Definition of Values of Property Vertical_Orientation

[Markus Scherer]

On Sun, Aug 21, 2022 at 7:24 AM Richard Wordingham via Unicode <
unicode at corp.unicode.org> wrote:

> I've just spent a painful time verifying the loading of the values of
> Vertical_Orientation.  After the list of codepoints and ranges in the
> comments of VerticalOrientation.txt for which the value defaults to
> Upright, is there any reason for having the ominous wording
>
> "All other code points, assigned and unassigned, that are not listed
> explicitly in the data section of this file are given the value R."
>
> Given the current (Version 14.0) and candidate (Version 15.0) data
> sections, is there any reason for not having the more reassuring
>
> "All code points, assigned and unassigned, that are not listed
> explicitly in the data section of this file are given the value R."
>

sgtm

One could then set up the default value of the property as Rotated and
> then just read in the data section as overrides, as with other files
> just defining the value of one enumeration property.


You can do that today.

As things stand,
> loading the property values into an application involves three steps:
>
> 1) Set up the default value.
>

Which you can also read from the @missing line.

# @missing: 0000..10FFFF; R

https://www.unicode.org/reports/tr44/#Missing_Conventions

2) Set up the default values for the Upright regions listed in the
> comments.
> 3) Set up the explicit values from the data file.
>
> Given the current explicit data, Step 2 is redundant.
>

Right. The comments document which ranges default to Upright, but the
unassigned and private use code points that have that value are also
explicitly listed.

We intend, for some version after 15, to add additional @missing lines in
this file so that we no longer need to set those not-assigned code points
to U, but either way you can just parse the file without hardcoding
assumptions.
(Unicode 15 has three files with multiple @missing lines.)

markus
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