Android: Add runOnMainAndroidThread() under QNativeInterface

This replaces QtAndroidPrivate::runOnAndroidThread{Sync} calls.
This also now allows passing std::function<> that can return values,
and not only an std::function<void()>.

This adds some tests for this calls as well.

Fixes: QTBUG-90501
Change-Id: I138d2aae64be17347f7ff712d8a86edb49ea8350
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

6 files changed, 291 insertions, 1 deletions

diff --git a/src/corelib/doc/src/external-resources.qdoc b/src/corelib/doc/src/external-resources.qdoc
index e8f1d3348d..62e6b7ea1d 100644
--- a/src/corelib/doc/src/external-resources.qdoc
+++ b/src/corelib/doc/src/external-resources.qdoc
@@ -105,3 +105,8 @@
     \externalpage https://doc.qt.io/qtcreator/creator-deploying-android.html#editing-manifest-files
     \title Qt Creator: Editing Manifest Files
 */
+
+/*!
+    \externalpage https://developer.android.com/training/articles/perf-anr
+    \title Android: Keeping your app responsive
+*/
diff --git a/src/corelib/kernel/qcoreapplication_platform.h b/src/corelib/kernel/qcoreapplication_platform.h
index 6830e4d3ab..c65010faee 100644
--- a/src/corelib/kernel/qcoreapplication_platform.h
+++ b/src/corelib/kernel/qcoreapplication_platform.h
@@ -44,6 +44,11 @@
 #include <QtCore/qnativeinterface.h>
 #include <QtCore/qcoreapplication.h>
 
+#if QT_CONFIG(future) && !defined(QT_NO_QOBJECT)
+#include <QtCore/qfuture.h>
+#include <QtCore/qvariant.h>
+#endif
+
 #if defined(Q_OS_ANDROID) && !defined(Q_OS_ANDROID_EMBEDDED)
 class _jobject;
 typedef _jobject* jobject;
@@ -61,6 +66,22 @@ struct Q_CORE_EXPORT QAndroidApplication
     static bool isActivityContext();
     static int sdkVersion();
     static void hideSplashScreen(int duration = 0);
+
+#if QT_CONFIG(future) && !defined(QT_NO_QOBJECT)
+    static QFuture<QVariant> runOnAndroidMainThread(const std::function<QVariant()> &runnable,
+                                                    const QDeadlineTimer
+                                                    &timeout = QDeadlineTimer(-1));
+
+    template <class T>
+    std::enable_if_t<std::is_invocable_v<T> && std::is_same_v<std::invoke_result_t<T>, void>,
+    QFuture<void>> static runOnAndroidMainThread(const T &runnable,
+                                                 const QDeadlineTimer
+                                                 &timeout = QDeadlineTimer(-1))
+    {
+        std::function<QVariant()> func = [&](){ runnable(); return QVariant(); };
+        return static_cast<QFuture<void>>(runOnAndroidMainThread(func, timeout));
+    }
+#endif
 };
 #endif
 }
diff --git a/src/corelib/kernel/qjnihelpers.cpp b/src/corelib/kernel/qjnihelpers.cpp
index edb07b47cf..46143d4c2c 100644
--- a/src/corelib/kernel/qjnihelpers.cpp
+++ b/src/corelib/kernel/qjnihelpers.cpp
@@ -358,6 +358,9 @@ jint QtAndroidPrivate::initJNI(JavaVM *vm, JNIEnv *env)
     if (!registerPermissionNatives())
         return JNI_ERR;
 
