search

w3c / wcag21

Repository used during WCAG 2.1 development. New issues, Technique ideas, and comments should be filed at the WCAG repository at https://github.com/w3c/wcag.
https://w3c.github.io/wcag/21/guidelines/
Other
140 stars 55 forks source link

Reflow to Single Column #58

Closed allanj-uaag closed 7 years ago

allanj-uaag commented 7 years ago

Current versions of SC and Definitions

SC Shortname

Linearization

SC Text

A mechanism is available to view content as a single column, except for parts of the content where the spatial layout is essential to the function and understanding of the content.

Suggested Priority Level

Level A

Related Glossary additions or changes

none

Relevant Guidelines and Success Criteria

Guideline 1.3 (Flexible Date) is essential for reflow. SC 1.3.2 (Meaningful Sequences) establishes the necessary structure for reflow to occur. Without reflow SC 1.4.4 (Resize Text) could not be extended to enable very large text. Finally, without reflow restriction of column size would be difficult. This allows raising the level of SC 1.4.8(2) (Visual Presentation (width)) to Level A.

Principle 1, Guideline 1.4 (Distinguishable) is the most appropriate location for this new success criteria. This is because it focuses on presentation of content in a single column of elements with all text in single column format.

The final fit for reflow is in Principle 2, Guideline 2.4 (Navigation). Most people with low vision could benefit from a single column view of a page. This is because items get lost in a two dimensional presentation. (See Benefits below)

Description

Content can be viewed in a single column. All text is presented in single column format and the Line Length SC ensures that all lines of text word wrap to fit the available space. Data tables will have a standard tabular display, a two-dimensional matrix. Some user agents do not support active data such as form controls in reflow. In these cases the content author is not responsible for creating content that reflows.

Reflowed HTML
This good reflow of HTML was accomplished by a custom style sheet.

good PDF reflow

Properly reflowed PDF text.

bad PDF relow

Improper characters used by the author for spaces. This causes words to jam together with reflow. This authoring problem occurs frequently with PDF.

Benefits

One important need of most people with low vision is to reconfigure a presentation from a normal two-dimensional page to a one-dimensional organization of data. This is not always the case, but it is a frequent need. For quick scanning the original structure may be useful to scan for recognizable items. This is usually done when the user knows a page and is looking for just one thing. In cases where careful examination of the page is necessary one column presentation is needed. The reasons are given below.

  1. Continuous Reading: Many people, with and without disabilities, find it more difficult to read when they must scroll from the bottom of a column of text to the top of another column. With low vision the need is greater. To go from one column to next frequently requires paging up several screens to get from the bottom of one column to the top of the next. Additionally, using a small scrollbar and cursor is difficult with limited sight. This makes getting from the bottom of a column and finding the top of the next column more difficult. Reading flow degrades and comprehension suffers.
  2. Reliable Searching: (visual navigation of the viewport) Searching for a specific item within a page of information is difficult for almost everyone with low vision. This is because the field of vision is limited either by enlargement requirements, or physical visual field loss due to tunnel vision. The ability to only scroll in one dimension vertical only or horizontal only but not two dimensions, dramatically simplifies this problem. A person can start at the top of the page and move element by element down the page until the bottom, and be certain that every item has been scanned. (TSBVI,Specific Eye Conditions, Corresponding Impact on Vision, And Related Educational Considerations)
  3. Resizing Text on a Large Scale: Two column or more do not support large print text. Even if text stays within column boundaries, multi-column format will not provide enough space for text in large print. Even medium length words will not fit for sizes exceeding 250%. This causes excessive hyphenation and becomes distracting. This criterion is a necessary condition for useful text resize criterion for people with visual acuity worse than 20/70. Many people in this range require print size greater than 1/2 in. (1 cm.). This cannot be sustained with standard formats. content.
User Need: Users can set blocks of text in one continuous block, instead of in multiple columns. Source: Accessibility Requirements for People with Low Vision, Section 3.2.2

