feat: make parent node visually centered

rust/crates/tidy-tree/src/layout/basic_layout.rs

@@ -19,8 +19,12 @@ pub struct BasicLayout {
 pub struct BoundingBox {
  pub total_width: Coord,
  pub total_height: Coord,
+ /// node x position relative to its parent
  pub relative_x: Coord,
+ /// node y position relative to its parent
  pub relative_y: Coord,
+ /// bounding box shift relative to the node
+ pub shift_x: Coord,
 }
 
 impl Default for BoundingBox {
@@ -30,6 +34,7 @@ impl Default for BoundingBox {
  total_width: 0.,
  relative_x: 0.,
  relative_y: 0.,
+ shift_x: 0.,
  }
  }
 }
@@ -65,6 +70,7 @@ impl BasicLayout {
  total_width: node.width,
  relative_x: 0.,
  relative_y: 0.,
+ shift_x: -node.width / 2.,
  };
  let children: *mut _ = &mut node.children;
  let children = unsafe { &mut *children };
@@ -74,18 +80,34 @@ impl BasicLayout {
  for child in children.iter() {
  total_width += child.meta.total_width;
  }
+
  total_width += (n - 1.) * self.peer_margin;
- let mut relative_x = -total_width / 2.;
+ let mut relative_x = 0.;
  let mut max_height = 0.;
- for child in children.iter_mut() {
+ let mut mid_x: Vec<Coord> = vec![];
+ let n = children.len();
+ for (i, child) in children.iter_mut().enumerate() {
  child.meta.relative_y = node.height + self.parent_child_margin;
- child.meta.relative_x = relative_x + child.meta.total_width / 2.;
- relative_x += child.meta.total_width + self.peer_margin;
+ relative_x += -child.meta.shift_x;
+ child.meta.relative_x = relative_x;
+ if i == (n - 1) / 2 {
+ mid_x.push(relative_x);
+ }
+ if i == n / 2 {
+ mid_x.push(relative_x);
+ }
+ relative_x += child.meta.total_width + child.meta.shift_x + self.peer_margin;
  max_height = Float::max(child.meta.total_height, max_height);
  }
 
+ let shift_x = -(mid_x[0] + mid_x[1]) / 2.;
+ for child in children.iter_mut() {
+ child.meta.relative_x += shift_x;
+ }
+
  node.meta.total_width = total_width;
  node.meta.total_height = node.height + self.parent_child_margin + max_height;
+ node.meta.shift_x = shift_x;
  }
  }
 }

rust/crates/tidy-tree/tests/aesthetic_rules.rs

@@ -71,20 +71,40 @@ pub fn assert_no_crossed_lines<D: Debug>(root: &Node<D>) {
  });
 }
 
+pub fn assert_parent_visually_centered<D: Debug>(root: &Node<D>) {
+ root.pre_order_traversal(|node| {
+ let n = node.children.len();
+ if n == 0 {
+ return;
+ }
+
+ let middle = if n % 2 == 0 {
+ let m = n / 2;
+ let a = &node.children[m - 1];
+ let b = &node.children[m];
+ (a.x + b.x) / 2.
+ } else {
+ node.children[n / 2].x
+ };
+ assert!(
+ (node.x - middle).abs() < 1e-6,
+ "parent node is not centered {} {}",
+ node.x,
+ middle
+ );
+ });
+}
+
 pub fn assert_symmetric<D: Debug + Clone>(root: &Node<D>, layout: &mut dyn Layout<Meta = D>) {
  let mut mirrored = mirror(root);
  layout.layout(&mut mirrored);
  let mut point_origin: Vec<Coord> = vec![];
  let mut point_mirrored: Vec<Coord> = vec![];
  root.pre_order_traversal(|node| {
- if let Some(parent) = node.parent {
- point_origin.push(node.x);
- }
+ point_origin.push(node.x);
  });
  pre_order_traversal_rev(&mirrored, |node| {
- if let Some(parent) = node.parent {
- point_mirrored.push(node.x);
- }
+ point_mirrored.push(node.x);
  });
  // println!("{:#?}", root);
  // println!("{:#?}", mirrored);

rust/crates/tidy-tree/tests/layout_test.rs

@@ -13,6 +13,7 @@ pub fn test_layout<D: Default + Debug + Clone>(layout: &mut dyn Layout<Meta = D>
  aesthetic_rules::assert_symmetric(&tree, layout);
  aesthetic_rules::check_nodes_order(&tree);
  aesthetic_rules::check_y_position_in_same_level(&tree);
+ aesthetic_rules::assert_parent_visually_centered(&tree);
 }
 
 pub fn gen_tree<Meta: Default>(rng: &mut StdRng, num: usize) -> Node<Meta> {