Professional font designers know that the internals of an OpenType font can become very complex, especially when it contains numerous OpenType layout features. Glyph substitutions and glyph positioning are often required with international and high-end typographic fonts, to ensure layout engines correctly render text.

A font with a couple of substitution tables along with a single class based kern lookup is fairly easy to maintain, but when your font supports complex scripts like Arabic, it soon becomes next to impossible to keep oversight of all features and lookups that work together.

Microsoft VOLT

In the good old days, people had to use Microsoft VOLT (Visual OpenType Layout Tool) to add OpenType layout features to a font. It had to be used in conjunction with a font editor, as VOLT is not a full-fledged font editor. It contains a basic proofing tool, that allows you to step through features and lookups. You had to compile and install the font to test it. Two decades ago, this was all we got, so we accepted its limitations.

Advanced OpenType Proofing

FontCreator combines the power of an advanced font editor along with a visual OpenType designer. It also allows you to edit the feature code, and it can even import fonts with VOLT production data. With FontCreator 13 we’ve added an interactive proofing tool, which allows you to focus on the specific features and lookups that need your attention. It relies on our custom shaping engine, which currently supports numerous scripts.

To use the proofing tool, open the OpenType Designer window, and click the second toolbar icon in the upper left corner. Here you see the same font, but now in FontCreator.

It uses the preview text and selected script, language, and features as defined in the OpenType Designer window, but the proofing window allows you to see exactly what features, lookups, and specific items have been applied to turn your original input into the visual appearance as shown in the preview area.

Debug and inspect a line of text

To use the proofing tool to the max, ensure you use the internal shaping engine (_shaper) and provide the text you want to inspect in the text box above the text preview area.

Within the tree view, you can click an item, and it will be shown within the OpenType Designer window. This interactive proofing greatly speeds up the process of understanding how OpenType features work together.

To zoom into a specific part of the text, click and drag a rectangle within the Proofing preview area. This will enable the filter so only relevant OpenType layout features for the selection are shown.

As soon as you start using the proofing tool you’ll soon forget how much time you’ve wasted with manually writing down feature and lookup names in order to fix an issue in your OpenType features!