session-android/res/values/text_styles.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="Signal.Text.Headline" parent="Base.TextAppearance.AppCompat.Headline">
        <item name="android:textSize">28sp</item>
        <item name="android:lineSpacingExtra">6sp</item>
        <item name="android:fontFamily">sans-serif</item>
        <item name="android:letterSpacing">0</item>
    </style>

    <style name="Signal.Text.Body" parent="Base.TextAppearance.AppCompat.Body1">
        <item name="android:textSize">16sp</item>
        <item name="android:lineSpacingExtra">8sp</item>
        <item name="android:fontFamily">sans-serif</item>
        <item name="android:letterSpacing">0.15</item>
    </style>

    <style name="Signal.Text.Preview" parent="Base.TextAppearance.AppCompat.Body2">
        <item name="android:textSize">14sp</item>
        <item name="android:lineSpacingExtra">6sp</item>
        <item name="android:fontFamily">sans-serif</item>
        <item name="android:letterSpacing">0.25</item>
    </style>

    <style name="Signal.Text.Caption" parent="Base.TextAppearance.AppCompat.Caption">
        <item name="android:textSize">12sp</item>
        <item name="android:lineSpacingExtra">4sp</item>
        <item name="android:fontFamily">sans-serif</item>
        <item name="android:letterSpacing">0.40</item>
    </style>
</resources>