Gui: add missing PropertyItemDelegate::eventFilter()

For handling focus change when editing property

src/Gui/propertyeditor/PropertyItemDelegate.cpp

@@ -37,6 +37,8 @@
 #include "PropertyItemDelegate.h"
 #include "PropertyItem.h"
 #include "PropertyEditor.h"
+#include "MDIView.h"
+#include "Tree.h"
 
 FC_LOG_LEVEL_INIT("PropertyView",true,true)
 
@@ -124,6 +126,40 @@ bool PropertyItemDelegate::editorEvent (QEvent * event, QAbstractItemModel* mode
     return QItemDelegate::editorEvent(event, model, option, index);
 }
 
+bool PropertyItemDelegate::eventFilter(QObject *o, QEvent *ev)
+{
+    if (ev->type() == QEvent::FocusOut) {
+        PropertyEditor *parentEditor = qobject_cast<PropertyEditor*>(this->parent());
+        auto widget = qobject_cast<QWidget*>(o);
+        if (widget && parentEditor && parentEditor->activeEditor
+                   && widget != parentEditor->activeEditor)
+        {
+            // We event filter child QAbstractButton and QLabel of an editor,
+            // which requires special focus change in order to not mess up with
+            // QItemDelegate's logic.
+            QWidget *w = QApplication::focusWidget();
+            // For some reason, Qt (5.15) on Windows will remove current focus
+            // before bringing up a modal dialog.
+            if (!w)
+                return false;
+            while (w) { // don't worry about focus changes internally in the editor
+                if (w == widget || w == parentEditor->activeEditor)
+                    return false;
+
+                // ignore focus change to 3D view or tree view, because, for
+                // example DlgPropertyLink is implemented as modeless dialog
+                // to allow selection in 3D and tree view.
+                if (qobject_cast<MDIView*>(w))
+                    return false;
+                if (qobject_cast<TreeWidget*>(w))
+                    return false;
+                w = w->parentWidget();
+            }
+        }
+    }
+    return QItemDelegate::eventFilter(o, ev);
+}
+
 QWidget * PropertyItemDelegate::createEditor (QWidget * parent, const QStyleOptionViewItem & /*option*/, 
                                               const QModelIndex & index ) const
 {

src/Gui/propertyeditor/PropertyItemDelegate.h

@@ -44,6 +44,9 @@ public:
     virtual QSize sizeHint(const QStyleOptionViewItem & option, const QModelIndex & index) const;
     virtual bool editorEvent (QEvent *event, QAbstractItemModel *model,
                               const QStyleOptionViewItem& option, const QModelIndex& index);
+protected:
+    bool eventFilter(QObject *, QEvent *);
+
 public Q_SLOTS:
     void valueChanged();