+    if (!registerNativeInterfaceNatives())
+        return JNI_ERR;
+
     g_runPendingCppRunnablesMethodID = env->GetStaticMethodID(jQtNative,
                                                        "runPendingCppRunnablesOnAndroidThread",
                                                        "()V");
diff --git a/src/corelib/kernel/qjnihelpers_p.h b/src/corelib/kernel/qjnihelpers_p.h
index 90dbcd1cd8..07f5ff8e8a 100644
--- a/src/corelib/kernel/qjnihelpers_p.h
+++ b/src/corelib/kernel/qjnihelpers_p.h
@@ -128,7 +128,9 @@ namespace QtAndroidPrivate
     Q_CORE_EXPORT PermissionsHash requestPermissionsSync(JNIEnv *env, const QStringList &permissions, int timeoutMs = INT_MAX);
     Q_CORE_EXPORT PermissionsResult checkPermission(const QString &permission);
     Q_CORE_EXPORT bool shouldShowRequestPermissionRationale(const QString &permission);
+
     bool registerPermissionNatives();
+    bool registerNativeInterfaceNatives();
 
     Q_CORE_EXPORT void handleActivityResult(jint requestCode, jint resultCode, jobject data);
     Q_CORE_EXPORT void registerActivityResultListener(ActivityResultListener *listener);
diff --git a/src/corelib/platform/android/qandroidnativeinterface.cpp b/src/corelib/platform/android/qandroidnativeinterface.cpp
index 296027340a..86723cc33b 100644
--- a/src/corelib/platform/android/qandroidnativeinterface.cpp
+++ b/src/corelib/platform/android/qandroidnativeinterface.cpp
@@ -37,12 +37,27 @@
 **
 ****************************************************************************/
 
-#include <QtCore/qcoreapplication.h>
+#include <QtCore/qcoreapplication_platform.h>
+
 #include <QtCore/private/qjnihelpers_p.h>
 #include <QtCore/qjniobject.h>
+#if QT_CONFIG(future) && !defined(QT_NO_QOBJECT)
+#include <QtConcurrent/QtConcurrent>
+#include <QtCore/qpromise.h>
+#include <deque>
+#endif
 
 QT_BEGIN_NAMESPACE
 
+#if QT_CONFIG(future) && !defined(QT_NO_QOBJECT)
+static const char qtNativeClassName[] = "org/qtproject/qt/android/QtNative";
+
+typedef std::pair<std::function<QVariant()>, QSharedPointer<QPromise<QVariant>>> RunnablePair;
+typedef std::deque<RunnablePair> PendingRunnables;
+Q_GLOBAL_STATIC(PendingRunnables, g_pendingRunnables);
+static QBasicMutex g_pendingRunnablesMutex;
+#endif
+
 /*!
     \class QNativeInterface::QAndroidApplication
     \since 6.2
@@ -110,4 +125,136 @@ void QNativeInterface::QAndroidApplication::hideSplashScreen(int duration)
                                        "hideSplashScreen", "(I)V", duration);
 }
 
