fix viewport translation with nonzero x,y

src/converter.rs

@@ -84,8 +84,8 @@ pub fn svg2program<'input>(
         if let Some(view_box) = node.attribute("viewBox") {
             let view_box = ViewBox::from_str(view_box).expect("could not parse viewBox");
             transforms.push(
-                Transform2D::scale(1. / view_box.w, 1. / view_box.h)
-                    .then_translate(vector(view_box.x, view_box.y)),
+                Transform2D::translation(-view_box.x, -view_box.y)
+                    .then_scale(1. / view_box.w, 1. / view_box.h),
             );
         }
 

src/main.rs

@@ -250,4 +250,12 @@ mod test {
 
         assert_eq!(actual, include_str!("../tests/square_transformed.gcode"))
     }
+
+    #[test]
+    fn square_viewport_produces_expected_gcode() {
+        let square_transformed = include_str!("../tests/square_viewport.svg");
+        let actual = get_actual(square_transformed);
+
+        assert_eq!(actual, include_str!("../tests/square_viewport.gcode"))
+    }
 }

tests/square_viewport.gcode

@@ -0,0 +1,45 @@
+G21
+G90;svg#svg8 > g#layer1 > path#path838
+G0 X1 Y9
+G1 X9 Y9 F300
+G1 X9 Y1 F300
+G1 X1 Y1 F300
+G1 X1 Y9 F300;svg#svg8 > g#layer1 > path#path832
+G0 X8 Y2.5
+G1 X7.992016 Y2.4110041813117045 F300
+G1 X7.9683189770239995 Y2.324850533089038 F300
+G1 X7.929665719197761 Y2.24429045824164 F300
+G1 X7.877290656963224 Y2.171896723319837 F300
+G1 X7.812866440307907 Y2.1099812946420924 F300
+G1 X7.738450521014919 Y2.060521503338657 F300
+G1 X7.656419445882797 Y2.025096897304599 F300
+G1 X7.569392959326962 Y2.0048387967582206 F300
+G1 X7.5 Y2 F300
+G1 X7.4110041813117045 Y2.007984 F300
+G1 X7.324850533089037 Y2.031681022976 F300
+G1 X7.24429045824164 Y2.0703342808022382 F300
+G1 X7.171896723319837 Y2.1227093430367767 F300
+G1 X7.1099812946420915 Y2.1871335596920924 F300
+G1 X7.0605215033386575 Y2.261549478985082 F300
+G1 X7.025096897304598 Y2.343580554117203 F300
+G1 X7.004838796758221 Y2.430607040673038 F300
+G1 X7 Y2.5000000000000004 F300
+G1 X7.007984 Y2.5889958186882964 F300
+G1 X7.0316810229760005 Y2.6751494669109626 F300
+G1 X7.070334280802239 Y2.7557095417583604 F300
+G1 X7.122709343036777 Y2.8281032766801633 F300
+G1 X7.187133559692093 Y2.8900187053579085 F300
+G1 X7.261549478985082 Y2.9394784966613434 F300
+G1 X7.343580554117204 Y2.9749031026954014 F300
+G1 X7.4306070406730385 Y2.9951612032417794 F300
+G1 X7.5 Y3 F300
+G1 X7.5889958186882955 Y2.992016 F300
+G1 X7.675149466910963 Y2.968318977024 F300
+G1 X7.75570954175836 Y2.9296657191977618 F300
+G1 X7.828103276680163 Y2.8772906569632233 F300
+G1 X7.890018705357908 Y2.8128664403079076 F300
+G1 X7.9394784966613425 Y2.7384505210149186 F300
+G1 X7.974903102695401 Y2.656419445882797 F300
+G1 X7.995161203241779 Y2.5693929593269624 F300
+G1 X8 Y2.5 F300
+M2

tests/square_viewport.svg

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   sodipodi:docname="square_viewport.svg"
+   inkscape:version="1.1 (c4e8f9ed74, 2021-05-24)"
+   id="svg8"
+   version="1.1"
+   viewBox="-10 -10 10 10"
+   height="10mm"
+   width="10mm"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:dc="http://purl.org/dc/elements/1.1/">
+  <defs
+     id="defs2" />
+  <sodipodi:namedview
+     inkscape:window-maximized="1"
+     inkscape:window-y="0"
+     inkscape:window-x="0"
+     inkscape:window-height="2160"
+     inkscape:window-width="3840"
+     units="mm"
+     showgrid="true"
+     inkscape:document-rotation="0"
+     inkscape:current-layer="layer1"
+     inkscape:document-units="mm"
+     inkscape:cy="43.362194"
+     inkscape:cx="-1.7671114"
+     inkscape:zoom="18.391597"
+     inkscape:pageshadow="2"
+     inkscape:pageopacity="0.0"
+     borderopacity="1.0"
+     bordercolor="#666666"
+     pagecolor="#ffffff"
+     id="base"
+     inkscape:pagecheckerboard="0">
+    <inkscape:grid
+       spacingy="1"
+       spacingx="1"
+       units="mm"
+       id="grid836"
+       type="xygrid" />
+  </sodipodi:namedview>
+  <metadata
+     id="metadata5">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+      </cc:Work>
+    </rdf:RDF>
+  </metadata>
+  <g
+     id="layer1"
+     inkscape:groupmode="layer"
+     inkscape:label="Layer 1">
+    <path
+       id="path838"
+       d="m -9,-9 h 8 v 8 h -8 z"
+       style="fill:none;stroke:#000000;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" />
+    <path
+       id="path832"
+       style="fill:#000000;fill-opacity:1;stroke:#000000;stroke-width:0.396875;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none"
+       d="M -2,-2.5 A 0.5,0.5 0 0 1 -2.5,-2 0.5,0.5 0 0 1 -3,-2.5 0.5,0.5 0 0 1 -2.5,-3 0.5,0.5 0 0 1 -2,-2.5 Z" />
+  </g>
+</svg>