Improve BoxBorder correctness

@@ -12,6 +12,7 @@
 - Document.save() now returns a Future
 - Add Widget.draw() to paint any widget on a canvas
 - Improve Chart labels
+- Improve BoxBorder correctness
 
 ## 1.13.0
 

@@ -582,6 +582,7 @@ class PdfGraphics {
 
   /// Set line joint miter limit, applies if the
   void setMiterLimit(double limit) {
+    assert(limit >= 1.0);
     PdfNum(limit).output(buf);
     buf.putString(' M\n');
   }

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+import 'dart:math' as math;
+
 import 'package:pdf/pdf.dart';
 import 'package:xml/xml.dart';
 
@@ -225,7 +227,7 @@ class SvgPath extends SvgOperation {
         ..drawShape(d)
         ..setLineCap(brush.strokeLineCap)
         ..setLineJoin(brush.strokeLineJoin)
-        ..setMiterLimit(brush.strokeMiterLimit)
+        ..setMiterLimit(math.max(1.0, brush.strokeMiterLimit))
         ..setLineDashPattern(
             brush.strokeDashArray, brush.strokeDashOffset.toInt())
         ..setLineWidth(brush.strokeWidth.sizeValue)

@@ -87,6 +87,8 @@ abstract class BoxBorder {
       BorderSide side, BorderRadius borderRadius) {
     _setStyle(context, side.style);
     context.canvas
+      ..setLineJoin(PdfLineJoin.miter)
+      ..setMiterLimit(4)
       ..setStrokeColor(side.color)
       ..setLineWidth(side.width);
     borderRadius.paint(context, box);
@@ -98,6 +100,8 @@ abstract class BoxBorder {
       Context context, PdfRect box, BorderSide side) {
     _setStyle(context, side.style);
     context.canvas
+      ..setLineJoin(PdfLineJoin.miter)
+      ..setMiterLimit(4)
       ..setStrokeColor(side.color)
       ..setLineWidth(side.width)
       ..drawBox(box)
@@ -254,7 +258,10 @@ class Border extends BoxBorder {
     assert(borderRadius == null,
         'A borderRadius can only be given for a uniform Border.');
 
-    context.canvas.setLineCap(PdfLineCap.square);
+    context.canvas
+      ..setLineCap(PdfLineCap.square)
+      ..setMiterLimit(4)
+      ..setLineJoin(PdfLineJoin.miter);
 
     if (top.style != BorderStyle.none) {
       BoxBorder._setStyle(context, top.style);