+/*!
+    Posts the function \a runnable to the Android thread. The function will be
+    queued and executed on the Android UI thread. If the call is made on the
+    Android UI thread \a runnable will be executed immediately. If the Android
+    app is paused or the main Activity is null, \c runnable is added to the
+    Android main thread's queue.
+
+    This call returns a QFuture<QVariant> which allows doing both synchronous
+    and asynchronous calls, and can handle any return type. However, to get
+    a result back from the QFuture::result(), QVariant::value() should be used.
+
+    If the \a runnable execution takes longer than the period of \a timeout,
+    the blocking calls \l QFuture::waitForFinished() and \l QFuture::result()
+    are ended once \a timeout has elapsed. However, if \a runnable has already
+    started execution, it won't be cancelled.
+
+    The following example shows how to run an asynchronous call that expects
+    a return type:
+
+    \code
+    auto task = QNativeInterface::QAndroidApplication::runOnAndroidMainThread([=]() {
+        QJniObject surfaceView;
+        if (!surfaceView.isValid())
+            qDebug() << "SurfaceView object is not valid yet";
+
+        surfaceView = QJniObject("android/view/SurfaceView",
+                                 "(Landroid/content/Context;)V",
+                                 QNativeInterface::QAndroidApplication::context());
+
+        return QVariant::fromValue(surfaceView);
+    }).then([](QFuture<QVariant> future) {
+        auto surfaceView = future.result().value<QJniObject>();
+        if (surfaceView.isValid())
+            qDebug() << "Retrieved SurfaceView object is valid";
+    });
+    \endcode
+
+    The following example shows how to run a synchronous call with a void
+    return type:
+
+    \code
+    QNativeInterface::QAndroidApplication::runOnAndroidMainThread([]() {
+       QJniObject activity = QNativeInterface::QAndroidApplication::context();
+       // Hide system ui elements or go full screen
+       activity.callObjectMethod("getWindow", "()Landroid/view/Window;")
+               .callObjectMethod("getDecorView", "()Landroid/view/View;")
+               .callMethod<void>("setSystemUiVisibility", "(I)V", 0xffffffff);
+    }).waitForFinished();
+    \endcode
+
+    \note Becareful about the type of operations you do on the Android's main
+    thread, as any long operation can block the app's UI rendering and input
+    handling. If the function is expected to have long execution time, it's
+    also good to use a \l QDeadlineTimer() in your \a runnable to manage
+    the execution and make sure it doesn't block the UI thread. Usually,
+    any operation longer than 5 seconds might block the app's UI. For more
+    information, see \l {Android: Keeping your app responsive}{Keeping your app responsive}.
+
+    \since 6.2
+*/
+#if QT_CONFIG(future) && !defined(QT_NO_QOBJECT)
+QFuture<QVariant> QNativeInterface::QAndroidApplication::runOnAndroidMainThread(
+                                                    const std::function<QVariant()> &runnable,
+                                                    const QDeadlineTimer &timeout)
+{
+    QSharedPointer<QPromise<QVariant>> promise(new QPromise<QVariant>());
+    QFuture<QVariant> future = promise->future();
+    promise->start();
+
+    (void) QtConcurrent::run([=, &future]() {
+        if (!timeout.isForever()) {
+            QEventLoop loop;
+            QTimer::singleShot(timeout.remainingTime(), &loop, [&]() {
+                future.cancel();
+                promise->finish();
+                loop.quit();
+            });
+
+            QFutureWatcher<QVariant> watcher;
+            QObject::connect(&watcher, &QFutureWatcher<QVariant>::finished, &loop, [&]() {
+                loop.quit();
+            });
+            QObject::connect(&watcher, &QFutureWatcher<QVariant>::canceled, &loop, [&]() {
+                loop.quit();
+            });
+            watcher.setFuture(future);
+            loop.exec();
+        }
+    });
+
+    QMutexLocker locker(&g_pendingRunnablesMutex);
+    g_pendingRunnables->push_back(std::pair(runnable, promise));
+    locker.unlock();
+
+    QJniObject::callStaticMethod<void>(qtNativeClassName,
+                                       "runPendingCppRunnablesOnAndroidThread",
+                                       "()V");
+    return future;
+}
+
+// function called from Java from Android UI thread
+static void runPendingCppRunnables(JNIEnv */*env*/, jobject /*obj*/)
+{
+    // run all posted runnables
+    for (;;) {
+        QMutexLocker locker(&g_pendingRunnablesMutex);
+        if (g_pendingRunnables->empty())
+            break;
+
+        std::pair pair = std::move(g_pendingRunnables->front());
+        g_pendingRunnables->pop_front();
+        locker.unlock();
+
+        // run the runnable outside the sync block!
+        auto promise = pair.second;
+        if (!promise->isCanceled())
+            promise->addResult(pair.first());
+        promise->finish();
+    }
+}
+#endif
+
+bool QtAndroidPrivate::registerNativeInterfaceNatives()
+{
+#if QT_CONFIG(future) && !defined(QT_NO_QOBJECT)
+    JNINativeMethod methods = {"runPendingCppRunnables", "()V", (void *)runPendingCppRunnables};
+    return QJniEnvironment().registerNativeMethods(qtNativeClassName, &methods, 1);
+#else
+    return true;
+#endif
+}
+
 QT_END_NAMESPACE
diff --git a/tests/auto/corelib/platform/android/tst_android.cpp b/tests/auto/corelib/platform/android/tst_android.cpp
index 3a00d9414b..710e5b2ecf 100644
--- a/tests/auto/corelib/platform/android/tst_android.cpp
+++ b/tests/auto/corelib/platform/android/tst_android.cpp
@@ -40,6 +40,7 @@ private slots:
     void assetsNotWritable();
     void testAndroidSdkVersion();
     void testAndroidActivity();
+    void testRunOnAndroidMainThread();
 };
 
