From 7d9ba355d1dbe19878c85bf5eb7607a31d9e340c Mon Sep 17 00:00:00 2001
From: Sameer Puri <sameer@users.noreply.github.com>
Date: Thu, 25 Apr 2019 19:41:48 -0500
Subject: [PATCH] Add viewbox handling, fix ellipse handling for large_arc case

---
 README.md     |  1 +
 src/main.rs   | 14 ++++++++++----
 src/turtle.rs | 13 +++++++------
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/README.md b/README.md
index 59430a5..4ca700c 100644
--- a/README.md
+++ b/README.md
@@ -13,3 +13,4 @@ Convert any SVG 1.1 path to gcode for a pen plotter, laser engraver, etc.
 - [ ] Smooth curves should not use the control point when the previous curve is not of the same type (quadratic -> smooth cubic, cubic -> smooth quadratic)
 - [x] Image coordinates mirrored in the y-axis because SVGs uses upper left corner as (0,0) while GCode uses lower left as (0,0)
 - [x] Close path command connects back to (0.0, 0.0) instead of the last move
+- [ ] Ellipse paths are dubious -- large_arc, sweep may need to be inverted
diff --git a/src/main.rs b/src/main.rs
index a4dfb6b..d8bfa07 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,7 +10,7 @@ use std::env;
 use std::fs::File;
 use std::io::{self, Read};
 
-use lyon_geom::{math, euclid};
+use lyon_geom::{euclid, math};
 use svgdom::{AttributeId, AttributeValue, ElementId, ElementType, PathSegment};
 
 mod code;
@@ -123,16 +123,22 @@ fn svg2program(doc: &svgdom::Document, opts: ProgramOptions, mach: Machine) -> P
         };
         let attrs = node.attributes();
         if let (ElementId::Svg, true) = (id, is_start) {
+            if let Some(&AttributeValue::ViewBox(vbox)) = attrs.get_value(AttributeId::ViewBox) {
+                t.stack_scaling(
+                    euclid::Transform2D::create_scale(1. / vbox.w, 1. / vbox.h)
+                        .post_translate(math::vector(vbox.x, vbox.y)),
+                );
+            }
             if let (Some(&AttributeValue::Length(width)), Some(&AttributeValue::Length(height))) = (
                 attrs.get_value(AttributeId::Width),
                 attrs.get_value(AttributeId::Height),
             ) {
                 let width_in_mm = length_to_mm(width, opts.dpi);
                 let height_in_mm = length_to_mm(height, opts.dpi);
-                t.set_scaling(
+                t.stack_scaling(
                     euclid::Transform2D::create_scale(
-                        width_in_mm / width.num,
-                        -height_in_mm / height.num,
+                        width_in_mm,
+                        -height_in_mm,
                     )
                     .post_translate(math::vector(0.0, height_in_mm)),
                 );
diff --git a/src/turtle.rs b/src/turtle.rs
index e671329..1be7b21 100644
--- a/src/turtle.rs
+++ b/src/turtle.rs
@@ -328,7 +328,7 @@ impl Turtle {
                 radians: x_axis_rotation,
             },
             flags: ArcFlags {
-                large_arc: large_arc,
+                large_arc: !large_arc,
                 sweep: sweep,
             },
         };
@@ -353,12 +353,13 @@ impl Turtle {
             .collect()
     }
 
-    pub fn set_scaling(&mut self, scaling: Transform2D<f64>) {
-        if let Some(ref old_scaling) = self.scaling {
-            self.curtran = self.curtran.post_mul(&old_scaling.inverse().unwrap());
-        }
-        self.scaling = Some(scaling);
+    pub fn stack_scaling(&mut self, scaling: Transform2D<f64>) {
         self.curtran = self.curtran.post_mul(&scaling);
+        if let Some(ref current_scaling) = self.scaling {
+            self.scaling = Some(current_scaling.post_mul(&scaling));
+        } else {
+            self.scaling = Some(scaling);
+        }
     }
 
     pub fn push_transform(&mut self, trans: Transform2D<f64>) {