Fix crash caused by setting Tray window screen pointer on the QML side

Seems like Qt sometimes doesn't like the QML window's screen property to be set
to a C++ (QVariant) pointer value, so we use the index: Qt.application.screens[]

See Qt docs: https://doc.qt.io/qt-5/qml-qtquick-window-window.html#screen-prop

This fix returns the matching window's index from the QGuiApplication::screens()
list to the QML side, instead of the window pointer.

Steps to reproduce the crash with the previous code:
- Open the Tray menu and close it a few times,
  or scroll randomly up and down in its activity list.

Tested with Qt 5.12.5

Signed-off-by: Michael Schuster <michael@schuster.ms>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/gui/systray.cpp b/src/gui/systray.cpp
index 97f19765c..ebcefc4df 100644
--- a/src/gui/systray.cpp
+++ b/src/gui/systray.cpp
@@ -158,9 +158,11 @@ QScreen *Systray::currentScreen() const
     return nullptr;
 }
 
-QVariant Systray::currentScreenVar() const
+int Systray::currentScreenIndex() const
 {
-    return QVariant::fromValue(currentScreen());
+    const auto screens = QGuiApplication::screens();
+    const auto screenIndex = screens.indexOf(currentScreen());
+    return screenIndex > 0 ? screenIndex : 0;
 }
 
 Systray::TaskBarPosition Systray::taskbarOrientation() const