 void tst_Android::assetsRead()
@@ -77,6 +78,117 @@ void tst_Android::testAndroidActivity()
     QVERIFY(activity.callMethod<jboolean>("isTaskRoot"));
 }
 
+void tst_Android::testRunOnAndroidMainThread()
+{
+    // async void
+    {
+        int res = 0;
+        QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{ res = 1; });
+        QTRY_COMPARE(res, 1);
+    }
+
+    // sync void
+    {
+        int res = 0;
+        auto task = QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+            res = 1;
+        });
+        task.waitForFinished();
+        QCOMPARE(res, 1);
+    }
+
+    // sync return value
+    {
+        auto task = QNativeInterface::QAndroidApplication::runOnAndroidMainThread([]{
+            return 1;
+        });
+        task.waitForFinished();
+        QVERIFY(task.isResultReadyAt(0));
+        QCOMPARE(task.result().value<int>(), 1);
+    }
+
+    // nested calls
+    {
+        // nested async/async
+        int res = 0;
+        QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+            QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+                res = 3;
+            });
+        });
+        QTRY_COMPARE(res, 3);
+
+        // nested async/sync
+        QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+            QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+                res = 5;
+            }).waitForFinished();
+        });
+        QTRY_COMPARE(res, 5);
+
+        // nested sync/sync
+        QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+            QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+                res = 4;
+            }).waitForFinished();
+        }).waitForFinished();
+        QCOMPARE(res, 4);
+
+
+        // nested sync/async
+        QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+            QNativeInterface::QAndroidApplication::runOnAndroidMainThread([&res]{
+                res = 6;
+            });
+        }).waitForFinished();
+        QCOMPARE(res, 6);
+    }
+
+    // timeouts
+    {
+        auto task = QNativeInterface::QAndroidApplication::runOnAndroidMainThread([]{
+            QThread::msleep(500);
+            return 1;
+        }, QDeadlineTimer(100));
+        task.waitForFinished();
+        QVERIFY(task.isCanceled());
+        QVERIFY(task.isFinished());
+        QVERIFY(!task.isResultReadyAt(0));
+
+        auto task2 = QNativeInterface::QAndroidApplication::runOnAndroidMainThread([]{
+            return 2;
+        }, QDeadlineTimer(0));
+        task2.waitForFinished();
+        QVERIFY(task2.isCanceled());
+        QVERIFY(task2.isFinished());
+        QVERIFY(!task2.isResultReadyAt(0));
+
+        QDeadlineTimer deadline(1000);
+        auto task3 = QNativeInterface::QAndroidApplication::runOnAndroidMainThread([]{
+            return 3;
+        }, QDeadlineTimer(10000));
+        task3.waitForFinished();
+        QVERIFY(deadline.remainingTime() > 0);
+        QVERIFY(task3.isFinished());
+        QVERIFY(!task3.isCanceled());
+        QVERIFY(task3.isResultReadyAt(0));
+        QCOMPARE(task3.result().value<int>(), 3);
+    }
+
+    // cancelled future
+    {
+        auto task = QNativeInterface::QAndroidApplication::runOnAndroidMainThread([]{
+            QThread::msleep(2000);
+            return 1;
+        });
+        task.cancel();
+        QVERIFY(task.isCanceled());
+        task.waitForFinished();
+        QVERIFY(task.isFinished());
+        QVERIFY(!task.isResultReadyAt(0));
+    }
+}
+
 QTEST_MAIN(tst_Android)
 #include "tst_android.moc"