Notable Rendering and Layout Changes after v3.7



This section lists the notable non-API breaking changes.

(Only Affects Tests) FlutterTest is now the default test font


The FlutterTest font replaced Ahem as the default font in tests: when fontFamily isn't specified, or the font families specified are not registered, tests use the FlutterTest font to render text. The Ahem font is still available in tests if specified as the fontFamily to use.

The FlutterTest font produces more precise font and glyph metrics than Ahem, and the metrics are generally font-engine agnostic. Check out the Flutter Test Fonts wiki page for more details about the test font.


The FlutterTest font looks almost identical to the old default Ahem: the glyph for most characters is a box that fills the em square. The notable differences between the FlutterTest font and Ahem font are:

1. Different baseline location

The FlutterTest font's ascent and descent are 0.75 em and 0.25 em, while Ahem's are 0.8 em and 0.2 em, respectively.

In the example golden image change below, the white blocks are text rendered using Ahem and FlutterTest. The second character is taller in the new font since it has a larger descent.

Before (Ahem)AfterAnimated Diff

2. Different decoration position

The underline location is slightly higher in FlutterTest than Ahem.

In the example golden image change below, the 3 lines of white blocks are text rendered using Ahem and FlutterTest. The blue dashed lines indicate the TextDecoration.overline/TextDecoration.lineThrough/TextDecoration.underline positions for each line.

Before (Ahem)AfterAnimated Diff

3. The glyph used for unmapped characters are slightly different

Unmapped characters are rendered as hollow boxes in both fonts, with a slight difference:

Before (Ahem)AfterDiff



Relevant PRs:

Wiki page: