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3.6.2 rewrite and addition

From: by way of Judy Brewer <gcl-0039@access-research.org>
Date: Thu, 14 May 2009 01:15:18 -0400
To: UAWG <w3c-wai-ua@w3.org>
Message-Id: <20090514052036.38D984EF7D@homer.w3.org>
[Hi, I am redirecting a message from Greg Lowney which got stuck in a 
filter -- Judy]

Rewriting 3.6.2 Preserve Distinctions

Greg Lowney, 2009-05-11


Summary

Per my action item from the 2009-05-07 conference call, I've:

1. modified the existing 3.6.2 to allow for functionality in which 
the user chooses to lose size distinctions.

2. added 3.6.x requiring the user to be able to set minimum and 
maximum rendered text sizes. I've included four differently worded 
versions and six notes/questions explaining issues I encountered in 
thinking this one through. It proved to be thornier than I'd anticipated.


Existing Draft Text

3.6.1  Configure Text:  The user can globally set the following 
characteristics of visually rendered text content, overriding any 
specified by the author or user agent defaults (Level A) (a) text 
scale (i.e., the general size of text) , (b) font family, and (c) 
text color (i.e., foreground and background).

3.6.2  Preserve Distinctions:  When rendered text is rescaled, 
distinctions in the size of rendered text are preserved (e.g., 
headers continue to be larger than body text). (Level A)


Greg Lowney's Submitted Comment

Combined:  #38. (Re 3.6.2) Give user option whether to preserve font 
size restrictions: Give the user control over whether font size 
distinctions are reserved when rendered. Most users will benefit from 
the ability to scale up all text while maintaining size distinctions 
between different types of elements, but there are cases where it is 
equally important to some users that they be able to choose to hide 
such distinctions and instead use a single font size or a very 
restricted range of such sizes. An example would be a user with low 
visual acuity who chooses to have all text rendered at an extremely 
large size (e.g. the text nearly as large as the window); such a user 
would be hampered if the UA is forced to render titles in a size 
larger than the height of the window. Thus I recommend changing the 
wording from "When rendered text is rescaled..." to "The user has the 
option whether, when rendered text is rescaled...". (Priority: 1 High)


Draft new wording:

3.6.2 (modified) When rendered text is rescaled, the user has the 
option to preserve distinctions in the size of rendered text (e.g., 
headers continue to be larger than body text), subject to any

3.6.x (new, version 1) The user has the option to specify minimum and 
maximum sizes for all visually rendered text, overriding any 
specified by the author, user agent defaults, style sheets, and 
scaling factors.

3.6.x (new, version 2) The user has the option to specify minimum and 
maximum sizes for all visually rendered text, overriding all other 
relative sizes, absolute sizes, or scalings specified by the author, 
user agent, administrator, or user (but not absolute limitations 
imposed by the platform).

3.6.x (new, version 3) The user has the option to specify minimum and 
maximum sizes for all visually rendered text, overriding all other 
relative sizes, absolute sizes, or scalings except for absolute 
limitations imposed by the platform.

3.6.x (new, version 4) The user has the option to specify minimum and 
maximum sizes for all visually rendered text, the values being 
expressed in units which are not scaled, and overriding all elsewhere 
specified sizes, relationships, and scalings except for absolute 
limitations imposed by the platform.


Issues with this:

1. When the user is allowed to specify a font size, is it acceptable 
if the user agent restricts them to a limited set of units? For 
example, if it allows specifying sizes in pixels rather than in 
points or inches, or vice versa? The user can probably adjust to 
anything through trial and error, but it would make a difference in 
that pixels are probably less consistent when a user preferences 
profile is moved between systems; something specified as 16 pixels 
appears approximately 0.5mm tall on my current display (which reports 
being 96 dots per inch), but would be physically twice as large on a 
display running at half as many pixels per inch.

2. Similarly, do we need to specify that this is in *physical* size, 
rather than the logical size? That is, is it clear that the user 
would say "I don't want any text over 6 inches high", rather than 
saying "I don't want any text over 20pt, which when scaled at the 
current settings would be 6" high"? One difficulty in discussing font 
sizes is that they can be specified in so many ways. For example, 
CSS2 allows specifying font sizes in points (1/72"), pixels, or 
inches. However, none of those predict the physical size on the 
screen, as the system doesn't really know how many pixels are in a 
physical inch on the particular monitor. (It probably *thinks* it 
knows, but it's often wrong.) If pixels are the only standard 
measurement that is not scaled by software (only by the pixel size of 
the hardware) then do we need to that the setting is expressed in 
pixels? Probably better to be general and not omit the possibility of 
raster-based displays and the like. (Who's to say they'll never make 
a comeback? :-) I'm hoping we can simply clarify this in 
explanatory/supplemental material, but if we have to be rigorous then 
we could include something like "in units which are not scaled" (see 
version 4 above).

3. Do we need to spell out all the places where the font sizes can 
come from, all of which are overridden using this feature? For 
example, they can be (a) author specified in the document or style 
sheets, (b) user agent defaults, (c) style sheets selected by the 
user or administrator, (d) user-specified scaling factors. Versions 1 
and 2 use the explicit approach, while versions 3 and 4 use more 
generalized categories.

4. Do we need to explicitly note that the system may impose upper or 
lower size limits, and that it is expected that text sizes rendered 
by the user agent may also be limited by the capabilities of the 
platform (e.g. if the platform only supports text down to 5pt in 
size, the user agent is not expected to render text smaller than that 
even if the user specifies a minimum size of 4 pt). In case so, I've 
included wording like "except for absolute limitations imposed by the 
platform" in versions 3 and 4 above.

5. "Preserving distinction in the size of rendered text" does not 
specify whether relative scales are to be preserved (e.g. level 2 
headings continue to be 1.5 times the height of the paragraph text) 
or only the distinctions in relatives sizes (e.g. level 2 headings 
continue to be larger than paragraph text and smaller than level 1 
headings). The former make the scaled document look as much as 
possible like the original, but the latter allows for transformations 
that are easier to use on handheld devices, with screen enlargers, 
etc. On the other hand, the latter gives the UA developer a lot more 
control over the user's experience, which may not always benefit a 
given user. I don't have a good answer to this yet.

6. Do we need to explicitly say that the user shall be allowed to set 
the minimum and maximum to the same value, such that all text would 
be rendered at a single size (i.e. like Draft Mode in Microsoft 
Word), or is that sufficiently implied by the current wording? I'm 
assuming we don't have to explicitly say it in the success criteria 
itself, but if we decide to we can add a phrase such as "which can be 
the same value".

     Thanks,
     Greg
Received on Thursday, 14 May 2009 05:20:47 GMT

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