Fix incorrect screen number reported by QDesktopWidget

Screens connected to separate graphics cards are detected as
separate screens which don't have offset. This patch fixes obtaining
the screen number by QWidget: it uses the screen assigned to the root
widget. The patch also assigns a proper QScreen to each QDesktopWidget
screen().

It also fixes closing a popup menu by clicking on another screen.

Task-number: QTBUG-48545
Change-Id: I3d76261c0c067293d39949c4428b2d8dfd085dc7
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>

1 files changed, 26 insertions, 5 deletions

diff --git a/src/widgets/kernel/qdesktopwidget.cpp b/src/widgets/kernel/qdesktopwidget.cpp
index b88b3cc61d..d21e60198e 100644
--- a/src/widgets/kernel/qdesktopwidget.cpp
+++ b/src/widgets/kernel/qdesktopwidget.cpp
@@ -36,6 +36,7 @@
 #include "qdesktopwidget_p.h"
 #include "qscreen.h"
 #include "qwidget_p.h"
+#include "qwindow.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -99,13 +100,18 @@ void QDesktopWidgetPrivate::_q_updateScreens()
 
     QRegion virtualGeometry;
 
-    // update the geometry of each screen widget, determine virtual geometry
-    // and emit change signals afterwards.
+    // update the geometry of each screen widget, determine virtual geometry,
+    // set the new screen for window handle and emit change signals afterwards.
     QList<int> changedScreens;
     for (int i = 0; i < screens.length(); i++) {
-        const QRect screenGeometry = screenList.at(i)->geometry();
-        if (screenGeometry != screens.at(i)->geometry()) {
-            screens.at(i)->setGeometry(screenGeometry);
+        QDesktopScreenWidget *screenWidget = screens.at(i);
+        QScreen *qScreen = screenList.at(i);
+        QWindow *winHandle = screenWidget->windowHandle();
+        if (winHandle && winHandle->screen() != qScreen)
+            winHandle->setScreen(qScreen);
+        const QRect screenGeometry = qScreen->geometry();
+        if (screenGeometry != screenWidget->geometry()) {
+            screenWidget->setGeometry(screenGeometry);
             changedScreens.push_back(i);
         }
         virtualGeometry += screenGeometry;
@@ -191,6 +197,21 @@ int QDesktopWidget::screenNumber(const QWidget *w) const
     if (!w)
         return 0;
 
+    // Find the root widget, get a QScreen pointer from it and find
+    // the screen number.
+    const QWidget *root = w;
+    const QWidget *tmp = w;
+    while ((tmp = tmp->parentWidget()))
+        root = tmp;
+    QWindow *winHandle = root->windowHandle();
+    if (winHandle) {
+        int screenIdx = QGuiApplication::screens().indexOf(winHandle->screen());
+        if (screenIdx > -1)
+            return screenIdx;
+    }
+
+    // If the screen number cannot be obtained using QScreen pointer,
+    // get it from window position using screen geometry.
     QRect frame = w->frameGeometry();
     if (!w->isWindow())
         frame.moveTopLeft(w->mapToGlobal(QPoint(0, 0)));