棄用 textScaleFactor，改用 TextScaler

abstract class TextScaler { 
  double scale(double fontSize);
  double get textScaleFactor; // Deprecated. 
}

abstract class _MyCustomPaintDelegate { 
  void paint(PaintingContext context, Offset offset, double textScaleFactor) { 
  }
}

abstract class _MyCustomPaintDelegate { 
  void paint(PaintingContext context, Offset offset, TextScaler textScaler) { 
  }
}

RichText( 
  textScaleFactor: MediaQuery.textScaleFactorOf(context),
  ...
)

RichText( 
  textScaler: MediaQuery.textScalerOf(context),
  ...
)

final scaledFontSize = textStyle.fontSize * MediaQuery.textScaleFactorOf(context);

final scaledFontSize = MediaQuery.textScalerOf(context).scale(textStyle.fontSize);

MyTooltipBox( 
  size: chatBoxSize * textScaleFactor,
  child: RichText(..., style: TextStyle(fontSize: 20)),
)

MediaQuery( 
  data: MediaQuery.of(context).copyWith(textScaleFactor: 2.0),
  child: child,
)

MediaQuery( 
  data: MediaQuery.of(context).copyWith(textScaler: _myCustomTextScaler),
  child: child,
)

MediaQuery(
  data: MediaQuery.of(context).copyWith(textScaleFactor: 1.0),
  child: IconTheme(
    data: ..,
    child: icon,
  ),
)

MediaQuery.withNoTextScaling(
  child: IconTheme(
    data: ...
    child: icon,
  ),
)

final mediaQueryData = MediaQuery.of(context);
MediaQuery(
  data: mediaQueryData.copyWith(textScaleFactor: math.min(mediaQueryData.textScaleFactor, _kMaxTitleTextScaleFactor),
  child: child,
)

MediaQuery.withClampedTextScaling(
  maxScaleFactor: _kMaxTitleTextScaleFactor,
  child: title,
)

runApp(
  Builder(builder: (context) {
    final mediaQueryData = MediaQuery.of(context);
    final mediaQueryDataWithLinearTextScaling = mediaQueryData
      .copyWith(textScaler: TextScaler.linear(mediaQueryData.textScaler.textScaleFactor));
    return MediaQuery(data: mediaQueryDataWithLinearTextScaling, child: realWidgetTree);
  }),
);