Enable making window-screen associations from QML

Qt Quick provides a Screen attached property to query information
about the screen an item's window belongs to. This is a good start,
but has two problems: it lacks some virtual desktop related info
(e.g. the position in the virtual desktop) and it cannot be used in
combination with the Window element in order to achieve a QML
equivalent of QWindow::setScreen().

Therefore add the missing virtualX and virtualY properties and
introduce Qt.application.screens. The latter is an equivalent to
QGuiApplication::screens() and is a JS array the elements of which
can be set as the value of the new Window.targetScreen property.

This means that a call like
window->setScreen(QGuiApplication::screens()[0]) translates to
Window { targetScreen: Qt.application.screens[0]; ... } when using the
Window type from QML. Screen addition or removal can be acted upon via
onScreensChanged.

QQuickScreenAttached has been split into two in order to allow reusing the
QScreen wrapping queries for other purposes as well.

Task-number: QTBUG-56115
Change-Id: I4b2fbd873315b40d0afe878da2fc50966c00e2e0
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 118 insertions, 77 deletions

diff --git a/src/quick/items/qquickscreen.cpp b/src/quick/items/qquickscreen.cpp
index 5d01a2af9d..9347b55c70 100644
--- a/src/quick/items/qquickscreen.cpp
+++ b/src/quick/items/qquickscreen.cpp
@@ -207,100 +207,181 @@ QT_BEGIN_NAMESPACE
     By default it is set to the value of the QScreen that the window uses.
 */
 
-QQuickScreenAttached::QQuickScreenAttached(QObject* attachee)
-    : QObject(attachee)
-    , m_screen(NULL)
-    , m_window(NULL)
-    , m_updateMask(0)
-    , m_updateMaskSet(false)
+QQuickScreenInfo::QQuickScreenInfo(QObject *parent)
+    : QObject(parent),
+      m_screen(nullptr)
 {
-    m_attachee = qobject_cast<QQuickItem*>(attachee);
-
-    if (m_attachee) {
-        QQuickItemPrivate::get(m_attachee)->extra.value().screenAttached = this;
-
-        if (m_attachee->window()) //It might not be assigned to a window yet
-            windowChanged(m_attachee->window());
-    } else {
-        QQuickWindow *window = qobject_cast<QQuickWindow*>(attachee);
-        if (window)
-            windowChanged(window);
-    }
-
-    if (!m_screen)
-        screenChanged(QGuiApplication::primaryScreen());
 }
 
-QString QQuickScreenAttached::name() const
+QString QQuickScreenInfo::name() const
 {
     if (!m_screen)
         return QString();
     return m_screen->name();
 }
 
-int QQuickScreenAttached::width() const
+int QQuickScreenInfo::width() const
 {
     if (!m_screen)
         return 0;
     return m_screen->size().width();
 }
 
-int QQuickScreenAttached::height() const
+int QQuickScreenInfo::height() const
 {
     if (!m_screen)
         return 0;
     return m_screen->size().height();
 }
 
-int QQuickScreenAttached::desktopAvailableWidth() const
+int QQuickScreenInfo::desktopAvailableWidth() const
 {
     if (!m_screen)
         return 0;
     return m_screen->availableVirtualSize().width();
 }
 
-int QQuickScreenAttached::desktopAvailableHeight() const
+int QQuickScreenInfo::desktopAvailableHeight() const
 {
     if (!m_screen)
         return 0;
     return m_screen->availableVirtualSize().height();
 }
 
-qreal QQuickScreenAttached::logicalPixelDensity() const
+qreal QQuickScreenInfo::logicalPixelDensity() const
 {
     if (!m_screen)
         return 0.0;
     return m_screen->logicalDotsPerInch() / 25.4;
 }
 
-qreal QQuickScreenAttached::pixelDensity() const
+qreal QQuickScreenInfo::pixelDensity() const
 {
     if (!m_screen)
         return 0.0;
     return m_screen->physicalDotsPerInch() / 25.4;
 }
 
