Bug 186953

Ability to disable pinchzoom was brought up in a recent discussion with W3C/WCAG accessibility team where 
it was clarified [1] (emphasis mine) that the guidelines specify only:

"a *SHOULD NOT* author conformance requirement that has been in the spec since 2016 arronei/html@877b59c. It is an author conformance requirement only, that does not forbid the use but does ask authors to consider seriously the curtailment of user's ability to zoom. What apple have done in safari is beyond the scope of this issue as it does not require anything of browser implementers."

With recent changes to iOS Safari, Apple appears to have introduced a MUST NOT/CANNOT author conformance requirement instead and this affects the ability of web developers to implement certain type of websites which are more "app-like".

I'll quote our own app [2] where we need the clause…

QUOTE

<meta name="viewport" content="width=device-width, user-scalable=no" />`

UNQUOTE

…to work as per the specification or even original concept invented by iOS Safari/Apple team. 

We have no content inside of parent window so pinchzoom has to be disabled on parent frame all the time. The clause above was critical for us to implement such an interface without using hacks.


[1] https://github.com/w3c/html/issues/602#issuecomment-390490730
[2] https://bubblin.io/cover/the-death-of-dulgath-by-michael-j-sullivan