Simplify svgtree a bit.

usvg/src/svgtree/mod.rs

@@ -120,6 +120,7 @@ impl std::fmt::Debug for Document {
     }
 }
 
+// TODO: use u32
 #[derive(Clone, Copy, PartialEq, Debug)]
 pub struct NodeId(usize);
 
@@ -138,7 +139,6 @@ enum NodeKind {
 
 struct NodeData {
     parent: Option<NodeId>,
-    prev_sibling: Option<NodeId>,
     next_sibling: Option<NodeId>,
     children: Option<(NodeId, NodeId)>,
     kind: NodeKind,
@@ -363,10 +363,6 @@ impl<'a> Node<'a> {
         self.ancestors().skip(1).find(|n| n.is_element())
     }
 
-    pub fn prev_sibling(&self) -> Option<Self> {
-        self.d.prev_sibling.map(|id| self.gen_node(id))
-    }
-
     pub fn next_sibling(&self) -> Option<Self> {
         self.d.next_sibling.map(|id| self.gen_node(id))
     }
@@ -510,30 +506,18 @@ impl std::fmt::Debug for Node<'_> {
     }
 }
 
-macro_rules! axis_iterators {
-    ($($i:ident($f:path);)*) => {
-        $(
-            #[derive(Clone)]
-            pub struct $i<'a>(Option<Node<'a>>);
-
-            impl<'a> Iterator for $i<'a> {
-                type Item = Node<'a>;
+#[derive(Clone)]
+pub struct Ancestors<'a>(Option<Node<'a>>);
 
-                #[inline]
-                fn next(&mut self) -> Option<Self::Item> {
-                    let node = self.0.take();
-                    self.0 = node.as_ref().and_then($f);
-                    node
-                }
-            }
-        )*
-    };
-}
+impl<'a> Iterator for Ancestors<'a> {
+    type Item = Node<'a>;
 
-axis_iterators! {
-    Ancestors(Node::parent);
-    PrevSiblings(Node::prev_sibling);
-    NextSiblings(Node::next_sibling);
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        let node = self.0.take();
+        self.0 = node.as_ref().and_then(Node::parent);
+        node
+    }
 }
 
 #[derive(Clone)]
@@ -556,18 +540,6 @@ impl<'a> Iterator for Children<'a> {
     }
 }
 
-impl<'a> DoubleEndedIterator for Children<'a> {
-    fn next_back(&mut self) -> Option<Self::Item> {
-        let node = self.back.take();
-        if self.back == self.front {
-            self.front = None;
-        } else {
-            self.back = node.as_ref().and_then(Node::prev_sibling);
-        }
-        node
-    }
-}
-
 #[derive(Clone, Copy, PartialEq, Debug)]
 pub enum Edge<'a> {
     Open(Node<'a>),

usvg/src/svgtree/parse.rs

@@ -22,14 +22,12 @@ impl Document {
         let new_child_id = NodeId(self.nodes.len());
         self.nodes.push(NodeData {
             parent: Some(parent_id),
-            prev_sibling: None,
             next_sibling: None,
             children: None,
             kind,
         });
 
         let last_child_id = self.nodes[parent_id.0].children.map(|(_, id)| id);
-        self.nodes[new_child_id.0].prev_sibling = last_child_id;
 
         if let Some(id) = last_child_id {
             self.nodes[id.0].next_sibling = Some(new_child_id);
@@ -71,7 +69,6 @@ fn parse(xml: &roxmltree::Document) -> Result<Document, Error> {
     // Add a root node.
     doc.nodes.push(NodeData {
         parent: None,
-        prev_sibling: None,
         next_sibling: None,
         children: None,
         kind: NodeKind::Root,
@@ -251,10 +248,11 @@ pub(super) fn parse_svg_element(
     for rule in &style_sheet.rules {
         if rule.selector.matches(&XmlNode(xml_node)) {
             for declaration in &rule.declarations {
-                // TODO: preform XML attribute normalization
+                // TODO: perform XML attribute normalization
                 if let Some(aid) = AId::from_str(declaration.name) {
                     // Parse only the presentation attributes.
                     // `transform` isn't a presentation attribute, but should be parsed anyway.
+                    // TODO: `transform` is presentation in SVG 2?
                     if aid.is_presentation() || aid == AId::Transform {
                         insert_attribute(aid, declaration.value);
                     }
@@ -331,6 +329,7 @@ fn parse_svg_attribute(tag_name: EId, aid: AId, value: &str) -> Option<Attribute
             // `href` can contain base64 data and we do store it as is.
             match svgtypes::IRI::from_str(value) {
                 Ok(link) => AttributeValue::Link(link.0.to_string()),
+                // TODO: avoid string allocation
                 Err(_) => AttributeValue::String(value.to_string()),
             }
         }
@@ -551,6 +550,7 @@ fn parse_svg_attribute(tag_name: EId, aid: AId, value: &str) -> Option<Attribute
     })
 }
 
+// TODO: move to svgtypes
 #[inline(never)]
 fn parse_path(text: &str) -> crate::PathData {
     // Previous MoveTo coordinates.