Add QPlatformWindow::close()

Platforms can reimplement this function to control
how non-spontaneous window close is handled.

Make QWindow::close() call this function.

Change-Id: I3da13e6c8519de2af7e54334d8a1e833ce98cba1
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/gui/kernel/qplatformwindow.cpp

@@ -339,6 +339,20 @@ void QPlatformWindow::setWindowFilePath(const QString &filePath) { Q_UNUSED(file
 */
 void QPlatformWindow::setWindowIcon(const QIcon &icon) { Q_UNUSED(icon); }
 
+/*!
+  Reimplement to let the platform handle non-spontaneous window close.
+
+  When reimplementing make sure to call the base class implementation
+  or QWindowSystemInterface::handleCloseEvent(), which will prompt the
+  user to accept the window close (if needed) and then close the QWindow.
+*/
+bool QPlatformWindow::close()
+{
+    bool accepted = false;
+    QWindowSystemInterface::handleCloseEvent<QWindowSystemInterface::SynchronousDelivery>(window(), &accepted);
+    return accepted;
+}
+
 /*!
   Reimplement to be able to let Qt raise windows to the top of the desktop
 */

src/gui/kernel/qplatformwindow.h

@@ -100,6 +100,7 @@ public:
     virtual void setWindowTitle(const QString &title);
     virtual void setWindowFilePath(const QString &title);
     virtual void setWindowIcon(const QIcon &icon);
+    virtual bool close();
     virtual void raise();
     virtual void lower();
 

src/gui/kernel/qwindow.cpp

@@ -2144,10 +2144,7 @@ bool QWindow::close()
     if (!d->platformWindow)
         return true;
 
-    bool accepted = false;
-    QWindowSystemInterface::handleCloseEvent(this, &accepted);
-    QWindowSystemInterface::flushWindowSystemEvents();
-    return accepted;
+    return d->platformWindow->close();
 }
 
 /*!