From cebb415b08642d74a0f15db1aee80db39a8a8d67 Mon Sep 17 00:00:00 2001
From: Simon Hausmann <simon.hausmann@sixtyfps.io>
Date: Thu, 28 Oct 2021 14:35:45 +0200
Subject: [PATCH] Replace two uses of build_array_helper with a new
 recurse_elem variant

For the item index generation and the member population for the C++
structs, a level-order variant of `recurse_elem` is sufficient - as also
indicate by the unused item index parameters.
---
 sixtyfps_compiler/generator/cpp.rs             |  2 +-
 sixtyfps_compiler/object_tree.rs               | 18 ++++++++++++++++++
 .../passes/generate_item_indices.rs            |  2 +-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/sixtyfps_compiler/generator/cpp.rs b/sixtyfps_compiler/generator/cpp.rs
index 597fee486..3e8bf8eb1 100644
--- a/sixtyfps_compiler/generator/cpp.rs
+++ b/sixtyfps_compiler/generator/cpp.rs
@@ -1170,7 +1170,7 @@ fn generate_component(
 
     let mut repeater_count = 0;
 
-    super::build_array_helper(component, |item_rc, _, _| {
+    crate::object_tree::recurse_elem_level_order(&component.root_element, &mut |item_rc| {
         let item = item_rc.borrow();
         if item.base_type == Type::Void {
             assert!(component.is_global());
diff --git a/sixtyfps_compiler/object_tree.rs b/sixtyfps_compiler/object_tree.rs
index 0e6d7152d..d4ef7bc81 100644
--- a/sixtyfps_compiler/object_tree.rs
+++ b/sixtyfps_compiler/object_tree.rs
@@ -1419,6 +1419,24 @@ pub fn recurse_elem<State>(
     }
 }
 
+/// Call the visitor for each children of the element recursively, starting with the element itself.
+/// The traversal happens in level-order, meaning each level of the element tree is visisted before
+/// going to the next depth.
+///
+/// The state returned by the visitor is passed to the children
+pub fn recurse_elem_level_order(elem: &ElementRc, vis: &mut impl FnMut(&ElementRc)) {
+    vis(elem);
+    visit_children(elem, vis);
+    fn visit_children(elem: &ElementRc, vis: &mut impl FnMut(&ElementRc)) {
+        for child in &elem.borrow().children {
+            vis(child);
+        }
+        for child in &elem.borrow().children {
+            visit_children(child, vis);
+        }
+    }
+}
+
 /// Same as [`recurse_elem`] but include the elements form sub_components
 pub fn recurse_elem_including_sub_components<State>(
     component: &Component,
diff --git a/sixtyfps_compiler/passes/generate_item_indices.rs b/sixtyfps_compiler/passes/generate_item_indices.rs
index b7977c916..87d2c4146 100644
--- a/sixtyfps_compiler/passes/generate_item_indices.rs
+++ b/sixtyfps_compiler/passes/generate_item_indices.rs
@@ -10,7 +10,7 @@ LICENSE END */
 //! Assign the Element::item_index on each elements
 pub fn generate_item_indices(component: &std::rc::Rc<crate::object_tree::Component>) {
     let mut current_item_index: usize = 0;
-    crate::generator::build_array_helper(component, move |item_rc, _, _| {
+    crate::object_tree::recurse_elem_level_order(&component.root_element, &mut |item_rc| {
         let item = item_rc.borrow();
         if item.base_type == crate::langtype::Type::Void {
         } else {