Improve focusing the filter line with keyboard shortcut II

- Focus the filter line when setting something as filter.
- Instead of stopping focus cycling at the end of the filter header, pass
  the focus up to the table.
- Change keyReleaseEvent to comply with documentation.

See issue #3439

src/ExtendedTableWidget.cpp

@@ -880,6 +880,7 @@ void ExtendedTableWidget::useAsFilter(const QString& filterOperator, bool binary
         m_tableHeader->setFilter(column, value + filterOperator);
     else
         m_tableHeader->setFilter(column, filterOperator + value + operatorSuffix);
+    m_tableHeader->setFocusColumn(column);
 }
 
 void ExtendedTableWidget::duplicateUpperCell()

src/FilterLineEdit.cpp

@@ -67,20 +67,30 @@ void FilterLineEdit::delayedSignalTimerTriggered()
 
 void FilterLineEdit::keyReleaseEvent(QKeyEvent* event)
 {
+    bool actedUponKey = false;
     if(event->key() == Qt::Key_Tab)
     {
         if(filterList && columnNumber < filterList->size() - 1)
         {
             filterList->at(columnNumber + 1)->setFocus();
-            event->accept();
+        } else {
+            QWidget* grandParent = parentWidget()->parentWidget();
+            // Pass focus to the table (grandparent).
+            // Parent would be the table header, which would cycle back to the first
+            // column (due to proxying).
+            if(grandParent)
+                grandParent->setFocus();
         }
+        actedUponKey = true;
     } else if(event->key() == Qt::Key_Backtab) {
         if(filterList && columnNumber > 0)
         {
             filterList->at(columnNumber - 1)->setFocus();
-            event->accept();
+            actedUponKey = true;
         }
     }
+    if(!actedUponKey)
+        QLineEdit::keyReleaseEvent(event);
 }
 
 void FilterLineEdit::focusInEvent(QFocusEvent* event)