[Egyptian] Vertical vs horizontal writing-mode

[Mark-Jan Nederhof]

Dear Richard,

A belated thank you.

On Wednesday 20 Jul 2016 11:55:31 ishida at w3.org wrote:
> a. perhaps some combination of the above smoke and mirrors techniques 
> may be adequate to manage some of the differences between layout in 
> horizontal vs vertical writing-mode when the thing we are struggling 
> with is the spacial relationships between the elements circumscribed by 
> a quadrat when they are rendered.

I'm not aware of a fail-safe way to convert vertical to horizontal. If smoke and
mirrors do something reasonable, then that is better than nothing. Here
'nothing' could mean putting groups side by side horizontally, no matter
how high a group is. Note that the usual encodings of hieroglyphic text
place no restriction on the width of a group for horizontal writing, or the 
height of a group for vertical writing.

Our point in the original proposal was that if you want to do more than 'nothing',
then the rendering application must at the very least be able to detect that the
writing-mode has changed and that there is something to be done in the first
place. Horizontal and vertical text use the same code points, just in slightly
different ways, so there is no automatic way to detect a change of writing-mode. 
Unless there are characters that contain the needed information.

You mention other scripts where some characters are more likely to be
found in one or the other writing mode, but there seem to be no
existing scripts where some character uniquely identifies the intended
writing-mode. So there is no precedent for us to invoke to argue for something
similar for Ancient Egyptian.
 
> b. perhaps it's not particularly problematic that you can't 
> automatically flip between horizontal vs vertical without changing code 
> points, especially when one considers that there is anyway so much 
> variation in 'spelling' of egyptian content, often to fit the visual 
> space available.

It seems acceptable for now to assume all text is horizontal, and it is up to
the encoder to manually rearrange groups if not. But it is not ideal. I would
suggest to keep the issue on the agenda, and at least flag up that there is 
a problem to be solved. If it cannot be solved within the constraints of 
Unicode, too bad.

> c. if the control characters used to indicate the positioning of 
> hieroglyphs within the quadrat display space are treated like other 
> Unicode control characters, ie. they are not part of the semantics and 
> are ignored for sorting, searching, and processing the text for meaning, 
> rather they are just cues for visual arrangement, then perhaps it's not 
> a big issue either if they are different for vertical vs horizontally 
> rendered content.

You're right this matter is irrelevant for (most) sorting and searching. But
let me remark that as part of our investigations,  Stéphane and Serge 
analysed occurrences of certain groups, through automatic search, 
distinguishing between horizontal and vertical text. Unless I misunderstood 
this was possible because knowledge about the writing-mode was available in 
the Ramses corpus. So there is at least one example of text with indication
of writing mode being more useful than text without that indication.

Best regards,
 Mark-Jan