RE: DR 09-0295 — WML: gridCols measurement units

[Chris Rae]

Hi Jirka - I will let someone else justify the mandatory units, as I didn't actually agree with the idea and so I don't want to misrepresent it.

Regarding EMU, you're basically right. There are a couple of places where units were optional, but the default was actually EMUs (a unit that couldn't be specified in the string). ST_Coordinate being probably the biggest example, as it's used all over the place. As you surmise, we could of course convert these to other units before saving but given that EMUs are introduced elsewhere in the standard (they have their own whole subsection) I thought it made a bit more sense to add them to the units available. I would certainly be up for adding TWIPs if you think that's sensible.

I've added a definition to the table in 22.9.2.15, that's a good catch. I've also adopted the two-letter "uu" abbreviation, as I think that makes sense.

I've got a draft here but I'll wait for further comments before I circulate it again (mainly because my "turn track changes into formatting" macro doesn't deal very well with it!).

Chris

-----Original Message-----
From: Jirka Kosek [mailto:jirka at kosek.cz] 
Sent: 20 January 2011 07:56
To: Chris Rae
Cc: e-SC34-WG4 at ecma-international.org
Subject: Re: DR 09-0295 — WML: gridCols measurement units

Chris Rae wrote:

> This DR covers the introduction of the mandatory use of measurement 
> units in Strict for the various items that were given optional 
> measurement units at the BRM. We agreed in Beijing to accept the 
> resolution of this DR, and make measurement units mandatory in Strict.

Wow, I wasn't aware of this decision. I'm curious to know reasons why units were made mandatory if someone could spent some time elaborating on this (or is it in minutes from meeting, actually I don't see any minutes).

I haven't studied your documents with all consequences in mind, but definition of "emu" unit is missing. It should be part of table in
"22.9.2.15 ST_UniversalMeasure (Universal Measurement)".

More on this -- personally I see it quite strange to introduce artificial units like "emu". Is the reason to have clear migration path from existing files without units which will not introduce any rounding errors? If so then probably additional units like "twips" should be added.

Also for more efficient parsing I suggest to always use two letter unit codes if units are going to be mandatory. We can use "uu" (universal
unit) instead of "emu" (english/metric unit) as "em" has different meaning in languages like CSS and XSL-FO.

			Jirka

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