Never render <marker> or <symbol> directly

Related to #57, neither of these elements are meant to be directly
rendered.

Author: sameer

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "svg2gcode"
-version = "0.3.1"
+version = "0.3.2"
 authors = ["Sameer Puri <crates@purisa.me>"]
 edition = "2021"
 description = "Convert paths in SVG files to GCode for a pen plotter, laser engraver, or other machine."

lib/Cargo.toml

@@ -9,8 +9,8 @@ use svgtypes::Length;
 use uom::si::f64::Length as UomLength;
 use uom::si::length::{inch, millimeter};
 
-use crate::{turtle::*, Machine};
 use self::units::CSS_DEFAULT_DPI;
+use crate::{turtle::*, Machine};
 
 #[cfg(feature = "serde")]
 mod length_serde;

lib/src/converter/mod.rs

@@ -25,6 +25,8 @@ const LINE_TAG_NAME: &str = "line";
 const GROUP_TAG_NAME: &str = "g";
 const DEFS_TAG_NAME: &str = "defs";
 const USE_TAG_NAME: &str = "use";
+const MARKER_TAG_NAME: &str = "marker";
+const SYMBOL_TAG_NAME: &str = "symbol";
 
 pub trait XmlVisitor {
     fn visit_enter(&mut self, node: Node);
@@ -37,8 +39,10 @@ fn should_render_node(node: Node) -> bool {
         && !node
             .attribute("style")
             .map_or(false, |style| style.contains("display:none"))
-        // Defs are not rendered
-        && node.tag_name().name() != DEFS_TAG_NAME
+        // - Defs are not rendered
+        // - Markers are not directly rendered
+        // - Symbols are not directly rendered
+        && !matches!(node.tag_name().name(), DEFS_TAG_NAME | MARKER_TAG_NAME | SYMBOL_TAG_NAME)
 }
 
 pub fn depth_first_visit(doc: &Document, visitor: &mut impl XmlVisitor) {