wasm: enable event dispatcher asyncify support

Misc. fixes, including:

Fix a couple of typos in the JavaScript code. Also, macros-
within-macros don’t work, (without resorting to preprocessor
token pasting), so remove the debug output for now.

Limit the exec() “simulateInfiniteLoop” workaround to
top-level application exec() only. This way, asyncify
can be used for nested QEventLoop::exec() calls. (Emscripten
supports one level of suspend only, so we don’t want
to use that for the top-level exec(), but instead use it
for dialogs and such).

Use the new QEventLoop::ProcessEventsFlag::ApplicationExec
enum value to detect the exec() call type.

Change-Id: Ic702bfc31faf2e9f84ac5d3ccf43d067c5c61bf0
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

cmake/QtWasmHelpers.cmake

@@ -104,7 +104,7 @@ 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("${wasmTarget}" INTERFACE "SHELL:-s ASYNCIFY" "-Os")
+        target_link_options("${wasmTarget}" INTERFACE "SHELL:-s ASYNCIFY" "-Os" "-s" "ASYNCIFY_IMPORTS=[qt_asyncify_suspend_js, qt_asyncify_resume_js]")
         target_compile_definitions("${wasmTarget}" INTERFACE QT_HAVE_EMSCRIPTEN_ASYNCIFY)
     endif()
 endfunction()

src/corelib/kernel/qeventdispatcher_wasm.cpp

@@ -56,13 +56,6 @@ Q_LOGGING_CATEGORY(lcEventDispatcherTimers, "qt.eventdispatcher.timers");
 
 #ifdef QT_HAVE_EMSCRIPTEN_ASYNCIFY
 
-// Enable/disable JavaScript-side debugging
-#if 0
-    #define QT_ASYNCIFY_DEBUG(X) out(X)
-#else
-    #define QT_ASYNCIFY_DEBUG(X)
-#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
@@ -70,28 +63,21 @@ Q_LOGGING_CATEGORY(lcEventDispatcherTimers, "qt.eventdispatcher.timers");
 static bool g_is_asyncify_suspended = false;
 
 EM_JS(void, qt_asyncify_suspend_js, (), {
-    QT_ASYNCIFY_DEBUG("qt_asyncify_suspend_js");
-    let sleepFn = (wakeUp) = >
-    {
-        QT_ASYNCIFY_DEBUG("setting Module.qtAsyncifyWakeUp")
-        Module.qtAsyncifyWakeUp = wakeUp; // ### not "Module" any more
+    let sleepFn = (wakeUp) => {
+        Module.qtAsyncifyWakeUp = wakeUp;
     };
     return Asyncify.handleSleep(sleepFn);
 });
 
 EM_JS(void, qt_asyncify_resume_js, (), {
-    QT_ASYNCIFY_DEBUG("qt_asyncify_resume_js");
     let wakeUp = Module.qtAsyncifyWakeUp;
-    if (wakeUp == = undefined) {
-        QT_ASYNCIFY_DEBUG("qt_asyncify_resume_js no wakeup fn set - did not wake");
+    if (wakeUp == undefined)
         return;
-    }
     Module.qtAsyncifyWakeUp = undefined;
 
     // Delayed wakeup with zero-timer. Workaround/fix for
     // https://github.com/emscripten-core/emscripten/issues/10515
     setTimeout(wakeUp);
-    QT_ASYNCIFY_DEBUG("qt_asyncify_resume_js done");
 });
 
 // Suspends the main thread until qt_asyncify_resume() is called. Returns
@@ -209,8 +195,8 @@ bool QEventDispatcherWasm::processEvents(QEventLoop::ProcessEventsFlags flags)
     if (isMainThreadEventDispatcher()) {
         if (flags & QEventLoop::DialogExec)
             handleDialogExec();
-        else if (flags & QEventLoop::EventLoopExec)
-            handleEventLoopExec();
+        else if (flags & QEventLoop::ApplicationExec)
+            handleApplicationExec();
     }
 
     if (!(flags & QEventLoop::ExcludeUserInputEvents))
@@ -368,7 +354,7 @@ void QEventDispatcherWasm::wakeUp()
     emscripten_async_call(&QEventDispatcherWasm::callProcessEvents, this, 0);
 }
 
-void QEventDispatcherWasm::handleEventLoopExec()
+void QEventDispatcherWasm::handleApplicationExec()
 {
     // Start the main loop, and then stop it on the first callback. This
     // is done for the "simulateInfiniteLoop" functionality where
@@ -386,7 +372,7 @@ void QEventDispatcherWasm::handleEventLoopExec()
 
 void QEventDispatcherWasm::handleDialogExec()
 {
-#if !QT_HAVE_EMSCRIPTEN_ASYNCIFY
+#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"
@@ -432,7 +418,7 @@ bool QEventDispatcherWasm::waitForForEvents()
 
     Q_ASSERT(emscripten_is_main_runtime_thread());
 
-#if QT_HAVE_EMSCRIPTEN_ASYNCIFY
+#ifdef QT_HAVE_EMSCRIPTEN_ASYNCIFY
         // We can block on the main thread using asyncify:
         bool didSuspend = qt_asyncify_suspend();
         if (!didSuspend)

src/corelib/kernel/qeventdispatcher_wasm_p.h

@@ -90,7 +90,7 @@ private:
     bool isMainThreadEventDispatcher();
     bool isSecondaryThreadEventDispatcher();
 
-    void handleEventLoopExec();
+    void handleApplicationExec();
     void handleDialogExec();
     void pollForNativeEvents();
     bool waitForForEvents();