Glyph issue in the ExtraLight master for characters with the 里 component

[tamcy]

(This issue supercedes #334, where you can find some additional screenshots which I am not going to repost here.)

Preface

One challange of designing CJK glyphs for the Heavy master is about maintaining the visual balnace of the strokes in a component which have a different density. For instance, since 田 consists of more closely distanced strokes than 土, it will appear visually heavier than 土 if the same stroke width is employed. To combat with this, and to maintain legibility, designers will use a lighter stroke width for 田 than that of 土 so that they appear to be visually of the same weight.

This optical trick will also apply to components like 里, 西, 革, etc., and this is purely a decision design and has nothing to do with how a component is actually written in hands, or the etymology of it. For instance:

Here, while the veritcal stroke of the lower part of 革 is a single stroke, it is purposely broken into three strokes with different widths. This is mostly because the middle vertical stroke inside 口 cannot be too wide, otherwise the component will appear too "crowded" and comprehensibility will be hurt.

What this issue report is about

Although this optical trick isn't needed for lighter weights, it is still required in Source Han Sans because of its multiple-master nature. The ExtraLight (EL) master has to maintain the very same contour form. But of course, in the EL master, the contour width/height could be (and should be) the same.

There are basically two ways to achieve this optical trick: (1) by using different contours for a originally single stroke, or (2) by adding additional points in the contours and apply different width or height to the regions where necessary.

This issue is mainly about (2), i.e. where these additional points are placed incorrectly in the vertical stroke for the EL master of the 里 component. While the EL master isn't affected, it can cause the optical trick to appear at the wrong position in intermediate weights.

Affected glyphs

Here are the glyphs I found to have problems. Also, I suggest to also refer to the same codepoint in JP to see whether such optical trick is really necessary where applicable.

Glyph Name	Remarks
uni50EE-CN
uni5398-CN
uni55B1-CN
uni5A0C-CN
uni5A0C-TW
uni5E62-CN	The vertical stroke isn't overlapping with the top of the 日 component.
uni649E-CN
uni6E79-JP
uni6F7C-CN
uni7F20-CN
uni91CC-CN
uni91CE-CN
uni9502-CN
uni973E-CN
uni973E-TW
uni9ED9-JP	里 is fine. For the 丿 stroke of 犬, its position for the optical trick should lie inside the horizontal stroke of the component.
u23638-JP	The vertical stroke of 里 isn't overlapping with the bottom horizontal stroke.

Thank you!

[punchcutter]

Thanks for the detailed notes. This happened because of a change in tools and a bug in the way certain components are handled. Since it all comes from the same problem it's easy to fix.