corrected GetBestSize() implementation: take all items, not just the currently visible ones

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@35860 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/treectrl.cpp

@@ -2140,12 +2140,20 @@ bool wxTreeCtrl::GetBoundingRect(const wxTreeItemId& item,
 wxSize wxTreeCtrl::DoGetBestSize() const
 {
     wxSize size;
-    wxRect rect;
-    for ( wxTreeItemId node = GetFirstVisibleItem();
-          node.IsOk();
-          node = GetNextVisible(node) )
+
+    // this doesn't really compute the total bounding rectangle of all items
+    // but a not too bad guess of it which has the advantage of not having to
+    // examine all (potentially hundreds or thousands) items in the control
+    for ( wxTreeItemId item = GetRootItem();
+          item.IsOk();
+          item = GetLastChild(item) )
     {
-        if ( GetBoundingRect(node, rect) )
+        wxRect rect;
+
+        // last parameter is "true" to get only the dimensions of the text
+        // label, we don't want to get the entire item width as it's determined
+        // by the current size
+        if ( GetBoundingRect(item, rect, true) )
         {
             if ( size.x < rect.x + rect.width )
                 size.x = rect.x + rect.width;
@@ -2154,6 +2162,10 @@ wxSize wxTreeCtrl::DoGetBestSize() const
         }
     }
 
+    // need some minimal size even for empty tree
+    if ( !size.x || !size.y )
+        size = wxControl::DoGetBestSize();
+
     return size;
 }