On Screen Ruler

Draw overlay 8px square on top of your apps, you're going to need this if your client has an eagle eye.

Installing

1. Get the package

Add this to your pubspec.yaml file:

dependencies:
  on_screen_ruler: ^0.0.1

2. Install

Install with:

flutter packages get

3. Import

import 'package:on_screen_ruler/on_screen_ruler.dart';

How to use

Put this piece of code inside your Material Widget

builder: (context, widget) {
  return OnScreenRulerWidget(child: widget!);
},

Full code:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      builder: (context, widget) {
        return OnScreenRulerWidget(child: widget!);
      },
      home: MyHomePage(),
    );
  }
}

Double Tap Icon on the top to activate the virtual ruler...

If you don't want the Icons and bacground on top of your apps you can set background color to transparent and pass null for the icon

OnScreenRulerWidget(
  child: widget!,
  activateBgColor: Colors.transparent,
  activateIcon: null,
);

You still can enable the virtual ruler by double tap on top of the screen

Widget Option