New view of horizontal scrolling

Horizontal scrolling May be a legibility issue.

“Legibility” refers to perceptual properties of text that influence
readability. Text which is hard to read because of obscure vocabulary, or
complex syntax or meaning may be incomprehensible, but still highly
legible. Legibility depends on both local and global properties of text.
Local properties refer to characteristics of individual letters or pairs of
letters such as font, print size, and letter spacing. Global properties
refer to layout characteristics such as line length, line spacing, and page
format. [Legge, Psychophysics of Reading (ch 4)]

G. Legge identifies two types of legibility issues: Local and Global. Local
covers issues like letter spacing, font face etc. Global covers issues like
line length, line spacing etc. The key to Legge's definition is that
legibility is perceptual. He carefully rules out issues of understanding.
Now if line length is a global legibility issue then isn't a line that runs
off the view port a global legibility issue? Maybe we have been framing the
issue wrong by focusing on the solution, horizontal scrolling, and not the
need, legibility interference by lines that exceed the available space.

Gordon, am I off the wall. Could you send a reply to all so the Low Vision
Task Force can consider your comments. Also if you have the time could you
comment on my refinement of legibility at
https://github.com/w3c/low-vision-a11y-tf/issues/31 .

Thank You,
Wayne