Interesting to me that WebKit gets vertical form controls before MacOS. I don't have any experience with vertically written languages. How important are these controls to computer usage in Japan? Does Windows have them?
At least in Japan, not important. Japanese is written vertically in novels, comics, newspapers and some writing in school, but almost everything else is written horizontally. Textbooks, manuals, letters from the bank, websites. Restaurant menus often go vertical for a more Japanese feel or horizontal for a more western one.
That said, I think it's great to see this support added to webkit. A diverse web is good for everyone.
There's more usage of vertically written Japanese than you listed. Some signboards, some formal letters, many paperbooks (and ebook version), vast majority of non-technical magazines are still vertically written.
Fortunately, for forms, I haven't seen any vertically written forms except school work.
When drafting a formal letter, does the author write it horizontally and present it vertically? Or, is the author expected to have skill at writing a 90 degree rotated character? Or, is the character not rotated, but just written in columns not rows?
I suspect most of modern Japanese media is horizontal exactly because of a low support for vertical in digital. Multilingual applications and systems rarely favor i18n improvements for a smaller groups of users.
Japan has a pretty strong local tech industry. Microsoft Word needed to add all kinds of features, including both vertical writing and weirder stuff like a dictionary of seasonal greeting phrases to use in formal correspondence (https://learn.microsoft.com/en-us/archive/blogs/office_globa...) to compete successfully with Japanese word processors.
So I suspect the causality is the other way around; there wasn't much demand for vertical form controls for the same reason you don't write emails in cursive.
How many characters tall is a Japanese book? English paperbacks seem to be similarly sized on the number of characters/words wide. Interface guidelines put an optional number of characters on a screen somewhere between 60-80. Books being taller than they are wide seem like it would stretch the limit to something harder to track for vertical writing.
Note that Japanese characters are much bigger (+ meaning-packed) than Latin characters, so it's also harder to lose track of which line you are at IMHO.
Like 20ish seems common in my experience learning. But you have to consider that most words are 1-3 characters before comparing that to English line lengths.
The article mentions Korean but vertical writing is not used at all in Korea. It went out of fashion many decades ago. I'm not sure why safari decided to add this feature...
There's only one language in common use where vertical writing is effectively mandatory: Mongolian. They also use Cyrillic for historical reasons, and Latin script as a modern convenience for electronic communications, but the native script is vertical.
That's enough reason to support it, imho. Japanese and Chinese are also routinely printed vertically, so that adds another billion and a half people who stand to benefit from it.
At least in Mongolia, Cyrillic is dominant and usage of the traditional script is marginal, though there are efforts to bring it back.
Most users of traditional Mongolian script are in China, where websites are in Chinese by default and Mongolian form elements are rare. They do exist though, and it would be nice if the search bar of this bookstore https://mn.dayangds.com/ could be vertical like everything else.
Looks like mn.dayangds.com does UA sniffing so you only get the vertical search bar if the user-agent contains the string "Firefox/" followed by at least one digit. Ugh.
Japan has adopted LTR long ago in TV and the web. Never seen a Japanese site formatted vertically. Newspapers and books are still vertical, but it's not really difficult to read one way or the other.
That said, I think it's great to see this support added to webkit. A diverse web is good for everyone.