. + if (!qstdweb::haveJspi() && !wasBlocked && isMainThreadEventDispatcher()) { + { + LOCK_GUARD(m_mutex); + if (m_pendingProcessEvents) + return; + m_pendingProcessEvents = true; + } + runOnMainThreadAsync([this](){ + QEventDispatcherWasm::callProcessPostedEvents(this); + }); + } +} + +void QEventDispatcherWasm::handleApplicationExec() +{ + // Start the main loop, and then stop it on the first callback. This + // is done for the "simulateInfiniteLoop" functionality where + // emscripten_set_main_loop() throws a JS exception which returns + // control to the browser while preserving the C++ stack. + // + // Note that we don't use asyncify here: Emscripten supports one level of + // asyncify only and we want to reserve that for dialog exec() instead of + // using it for the one qApp exec(). + // When JSPI is used, awaited async calls are allowed to be nested, so we + // proceed normally. + if (!qstdweb::haveJspi()) { + const bool simulateInfiniteLoop = true; + emscripten_set_main_loop([](){ + emscripten_pause_main_loop(); + }, 0, simulateInfiniteLoop); + } +} + +void QEventDispatcherWasm::handleDialogExec() +{ + if (!useAsyncify()) { + qWarning() << "Warning: exec() is not supported on Qt for WebAssembly in this configuration. Please build" + << "with asyncify support, or use an asynchronous API like QDialog::open()"; + emscripten_sleep(1); // This call never returns + } + // For the asyncify case we do nothing here and wait for events in wait() +} + +// Blocks/suspends the calling thread. This is possible in two cases: +// - Caller is a secondary thread: block on m_moreEvents +// - Caller is the main thread and asyncify is enabled: suspend using qt_asyncify_suspend() +// Returns false if the wait timed out. +bool QEventDispatcherWasm::wait(int timeout) +{ +#if QT_CONFIG(thread) + using namespace std::chrono_literals; + Q_ASSERT(QThread::currentThread() == thread()); + + if (isSecondaryThreadEventDispatcher()) { + std::unique_lock<std::mutex> lock(m_mutex); + + // If wakeUp() was called there might be pending events in the event + // queue which should be processed. Don't block, instead return + // so that the event loop can spin and call processEvents() again. + if (m_wakeUpCalled) + return true; + + auto wait_time = timeout > 0 ? timeout * 1ms : std::chrono::duration<int, std::micro>::max(); + bool wakeUpCalled = m_moreEvents.wait_for(lock, wait_time, [=] { return m_wakeUpCalled; }); + return wakeUpCalled; + } +#endif + Q_ASSERT(emscripten_is_main_runtime_thread()); + Q_ASSERT(isMainThreadEventDispatcher()); + if (useAsyncify()) { + if (timeout > 0) + qWarning() << "QEventDispatcherWasm asyncify wait with timeout is not supported; timeout will be ignored"; // FIXME + + if (useJspi()) { + qt_jspi_suspend_js(); + } else { + bool didSuspend = qt_asyncify_suspend(); + if (!didSuspend) { + qWarning("QEventDispatcherWasm: current thread is already suspended; could not asyncify wait for events"); + return false; + } + } + return true; + } else { + qWarning("QEventLoop::WaitForMoreEvents is not supported on the main thread without asyncify"); + Q_UNUSED(timeout); + } + return false; +} + +// Wakes a blocked/suspended event dispatcher thread. Returns true if the +// thread is unblocked or was resumed, false if the thread state could not +// be determined. +bool QEventDispatcherWasm::wakeEventDispatcherThread() +{ +#if QT_CONFIG(thread) + if (isSecondaryThreadEventDispatcher()) { + std::lock_guard<std::mutex> lock(m_mutex); + m_wakeUpCalled = true; + m_moreEvents.notify_one(); + return true; + } +#endif + Q_ASSERT(isMainThreadEventDispatcher()); + if (useJspi()) { + +#if QT_CONFIG(thread) + return