main: recursively load all nav state at connection time

main.go

@@ -311,31 +311,41 @@ func (f *TMainForm) OnNavExpanding(sender vcl.IObject, node *vcl.TTreeNode, allo
 
 	ndata := (*navData)(node.Data())
 
-	if ndata.childrenLoaded {
+	err := f.NavLoadChildren(node, ndata)
+	if err != nil {
+		vcl.ShowMessage(err.Error())
+		*allowExpansion = false // Permanently block
 		return
 	}
 
+	*allowExpansion = node.HasChildren()
+}
+
+func (f *TMainForm) NavLoadChildren(node *vcl.TTreeNode, ndata *navData) error {
+
+	if ndata.childrenLoaded {
+		return nil // Nothing to do
+	}
+
 	// Find the child buckets from this point under the element
 	nextBucketNames, err := ndata.ld.NavChildren(ndata)
 	if err != nil {
-		vcl.ShowMessage(fmt.Sprintf("Failed to find child buckets under %q: %s", strings.Join(ndata.bucketPath, `/`), err.Error()))
+		return fmt.Errorf("Failed to find child buckets under %q: %w", strings.Join(ndata.bucketPath, `/`), err)
-		*allowExpansion = false
-		return
 	}
 
 	ndata.childrenLoaded = true // don't repeat this work
 
 	if len(nextBucketNames) == 0 {
 		node.SetHasChildren(false)
-		*allowExpansion = false
 
 	} else {
+		node.SetHasChildren(true)
 
 		// Populate LCL child nodes
 		for _, bucketName := range nextBucketNames {
 
 			node := f.Buckets.Items().AddChild(node, formatUtf8([]byte(bucketName)))
-			node.SetHasChildren(true) // dynamically populate in OnNavExpanding
+			// node.SetHasChildren(true) // dynamically populate in OnNavExpanding
 			node.SetImageIndex(imgTable)
 			node.SetSelectedIndex(imgTable)
 			navData := &navData{
@@ -348,8 +358,11 @@ func (f *TMainForm) OnNavExpanding(sender vcl.IObject, node *vcl.TTreeNode, allo
 			node.SetData(unsafe.Pointer(navData))
 
 			ndata.ld.Keepalive(navData)
+
+			// Recurse to see if it has any children of its own
+			f.NavLoadChildren(node, ndata)
+		}
 	}
 
-		*allowExpansion = true
+	return nil
-	}
 }