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RE: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0]

From: John Birch <John.Birch@screensystems.tv>
Date: Tue, 13 Mar 2012 17:30:51 +0000
To: Glenn Adams <glenn@skynav.com>
CC: Timed Text Working Group <public-tt@w3.org>
Message-ID: <0981DC6F684DE44FBE8E2602C456E8ABFC3DED@SS-IP-EXMB-01.screensystems.tv>
Actually I have no problem with 0.1c, that makes complete sense to me…
IMHO, it is ‘up to an implementation’ the sense (if any) it makes of a calculated value for e.g. an outline ‘length’ of 0.1c where c is 7x7 pels… and thus outline ends up being 0.7 pixel.
It might round this up to 1 pixel…

Cell grid is taken from root extent, which implies that cell 0, 0 is at the top left boundary of the root extent.
Unfortunately in practise this is often undesirable as it is unlikely that you would want text placed so close to the boundary of the root extent.
Is there any padding like mechanism that would allow a ‘safe area’ to be defined around the edge of the ‘virtual grid’ created by cell resolution.

Best regards,

From: Glenn Adams [mailto:glenn@skynav.com]
Sent: 13 March 2012 17:22
To: John Birch
Cc: Timed Text Working Group
Subject: Re: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0]

On Tue, Mar 13, 2012 at 3:23 AM, John Birch <John.Birch@screensystems.tv<mailto:John.Birch@screensystems.tv>> wrote:
Further: There appears to be nothing preventing the use of a fractional cell value for length... so 0.1c is permissible. :-)

technically, 0.1c is computable but not made explicit in the spec; it is computable since a cell's dimension is computed from knowledge of the root extent's dimensions, which yields a integer or real number dimensions of a cell (in pixels)

nonetheless, we may wish to consider restricting <length> to integral numbers for some units, e.g., px and c

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Received on Tuesday, 13 March 2012 17:33:16 UTC

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