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wasm: include asyncify support unconditionally

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Emscripten's option for enabling asyncify (-sASYNCIFY) is a link-time
option, which means there is no requirement to have a separate asyncify
build, at least for static builds.

Replace the current QT_HAVE_EMSCRIPTEN_ASYNCIFY compile-time option
with a run-time option which checks if the asyncify API is available.

Keep support for configuring with "-device-option QT_EMSCRIPTEN_ASYNCIFY=1"
for backwards compatibility and for the use case where want asyncify
support to be on by default for a given Qt build.

Enable asyncify for the asyncify_exec example.

Pick-to: 6.4
Change-Id: I301fd7e2d3c0367532c886f4e34b23e1093646ad
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
This commit is contained in:
Morten Sørvig 2022-08-09 00:05:33 +02:00
parent 238e90cd58
commit f347682fd5
5 changed files with 47 additions and 40 deletions
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6
cmake/QtWasmHelpers.cmake
View File

@ -75,9 +75,13 @@ function (qt_internal_setup_wasm_target_properties wasmTarget)
set(QT_CFLAGS_OPTIMIZE_DEBUG "-Os" CACHE STRING INTERNAL FORCE)
set(QT_FEATURE_optimize_debug ON CACHE BOOL INTERNAL FORCE)
target_link_options("${wasmTarget}" INTERFACE "SHELL:-s ASYNCIFY" "-Os" "-s" "ASYNCIFY_IMPORTS=[qt_asyncify_suspend_js, qt_asyncify_resume_js]")
target_link_options("${wasmTarget}" INTERFACE "SHELL:-s ASYNCIFY" "-Os")
target_compile_definitions("${wasmTarget}" INTERFACE QT_HAVE_EMSCRIPTEN_ASYNCIFY)
endif()
# Set ASYNCIFY_IMPORTS unconditionally in order to support enabling asyncify at link time.
target_link_options("${wasmTarget}" INTERFACE "SHELL:-sASYNCIFY_IMPORTS=qt_asyncify_suspend_js,qt_asyncify_resume_js")
endfunction()
function(qt_internal_wasm_add_finalizers target)

6
mkspecs/wasm-emscripten/qmake.conf
View File

@ -22,12 +22,12 @@ load(emcc_ver)
# (with "wasm validation error: too many locals" type errors) if optimizations
# are omitted. Enable optimizations also for debug builds.
QMAKE_LFLAGS_DEBUG += -Os
# Declare all async functions
QMAKE_LFLAGS += -s \'ASYNCIFY_IMPORTS=[\"qt_asyncify_suspend_js\", \"qt_asyncify_resume_js\", \"emscripten_sleep\"]\'
}
}
# Declare async functions
QMAKE_LFLAGS += -s \'ASYNCIFY_IMPORTS=qt_asyncify_suspend_js,qt_asyncify_resume_js\'
EMCC_COMMON_LFLAGS += \
-s WASM=1 \
-s MAX_WEBGL_VERSION=2 \

