Fix bug where scaling wasn't properly applied to stroke widths

Author: LaurenzV

src/render.rs

@@ -173,7 +173,9 @@ fn render_path_partial(
 
     if stroke {
         if let Some(stroke) = &path.stroke {
-            content.set_line_width(ctx.c.px_to_pt(stroke.width.get()));
+            content.set_line_width(
+                ctx.c.px_to_pt(stroke.width.get() * ctx.c.compute_scale()),
+            );
 
             match stroke.linecap {
                 LineCap::Butt => content.set_line_cap(LineCapStyle::ButtCap),

src/scale.rs

@@ -184,6 +184,22 @@ impl CoordToPdf {
         self.transform.apply(point.0, point.1)
     }
 
+    /// Compute the scale (e.g. to adapt the stroke width).
+    pub fn compute_scale(&self) -> f64 {
+        let mut complete_transform = Transform::new_scale(self.factor_x, self.factor_y);
+        complete_transform.append(&self.transform);
+        let (x_scale, y_scale) = complete_transform.get_scale();
+
+        if x_scale.is_finite() && y_scale.is_finite() {
+            let scale = x_scale.max(y_scale);
+            if scale > 0.0 {
+                return scale;
+            }
+        }
+
+        1.0
+    }
+
     /// Set a pre-transformation, overriding the old one.
     pub fn concat_transform(&mut self, add_transform: Transform) -> Transform {
         let old = self.transform.clone();