High-dpi configuration change testing

Export configuration() and setConfiguration() from the offscreen
platform plugin using QPlatformNativeInterface. tst_qighdpi can
then resolve and make use of them since it always uses the offscreen
platform plugin.

Add screenDpiChange() auto test.

Change-Id: I459b4df5d94ec4991234a346e3a94618cb3485e9
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

4 files changed, 153 insertions, 1 deletions

diff --git a/src/plugins/platforms/offscreen/qoffscreencommon.cpp b/src/plugins/platforms/offscreen/qoffscreencommon.cpp
index 29e2cc417d..f485b4eed8 100644
--- a/src/plugins/platforms/offscreen/qoffscreencommon.cpp
+++ b/src/plugins/platforms/offscreen/qoffscreencommon.cpp
@@ -236,6 +236,38 @@ void QOffscreenBackingStore::clearHash()
 
 QHash<WId, QOffscreenBackingStore *> QOffscreenBackingStore::m_backingStoreForWinIdHash;
 
+QOffscreenPlatformNativeInterface::QOffscreenPlatformNativeInterface(QOffscreenIntegration *integration)
+    : m_integration(integration)
+{
+
+}
+
 QOffscreenPlatformNativeInterface::~QOffscreenPlatformNativeInterface() = default;
 
+/*
+    Set platform configuration, e.g. screen configuration
+*/
+void QOffscreenPlatformNativeInterface::setConfiguration(const QJsonObject &configuration, QOffscreenPlatformNativeInterface *iface)
+{
+    iface->m_integration->setConfiguration(configuration);
+}
+
+/*
+    Get the current platform configuration
+*/
+QJsonObject QOffscreenPlatformNativeInterface::configuration(QOffscreenPlatformNativeInterface *iface)
+{
+    return iface->m_integration->configuration();
+}
+
+void *QOffscreenPlatformNativeInterface::nativeResourceForIntegration(const QByteArray &resource)
+{
+    if (resource == "setConfiguration")
+        return reinterpret_cast<void*>(&QOffscreenPlatformNativeInterface::setConfiguration);
+    else if (resource == "configuration")
+        return reinterpret_cast<void*>(&QOffscreenPlatformNativeInterface::configuration);
+    else
+        return nullptr;
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/offscreen/qoffscreencommon.h b/src/plugins/platforms/offscreen/qoffscreencommon.h
index 7f92c5b4d9..d0edfcc48b 100644
--- a/src/plugins/platforms/offscreen/qoffscreencommon.h
+++ b/src/plugins/platforms/offscreen/qoffscreencommon.h
@@ -51,6 +51,7 @@
 
 #include <qscopedpointer.h>
 #include <qimage.h>
+#include <qjsonobject.h>
 #include <qhash.h>
 
 QT_BEGIN_NAMESPACE
@@ -120,7 +121,15 @@ private:
 class QOffscreenPlatformNativeInterface : public QPlatformNativeInterface
 {
 public:
+    QOffscreenPlatformNativeInterface(QOffscreenIntegration *integration);
     ~QOffscreenPlatformNativeInterface();
+
+    static void setConfiguration(const QJsonObject &configuration, QOffscreenPlatformNativeInterface *iface);
+    static QJsonObject configuration(QOffscreenPlatformNativeInterface *iface);
+
+    void *nativeResourceForIntegration(const QByteArray &resource) override;
+private:
+    QOffscreenIntegration *m_integration;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/offscreen/qoffscreenintegration.cpp b/src/plugins/platforms/offscreen/qoffscreenintegration.cpp
index a8504316d8..2613a42755 100644
--- a/src/plugins/platforms/offscreen/qoffscreenintegration.cpp
+++ b/src/plugins/platforms/offscreen/qoffscreenintegration.cpp
@@ -388,7 +388,7 @@ QAbstractEventDispatcher *QOffscreenIntegration::createEventDispatcher() const
 QPlatformNativeInterface *QOffscreenIntegration::nativeInterface() const
 {
     if (!m_nativeInterface)
-        m_nativeInterface.reset(new QOffscreenPlatformNativeInterface);
+        m_nativeInterface.reset(new QOffscreenPlatformNativeInterface(const_cast<QOffscreenIntegration*>(this)));
     return m_nativeInterface.get();
 }
 
diff --git a/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp b/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
index f0b1cab41a..b732954230 100644
--- a/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
+++ b/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
@@ -28,11 +28,13 @@
 
 #include <private/qhighdpiscaling_p.h>
 #include <qpa/qplatformscreen.h>
+#include <qpa/qplatformnativeinterface.h>
 
 #include <QTest>
 #include <QJsonArray>
 #include <QJsonObject>
 #include <QJsonDocument>
+#include <QStringView>
 
 Q_LOGGING_CATEGORY(lcTests, "qt.gui.tests")
 
