Add dashed lines to Decoration Widgets

@@ -4,6 +4,7 @@
 
 - Implement Linear and Radial gradients in BoxDecoration
 - Fix PdfColors.shade()
+- Add dashed lines to Decoration Widgets
 
 ## 1.6.2
 

@@ -700,4 +700,9 @@ class PdfGraphics {
     PdfNum(limit).output(buf);
     buf.putString(' M\n');
   }
+
+  void setLineDashPattern([List<int> array = const <int>[], int phase = 0]) {
+    PdfArray.fromNum(array).output(buf);
+    buf.putString(' $phase d\n');
+  }
 }

@@ -20,24 +20,30 @@ part of widget;
 
 enum DecorationPosition { background, foreground }
 
+enum BorderStyle { none, solid, dashed, dotted }
+
 @immutable
 class BoxBorder {
-  const BoxBorder(
-      {this.left = false,
+  const BoxBorder({
+    this.left = false,
     this.top = false,
     this.right = false,
     this.bottom = false,
     this.color = PdfColors.black,
-      this.width = 1.0})
-      : assert(color != null),
+    this.width = 1.0,
+    this.style = BorderStyle.solid,
+  })  : assert(color != null),
         assert(width != null),
-        assert(width >= 0.0);
+        assert(width >= 0.0),
+        assert(style != null);
 
   final bool top;
   final bool bottom;
   final bool left;
   final bool right;
 
+  final BorderStyle style;
+
   /// The color of the
   final PdfColor color;
 
@@ -50,7 +56,27 @@ class BoxBorder {
     assert(box.width != null);
     assert(box.height != null);
 
-    if (top || bottom || left || right) {
+    if (!(top || bottom || left || right)) {
+      return;
+    }
+
+    switch (style) {
+      case BorderStyle.none:
+        return;
+      case BorderStyle.solid:
+        break;
+      case BorderStyle.dashed:
+        context.canvas
+          ..saveContext()
+          ..setLineDashPattern(const <int>[3, 3]);
+        break;
+      case BorderStyle.dotted:
+        context.canvas
+          ..saveContext()
+          ..setLineDashPattern(const <int>[1, 1]);
+        break;
+    }
+
     context.canvas
       ..setStrokeColor(color)
       ..setLineWidth(width);
@@ -85,6 +111,8 @@ class BoxBorder {
     }
 
     context.canvas.strokePath();
+    if (style != BorderStyle.solid) {
+      context.canvas.restoreContext();
     }
   }
 
@@ -349,6 +377,8 @@ class RadialGradient extends Gradient {
 
 enum BoxShape { circle, rectangle }
 
+enum PaintPhase { all, background, foreground }
+
 @immutable
 class BoxDecoration {
   const BoxDecoration(
@@ -368,12 +398,17 @@ class BoxDecoration {
   final DecorationImage image;
   final Gradient gradient;
 
-  void paint(Context context, PdfRect box) {
+  void paint(
+    Context context,
+    PdfRect box, [
+    PaintPhase phase = PaintPhase.all,
+  ]) {
     assert(box.x != null);
     assert(box.y != null);
     assert(box.width != null);
     assert(box.height != null);
 
+    if (phase == PaintPhase.all || phase == PaintPhase.background) {
       if (color != null) {
         switch (shape) {
           case BoxShape.rectangle:
@@ -435,7 +470,9 @@ class BoxDecoration {
         image.paint(context, box);
         context.canvas.restoreContext();
       }
+    }
 
+    if (phase == PaintPhase.all || phase == PaintPhase.foreground) {
       if (border != null) {
         switch (shape) {
           case BoxShape.circle:
@@ -451,4 +488,5 @@ class BoxDecoration {
         }
       }
     }
+  }
 }