qstdweb::runTaskOnMainThread<bool>( + []() { return qt_jspi_can_resume_js() && qt_jspi_resume_js(); }, &g_proxyingQueue); +#else + return qstdweb::runTaskOnMainThread<bool>( + []() { return qt_jspi_can_resume_js() && qt_jspi_resume_js(); }); +#endif + + } else { + if (!g_is_asyncify_suspended) + return false; + runOnMainThread([]() { qt_asyncify_resume(); }); + } + return true; +} + +// Process event activation callbacks for the main thread event dispatcher. +// Must be called on the main thread. +void QEventDispatcherWasm::callProcessPostedEvents(void *context) +{ + Q_ASSERT(emscripten_is_main_runtime_thread()); + + // Bail out if Qt has been shut down. + if (!g_mainThreadEventDispatcher) + return; + + // In the unlikely event that we get a callProcessPostedEvents() call for + // a previous main thread event dispatcher (i.e. the QApplication + // object was deleted and created again): just ignore it and return. + if (context != g_mainThreadEventDispatcher) + return; + + { + LOCK_GUARD(g_mainThreadEventDispatcher->m_mutex); + g_mainThreadEventDispatcher->m_pendingProcessEvents = false; + } + + g_mainThreadEventDispatcher->processPostedEvents(); +} + +bool QEventDispatcherWasm::processPostedEvents() +{ + QCoreApplication::sendPostedEvents(); + return false; +} + +void QEventDispatcherWasm::processTimers() +{ + m_timerInfo->activateTimers(); + updateNativeTimer(); // schedule next native timer, if any +} + +// Updates the native timer based on currently registered Qt timers. +// Must be called on the event dispatcher thread. +void QEventDispatcherWasm::updateNativeTimer() +{ +#if QT_CONFIG(thread) + Q_ASSERT(QThread::currentThread() == thread()); +#endif + + // Multiplex Qt timers down to a single native timer, maintained + // to have a timeout corresponding to the shortest Qt timer. This + // is done in two steps: first determine the target wakeup time + // on the event dispatcher thread (since this thread has exclusive + // access to m_timerInfo), and then call native API to set the new + // wakeup time on the main thread. + + const std::optional<std::chrono::nanoseconds> wait = m_timerInfo->timerWait(); + const auto toWaitDuration = duration_cast<milliseconds>(wait.value_or(0ms)); + const auto newTargetTimePoint = m_timerInfo->currentTime + toWaitDuration; + auto epochNsecs = newTargetTimePoint.time_since_epoch(); + auto newTargetTime = std::chrono::duration_cast<std::chrono::milliseconds>(epochNsecs); + auto maintainNativeTimer = [this, wait, toWaitDuration, newTargetTime]() { + Q_ASSERT(emscripten_is_main_runtime_thread()); + + if (!wait) { + if (m_timerId > 0) { + emscripten_clear_timeout(m_timerId); + m_timerId = 0; + m_timerTargetTime = 0ms; + } + return; + } + + if (m_timerTargetTime != 0ms && newTargetTime >= m_timerTargetTime) + return; // existing timer is good + + qCDebug(lcEventDispatcherTimers) + << "Created new native timer with wait" << toWaitDuration.count() << "ms" + << "timeout" << newTargetTime.count() << "ms"; + emscripten_clear_timeout(m_timerId); + m_timerId = emscripten_set_timeout(&QEventDispatcherWasm::callProcessTimers, + toWaitDuration.count(), this); + m_timerTargetTime = newTargetTime; + }; + + // Update the native timer for this thread/dispatcher. This must be + // done on the main thread where we have access to native API. + runOnMainThread([this, maintainNativeTimer]() { + Q_ASSERT(emscripten_is_main_runtime_thread()); + + // "this" may have been deleted, or may be about to be deleted. + // Check if the pointer we have is still a valid event dispatcher, + // and keep the mutex locked while updating the native timer to + // prevent it from