QWindow: Remove "_q_foreignWinId" dynamic property

The platform plugins reading this out of the QWindow was a layering
violation, and propagates the notion that a window can shape shift
into representing a new native handle, while none of the platform
plugins support this.

A foreign QWindow is created via the factory function fromWinId(),
at which point we can pass the WId all the way to the platform
plugin as function arguments, where the platform will create a
corresponding platform-window.

The platform window can then answer the question of whether or
not it's representing a foreign window, which determines a few
behavioral changes here and there, as well as supplying the
native window handle back for QWindow::winId();

[ChangeLog][QtGui][QWindow] The "_q_foreignWinId" dynamic property
is no longer set nor read.

[ChangeLog][QtGui][QPA] The function createForeignWindow() has been
added to QPlatormIntegration and is now responsible for creating
foreign windows. The function isForeignWindow() in QPlatformWindow
has been added, and platforms should implement this to return true
for windows created by createForeignWindow().

Task-number: QTBUG-58383
Change-Id: If84142f95172f62b9377eb5d2a4d792cad36010b
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>

4 files changed, 17 insertions, 4 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.h b/src/plugins/platforms/cocoa/qcocoaintegration.h
index a3c375881d..ecdd20c4dc 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.h
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.h
@@ -126,6 +126,7 @@ public:
 
     bool hasCapability(QPlatformIntegration::Capability cap) const Q_DECL_OVERRIDE;
     QPlatformWindow *createPlatformWindow(QWindow *window) const Q_DECL_OVERRIDE;
+    QPlatformWindow *createForeignWindow(QWindow *window, WId nativeHandle) const Q_DECL_OVERRIDE;
 #ifndef QT_NO_OPENGL
     QPlatformOpenGLContext *createPlatformOpenGLContext(QOpenGLContext *context) const Q_DECL_OVERRIDE;
 #endif
diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index 291d39ea9d..91f408e5c2 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -524,6 +524,11 @@ QPlatformWindow *QCocoaIntegration::createPlatformWindow(QWindow *window) const
     return new QCocoaWindow(window);
 }
 
+QPlatformWindow *QCocoaIntegration::createForeignWindow(QWindow *window, WId nativeHandle) const
+{
+    return new QCocoaWindow(window, nativeHandle);
+}
+
 #ifndef QT_NO_OPENGL
 QPlatformOpenGLContext *QCocoaIntegration::createPlatformOpenGLContext(QOpenGLContext *context) const
 {
diff --git a/src/plugins/platforms/cocoa/qcocoawindow.h b/src/plugins/platforms/cocoa/qcocoawindow.h
index f60597fe42..8e2c441465 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.h
+++ b/src/plugins/platforms/cocoa/qcocoawindow.h
@@ -156,7 +156,7 @@ class QCocoaWindow : public QObject, public QPlatformWindow
 {
     Q_OBJECT
 public:
-    QCocoaWindow(QWindow *tlw);
+    QCocoaWindow(QWindow *tlw, WId nativeHandle = 0);
     ~QCocoaWindow();
 
     void setGeometry(const QRect &rect) Q_DECL_OVERRIDE;
@@ -186,6 +186,8 @@ public:
     QMargins frameMargins() const Q_DECL_OVERRIDE;
     QSurfaceFormat format() const Q_DECL_OVERRIDE;
 
+    bool isForeignWindow() const Q_DECL_OVERRIDE;
+
     void requestActivateWindow() Q_DECL_OVERRIDE;
 
     WId winId() const Q_DECL_OVERRIDE;
diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index 60cababba4..2dd151e324 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -433,7 +433,7 @@ Q_CONSTRUCTOR_FUNCTION(qRegisterNotificationCallbacks)
 
 const int QCocoaWindow::NoAlertRequest = -1;
 
-QCocoaWindow::QCocoaWindow(QWindow *tlw)
+QCocoaWindow::QCocoaWindow(QWindow *tlw, WId nativeHandle)
     : QPlatformWindow(tlw)
     , m_view(nil)
     , m_nsWindow(0)
@@ -470,8 +470,8 @@ QCocoaWindow::QCocoaWindow(QWindow *tlw)
 
     QMacAutoReleasePool pool;
 
-    if (tlw->type() == Qt::ForeignWindow) {
-        m_view = (NSView *)WId(tlw->property("_q_foreignWinId").value<WId>());
+    if (nativeHandle) {
+        m_view = reinterpret_cast<NSView *>(nativeHandle);
         [m_view retain];
     } else {
         m_view = [[QNSView alloc] initWithCocoaWindow:this];
@@ -563,6 +563,11 @@ void QCocoaWindow::setGeometry(const QRect &rectIn)
     setCocoaGeometry(rect);
 }
 
+bool QCocoaWindow::isForeignWindow() const
+{
+    return ![m_view isKindOfClass:[QNSView class]];
+}
+
 QRect QCocoaWindow::geometry() const
 {
     // QWindows that are embedded in a NSView hiearchy may be considered