Insertions

Below is a list of conceivable insertions, corresponding to insertions.json. Not all of these insertions have been attested yet, and we have erred on the side on anticipating more potential insertions than may occur in actual texts. The motivation is that we do not wish to place undue limitations on encoding projects in the near future. Even so, it is very likely that encoders will come across insertions that have been overlooked so far.

Two kinds of information are provided here:

1. Per sign, the potential insertions.
2. The positions where inserted groups would be placed.

The choice of insertions can seem somewhat arbitrary. For some signs, both T and TS (or TE) might seem plausible. For some other signs, one could even differ whether TS or BS is the most appropriate choice, if an inserted group would be neither strictly in the top-left corner nor in the bottom-left corner, but somewhere in between. We have followed these guidelines:

• If the inserted group would appear immediately above the feet of a bird (or other animal or human), then this is generally seen as BS or BE insertion, provided the bird or animal is not placed on top of another object (in which case this is seen as TS or TE insertion instead, reserving BS or BE for potential groups to be inserted below that object).
• Consistency between related signs takes precedent over absolute position. For example, we do not necessarily opt for TS rather than BS just because the inserted group could be placed slightly closer to the top rather than to the bottom.
• The M insertion generally encodes that the inserted group appears entirely within the bounding box of the base sign, whereas in the case of T and B, the inserted group might (but is not guaranteed to) protrude outside the bounding box.

For some signs, there is a list of alternative glyphs. For example, for signs with an M insertion, a bigger glyph may be chosen to make more space for the inserted group. From a list of glyphs, an implementation would choose the first for which all the required insertions are defined.

A sign that is mirrored requires any insertion operators to be replaced by their mirrored equivalents. For example, if an unmirrored sign has a TS insertion, then its mirrored form requires a TE insertion. An overlay is always allowed to have TS, BS, TE, BE insertions. For M, T or B insertions in overlays, it is best to introduce a ligature.

However, insertion needs to be specified individually for each angle of rotation of a sign. This is because, for example, T and B do not have obvious equivalents if a sign is rotated by 90 degrees. This is even more problematic for multiples of 45 degrees.

Insertions in ligatures for overlays