Avoid temporary no-selection state when selecting a new item

in layouts using mouse interactions

src/gui/layout/qgslayoutviewtoolselect.cpp

@@ -62,11 +62,12 @@ void QgsLayoutViewToolSelect::layoutPressEvent( QgsLayoutViewMouseEvent *event )
   QgsLayoutItem *selectedItem = nullptr;
   QgsLayoutItem *previousSelectedItem = nullptr;
 
+  QList<QgsLayoutItem *> selectedItems = layout()->selectedLayoutItems();
+
   if ( event->modifiers() & Qt::ControlModifier )
   {
     //CTRL modifier, so we are trying to select the next item below the current one
     //first, find currently selected item
-    QList<QgsLayoutItem *> selectedItems = layout()->selectedLayoutItems();
     if ( !selectedItems.isEmpty() )
     {
       previousSelectedItem = selectedItems.at( 0 );
@@ -100,12 +101,6 @@ void QgsLayoutViewToolSelect::layoutPressEvent( QgsLayoutViewMouseEvent *event )
     return;
   }
 
-  if ( ( !selectedItem->isSelected() ) &&       //keep selection if an already selected item pressed
-       !( event->modifiers() & Qt::ShiftModifier ) ) //keep selection if shift key pressed
-  {
-    layout()->deselectAll();
-  }
-
   if ( ( event->modifiers() & Qt::ShiftModifier ) && ( selectedItem->isSelected() ) )
   {
     //SHIFT-clicking a selected item deselects it
@@ -120,7 +115,15 @@ void QgsLayoutViewToolSelect::layoutPressEvent( QgsLayoutViewMouseEvent *event )
   }
   else
   {
-    selectedItem->setSelected( true );
+    if ( ( !selectedItem->isSelected() ) &&       //keep selection if an already selected item pressed
+         !( event->modifiers() & Qt::ShiftModifier ) ) //keep selection if shift key pressed
+    {
+      layout()->setSelectedItem( selectedItem ); // clears existing selection
+    }
+    else
+    {
+      selectedItem->setSelected( true );
+    }
     event->ignore();
     emit itemFocused( selectedItem );
   }