About issue 13376 Wrong TextMorph extent for ButtonMorphs <https://pharo.fogbugz.com/default.asp?13376> :
If you use different fonts as default font and button font, buttons labels may get truncated. One solution would be to always recompute the TextMorphs extent when its font changes, but I don't know if this is always desirable. Otherwise, if we recompute the extent on the creation time of the button, I am not sure if all buttonlabels have styled text.