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Re: [css3-writing-modes] horizontal-bt writing mode

From: John Daggett <jdaggett@mozilla.com>
Date: Tue, 26 Oct 2010 19:04:21 -0700 (PDT)
To: David Hyatt <hyatt@apple.com>
Cc: www-style list <www-style@w3.org>, fantasai <fantasai.lists@inkedblade.net>
Message-ID: <1347746919.193311.1288145061451.JavaMail.root@cm-mail03.mozilla.org>
David Hyatt wrote:

> There is really no reason to leave it out.  Once you've abstracted
> your engine, horizontal-bt just comes along for free.

In terms of initial implementation sure, but you still have to have
someone make tests for those extra values, and run those tests each time
a test suite is run.  Running a minor test a zillion times means a real
cost.

Although the current CSS3 Writing Mode spec says nothing about this,
writing-mode affects UI interactions.  For example, in vertical-rl mode
IE8 alters the default viewport and how the mouse scroll wheel interacts
with it, scrolling the wheel "down" scrolls left in the vertical case. 
Oddly, the page-up/page-down/home/end keys are all "logicalized" but
up/down/left/right arrow keys are not.

To see this, view the examples below.  The Flash example mimics the IE
UI behavior:

Testcase for IE:

  http://nadita.com/murakami/tests/wagahaiwanekodearu-vert-1.html

Nice example layout using Flash:
 
  http://macromarionette.com/#/p/25

So in the horizontal-bt case what happens?  Using the model above the
viewport would be set to the bottom left/right and
page-up/page-down/home/end would all be reversed.  That's consistent and
simple to implement but some poor tester in Beijing is going to have to
test this each time some test suite is run.  Why waste people's time
this way?

I don't see any reason that "completeness" justifies additional testing
and maintenance costs for a feature that has no use case other than
effects than can be achieved in other ways.

John Daggett
Received on Wednesday, 27 October 2010 02:05:05 GMT

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