The editor Source Insight had/has this feature, code was in one of two modes, draft or preview. I think that the syntax algorithm was the same, but draft was fi

The editor Source Insight had/has this feature, code was in one of two modes, draft or preview. I think that the syntax algorithm was the same, but draft was fixed pitch, syntax colored only, whereas preview had proportional fonts, different sizes and styles in addition to color I last used SourceInsight circa 2005 so I have no idea about its current status