-qreal QQuickScreenAttached::devicePixelRatio() const
+qreal QQuickScreenInfo::devicePixelRatio() const
 {
     if (!m_screen)
         return 1.0;
     return m_screen->devicePixelRatio();
 }
 
-Qt::ScreenOrientation QQuickScreenAttached::primaryOrientation() const
+Qt::ScreenOrientation QQuickScreenInfo::primaryOrientation() const
 {
     if (!m_screen)
         return Qt::PrimaryOrientation;
     return m_screen->primaryOrientation();
 }
 
-Qt::ScreenOrientation QQuickScreenAttached::orientation() const
+Qt::ScreenOrientation QQuickScreenInfo::orientation() const
 {
     if (!m_screen)
         return Qt::PrimaryOrientation;
     return m_screen->orientation();
 }
 
+int QQuickScreenInfo::virtualX() const
+{
+    if (!m_screen)
+        return 0;
+    return m_screen->geometry().topLeft().x();
+}
+
+int QQuickScreenInfo::virtualY() const
+{
+    if (!m_screen)
+        return 0;
+    return m_screen->geometry().topLeft().y();
+}
+
+void QQuickScreenInfo::setWrappedScreen(QScreen *screen)
+{
+    if (screen == m_screen)
+        return;
+
+    QScreen *oldScreen = m_screen;
+    m_screen = screen;
+
+    if (oldScreen)
+        oldScreen->disconnect(this);
+
+    if (!screen) //Don't bother emitting signals, because the new values are garbage anyways
+        return;
+
+    if (!oldScreen || screen->geometry() != oldScreen->geometry()) {
+        emit virtualXChanged();
+        emit virtualYChanged();
+    }
+    if (!oldScreen || screen->size() != oldScreen->size()) {
+        emit widthChanged();
+        emit heightChanged();
+    }
+    if (!oldScreen || screen->name() != oldScreen->name())
+        emit nameChanged();
+    if (!oldScreen || screen->orientation() != oldScreen->orientation())
+        emit orientationChanged();
+    if (!oldScreen || screen->primaryOrientation() != oldScreen->primaryOrientation())
+        emit primaryOrientationChanged();
+    if (!oldScreen || screen->availableVirtualGeometry() != oldScreen->availableVirtualGeometry())
+        emit desktopGeometryChanged();
+    if (!oldScreen || screen->logicalDotsPerInch() != oldScreen->logicalDotsPerInch())
+        emit logicalPixelDensityChanged();
+    if (!oldScreen || screen->physicalDotsPerInch() != oldScreen->physicalDotsPerInch())
+        emit pixelDensityChanged();
+    if (!oldScreen || screen->devicePixelRatio() != oldScreen->devicePixelRatio())
+        emit devicePixelRatioChanged();
+
+    connect(screen, SIGNAL(geometryChanged(QRect)),
+            this, SIGNAL(widthChanged()));
+    connect(screen, SIGNAL(geometryChanged(QRect)),
+            this, SIGNAL(heightChanged()));
+    connect(screen, SIGNAL(geometryChanged(QRect)),
+            this, SIGNAL(virtualXChanged()));
+    connect(screen, SIGNAL(geometryChanged(QRect)),
+            this, SIGNAL(virtualYChanged()));
+    connect(screen, SIGNAL(orientationChanged(Qt::ScreenOrientation)),
+            this, SIGNAL(orientationChanged()));
+    connect(screen, SIGNAL(primaryOrientationChanged(Qt::ScreenOrientation)),
+            this, SIGNAL(primaryOrientationChanged()));
+    connect(screen, SIGNAL(virtualGeometryChanged(QRect)),
+            this, SIGNAL(desktopGeometryChanged()));
+    connect(screen, SIGNAL(logicalDotsPerInchChanged(qreal)),
+            this, SIGNAL(logicalPixelDensityChanged()));
+    connect(screen, SIGNAL(physicalDotsPerInchChanged(qreal)),
+            this, SIGNAL(pixelDensityChanged()));
+}
+
+QScreen *QQuickScreenInfo::wrappedScreen() const
+{
+    return m_screen;
+}
+
+QQuickScreenAttached::QQuickScreenAttached(QObject* attachee)
+    : QQuickScreenInfo(attachee)
+    , m_window(NULL)
+    , m_updateMask(0)
