Layout Behavior of Characters (question about unicode standard)

Question

I've been reading Unicode's core specification (see https://www.unicode.org/versions/latest/). I mostly understood what the text was explaining in section 2.1 Architectural Context until it started talking about layout behaviors. It feels like there's no preface or explanation of the phrase 'layout behavior of characters'.

Section 2.1 explains how a character encoding must be designed with text processes and algorithms in mind since an encoding choice can make text rendering and other processes more complex (or simpler, depending on the choice).

The specification then continues with a Character Identify sub-header that uses multiple phrases including the word 'layout'. Here are some examples from the text:

• "Whenever Unicode makes statements about the default layout behavior of characters, it is done to ensure that users..."
• "The actual layout in an implementation may differ in detail."
• "A mathematical layout system, .., will have many domain-specific rules for layout.."
• "The purpose of defining Unicode default layout behavior is not to enforce a single and specific aesthetic layout for each script.."

What does 'layout' and/or 'layout behavior of characters' mean in this context?

Answer 1

Layout probably refers to how you are placing characters relative to other characters: left-to-right, right-to-left, top-to-bottom, etc.

And layout behavior of a characters refers to the fact that some characters have different representations in different layouts.

E.g. the character U+232A (RIGHT-POINTING ANGLE BRACKET) renders as

in a horizontal layout but in a vertical layout it will render as

Here are some more examples:
https://www.unicode.org/reports/tr50/tr50-22.html