How to format the background color for a positioned block of text?

Question

I have a Text positional element that sits on top of an image element on the stack. I would like to apply a simple background color to this Text element so that it formats the text as a box with the inscription:

I can do this by inserting a Container as another positioned child on this stack. But I will have to recalculate the width every time the text string changes, which is not optimal. Is there a better way?

var stack = new Stack(
  children: <Widget>[
    new Image.asset ( // background photo
      "assets/texture.jpg",
      fit: ImageFit.cover,
      height: 600.0,
    ),
    new Positioned ( // headline
      child: new Container(
        decoration: new BoxDecoration (
          backgroundColor: Colors.black
        ),
      ),
      left: 0.0,
      bottom: 108.0,
      width: 490.0,
      height: 80.0,
    ),
    new Positioned (
      child: new Text (
        "Lorem ipsum dolor.",
        style: new TextStyle(
          color: Colors.blue[500],
          fontSize: 42.0,
          fontWeight: FontWeight.w900
        )
      ),
      left: 16.0,
      bottom: 128.0,
    )
  ]
);

Answer 1

Text , BoxDecoration (.. ); , . , , / .

var stack = new Stack(
  children: <Widget>[
    new Image.asset ( // background photo
      "assets/texture.jpg",
      fit: ImageFit.cover,
      height: 600.0,
    ),
    new Positioned ( // headline
      child: new Container(
        child: new Text (
          "Lorem ipsum dolor.",
          style: new TextStyle(
            color: Colors.blue[500],
            fontSize: 42.0,
            fontWeight: FontWeight.w900
          )
        ),
        decoration: new BoxDecoration (
          backgroundColor: Colors.black
        ),
        padding: new EdgeInsets.fromLTRB(16.0, 16.0, 16.0, 16.0),
      ),
      left: 0.0,
      bottom: 108.0,
    ),
  ]
);