Start on the foundations of a tree-drawing algorithm

I don't actually know what I'm doing. I've done some reading and from
that I'm doing experiments until I can better understand what I've read.

otg/gtk/src/components/review_tree.rs

@@ -16,9 +16,9 @@ You should have received a copy of the GNU General Public License along with On
 
 use cairo::Context;
 use glib::Object;
-use gtk::{ prelude::*, subclass::prelude::*, };
+use gtk::{prelude::*, subclass::prelude::*};
-use sgf::GameRecord;
+use sgf::{GameNode, GameRecord};
-use std::{rc::Rc, cell::RefCell};
+use std::{cell::RefCell, rc::Rc};
 
 const WIDTH: i32 = 200;
 const HEIGHT: i32 = 800;
@@ -61,5 +61,177 @@ impl ReviewTree {
     }
 
     pub fn redraw(&self, ctx: &Context, width: i32, height: i32) {
+        // Implement the tree-drawing algorithm here
+    }
+}
+
+// https://llimllib.github.io/pymag-trees/
+// I want to take advantage of the Wetherell Shannon algorithm, but I want some variations. In
+// their diagram, they got a tree that looks like this.
+//
+// O
+// |\
+// O O
+// |\ \ \
+// O O O O
+// |\  |\
+// O O O O
+//
+// In the same circumstance, what I want is this:
+//
+// O--
+// |  \
+// O   O
+// |\  |\
+// O O O O
+// |\
+// O O
+//
+// In order to keep things from being overly smooshed, I want to ensure that if a branch overlaps
+// with another branch, there is some extra drawing space. This might actually be similar to adding
+// the principal that "A parent should be centered over its children".
+//
+// So, given a tree, I need to know how many children exist at each level. Then I build parents
+// atop the children. At level 3, I have four children, and that happens to be the maximum width of
+// the graph.
+//
+// A bottom-up traversal:
+// - Figure out the number of nodes at each depth
+
+/*
+struct Tree {
+    width: Vec<usize>, // the total width of the tree at each depth
+}
+*/
+
+// Given a node, do a postorder traversal to figure out the width of the node based on all of its
+// children. This is equivalent to the widest of all of its children at all depths.
+//
+// There are some collapse rules that I could take into account here, but that I haven't figured
+// out yet. If two nodes are side by side, and one of them has some wide children but the other has
+// no children, then they are effectively the same width. The second node only needs to be moved
+// out if it has children that would overlap the children of the first node.
+//
+// My algorithm right now is likely to generate unnecessarily wide trees in a complex game review.
+fn node_width(node: &GameNode) -> usize {
+    let children: &Vec<GameNode> = match node {
+        GameNode::MoveNode(mn) => &mn.children,
+        GameNode::SetupNode(sn) => &sn.children,
+    };
+
+    if children.len() == 0 {
+        return 1;
+    }
+
+    // If there is more than one child, run node_width on each one and add them together.
+    children.iter().fold(0, |acc, child| acc + node_width(child))
+}
+
+// Since I know the width of a node, now I want to figure out its placement in the larger scheme of
+// things.
+//
+// One thought I have is that I could just develop a grid virtually and start placing nodes.
+// Whenever I notice a collision, I can just move the node over. But I'd like to see if I can be a
+// bit smarter than doing it as just a vec into which I place things, as though it's a game board.
+// So, given a game node, I want to figure out it's position along the X axis.
+//
+// Just having the node is greatly insufficient. I can get better results if I'm calculating the
+// position of its children.
+fn node_children_columns(node: &GameNode) -> Vec<usize> {
+    vec![0, 1, 2]
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use sgf::{Color, GameNode, Move, MoveNode};
+
+    #[test]
+    fn it_calculates_width_for_single_node() {
+        let node = GameNode::MoveNode(MoveNode::new(Color::Black, Move::Move("dp".to_owned())));
+
+        assert_eq!(node_width(&node), 1);
+    }
+
+    #[test]
+    fn it_calculates_width_for_node_with_children() {
+        let mut node_a = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let node_b = GameNode::MoveNode(MoveNode::new(Color::Black, Move::Move("dp".to_owned())));
+        let node_c = GameNode::MoveNode(MoveNode::new(Color::Black, Move::Move("dp".to_owned())));
+        let node_d = GameNode::MoveNode(MoveNode::new(Color::Black, Move::Move("dp".to_owned())));
+
+        node_a.children.push(node_b);
+        node_a.children.push(node_c);
+        node_a.children.push(node_d);
+
+        assert_eq!(node_width(&GameNode::MoveNode(node_a)), 3);
+    }
+
+    // A
+    // B   E
+    // C D
+    #[test]
+    fn it_calculates_width_with_one_deep_child() {
+        let mut node_a = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_b = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_c = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_d = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_e = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+
+        node_b.children.push(GameNode::MoveNode(node_c));
+        node_b.children.push(GameNode::MoveNode(node_d));
+        assert_eq!(node_width(&GameNode::MoveNode(node_b.clone())), 2);
+
+        node_a.children.push(GameNode::MoveNode(node_b));
+        node_a.children.push(GameNode::MoveNode(node_e));
+        assert_eq!(node_width(&GameNode::MoveNode(node_a)), 3);
+    }
+
+    // A
+    // B G   H
+    // C     I
+    // D E F
+    #[test]
+    fn it_calculates_a_complex_tree() {
+        let mut node_a = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_b = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_c = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_d = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_e = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_f = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_g = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_h = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let mut node_i = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+
+        node_c.children.push(GameNode::MoveNode(node_d));
+        node_c.children.push(GameNode::MoveNode(node_e));
+        node_c.children.push(GameNode::MoveNode(node_f));
+        assert_eq!(node_width(&GameNode::MoveNode(node_c.clone())), 3);
+
+        node_b.children.push(GameNode::MoveNode(node_c));
+        assert_eq!(node_width(&GameNode::MoveNode(node_b.clone())), 3);
+
+        node_h.children.push(GameNode::MoveNode(node_i));
+
+        node_a.children.push(GameNode::MoveNode(node_b));
+        node_a.children.push(GameNode::MoveNode(node_g));
+        node_a.children.push(GameNode::MoveNode(node_h));
+        // This should be 4 if I were collapsing levels correctly, but it is 5 until I return to
+        // figure that step out.
+        assert_eq!(node_width(&GameNode::MoveNode(node_a.clone())), 5);
+    }
+
+    #[test]
+    fn a_nodes_children_get_separate_columns() {
+        let mut node_a = MoveNode::new(Color::Black, Move::Move("dp".to_owned()));
+        let node_b = GameNode::MoveNode(MoveNode::new(Color::Black, Move::Move("dp".to_owned())));
+        let node_c = GameNode::MoveNode(MoveNode::new(Color::Black, Move::Move("dp".to_owned())));
+        let node_d = GameNode::MoveNode(MoveNode::new(Color::Black, Move::Move("dp".to_owned())));
+
+        node_a.children.push(node_b.clone());
+        node_a.children.push(node_c.clone());
+        node_a.children.push(node_d.clone());
+
+        assert_eq!(node_children_columns(&GameNode::MoveNode(node_a)), vec![0, 1, 2]);
     }
 }

sgf/src/game.rs

@@ -460,8 +460,8 @@ impl TryFrom<&parser::Node> for MoveNode {
 pub struct SetupNode {
     id: Uuid,
 
-    positions: Vec<parser::SetupInstr>,
+    pub positions: Vec<parser::SetupInstr>,
-    children: Vec<GameNode>,
+    pub children: Vec<GameNode>,
 }
 
 impl SetupNode {