iOS: Add support for foreign windows

Task-number: QTBUG-116183
Pick-to: 6.6
Change-Id: Ia92ee2d15f2e91a326ad342237fb0a83305c019f
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/corelib/kernel/qcore_mac_p.h

@@ -441,6 +441,20 @@ private:
 
 // -------------------------------------------------------------------------
 
+#ifdef __OBJC__
+template <typename T>
+typename std::enable_if<std::is_pointer<T>::value, T>::type
+qt_objc_cast(id object)
+{
+    if ([object isKindOfClass:[typename std::remove_pointer<T>::type class]])
+        return static_cast<T>(object);
+
+    return nil;
+}
+#endif
+
+// -------------------------------------------------------------------------
+
 QT_END_NAMESPACE
 
 #endif // QCORE_MAC_P_H

src/plugins/platforms/cocoa/qcocoahelpers.h

@@ -56,16 +56,6 @@ NSDragOperation qt_mac_mapDropActions(Qt::DropActions actions);
 Qt::DropAction qt_mac_mapNSDragOperation(NSDragOperation nsActions);
 Qt::DropActions qt_mac_mapNSDragOperations(NSDragOperation nsActions);
 
-template <typename T>
-typename std::enable_if<std::is_pointer<T>::value, T>::type
-qt_objc_cast(id object)
-{
-    if ([object isKindOfClass:[typename std::remove_pointer<T>::type class]])
-        return static_cast<T>(object);
-
-    return nil;
-}
-
 QT_MANGLE_NAMESPACE(QNSView) *qnsview_cast(NSView *view);
 
 // Misc

src/plugins/platforms/ios/qiosintegration.h

@@ -31,6 +31,7 @@ public:
     bool hasCapability(Capability cap) const override;
 
     QPlatformWindow *createPlatformWindow(QWindow *window) const override;
+    QPlatformWindow *createForeignWindow(QWindow *window, WId nativeHandle) const override;
     QPlatformBackingStore *createPlatformBackingStore(QWindow *window) const override;
 
 #if QT_CONFIG(opengl)

src/plugins/platforms/ios/qiosintegration.mm

@@ -150,6 +150,8 @@ bool QIOSIntegration::hasCapability(Capability cap) const
         return false;
     case ApplicationState:
         return true;
+    case ForeignWindows:
+        return true;
     default:
         return QPlatformIntegration::hasCapability(cap);
     }
@@ -160,6 +162,11 @@ QPlatformWindow *QIOSIntegration::createPlatformWindow(QWindow *window) const
     return new QIOSWindow(window);
 }
 
+QPlatformWindow *QIOSIntegration::createForeignWindow(QWindow *window, WId nativeHandle) const
+{
+    return new QIOSWindow(window, nativeHandle);
+}
+
 QPlatformBackingStore *QIOSIntegration::createPlatformBackingStore(QWindow *window) const
 {
     return new QRhiBackingStore(window);

src/plugins/platforms/ios/qioswindow.h

@@ -21,7 +21,7 @@ class QIOSWindow : public QObject, public QPlatformWindow
     Q_OBJECT
 
 public:
-    explicit QIOSWindow(QWindow *window);
+    explicit QIOSWindow(QWindow *window, WId nativeHandle = 0);
     ~QIOSWindow();
 
     void setGeometry(const QRect &rect) override;
@@ -66,7 +66,7 @@ private:
     void applicationStateChanged(Qt::ApplicationState state);
     void applyGeometry(const QRect &rect);
 
-    QUIView *m_view;
+    UIView *m_view;
 
     QRect m_normalGeometry;
     int m_windowLevel;
@@ -82,6 +82,8 @@ private:
 QDebug operator<<(QDebug debug, const QIOSWindow *window);
 #endif
 
