To complete what Ian said, I use a font I found in HaxeUI_Base (). I had to add this bit to make it work :

// HaxeUI fonts registration
var files = hxd.res.Loader.currentInstance.dir("ui/theme/fonts");
for ( file in files )
{
    if ( file.entry.path.indexOf(".fnt", file.entry.path.length-4) != -1 )
    {
        SDFFonts.register(file.entry.path, h2d.Font.SDFChannel.Alpha);
    }
}