InheritedWidget and screen

self:

import 'package:flutter/material.dart';

class GrantScreen {
  static double _width, _height;
  static double _physicalWidth, _physicalHeight;
  static double _top, _bottom;
  static double _scaleWidth, _scaleHeight;
  static double _textScale;
  static double _pixelRatio;

  GrantScreen(BuildContext context){
    _physicalWidth = MediaQuery.of(context).size.width;
    _physicalHeight = MediaQuery.of(context).size.height;
    _top = MediaQuery.of(context).padding.top;
    _bottom = MediaQuery.of(context).padding.bottom;
    _textScale = MediaQuery.of(context).textScaleFactor;
    _width = 375.0;
    _height = 667.0;
    _scaleWidth = _physicalWidth / _width;
    _scaleHeight = _physicalHeight / _height;
    _pixelRatio = MediaQuery.of(context).devicePixelRatio;
  }

  get top => _top / _scaleHeight;
  get bottom => _bottom / _scaleHeight;
  get scaleWidth => _scaleWidth;
  get scaleHeight => _scaleHeight;
  get width => _width;
  get height => _height;
  get pixelRatio => _pixelRatio;
  get physicalWidth => _physicalWidth;
  get physicalHeight => _physicalHeight;

  setWidth(double w) => w * _scaleWidth;
  setHeight(double h) => h * _scaleHeight;

  setFontSize(double f, [bool allowScale=true]) =>
      allowScale? setWidth(f)/_textScale : f/_textScale;

  getGlobalPosition(DragDownDetails details){
    double dx = details.globalPosition.dx / _scaleWidth;
    double dy = details.globalPosition.dy / _scaleHeight;
    return DragDownDetails(globalPosition: Offset(dx, dy));
  }
}

　　

main

import 'package:flutter/material.dart';
import 'screen.dart';

main() => runApp(MaterialApp(
  home: MyApp(),
));

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    var x = MediaQuery.of(context).size;
    print('original size: $x');

    GrantScreen screen = GrantScreen(222, 444, context);
    return RootWidget(
      child: HomePage(),
      screen: screen,
    );
  }
}

class RootWidget extends InheritedWidget {
  RootWidget({Key key, @required this.child, this.screen}):super(key:key);
  final GrantScreen screen;
  final Widget child;

  static RootWidget of(BuildContext context){
    return context.inheritFromWidgetOfExactType(RootWidget);
  }

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) {
    return true;
  }
}

class HomePage extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    var s = RootWidget.of(context).screen;
    return Scaffold(
      appBar: AppBar(title: Text('ABC', style: TextStyle(fontSize: 22),),),
      body: GestureDetector(
        onPanDown: (DragDownDetails details){
          print('mmmmmmmmmmmmmmmmmmmmmm');
          print(details);
          print(s.getGlobalPosition(details));
          print('new top: ${s.top}');
          print(MediaQuery.of(context).padding.top);
          print('mmmmmmmmmmmmmmmmmmmmmmmm');
        },
        child: Container(
        width: double.infinity,height: double.infinity,
        color: Colors.grey,
        child: Column(
          children: <Widget>[
            Text('Text', style: TextStyle(fontSize: s.setFontSize(44, true)),),
            Text('Text', style: TextStyle(fontSize: s.setFontSize(44, false)),),
            Text('Text', style: TextStyle(fontSize: 44),),
          ],
        ),
      ),),
    );
  }
}

　　

screen:

import 'package:flutter/material.dart';

class GrantScreen {
  static double _width, _height;
  static double _physicalWidth, _physicalHeight;
  static double _top, _bottom;
  static double _scaleWidth, _scaleHeight;
  static double _textScale;
  static double _pixelRatio;

  GrantScreen(double w, double h, BuildContext context){
    _physicalWidth = MediaQuery.of(context).size.width;
    _physicalHeight = MediaQuery.of(context).size.height;
    _top = MediaQuery.of(context).padding.top;
    _bottom = MediaQuery.of(context).padding.bottom;
    _textScale = MediaQuery.of(context).textScaleFactor;
    _width = w;
    _height = h;
    _scaleWidth = _physicalWidth / w;
    _scaleHeight = _physicalHeight / h;
    _pixelRatio = MediaQuery.of(context).devicePixelRatio;
  }

  get top => _top / _scaleHeight;
  get bottom => _bottom / _scaleHeight;
  get scaleWidth => _scaleWidth;
  get scaleHeight => _scaleHeight;
  get width => _width;
  get height => _height;
  get pixelRatio => _pixelRatio;
  get physicalWidth => _physicalWidth;
  get physicalHeight => _physicalHeight;

  setWidth(double w) => w * _scaleWidth;
  setHeight(double h) => h * _scaleHeight;

  setFontSize(double f, [bool allowScale=true]) =>
    allowScale? setWidth(f)/_textScale : f/_textScale;

  getGlobalPosition(DragDownDetails details){
    double dx = details.globalPosition.dx / _scaleWidth;
    double dy = details.globalPosition.dy / _scaleHeight;
    return DragDownDetails(globalPosition: Offset(dx, dy));
  }
}