QWinRTFileEngine: Implement setSize

Fixes: QTBUG-77132
Change-Id: Ic0410297a2215f1b7b656966cbe84b925706532f
Reviewed-by: André de la Rocha <andre.rocha@qt.io>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>

src/plugins/platforms/winrt/qwinrtfileengine.cpp

@@ -257,6 +257,29 @@ qint64 QWinRTFileEngine::size() const
     return qint64(size);
 }
 
+bool QWinRTFileEngine::setSize(qint64 size)
+{
+    Q_D(QWinRTFileEngine);
+    if (!d->stream) {
+        setError(QFileDevice::ResizeError, QLatin1String("File must be open to be resized"));
+        return false;
+    }
+
+    if (size < 0) {
+        setError(QFileDevice::ResizeError, QLatin1String("File size cannot be negative"));
+        return false;
+    }
+
+    HRESULT hr = d->stream->put_Size(static_cast<quint64>(size));
+    RETURN_AND_SET_ERROR_IF_FAILED(QFileDevice::ResizeError, false);
+    if (!flush()) {
+        setError(QFileDevice::ResizeError, QLatin1String("Could not flush file"));
+        return false;
+    }
+
+    return true;
+}
+
 qint64 QWinRTFileEngine::pos() const
 {
     Q_D(const QWinRTFileEngine);

src/plugins/platforms/winrt/qwinrtfileengine.h

@@ -79,6 +79,7 @@ public:
     bool close() override;
     bool flush() override;
     qint64 size() const override;
+    bool setSize(qint64 size) override;
     qint64 pos() const override;
     bool seek(qint64 pos) override;
     bool remove() override;