Treeview may lose focus when left/right arrow is used

In a treeview, for example the hierarchal view of the
styles and formatting panel, if your not on a node that is
expandable or collapsable when you press the left or right
arrow key, the focus will move away from the tree view in
a very awkward way. This patch makes the control work more
like a native treeview.

At this point I don't feel confident about the surrounding
code to avoid the code duplication that this patch adds.

Change-Id: Ibd04cf5329b4d226aac102d214a45e45811982e7
Reviewed-on: https://gerrit.libreoffice.org/10956
Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>

svtools/source/contnr/svimpbox.cxx

@@ -2237,8 +2237,13 @@ bool SvImpLBox::KeyInput( const KeyEvent& rKEvt)
 
         case KEY_RIGHT:
         {
-            if( bSubLstOpLR && IsNowExpandable() )
+            if( bSubLstOpLR )
-                pView->Expand( pCursor );
+            {
+                // only try to expand if sublist is expandable,
+                // otherwise ignore the key press
+                if( IsNowExpandable() )
+                    pView->Expand( pCursor );
+            }
             else if ( bIsCellFocusEnabled && pCursor )
             {
                 if ( nCurTabPos < ( pView->TabCount() - 1 /*!2*/ ) )
@@ -2304,8 +2309,17 @@ bool SvImpLBox::KeyInput( const KeyEvent& rKEvt)
                     }
                 }
             }
-            else if( bSubLstOpLR && IsExpandable() )
+            else if( bSubLstOpLR )
-                pView->Collapse( pCursor );
+            {
+                if( IsExpandable() && pView->IsExpanded( pCursor ) )
+                    pView->Collapse( pCursor );
+                else
+                {
+                    pNewCursor = pView->GetParent( pCursor );
+                    if( pNewCursor )
+                        SetCursor( pNewCursor );
+                }
+            }
             else
                 bKeyUsed = false;
             break;