Fix transformation matrix order of operations

src/main.rs

@@ -132,7 +132,7 @@ fn svg2program(doc: &svgdom::Document, opts: ProgramOptions, mach: Machine) -> P
                 t.set_scaling(
                     euclid::Transform2D::create_scale(
                         width_in_mm / width.num,
-                        height_in_mm / height.num,
+                        -height_in_mm / height.num,
                     )
                     .post_translate(math::vector(0.0, height_in_mm)),
                 );

src/turtle.rs

@@ -330,8 +330,8 @@ impl Turtle {
     }
 
     pub fn set_scaling(&mut self, scaling: Transform2D<f64>) {
-        if let Some(ref scaling) = self.scaling {
-            self.curtran = self.curtran.post_mul(&scaling.inverse().unwrap());
+        if let Some(ref old_scaling) = self.scaling {
+            self.curtran = self.curtran.post_mul(&old_scaling.inverse().unwrap());
         }
         self.scaling = Some(scaling);
         self.curtran = self
@@ -342,12 +342,13 @@ impl Turtle {
     pub fn push_transform(&mut self, trans: Transform2D<f64>) {
         self.transtack.push(self.curtran);
         if let Some(ref scaling) = self.scaling {
-            println!("{:?}", trans);
             self.curtran = self
                 .curtran
                 .post_mul(&scaling.inverse().unwrap())
-                .post_mul(&trans)
-                .post_mul(&scaling);
+                .pre_mul(&trans)
+            .post_mul(&scaling);
+        } else {
+            self.curtran = self.curtran.post_mul(&trans);
         }
     }