being deleted. + LOCK_GUARD(g_staticDataMutex); + if (isValidEventDispatcherPointer(this)) + maintainNativeTimer(); + }); +} + +// Static timer activation callback. Must be called on the main thread +// and will then either process timers on the main thread or wake and +// process timers on a secondary thread. +void QEventDispatcherWasm::callProcessTimers(void *context) +{ + Q_ASSERT(emscripten_is_main_runtime_thread()); + + // Note: "context" may be a stale pointer here, + // take care before casting and dereferencing! + + // Process timers on this thread if this is the main event dispatcher + if (reinterpret_cast<QEventDispatcherWasm *>(context) == g_mainThreadEventDispatcher) { + g_mainThreadEventDispatcher->m_timerTargetTime = 0ms; + g_mainThreadEventDispatcher->processTimers(); + return; + } + + // Wake and process timers on the secondary thread if this a secondary thread dispatcher +#if QT_CONFIG(thread) + std::lock_guard<std::mutex> lock(g_staticDataMutex); + if (g_secondaryThreadEventDispatchers.contains(context)) { + QEventDispatcherWasm *eventDispatcher = reinterpret_cast<QEventDispatcherWasm *>(context); + eventDispatcher->m_timerTargetTime = 0ms; + eventDispatcher->m_processTimers = true; + eventDispatcher->wakeUp(); + } +#endif +} + +void QEventDispatcherWasm::setEmscriptenSocketCallbacks() +{ + qCDebug(lcEventDispatcher) << "setEmscriptenSocketCallbacks"; + + emscripten_set_socket_error_callback(nullptr, QEventDispatcherWasm::socketError); + emscripten_set_socket_open_callback(nullptr, QEventDispatcherWasm::socketOpen); + emscripten_set_socket_listen_callback(nullptr, QEventDispatcherWasm::socketListen); + emscripten_set_socket_connection_callback(nullptr, QEventDispatcherWasm::socketConnection); + emscripten_set_socket_message_callback(nullptr, QEventDispatcherWasm::socketMessage); + emscripten_set_socket_close_callback(nullptr, QEventDispatcherWasm::socketClose); +} + +void QEventDispatcherWasm::clearEmscriptenSocketCallbacks() +{ + qCDebug(lcEventDispatcher) << "clearEmscriptenSocketCallbacks"; + + emscripten_set_socket_error_callback(nullptr, nullptr); + emscripten_set_socket_open_callback(nullptr, nullptr); + emscripten_set_socket_listen_callback(nullptr, nullptr); + emscripten_set_socket_connection_callback(nullptr, nullptr); + emscripten_set_socket_message_callback(nullptr, nullptr); + emscripten_set_socket_close_callback(nullptr, nullptr); +} + +void QEventDispatcherWasm::socketError(int socket, int err, const char* msg, void *context) +{ + Q_UNUSED(err); + Q_UNUSED(msg); + Q_UNUSED(context); + + // Emscripten makes socket callbacks while the main thread is busy-waiting for a mutex, + // which can cause deadlocks if the callback code also tries to lock the same mutex. + // This is most easily reproducible by adding print statements, where each print requires + // taking a mutex lock. Work around this by running the callback asynchronously, i.e. by using + // a native zero-timer, to make sure the main thread stack is completely unwond before calling + // the Qt handler. + // It is currently unclear if this problem is caused by code in Qt or in Emscripten, or + // if this completely fixes the problem. + runAsync([socket](){ + auto notifiersRange = g_socketNotifiers.equal_range(socket); + std::vector<std::pair<int, QSocketNotifier *>> notifiers(notifiersRange.first, notifiersRange.second); + for (auto [_, notifier]: notifiers) { + QCoreApplication::postEvent(notifier, new QEvent(QEvent::SockAct)); + } + setSocketState(socket, true, true); + }); +} + +void QEventDispatcherWasm::socketOpen(int socket, void *context) +{ + Q_UNUSED(context); + + runAsync([socket](){ + auto notifiersRange = g_socketNotifiers.equal_range(socket); + std::vector<std::pair<int, QSocketNotifier *>> notifiers(notifiersRange.first, notifiersRange.second); + for (auto [_, notifier]: notifiers) { + if (notifier->type() == QSocketNotifier::Write) { + QCoreApplication::postEvent(notifier, new QEvent(QEvent::SockAct)); + } + } + setSocketState(socket, false, true); + }); +} + +void QEventDispatcherWasm::socketListen(int socket, void *context) +{ + Q_UNUSED(socket); + Q_UNUSED(context); +} + +void QEventDispatcherWasm::socketConnection(int socket, void *context) +{ + Q_UNUSED(socket); + Q_UNUSED(context); +} + +void QEventDispatcherWasm::socketMessage(int socket, void *context) +{ + Q_UNUSED(context); + + runAsync([socket](){ + auto notifiersRange = g_socketNotifiers.equal_range(socket); + std::vector<std::pair<int, QSocketNotifier *>> notifiers(notifiersRange.first, notifiersRange.second); + for (auto [_, notifier]: notifiers) { + if (notifier->type() == QSocketNotifier::Read) { + QCoreApplication::postEvent(notifier, new QEvent(QEvent::SockAct)); + } + } + setSocketState(socket, true, false); + }); +} + +void QEventDispatcherWasm::socketClose(int socket, void *context) +{ + Q_UNUSED(context); + + // Emscripten makes emscripten_set_socket_close_callback() calls to socket 0, + // which is not a valid socket. see https://github.com/emscripten-core/emscripten/issues/6596 + if (socket == 0) + return; + + runAsync([socket](){ + auto notifiersRange = g_socketNotifiers.equal_range(socket); + std::vector<std::pair<int, QSocketNotifier *>> notifiers(notifiersRange.first, notifiersRange.second); + for (auto [_, notifier]: notifiers) + QCoreApplication::postEvent(notifier, new QEvent(QEvent::SockClose)); + + setSocketState(socket, true, true); + clearSocketState(socket); + }); +} + +void QEventDispatcherWasm::setSocketState(int socket, bool setReadyRead, bool setReadyWrite) +{ + LOCK_GUARD(g_staticDataMutex); + SocketReadyState &state = g_socketState[socket]; + + // Additively update socket ready state, e.g. if it + // was already ready read then it stays ready read. + state.readyRead |= setReadyRead; + state.readyWrite |= setReadyWrite; + + // Wake any waiters for the given readiness. The waiter consumes + // the ready state, returning the socket to not-ready. + if (QEventDispatcherWasm *waiter = state.waiter) + if ((state.readyRead && state.waitForReadyRead) || (state.readyWrite && state.waitForReadyWrite)) + waiter->wakeEventDispatcherThread(); +} + +void QEventDispatcherWasm::clearSocketState(int socket) +{ + LOCK_GUARD(g_staticDataMutex); + g_socketState.erase(socket); +} + +void QEventDispatcherWasm::waitForSocketState(int timeout, int socket, bool checkRead, bool checkWrite, + bool *selectForRead, bool *selectForWrite, bool *socketDisconnect) +{ + // Loop until the socket becomes readyRead or readyWrite. Wait for + // socket activity if it currently is neither. + while (true) { + *selectForRead = false; + *selectForWrite = false; + + { + LOCK_GUARD(g_staticDataMutex); + + // Access or create socket state: we want to register that a thread is waitng + // even if we have not received any socket callbacks yet. + SocketReadyState &state = g_socketState[socket]; + if (state.waiter) { + qWarning() << "QEventDispatcherWasm::waitForSocketState: a thread is already waiting"; + break; + } + + bool shouldWait = true; + if (checkRead && state.readyRead) { + shouldWait = false; + state.readyRead = false; + *selectForRead = true; + } + if (checkWrite && state.readyWrite) { + shouldWait = false; + state.readyWrite = false; + *selectForRead = true; + } + if (!shouldWait) + break; + + state.waiter = this; + state.waitForReadyRead = checkRead; + state.waitForReadyWrite = checkWrite; + } + + bool didTimeOut = !wait(timeout); + { + LOCK_GUARD(g_staticDataMutex); + + // Missing socket state after a wakeup means that the socket has been closed. + auto it = g_socketState.find(socket); + if (it == g_socketState.end()) { + *socketDisconnect = true; + break; + } + it->second.waiter = nullptr; + it->second.waitForReadyRead = false; + it->second.waitForReadyWrite = false; + } + + if (didTimeOut) + break; + } +} + +void QEventDispatcherWasm::socketSelect(int timeout, int socket, bool waitForRead, bool waitForWrite, + bool *selectForRead, bool *selectForWrite, bool *socketDisconnect) +{ + QEventDispatcherWasm *eventDispatcher = static_cast<QEventDispatcherWasm *>( + QAbstractEventDispatcher::instance(QThread::currentThread())); + + if (!eventDispatcher) { + qWarning("QEventDispatcherWasm::socketSelect called without eventdispatcher instance"); + return; + } + + eventDispatcher->waitForSocketState(timeout, socket, waitForRead, waitForWrite, + selectForRead, selectForWrite, socketDisconnect); +} + +namespace { + int g_startupTasks = 0; +} + +// The following functions manages sending the "qtLoaded" event/callback +// from qtloader.js on startup, once Qt initialization has been completed +// and the application is ready to display the first frame. This can be +// either as soon as the event loop is running, or later, if additional +// startup tasks (e.g. local font loading) have been registered. + +void QEventDispatcherWasm::registerStartupTask() +{ + ++g_startupTasks; +} + +void QEventDispatcherWasm::completeStarupTask() +{ + --g_startupTasks; + callOnLoadedIfRequired(); +} + +void QEventDispatcherWasm::callOnLoadedIfRequired() +{ + if (g_startupTasks > 0) + return; + + static bool qtLoadedCalled = false; + if (qtLoadedCalled) + return; + qtLoadedCalled = true; + + Q_ASSERT(g_mainThreadEventDispatcher); + g_mainThreadEventDispatcher->onLoaded(); +} + +void QEventDispatcherWasm::onLoaded() +{ + // TODO: call qtloader.js onLoaded from here, in order to delay + // hiding the "Loading..." message until the app is ready to paint + // the first frame. Currently onLoaded must be called early before + // main() in order to ensure that the screen/container elements + // have valid geometry at startup. +} + +namespace { + void trampoline(void *context) { + + auto async_fn = [](void *context){ + std::function<void(void)> *fn = reinterpret_cast<std::function<void(void)> *>(context); + (*fn)(); + delete fn; + }; + + emscripten_async_call(async_fn, context, 0); + } +} + +// Runs a function right away +void QEventDispatcherWasm::run(std::function<void(void)> fn) +{ + fn(); +} + +void QEventDispatcherWasm::runOnMainThread(std::function<void(void)> fn) +{ +#if QT_CONFIG(thread) + qstdweb::runTaskOnMainThread<void>(fn, &g_proxyingQueue); +#else + qstdweb::runTaskOnMainThread<void>(fn); +#endif +} + +// Runs a function asynchronously. Main thread only. +void QEventDispatcherWasm::runAsync(std::function<void(void)> fn) +{ + trampoline(new std::function<void(void)>(fn)); +} + +// Runs a function on the main thread. The function always runs asynchronously, +// also if the calling thread is the main thread. +void QEventDispatcherWasm::runOnMainThreadAsync(std::function<void(void)> fn) +{ + void *context = new std::function<void(void)>(fn); +#if QT_CONFIG(thread) + if (!emscripten_is_main_runtime_thread()) { + g_proxyingQueue.proxyAsync(g_mainThread, [context]{ + trampoline(context); + }); + return; + } +#endif + trampoline(context); +} + +QT_END_NAMESPACE + +#include "moc_qeventdispatcher_wasm_p.cpp" |