decorationThickness property

double decorationThickness
final

The thickness of the decoration stroke as a muliplier of the thickness defined by the font.

The font provides a base stroke width for decorations which scales off of the fontSize. This property may be used to achieve a thinner or thicker decoration stroke, without changing the fontSize. For example, a decorationThickness of 2.0 will draw a decoration twice as thick as the font defined decoration thickness.

To achieve a bolded strike-through, we can apply a thicker stroke for the decoration.
Text(
  'This has a very BOLD strike through!',
  style: TextStyle(
    decoration: TextDecoration.lineThrough,
    decorationThickness: 2.85,
  ),
)

We can apply a very thin and subtle wavy underline (perhaps, when words are misspelled) by using a decorationThickness < 1.0.
Text(
  'oopsIforgottousespaces!',
  style: TextStyle(
    decoration: TextDecoration.underline,
    decorationStyle: TextDecorationStyle.wavy,
    decorationColor: Colors.red,
    decorationThickness: 0.5,
  ),
)

The default decorationThickness is 1.0, which will use the font's base stroke thickness/width.

Implementation

final double decorationThickness