Serialize QPicture using the latest QDataStream version.

The QDataStream version with which QPicture was previously serialized
with was hard-coded to 11 (Qt 4.5). This prevents features of
serializable types used by QPicture from being serialized if they
were added after Qt 4.5; namely features of QFont like
HintingPreference.

[ChangeLog][QtGui][QPicture] QPicture now serializes its data properly
by also accounting for QDataStream versions greater than Qt 4.5.

Task-number: QTBUG-20578

Change-Id: Idd27682b187f4d4a3695c52bbf68e84853c024a8
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

src/gui/image/qpicture.cpp

@@ -118,7 +118,7 @@ void qt_format_text(const QFont &fnt, const QRectF &_r,
 */
 
 const char  *qt_mfhdr_tag = "QPIC"; // header tag
-static const quint16 mfhdr_maj = 11; // major version #
+static const quint16 mfhdr_maj = QDataStream::Qt_DefaultCompiledVersion; // major version #
 static const quint16 mfhdr_min = 0; // minor version #
 
 /*!

tests/auto/gui/image/qpicture/tst_qpicture.cpp

@@ -45,6 +45,7 @@
 #include <qpicture.h>
 #include <qpainter.h>
 #include <qimage.h>
+#include <qpaintengine.h>
 #ifndef QT_NO_WIDGETS
 #include <qdesktopwidget.h>
 #include <qapplication.h>
@@ -64,7 +65,7 @@ private slots:
     void paintingActive();
     void boundingRect();
     void swap();
-    void operator_lt_lt();
+    void serialization();
 
 #ifndef QT_NO_WIDGETS
     void save_restore();
@@ -169,36 +170,94 @@ void tst_QPicture::swap()
     QCOMPARE(p2.boundingRect(), QRect(0,0,5,5));
 }
 
-// operator<< and operator>>
-void tst_QPicture::operator_lt_lt()
+Q_DECLARE_METATYPE(QDataStream::Version)
+Q_DECLARE_METATYPE(QPicture)
+
+void ensureSerializesCorrectly(const QPicture &picture, QDataStream::Version version)
  {
-    // streaming of null pictures
-    {
-        QPicture pic1, pic2;
-        QByteArray ba( 100, 0 );
-        QDataStream str1( &ba, QIODevice::WriteOnly );
-        str1 << pic1;
-        QDataStream str2( &ba, QIODevice::ReadOnly );
-        str2 >> pic2;
-        QVERIFY( pic2.isNull() );
+    QDataStream stream;
+
+    QBuffer buffer;
+    buffer.open(QIODevice::WriteOnly);
+    stream.setDevice(&buffer);
+    stream.setVersion(version);
+    stream << picture;
+    buffer.close();
+
+    buffer.open(QIODevice::ReadOnly);
+    QPicture readpicture;
+    stream >> readpicture;
+    QVERIFY2(memcmp(picture.data(), readpicture.data(), picture.size()) == 0,
+        qPrintable(QString::fromLatin1("Picture data does not compare equal for QDataStream version %1").arg(version)));
 }
 
-    // picture with a simple line, checking bitwise equality
+class PaintEngine : public QPaintEngine
 {
-        QPicture pic1, pic2;
-        QPainter p( &pic1 );
-        p.drawLine( 10, 20, 30, 40 );
-        p.end();
-        QByteArray ba( 10 * pic1.size(), 0 );
-        QDataStream str1( &ba, QIODevice::WriteOnly );
-        str1 << pic1;
-        QDataStream str2( &ba, QIODevice::ReadOnly );
-        str2 >> pic2;
-        QCOMPARE( pic1.size(), pic2.size() );
-        QVERIFY( memcmp( pic1.data(), pic2.data(), pic1.size() ) == 0 );
+public:
+    PaintEngine() : QPaintEngine() {}
+    bool begin(QPaintDevice *) { return true; }
+    bool end() { return true; }
+    void updateState(const QPaintEngineState &) {}
+    void drawPixmap(const QRectF &, const QPixmap &, const QRectF &) {}
+    Type type() const { return Raster; }
+
+    QFont font() { return state->font(); }
+};
+
+class Picture : public QPicture
+{
+public:
+    Picture() : QPicture() {}
+    QPaintEngine *paintEngine() const { return (QPaintEngine*)&mPaintEngine; }
+private:
+    PaintEngine mPaintEngine;
+};
+
+void tst_QPicture::serialization()
+{
+    QDataStream stream;
+    const int thisVersion = stream.version();
+
+    for (int version = QDataStream::Qt_1_0; version <= thisVersion; ++version) {
+        const QDataStream::Version versionEnum = static_cast<QDataStream::Version>(version);
+
+        {
+            // streaming of null pictures
+            ensureSerializesCorrectly(QPicture(), versionEnum);
+        }
+        {
+            // picture with a simple line, checking bitwise equality
+            QPicture picture;
+            QPainter painter(&picture);
+            painter.drawLine(10, 20, 30, 40);
+            ensureSerializesCorrectly(picture, versionEnum);
         }
     }
 
+    {
+        // Test features that were added after Qt 4.5, as that was hard-coded as the major
+        // version for a while, which was incorrect. In this case, we'll test font hints.
+        QPicture picture;
+        QPainter painter;
+        QFont font;
+        font.setStyleName("Blah");
+        font.setHintingPreference(QFont::PreferFullHinting);
+        painter.begin(&picture);
+        painter.setFont(font);
+        painter.drawText(20, 20, "Hello");
+        painter.end();
+
+        Picture customPicture;
+        painter.begin(&customPicture);
+        picture.play(&painter);
+        const QFont actualFont = ((PaintEngine*)customPicture.paintEngine())->font();
+        painter.end();
+        QCOMPARE(actualFont.styleName(), QStringLiteral("Blah"));
+        QCOMPARE(actualFont.hintingPreference(), QFont::PreferFullHinting);
+    }
+}
+
+
 #ifndef QT_NO_WIDGETS
 static QPointF scalePoint(const QPointF &point, QPaintDevice *sourceDevice, QPaintDevice *destDevice)
 {