FontWeight also controls the weight attribute of variable fonts

A FontWeight in a text style will also set the weight attribute of variable fonts. It is no longer necessary to separately use FontVariation to control the weight of these fonts.

Text styles can specify a FontWeight value that configures the thickness of the strokes used to paint the text. FontWeight will select the closest weight among a set of font files belonging to the same family.

However, some fonts are distributed as variable fonts where a single font file allows adjustment of attributes such as weight. For variable fonts, applications also had to use the FontVariation API to set the value of the weight variation axis within the selected font file.

Flutter has now changed the behavior of FontWeight so that it will both select the closest matching font file and set the weight attribute of variable fonts.

Setting the fontWeight property of objects such as TextStyle will now also set the value of the wght variation axis of fonts that support it. Flutter will internally apply the equivalent of adding a FontVariation('wght') attribute to the style whose value is the same as the FontWeight.

FontWeight instances can now be constructed using arbitrary integer values ranging from 1 to 1000. This allows usage of weights beyond the FontWeight.w100 through FontWeight.w900 range with values that are not multiples of 100. This also means that linear interpolation of fonts using FontWeight.lerp can yield values other than FontWeight.w100 through w900.

The FontWeight.index property is now deprecated because it only identifies the FontWeight.w100 through w900 weights. Applications should use FontWeight.value to obtain the thickness level of a font.

Applications may see changes in text rendering if they used variable fonts and were specifying FontWeight in text styles without a matching FontVariation('wght') value.

If these changes are undesirable, then the application should change the FontWeight to a value that achieves the intended rendering. For example, to restore the font's default weight, set fontWeight to FontWeight.normal.

Landed in version: 3.39.0-0.0.pre
In stable release: Not yet

API documentation: