Add border to rounded rectangle.

It's designed so that it works in exactly the same way as rectangle.

resources/qml/RoundedRectangle.qml

@@ -5,6 +5,7 @@ import UM 1.2 as UM
 // The rounded rectangle works mostly like a regular rectangle, but provides the option to have rounded corners on only one side of the rectangle.
 Item
 {
+    id: roundedRectangle
     // As per the regular rectangle
     property color color: "transparent"
 
@@ -15,6 +16,9 @@ Item
     // 1 is down, 2 is left, 3 is up and 4 is right.
     property int cornerSide: RoundedRectangle.Direction.None
 
+    // Simple object to ensure that border.width and border.color work
+    property BorderGroup border: BorderGroup {}
+
     enum Direction
     {
         None = 0,
@@ -31,6 +35,8 @@ Item
         anchors.fill: parent
         radius: cornerSide != RoundedRectangle.Direction.None ? parent.radius : 0
         color: parent.color
+        border.width: parent.border.width
+        border.color: parent.border.color
     }
 
     // The item that covers 2 of the corners to make them not rounded.
@@ -45,5 +51,22 @@ Item
             right: cornerSide == RoundedRectangle.Direction.Left ? parent.right: undefined
             bottom: cornerSide == RoundedRectangle.Direction.Up ? parent.bottom: undefined
         }
+
+        border.width: parent.border.width
+        border.color: parent.border.color
+
+        Rectangle
+        {
+            color: roundedRectangle.color
+            height: cornerSide % 2 ? roundedRectangle.border.width: roundedRectangle.height - 2 * roundedRectangle.border.width
+            width: cornerSide % 2 ? roundedRectangle.width - 2 * roundedRectangle.border.width: roundedRectangle.border.width
+            anchors
+            {
+                right: cornerSide == RoundedRectangle.Direction.Right ? parent.right : undefined
+                bottom: cornerSide  == RoundedRectangle.Direction.Down ? parent.bottom: undefined
+                horizontalCenter: cornerSide % 2 ? parent.horizontalCenter: undefined
+                verticalCenter: cornerSide % 2 ? undefined: parent.verticalCenter
+            }
+        }
     }
 }