@@ -45,6 +47,10 @@ private: // helpers
     QGuiApplication *createStandardOffscreenApp(const QList<qreal> &dpiValues);
     QGuiApplication *createStandardOffscreenApp(const QJsonArray &screens);
     static void standardScreenDpiTestData();
+
+    static void setOffscreenConfiguration(const QJsonObject &configuration);
+    static QJsonObject offscreenConfiguration();
+
 private slots:
     void cleanup();
     void qhighdpiscaling_data();
@@ -53,6 +59,7 @@ private slots:
     void noscreens();
     void screenDpiAndDpr_data();
     void screenDpiAndDpr();
+    void screenDpiChange();
     void environment_QT_SCALE_FACTOR();
     void environment_QT_SCREEN_SCALE_FACTORS_data();
     void environment_QT_SCREEN_SCALE_FACTORS();
@@ -178,6 +185,83 @@ void tst_QHighDpi::standardScreenDpiTestData()
     QTest::newRow("240-252-360") << QList<qreal> { 400./160 * 96, 420./160 * 96, 600./160 * 96 };
 }
 
+void tst_QHighDpi::setOffscreenConfiguration(const QJsonObject &configuration)
+{
+    Q_ASSERT(qApp->platformName() == QLatin1String("offscreen"));
+    QPlatformNativeInterface *platformNativeInterface = qApp->platformNativeInterface();
+    auto setConfiguration = reinterpret_cast<void (*)(QJsonObject, QPlatformNativeInterface *)>(
+        platformNativeInterface->nativeResourceForIntegration("setConfiguration"));
+    setConfiguration(configuration, platformNativeInterface);
+}
+
+QJsonObject tst_QHighDpi::offscreenConfiguration()
+{
+    Q_ASSERT(qApp->platformName() == QLatin1String("offscreen"));
+    QPlatformNativeInterface *platformNativeInterface = qApp->platformNativeInterface();
+    auto getConfiguration = reinterpret_cast<QJsonObject (*)(QPlatformNativeInterface *)>(
+        platformNativeInterface->nativeResourceForIntegration("configuration"));
+    return getConfiguration(platformNativeInterface);
+}
+
+// JsonValueRef implements support for mutating nested JSON structures, e.g.
+//
+//   JsonValueRef::get(&config)["screens"][0]["logicalDpi"] = 192
+//
+class JsonValueRef {
+public:
+    static JsonValueRef get(QJsonValue *value) {
+        return JsonValueRef(value);
+    }
+
+    JsonValueRef(QJsonValue *value)
+        : m_value(value) { }
+
+    JsonValueRef(QJsonValue *value, JsonValueRef *parent, QString key)
+        : m_value(value), m_parent(parent), m_key(key) { }
+
+    JsonValueRef(QJsonValue *value, JsonValueRef *parent, int index)
+        : m_value(value), m_parent(parent), m_index(index) { }
+
+    ~JsonValueRef() {
+        if (m_parent) {
+            if (!m_key.isNull()) {
+                QJsonObject parentObject = m_parent->m_value->toObject();
+                parentObject[m_key] = *m_value;
+                *m_parent->m_value = parentObject;
+            } else if (m_index > -1) {
+                QJsonArray parentArray = m_parent->m_value->toArray();
+                parentArray[m_index] = *m_value;
+                *m_parent->m_value = parentArray;
+            }
+            delete m_value; // owned if we have a parent, see operator[]
+        }
+    }
+
+    JsonValueRef operator[](const char *str) {
+        QString key = QString::fromUtf8(str);
+        return JsonValueRef(new QJsonValue((*m_value)[key]), this, key);
+    }
+
+    JsonValueRef operator[](int index) {
+        return JsonValueRef(new QJsonValue((*m_value)[index]), this, index);
+    }
+
+    void operator=(int value) {
+        *m_value = QJsonValue(value);
+    }
+
+    void operator=(const char *str) {
+        *m_value = QJsonValue(QString(str));
+    }
+
+private:
+    Q_DISABLE_COPY(JsonValueRef);
+    QJsonValue *m_value = nullptr;
+    JsonValueRef *m_parent = nullptr;
+    QString m_key;
+    int m_index = -1;
+};
+
 void tst_QHighDpi::cleanup()
 {
     // Some test functions set environment variables. Unset them here,
@@ -233,6 +317,33 @@ void tst_QHighDpi::screenDpiAndDpr()
     }
 }
 
+void tst_QHighDpi::screenDpiChange()
+{
+    QList<qreal> dpiValues = { 96, 96, 96};
+    std::unique_ptr<QGuiApplication> app(createStandardOffscreenApp(dpiValues));
+
+    QCOMPARE(app->devicePixelRatio(), 1);
+
+    // Set new DPI
+    int newDpi = 192;
+    QJsonValue config = offscreenConfiguration();
+    JsonValueRef::get(&config)["screens"][0]["logicalDpi"] = newDpi;
+    JsonValueRef::get(&config)["screens"][1]["logicalDpi"] = newDpi;
+    JsonValueRef::get(&config)["screens"][2]["logicalDpi"] = newDpi;
+    setOffscreenConfiguration(config.toObject());
+
+    // TODO check events
+
+    // Verify that the new DPI is in use
+    for (QScreen *screen : app->screens()) {
+        QCOMPARE(screen->devicePixelRatio(), newDpi / standardBaseDpi);
+        QCOMPARE(screen->logicalDotsPerInch(), newDpi / screen->devicePixelRatio());
+        QWindow window(screen);
+        QCOMPARE(window.devicePixelRatio(), screen->devicePixelRatio());
+    }
+    QCOMPARE(app->devicePixelRatio(), newDpi / standardBaseDpi);
+}
+
 void tst_QHighDpi::environment_QT_SCALE_FACTOR()
 {
     qreal factor = 3.1415;