62
src/corelib/kernel/qeventdispatcher_wasm.cpp
View File

@ -26,14 +26,16 @@ Q_LOGGING_CATEGORY(lcEventDispatcherTimers, "qt.eventdispatcher.timers");
#define LOCK_GUARD(M)
#endif
#ifdef QT_HAVE_EMSCRIPTEN_ASYNCIFY
// 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;
EM_JS(bool, qt_have_asyncify_js, (), {
return typeof Asyncify != "undefined";
});
EM_JS(void, qt_asyncify_suspend_js, (), {
let sleepFn = (wakeUp) => {
Module.qtAsyncifyWakeUp = wakeUp;
@ -52,6 +54,15 @@ EM_JS(void, qt_asyncify_resume_js, (), {
setTimeout(wakeUp);
});
// Returns true if asyncify is available.
bool qt_have_asyncify()
{
static bool have_asyncify = []{
return qt_have_asyncify_js();
}();
return have_asyncify;
}
// 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),
@ -76,8 +87,6 @@ bool qt_asyncify_resume()
return true;
}
#endif // QT_HAVE_EMSCRIPTEN_ASYNCIFY
Q_CONSTINIT QEventDispatcherWasm *QEventDispatcherWasm::g_mainThreadEventDispatcher = nullptr;
#if QT_CONFIG(thread)
Q_CONSTINIT QVector<QEventDispatcherWasm *> QEventDispatcherWasm::g_secondaryThreadEventDispatchers;
@ -359,16 +368,15 @@ void QEventDispatcherWasm::handleApplicationExec()
void QEventDispatcherWasm::handleDialogExec()
{
#ifndef QT_HAVE_EMSCRIPTEN_ASYNCIFY
qWarning() << "Warning: dialog exec() is not supported on Qt for WebAssembly in this"
<< "configuration. Please use show() instead, or enable experimental support"
<< "for asyncify.\n"
<< "When using exec() (without asyncify) the dialog will show, the user can interact"
<< "with it and the appropriate signals will be emitted on close. However, the"
<< "exec() call never returns, stack content at the time of the exec() call"
<< "is leaked, and the exec() call may interfere with input event processing";
emscripten_sleep(1); // This call never returns
#endif
if (!qt_have_asyncify()) {
qWarning() << "Warning: dialog exec() is not supported on Qt for WebAssembly in this"
<< "configuration. Please use show() instead, or enable experimental support"
<< "for asyncify.\n"
<< "When using exec() (without asyncify) the dialog will show, the user can interact"
<< "exec() call never returns, stack content at the time of the exec() call"
<< "is leaked, and the exec() call may interfere with input event processing";
emscripten_sleep(1); // This call never returns
}
// For the asyncify case we do nothing here and wait for events in wait()
}
@ -393,20 +401,20 @@ bool QEventDispatcherWasm::wait(int timeout)
#endif
Q_ASSERT(emscripten_is_main_runtime_thread());
Q_ASSERT(isMainThreadEventDispatcher());
#ifdef QT_HAVE_EMSCRIPTEN_ASYNCIFY
if (timeout > 0)
qWarning() << "QEventDispatcherWasm asyncify wait with timeout is not supported; timeout will be ignored"; // FIXME
if (qt_have_asyncify()) {
if (timeout > 0)
qWarning() << "QEventDispatcherWasm asyncify wait with timeout is not supported; timeout will be ignored"; // FIXME
bool didSuspend = qt_asyncify_suspend();
if (!didSuspend) {
qWarning("QEventDispatcherWasm: current thread is already suspended; could not asyncify wait for events");
return false;
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 true;
#else
qWarning("QEventLoop::WaitForMoreEvents is not supported on the main thread without asyncify");
Q_UNUSED(timeout);
#endif
return false;
}
@ -424,12 +432,10 @@ bool QEventDispatcherWasm::wakeEventDispatcherThread()
}
#endif
Q_ASSERT(isMainThreadEventDispatcher());
#ifdef QT_HAVE_EMSCRIPTEN_ASYNCIFY
if (g_is_asyncify_suspended) {
runOnMainThread([]{ qt_asyncify_resume(); });
return true;
}
#endif
return false;
}

3
tests/manual/wasm/eventloop/asyncify_exec/CMakeLists.txt
View File

@ -7,3 +7,6 @@ qt_internal_add_manual_test(asyncify_exec
LIBRARIES
Qt::Core
)
# Enable asyncify for this test. Also enable optimizations in order to reduce the binary size.
target_link_options(asyncify_exec PUBLIC -sASYNCIFY -Os)

10
tests/manual/wasm/eventloop/asyncify_exec/main.cpp
View File

@ -2,14 +2,12 @@
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include <QtCore>
// This test shows how to asyncify enables blocking
// the main thread on QEventLoop::exec(), while event
// provessing continues.
// This test shows how to use asyncify to enable blocking the main
// thread on QEventLoop::exec(), while event processing continues.
int main(int argc, char **argv)
{
QCoreApplication app(argc, argv);
#ifdef QT_HAVE_EMSCRIPTEN_ASYNCIFY
QTimer::singleShot(1000, []() {
QEventLoop loop;
@ -22,10 +20,6 @@ int main(int argc, char **argv)
loop.exec();
qDebug() << "Returned from QEventLoop::exec()";
});
#else
qDebug() << "This test requires Emscripten asyncify. To enable,"
<< "configure Qt with -device-option QT_EMSCRIPTEN_ASYNCIFY=1";
#endif
app.exec();
}