[MATH] Application of italics correction is not fully documented

[khaledhosny]

The spec has the following text:

Italics correction can be used in the following situations:

• When a run of slanted characters is followed by a straight character (such as an operator or a delimiter), the italics correction of the last glyph is added to its advance width.
• When positioning limits on an N-ary operator (e.g., integral sign), the horizontal position of the upper limit is moved to the right by ½ of the italics correction, while the position of the lower limit is moved to the left by the same distance.
• When positioning superscripts and subscripts, their default horizontal positions are also different by the amount of the italics correction of the preceding glyph.

The second point documents the special behavior of applying italics correction to N-ary operator limits above and below it. It does not mention what happens when the limits are positioned in the super and subscript position, and one would assume that the third point would apply in this case.

But the third point is rather vaguely worded, but probably it relies on the explanation when discussing MathKernInfo.

It probably makes since to expand slight about how italics correction is applied for superscript and subscript horizontal position.

Testing also shows that Microsoft Word will not change the horizontal position of the superscript of N-ary operator, and will move the horizontal position of the subscript to the right by the amount of italics correction. This is basically the opposite of what happens when italics correction is applied to other glyphs, so it should be explicitly documented.

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• ID: f0076fd2-52b0-2989-3142-fd9e456b9514
• Version Independent ID: 4aef8fa3-2ad3-7933-5a77-0a7473e66112
• Content: MATH - The mathematical typesetting table (OpenType 1.9) - Typography
• Content Source: typographydocs/opentype/spec/math.md
• Service: typography
• GitHub Login: @PeterCon
• Microsoft Alias: alib