Doc: QWebEngineUrlRequestJob: mention when to delete the device

It's used from another thread, so it shouldn't be deleted immediately,
and it's not deleted by the QtWebEngine code, so tell people to do it
themselves at the right time.

Change-Id: I54786be320f5fe82f144e7b1c2e6137260d9ceab
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

2 files changed, 22 insertions, 5 deletions

diff --git a/src/core/api/qwebengineurlrequestjob.cpp b/src/core/api/qwebengineurlrequestjob.cpp
index 1db23f6ab..e95f58863 100644
--- a/src/core/api/qwebengineurlrequestjob.cpp
+++ b/src/core/api/qwebengineurlrequestjob.cpp
@@ -114,6 +114,13 @@ QByteArray QWebEngineUrlRequestJob::requestMethod() const
 
 /*!
     Replies to the request with \a device and the MIME type \a contentType.
+
+    The device should remain available at least as long as the job exists.
+    When calling this method with a newly constructed device, one solution is to
+    make the device delete itself when closed, like this:
+    \code
+    connect(device, &QIODevice::aboutToClose, device, &QObject::deleteLater);
+    \endcode
  */
 void QWebEngineUrlRequestJob::reply(const QByteArray &contentType, QIODevice *device)
 {
diff --git a/tests/auto/widgets/qwebengineprofile/tst_qwebengineprofile.cpp b/tests/auto/widgets/qwebengineprofile/tst_qwebengineprofile.cpp
index 093bc2e43..639a8456f 100644
--- a/tests/auto/widgets/qwebengineprofile/tst_qwebengineprofile.cpp
+++ b/tests/auto/widgets/qwebengineprofile/tst_qwebengineprofile.cpp
@@ -162,20 +162,25 @@ public:
 
 class ReplyingUrlSchemeHandler : public QWebEngineUrlSchemeHandler
 {
-    QBuffer m_buffer;
-    QByteArray m_bufferData;
 public:
     ReplyingUrlSchemeHandler(QObject *parent = nullptr)
         : QWebEngineUrlSchemeHandler(parent)
     {
-        m_buffer.setBuffer(&m_bufferData);
+    }
+    ~ReplyingUrlSchemeHandler()
+    {
     }
 
     void requestStarted(QWebEngineUrlRequestJob *job)
     {
-        m_bufferData = job->requestUrl().toString().toUtf8();
-        job->reply("text/plain;charset=utf-8", &m_buffer);
+        QBuffer *buffer = new QBuffer;
+        buffer->setData(job->requestUrl().toString().toUtf8());
+        connect(buffer, &QIODevice::aboutToClose, buffer, &QObject::deleteLater);
+        m_buffers.append(buffer);
+        job->reply("text/plain;charset=utf-8", buffer);
     }
+
+    QList<QPointer<QBuffer>> m_buffers;
 };
 
 static bool loadSync(QWebEngineView *view, const QUrl &url, int timeout = 5000)
@@ -234,6 +239,11 @@ void tst_QWebEngineProfile::urlSchemeHandlers()
     url = QUrl(QStringLiteral("aviancarrier:inspector.mortensen@politistyrke.dk"));
     QVERIFY(loadSync(&view, url));
     QCOMPARE(toPlainTextSync(view.page()), url.toString());
+
+    // Check that all buffers got deleted
+    QCOMPARE(gopherHandler.m_buffers.count(), 2);
+    for (int i = 0; i < gopherHandler.m_buffers.count(); ++i)
+        QVERIFY(gopherHandler.m_buffers.at(i).isNull());
 }
 
 class FailingUrlSchemeHandler : public QWebEngineUrlSchemeHandler