+    , m_updateMaskSet(false)
+{
+    m_attachee = qobject_cast<QQuickItem*>(attachee);
+
+    if (m_attachee) {
+        QQuickItemPrivate::get(m_attachee)->extra.value().screenAttached = this;
+
+        if (m_attachee->window()) //It might not be assigned to a window yet
+            windowChanged(m_attachee->window());
+    } else {
+        QQuickWindow *window = qobject_cast<QQuickWindow*>(attachee);
+        if (window)
+            windowChanged(window);
+    }
+
+    if (!m_screen)
+        screenChanged(QGuiApplication::primaryScreen());
+}
+
 Qt::ScreenOrientations QQuickScreenAttached::orientationUpdateMask() const
 {
     return m_updateMask;
@@ -341,55 +422,15 @@ void QQuickScreenAttached::screenChanged(QScreen *screen)
 {
     //qDebug() << "QQuickScreenAttached::screenChanged" << (screen ? screen->name() : QString::fromLatin1("null"));
     if (screen != m_screen) {
-        QScreen* oldScreen = m_screen;
-        m_screen = screen;
-
-        if (oldScreen)
-            oldScreen->disconnect(this);
-
-        if (!screen)
-            return; //Don't bother emitting signals, because the new values are garbage anyways
-
+        setWrappedScreen(screen);
+        if (!m_screen)
+            return;
         if (m_updateMaskSet) {
-            screen->setOrientationUpdateMask(m_updateMask);
-        } else if (m_updateMask != screen->orientationUpdateMask()) {
-            m_updateMask = screen->orientationUpdateMask();
+            m_screen->setOrientationUpdateMask(m_updateMask);
+        } else if (m_updateMask != m_screen->orientationUpdateMask()) {
+            m_updateMask = m_screen->orientationUpdateMask();
             emit orientationUpdateMaskChanged();
         }
-
-        if (!oldScreen || screen->size() != oldScreen->size()) {
-            emit widthChanged();
-            emit heightChanged();
-        }
-        if (!oldScreen || screen->name() != oldScreen->name())
-            emit nameChanged();
-        if (!oldScreen || screen->orientation() != oldScreen->orientation())
-            emit orientationChanged();
-        if (!oldScreen || screen->primaryOrientation() != oldScreen->primaryOrientation())
-            emit primaryOrientationChanged();
-        if (!oldScreen || screen->availableVirtualGeometry() != oldScreen->availableVirtualGeometry())
-            emit desktopGeometryChanged();
-        if (!oldScreen || screen->logicalDotsPerInch() != oldScreen->logicalDotsPerInch())
-            emit logicalPixelDensityChanged();
-        if (!oldScreen || screen->physicalDotsPerInch() != oldScreen->physicalDotsPerInch())
-            emit pixelDensityChanged();
-        if (!oldScreen || screen->devicePixelRatio() != oldScreen->devicePixelRatio())
-            emit devicePixelRatioChanged();
-
-        connect(screen, SIGNAL(geometryChanged(QRect)),
-                this, SIGNAL(widthChanged()));
-        connect(screen, SIGNAL(geometryChanged(QRect)),
-                this, SIGNAL(heightChanged()));
-        connect(screen, SIGNAL(orientationChanged(Qt::ScreenOrientation)),
-                this, SIGNAL(orientationChanged()));
-        connect(screen, SIGNAL(primaryOrientationChanged(Qt::ScreenOrientation)),
-                this, SIGNAL(primaryOrientationChanged()));
-        connect(screen, SIGNAL(virtualGeometryChanged(QRect)),
-                this, SIGNAL(desktopGeometryChanged()));
-        connect(screen, SIGNAL(logicalDotsPerInchChanged(qreal)),
-                this, SIGNAL(logicalPixelDensityChanged()));
-        connect(screen, SIGNAL(physicalDotsPerInchChanged(qreal)),
-                this, SIGNAL(pixelDensityChanged()));
     }
 }