Add opt-in serde feature to enable serialization of Tree (#30)

* Add opt-in serde feature to enable serialization of Tree

Allows users to persist the `Tree` layout

* Fix: Tree::push_to_first_leaf no longer panics when used on empty Tree

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+### Added
+- Added opt-in `serde` feature to enable serialization of `Tree`.
+
+### Fixed
+* `Tree::push_to_first_leaf` no longer panics when used on an empty `Tree`
+
+
 ## 0.2.0 - 2022-09-04
 
 ### Added

Cargo.toml

@@ -10,8 +10,16 @@ readme = "README.md"
 repository = "https://github.com/Adanos020/egui_dock"
 categories = ["gui", "game-development"]
 
+[features]
+default = []
+
+# Enable serialization of `Tree`.
+serde = ["dep:serde", "egui/serde"]
+
+
 [dependencies]
 egui = "0.19"
+serde = { version = "1", optional = true, features = ["derive"] }
 
 [dev-dependencies]
 eframe = "0.19"

src/tree.rs

@@ -2,6 +2,7 @@ use egui::*;
 
 /// Identifies a tab within a [`Node`].
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Ord, PartialOrd)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct TabIndex(pub usize);
 
 impl From<usize> for TabIndex {
@@ -14,6 +15,7 @@ impl From<usize> for TabIndex {
 // ----------------------------------------------------------------------------
 
 /// Represents an abstract node of a `Tree`.
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub enum Node<Tab> {
     /// Empty node
     Empty,
@@ -154,6 +156,7 @@ impl<Tab> Node<Tab> {
 
 /// Wrapper around indices to the collection of nodes inside a `Tree`.
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct NodeIndex(pub usize);
 
 impl From<usize> for NodeIndex {
@@ -239,6 +242,7 @@ pub enum Split {
 // ----------------------------------------------------------------------------
 
 /// Binary tree representing the relationships between `Node`s.
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct Tree<Tab> {
     tree: Vec<Node<Tab>>,
     focused_node: Option<NodeIndex>,
@@ -570,7 +574,9 @@ impl<Tab> Tree<Tab> {
                 _ => {}
             }
         }
-        panic!();
+        assert!(self.tree.is_empty());
+        self.tree.push(Node::leaf_with(vec![tab]));
+        self.focused_node = Some(NodeIndex(0));
     }
 
     /// Currently focused leaf.