+QT_MANGLE_NAMESPACE(QUIView) *quiview_cast(UIView *view);
+
 QT_END_NAMESPACE
 
 #endif // QIOSWINDOW_H

src/plugins/platforms/ios/qioswindow.mm

@@ -29,19 +29,24 @@
 
 QT_BEGIN_NAMESPACE
 
-QIOSWindow::QIOSWindow(QWindow *window)
+QIOSWindow::QIOSWindow(QWindow *window, WId nativeHandle)
     : QPlatformWindow(window)
     , m_windowLevel(0)
 {
+    if (nativeHandle) {
+        m_view = reinterpret_cast<UIView *>(nativeHandle);
+        [m_view retain];
+    } else {
 #ifdef Q_OS_IOS
-    if (window->surfaceType() == QSurface::RasterSurface)
-        window->setSurfaceType(QSurface::MetalSurface);
+        if (window->surfaceType() == QSurface::RasterSurface)
+            window->setSurfaceType(QSurface::MetalSurface);
 
-    if (window->surfaceType() == QSurface::MetalSurface)
-        m_view = [[QUIMetalView alloc] initWithQIOSWindow:this];
-    else
+        if (window->surfaceType() == QSurface::MetalSurface)
+            m_view = [[QUIMetalView alloc] initWithQIOSWindow:this];
+        else
 #endif
-        m_view = [[QUIView alloc] initWithQIOSWindow:this];
+            m_view = [[QUIView alloc] initWithQIOSWindow:this];
+    }
 
     connect(qGuiApp, &QGuiApplication::applicationStateChanged, this, &QIOSWindow::applicationStateChanged);
 
@@ -80,7 +85,7 @@ QIOSWindow::~QIOSWindow()
 
     clearAccessibleCache();
 
-    m_view.platformWindow = 0;
+    quiview_cast(m_view).platformWindow = 0;
     [m_view removeFromSuperview];
     [m_view release];
 }
@@ -120,7 +125,7 @@ void QIOSWindow::setVisible(bool visible)
     if (visible && shouldAutoActivateWindow()) {
         if (!window()->property("_q_showWithoutActivating").toBool())
             requestActivateWindow();
-    } else if (!visible && [m_view isActiveWindow]) {
+    } else if (!visible && [quiview_cast(m_view) isActiveWindow]) {
         // Our window was active/focus window but now hidden, so relinquish
         // focus to the next possible window in the stack.
         NSArray<UIView *> *subviews = m_view.viewController.view.subviews;
@@ -340,8 +345,11 @@ void QIOSWindow::handleContentOrientationChange(Qt::ScreenOrientation orientatio
 
 void QIOSWindow::applicationStateChanged(Qt::ApplicationState)
 {
+    if (isForeignWindow())
+        return;
+
     if (window()->isExposed() != isExposed())
-        [m_view sendUpdatedExposeEvent];
+        [quiview_cast(m_view) sendUpdatedExposeEvent];
 }
 
 qreal QIOSWindow::devicePixelRatio() const
@@ -351,7 +359,10 @@ qreal QIOSWindow::devicePixelRatio() const
 
 void QIOSWindow::clearAccessibleCache()
 {
-    [m_view clearAccessibleCache];
+    if (isForeignWindow())
+        return;
+
+    [quiview_cast(m_view) clearAccessibleCache];
 }
 
 void QIOSWindow::requestUpdate()
@@ -394,6 +405,27 @@ QDebug operator<<(QDebug debug, const QIOSWindow *window)
 }
 #endif // !QT_NO_DEBUG_STREAM
 
+/*!
+    Returns the view cast to a QUIview if possible.
+
+    If the view is not a QUIview, nil is returned, which is safe to
+    send messages to, effectively making [quiview_cast(view) message]
+    a no-op.
+
+    For extra verbosity and clearer code, please consider checking
+    that the platform window is not a foreign window before using
+    this cast, via QPlatformWindow::isForeignWindow().
+
+    Do not use this method solely to check for foreign windows, as
+    that will make the code harder to read for people not working
+    primarily on iOS, who do not know the difference between the
+    UIView and QUIView cases.
+*/
+QUIView *quiview_cast(UIView *view)
+{
+    return qt_objc_cast<QUIView *>(view);
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qioswindow.cpp"