Cleaning up some shape ctors.

src/shapes/circle.rs

@@ -2,7 +2,7 @@ use crate::shapes::{RenderAttrsImpl, ToPlainPdfLine};
 use crate::{NumericUnit, Unit};
 use printpdf::Line;
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct Circle {
     render_attrs: RenderAttrsImpl,
 
@@ -14,19 +14,19 @@ pub struct Circle {
 impl Circle {
     pub fn at_zero(radius: Unit) -> Circle {
         Circle {
-            render_attrs: RenderAttrsImpl::default(),
             radius,
             x: Unit::zero(),
             y: Unit::zero(),
+            ..Self::default()
         }
     }
 
     pub fn unit_at(x: Unit, y: Unit) -> Circle {
         Circle {
-            render_attrs: RenderAttrsImpl::default(),
             radius: 1.0.mm(),
             x,
             y,
+            ..Self::default()
         }
     }
 

src/shapes/rect.rs

@@ -1,10 +1,11 @@
+use std::default::Default;
 use crate::pdfutils::point_pair;
 use crate::shapes::{RenderAttrsImpl, ToPlainPdfLine};
 use crate::units::Unit;
 use printpdf::*;
 
 /// A representation of rectangles and operations on them.
-#[derive(Debug, Clone)]
+#[derive(Debug, Default, Clone)]
 pub struct WRect {
     render_attrs: RenderAttrsImpl,
     corner_radius: Option<Unit>,
@@ -29,12 +30,9 @@ impl WRect {
 
     pub fn at(left: Unit, top: Unit) -> WRect {
         WRect {
-            render_attrs: RenderAttrsImpl::default(),
-            corner_radius: None,
             top,
             left,
-            width: Unit::zero(),
-            height: Unit::zero(),
+            ..Self::default()
         }
     }
 

src/units.rs

@@ -1,4 +1,4 @@
-#[derive(Debug, PartialEq, PartialOrd, Copy, Clone)]
+#[derive(Debug, Default, PartialEq, PartialOrd, Copy, Clone)]
 // A `Unit` is a number of millimeters (mm) internally.
 pub struct Unit(f64);