Fix race condition in async image response handling

It may happen that the finished() signal is emitted from a super quick
image loading thread in the implementation before we had a chance to
connect to the signal in Qt Quick. In that case, record the emission
through a private connection established in the constructor.

The unit test simulates this scenario by emitting the signal before
returning the object, but in a real world scenario it may happen
that the response object is used in a separate thread that ends up
emitting the signal. That may also happen before the thread that will
try to connect to the signal runs.

Task-number: QTBUG-59601
Change-Id: I14de9719db47f4bca2e8a2c6659343cfb4deb526
Reviewed-by: Albert Astals Cid <albert.astals.cid@kdab.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickimageprovider/tst_qquickimageprovider.cpp b/tests/auto/quick/qquickimageprovider/tst_qquickimageprovider.cpp
index d8464ebc74..4b75a7e008 100644
--- a/tests/auto/quick/qquickimageprovider/tst_qquickimageprovider.cpp
+++ b/tests/auto/quick/qquickimageprovider/tst_qquickimageprovider.cpp
@@ -65,6 +65,7 @@ private slots:
     void threadTest();
 
     void asyncTextureTest();
+    void instantAsyncTextureTest();
 
 private:
     QString newImageFileName() const;
@@ -550,6 +551,70 @@ void tst_qquickimageprovider::asyncTextureTest()
     }
 }
 
+class InstantAsyncImageResponse : public QQuickImageResponse
+{
+    public:
+        InstantAsyncImageResponse(const QString &id, const QSize &requestedSize)
+        {
+            QImage image(50, 50, QImage::Format_RGB32);
+            image.fill(QColor(id).rgb());
+            if (requestedSize.isValid())
+                image = image.scaled(requestedSize);
+            m_texture = QQuickTextureFactory::textureFactoryForImage(image);
+            emit finished();
+        }
+
+        QQuickTextureFactory *textureFactory() const
+        {
+            return m_texture;
+        }
+
+        QQuickTextureFactory *m_texture;
+};
+
+class InstancAsyncProvider : public QQuickAsyncImageProvider
+{
+    public:
+        InstancAsyncProvider()
+        {
+        }
+
+        ~InstancAsyncProvider() {}
+
+        QQuickImageResponse *requestImageResponse(const QString &id, const QSize &requestedSize)
+        {
+            return new InstantAsyncImageResponse(id, requestedSize);
+        }
+};
+
+void tst_qquickimageprovider::instantAsyncTextureTest()
+{
+    QQmlEngine engine;
+
+    InstancAsyncProvider *provider = new InstancAsyncProvider;
+
+    engine.addImageProvider("test_instantasync", provider);
+    QVERIFY(engine.imageProvider("test_instantasync") != nullptr);
+
+    QString componentStr = "import QtQuick 2.0\nItem { \n"
+            "Image { source: \"image://test_instantasync/blue\"; }\n"
+            "Image { source: \"image://test_instantasync/red\"; }\n"
+            "Image { source: \"image://test_instantasync/green\";  }\n"
+            "Image { source: \"image://test_instantasync/yellow\";  }\n"
+            " }";
+    QQmlComponent component(&engine);
+    component.setData(componentStr.toLatin1(), QUrl::fromLocalFile(""));
+    QScopedPointer<QObject> obj(component.create());
+
+    QVERIFY(!obj.isNull());
+    const QList<QQuickImage *> images = obj->findChildren<QQuickImage *>();
+    QCOMPARE(images.count(), 4);
+
+    for (QQuickImage *img: images) {
+        QTRY_COMPARE(img->status(), QQuickImage::Ready);
+    }
+}
+
 
 QTEST_MAIN(tst_qquickimageprovider)