Resolve QWidget window handle without depending on QtWidgets

Change-Id: If5b2f17283193d7a1718f476b72f380e9e67d0f0
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

4 files changed, 23 insertions, 15 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoadrag.mm b/src/plugins/platforms/cocoa/qcocoadrag.mm
index b4a16ab912..3525fddfd1 100644
--- a/src/plugins/platforms/cocoa/qcocoadrag.mm
+++ b/src/plugins/platforms/cocoa/qcocoadrag.mm
@@ -40,9 +40,6 @@
 #include "qcocoadrag.h"
 #include "qmacclipboard.h"
 #include "qcocoahelpers.h"
-#ifndef QT_NO_WIDGETS
-#include <QtWidgets/qwidget.h>
-#endif
 #include <QtGui/private/qcoregraphics_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -189,19 +186,17 @@ QPixmap QCocoaDrag::dragPixmap(QDrag *drag, QPoint &hotSpot) const
                 const int height = fm.height();
                 if (width > 0 && height > 0) {
                     qreal dpr = 1.0;
-                    if (const QWindow *sourceWindow = qobject_cast<QWindow *>(drag->source())) {
-                        dpr = sourceWindow->devicePixelRatio();
-                    }
-#ifndef QT_NO_WIDGETS
-                    else if (const QWidget *sourceWidget = qobject_cast<QWidget *>(drag->source())) {
-                        if (const QWindow *sourceWindow = sourceWidget->window()->windowHandle())
-                            dpr = sourceWindow->devicePixelRatio();
-                    }
-#endif
-                    else {
-                        if (const QWindow *focusWindow = qApp->focusWindow())
-                            dpr = focusWindow->devicePixelRatio();
+                    QWindow *window = qobject_cast<QWindow *>(drag->source());
+                    if (!window && drag->source()->metaObject()->indexOfMethod("_q_closestWindowHandle()") != -1) {
+                        QMetaObject::invokeMethod(drag->source(), "_q_closestWindowHandle",
+                            Q_RETURN_ARG(QWindow *, window));
                     }
+                    if (!window)
+                        window = qApp->focusWindow();
+
+                    if (window)
+                        dpr = window->devicePixelRatio();
+
                     pm = QPixmap(width * dpr, height * dpr);
                     pm.setDevicePixelRatio(dpr);
                     QPainter p(&pm);
diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 19945473da..79c8aba8cf 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -1112,6 +1112,17 @@ QWindow *QWidgetPrivate::windowHandle(WindowHandleMode mode) const
     return nullptr;
 }
 
+/*!
+    \internal
+
+    Used by clients outside of widgets to get a handle to the
+    closest QWindow without having to link to widgets.
+*/
+QWindow *QWidgetPrivate::_q_closestWindowHandle() const
+{
+    return windowHandle(QWidgetPrivate::WindowHandleMode::Closest);
+}
+
 QScreen *QWidgetPrivate::associatedScreen() const
 {
     if (auto window = windowHandle(WindowHandleMode::Closest))
diff --git a/src/widgets/kernel/qwidget.h b/src/widgets/kernel/qwidget.h
index 9ea4301428..68a9b7ca9b 100644
--- a/src/widgets/kernel/qwidget.h
+++ b/src/widgets/kernel/qwidget.h
@@ -742,6 +742,7 @@ private:
 private:
     Q_DISABLE_COPY(QWidget)
     Q_PRIVATE_SLOT(d_func(), void _q_showIfNotHidden())
+    Q_PRIVATE_SLOT(d_func(), QWindow *_q_closestWindowHandle())
 
     QWidgetData *data;
 };
diff --git a/src/widgets/kernel/qwidget_p.h b/src/widgets/kernel/qwidget_p.h
index 3c29b48973..a3eac8d9ec 100644
--- a/src/widgets/kernel/qwidget_p.h
+++ b/src/widgets/kernel/qwidget_p.h
@@ -270,6 +270,7 @@ public:
         TopLevel
     };
     QWindow *windowHandle(WindowHandleMode mode = WindowHandleMode::Direct) const;
+    QWindow *_q_closestWindowHandle() const; // Private slot in QWidget
 
     QScreen *associatedScreen() const;