Implement PartialEq for SVGMeasure

dyesub-tool/src/svg/measure.rs

@@ -1,4 +1,5 @@
 use super::SVGUnit;
+use std::cmp::Ordering;
 use std::fmt;
 use std::{
     fmt::Display,
@@ -40,6 +41,18 @@ impl PartialEq for SVGMeasure {
     }
 }
 
+impl PartialOrd for SVGMeasure {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(if self == other {
+            Ordering::Equal
+        } else if self.to_user_units() > other.to_user_units() {
+            Ordering::Greater
+        } else {
+            Ordering::Less
+        })
+    }
+}
+
 impl Display for SVGMeasure {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}{}", self.measure, self.unit)

dyesub-tool/src/svg/tests.rs

@@ -44,3 +44,11 @@ fn ne() {
     let b = SVGMeasure::new(10.0, SVGUnit::Pixel);
     assert_ne!(a, b);
 }
+
+#[test]
+fn cmp() {
+    let m_10cm = SVGMeasure::new(10.0, SVGUnit::Centimeter);
+    let m_5mm = SVGMeasure::new(5.0, SVGUnit::Millimeter);
+    assert!(m_10cm > m_5mm);
+    assert!(m_5mm < m_10cm);
+}