WebAssembly for QtBase

This is the squashed diff from wip/webassembly to dev.

Done-with: Peng Wu <peng.wu@intopalo.com>
Done-with: Sami Enne <sami.enne@intopalo.com>
Done-with: Morten Johan Sørvig <morten.sorvig@qt.io>
Started-by: Andrew Knight <andrew.knight@intopalo.com>
Change-Id: I6562433c0a38d6ec49ab675e0f104f2665f3392d
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/corelib/kernel/qeventloop.cpp b/src/corelib/kernel/qeventloop.cpp
index f1d32b15d1..a6cc51621a 100644
--- a/src/corelib/kernel/qeventloop.cpp
+++ b/src/corelib/kernel/qeventloop.cpp
@@ -48,6 +48,10 @@
 #include "qeventloop_p.h"
 #include <private/qthread_p.h>
 
+#ifdef Q_OS_WASM
+#include <emscripten.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 /*!
@@ -208,6 +212,15 @@ int QEventLoop::exec(ProcessEventsFlags flags)
     if (app && app->thread() == thread())
         QCoreApplication::removePostedEvents(app, QEvent::Quit);
 
+#ifdef Q_OS_WASM
+    // Partial support for nested event loops: Make the runtime throw a JavaSrcript
+    // exception, which returns control to the browser while preserving the C++ stack.
+    // Event processing then continues as normal. The sleep call below never returns.
+    // QTBUG-70185
+    if (d->threadData->loopLevel > 1)
+        emscripten_sleep(1);
+#endif
+
     while (!d->exit.loadAcquire())
         processEvents(flags | WaitForMoreEvents | EventLoopExec);
 
@@ -269,6 +282,17 @@ void QEventLoop::exit(int returnCode)
     d->returnCode.store(returnCode);
     d->exit.storeRelease(true);
     d->threadData->eventDispatcher.load()->interrupt();
+
+#ifdef Q_OS_WASM
+    // QEventLoop::exec() never returns in emscripten. We implement approximate behavior here.
+    // QTBUG-70185
+    if (d->threadData->loopLevel == 1) {
+        emscripten_force_exit(returnCode);
+    } else {
+        d->inExec = false;
+        --d->threadData->loopLevel;
+    }
+#endif
 }
 
 /*!