QtGui/Windows: Move the QRegion conversion functions into QtGui

Task-number: QTBUG-81876
Change-Id: I2297291a4157e7015f499b0a6127301d9cb58526
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/gui/painting/qregion.cpp

@@ -50,6 +50,10 @@
 
 #include <private/qdebug_p.h>
 
+#ifdef Q_OS_WIN
+#  include <qt_windows.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 /*!
@@ -4314,4 +4318,65 @@ bool QRegion::intersects(const QRect &rect) const
 
 
 #endif
+
+#if defined(Q_OS_WIN) || defined(Q_QDOC)
+
+static inline HRGN qt_RectToHRGN(const QRect &rc)
+{
+    return CreateRectRgn(rc.left(), rc.top(), rc.right() + 1, rc.bottom() + 1);
+}
+
+/*!
+    \since 6.0
+
+    Returns a HRGN that is equivalent to the given region.
+*/
+HRGN QRegion::toHRGN() const
+{
+    const int size = rectCount();
+    if (size == 0)
+        return nullptr;
+
+    HRGN resultRgn = nullptr;
+    const auto rects = begin();
+    resultRgn = qt_RectToHRGN(rects[0]);
+    for (int i = 1; i < size; ++i) {
+        HRGN tmpRgn = qt_RectToHRGN(rects[i]);
+        int err = CombineRgn(resultRgn, resultRgn, tmpRgn, RGN_OR);
+        if (err == ERROR)
+            qWarning("Error combining HRGNs.");
+        DeleteObject(tmpRgn);
+    }
+    return resultRgn;
+}
+
+/*!
+    \since 6.0
+
+    Returns a QRegion that is equivalent to the given \a hrgn.
+ */
+QRegion QRegion::fromHRGN(HRGN hrgn)
+{
+    DWORD regionDataSize = GetRegionData(hrgn, 0, nullptr);
+    if (regionDataSize == 0)
+        return QRegion();
+
+    auto regionData = reinterpret_cast<LPRGNDATA>(malloc(regionDataSize));
+    if (!regionData)
+        return QRegion();
+
+    QRegion region;
+    if (GetRegionData(hrgn, regionDataSize, regionData) == regionDataSize) {
+        auto pRect = reinterpret_cast<LPRECT>(regionData->Buffer);
+        for (DWORD i = 0; i < regionData->rdh.nCount; ++i)
+            region += QRect(pRect[i].left, pRect[i].top,
+                            pRect[i].right - pRect[i].left,
+                            pRect[i].bottom - pRect[i].top);
+    }
+
+    free(regionData);
+    return region;
+}
+#endif // Q_OS_WIN || Q_QDOC
+
 QT_END_NAMESPACE

src/gui/painting/qregion.h

@@ -134,6 +134,12 @@ public:
     inline bool operator!=(const QRegion &r) const { return !(operator==(r)); }
     operator QVariant() const;
 
+    // Platform specific conversion functions
+#if defined(Q_OS_WIN) || defined(Q_QDOC)
+    HRGN toHRGN() const;
+    static QRegion fromHRGN(HRGN hrgn);
+#endif
+
 #ifndef QT_NO_DATASTREAM
     friend Q_GUI_EXPORT QDataStream &operator<<(QDataStream &, const QRegion &);
     friend Q_GUI_EXPORT QDataStream &operator>>(QDataStream &, QRegion &);

tests/auto/gui/painting/qregion/tst_qregion.cpp

@@ -35,6 +35,10 @@
 #include <qpainterpath.h>
 #include <qpolygon.h>
 
+#ifdef Q_OS_WIN
+#  include <qt_windows.h>
+#endif
+
 class tst_QRegion : public QObject
 {
     Q_OBJECT
@@ -86,6 +90,10 @@ private slots:
     void regionToPath_data();
     void regionToPath();
 #endif
+
+#ifdef Q_OS_WIN
+    void winConversion();
+#endif
 };
 
 tst_QRegion::tst_QRegion()
@@ -1061,7 +1069,21 @@ void tst_QRegion::regionToPath()
         QCOMPARE(a.boundingRect(), b.boundingRect());
     }
 }
-#endif
+#endif // QT_BUILD_INTERNAL
+
+#ifdef Q_OS_WIN
+void tst_QRegion::winConversion()
+{
+    const QList<QRect> rects{QRect(10, 10, 10, 10), QRect(10, 20, 10, 10),
+                             QRect(30, 20, 10, 10), QRect(10, 30, 10, 10)};
+    QRegion region;
+    region.setRects(rects.constData(), rects.size());
+    auto hrgn = region.toHRGN();
+    QVERIFY(hrgn);
+    QRegion convertedBack = QRegion::fromHRGN(hrgn);
+    QCOMPARE(region, convertedBack);
+}
+#endif // Q_OS_WIN
 
 QTEST_MAIN(tst_QRegion)
 #include "tst_qregion.moc"