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[fxtf-drafts] [transforms-2] Dubious definition of perspective(0)

From: Anthony Ramine via GitHub <sysbot+gh@w3.org>
Date: Fri, 07 Apr 2017 09:17:19 +0000
To: public-fxtf-archive@w3.org
Message-ID: <issues.opened-220156811-1491556638-sysbot+gh@w3.org>
nox has just created a new issue for https://github.com/w3c/fxtf-drafts:

== [transforms-2] Dubious definition of perspective(0) ==
In the definition of [`perspective(<length>)`](https://drafts.csswg.org/css-transforms-2/#funcdef-perspective), the specification says:

> The value for depth must be greater than zero, otherwise the function is invalid.

I assume that "depth" is the argument passed to the `perspective()` function, but that's not really made clear. Usually when something is said to be "greater than zero", that means strictly greater than zero, and thus zero is invalid. Furthermore, the definition of a [perspective projection matrix](https://drafts.csswg.org/css-transforms-2/#PerspectiveDefined) says `m34` is set to `-1/d`, which clearly isn't defined when `d` equals zero.

Unfortunately, `perspective(0)` is actually mentioned by the specification itself, when defining [neutral elements for addition](https://drafts.csswg.org/css-transforms-2/#neutral-element). That doesn't seem right to me.

Please view or discuss this issue at https://github.com/w3c/fxtf-drafts/issues/126 using your GitHub account
Received on Friday, 7 April 2017 09:17:27 UTC

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