Testability

  1. HTML: Use the Easy Checks - A First Review of Web Accessibility document, Basic Structure check. Check that the sequence of text is in fact a correct reading sequence. Note: These tests remove all style. This means that items that the author did not intend to be seen become visible. It can be useful to display the pages side by side to compare what is intended to be visible and what is not. If this test passes the content can be restructured into an accessible format for low vision using CSS and JavaScript.
  2. PDF: With a user agent that enables reflow, use the reflow option to see content reflowed into one column. No lines should be truncated. If this operation is successful the document passes.

Techniques

Existing Relevant Techniques

New Techniques

  1. HTML: Write content so that the source order of perceivable elements defines a correct reading sequence. It is perfectly appropriate to include items that are not displayed to users in any convenient order. Such elements do not disrupt the correct reading sequence of the entire page. Make sure that elements that are not to be perceived are marked in a standard way like "display: none" or "visibility: hidden" so they can be ignored by a reformatting program. Test your document with no style in your user agent(s). See that it makes sense as a page and is fully operable. After this content is arranged and tested, positioning and other block formatting of the page. Use style sheets for positioning so that it can be removed and the resulting view is readable and operable.
  2. HTML: Use media queries based on em units for reflow to single column. Reason: When the line length shrinks below a certain number of characters, reflow to a single column is triggered whether the reduced character count is caused by shortened lines or increased font size. This makes the reflow to single column accessible on more devices.
  3. Fxx: Text becomes unreadable because of reflow.
  4. Fxx: Failure of Success Criteria Text Colors and Reflow to Single Column due to inserting important information by using the background-image property of CSS.
    Note: This is necessary because non-decorative images cannot be reflowed.

Related Information

Articles

Email

GitHub

Minutes

Surveys

Wiki Pages

WayneEDick commented 7 years ago

Hello All,

In our presentation at CSUN on LVTF work we re framed linearization as follows: Everyone with low vision has tunnel vision on the web: Either they have the medical condition and need a narrow view or they have impaired visual acuity and enlargement creates limited view.

The result is that everyone with low vision needs, "a sequence of single purpose windows," so that they can reliably find all important information on the sight and / or enlarge sufficiently with word wrapping to perceive the information.

The need is : A sequence of single purpose windows. Linearization to a single column is one way to do this.

Alan Cooper would refer to this as a sequence of sovereign postures.

For people who are running a normal web page, the ability to support responsive design is enough. For these pages a simple script would test the page.

What is certain is that this is the one SC that is needed by 100% of people with low vision, and it is essential.

WCAG WG based its strategy for low vision on three incorrect hypotheses:

1) Enlargement without word wrapping is accessibility support 2) 200% is sufficient enlargement for anyone who is classified as having low vision because of reduced visual acuity 3) More contrast is better

Before we start to pick apart the SCs one by one, I think it is time to absorb impact of basing an accessibility strategy on fallacy. It means that we may need to ask developers to go back and do extra work we did not ask the first time around.

We need new foundations: The following are necessary:

1) Enlargement of all text with word wrapping. 2) Access to a sequence of sovereign windows. 3) Ability to override visual style for text.

These have been established as minimal necessities. It is time to figure out how to do it. We need to take a deep breath and ask developers to do what is needed, after doing our best to determine exactly what that is.

alastc commented 7 years ago

Hi Wayne, I'm not clear what the 'fallacy' is you are referring to?

ask developers to do what is needed, after doing our best to determine exactly what that is.

Indeed.

awkawk commented 7 years ago

The main problems I see with this generally good idea are: 1) Clarity - where do we draw the line with what does and does not need to reflow? I think that it is clear that an image that is wider than the screen wouldn't need to magically wrap (and how would it?) but tables are a big topic in the discussion, and there are other structure types that we need to feel confident that we aren't causing problems for. 2) Implementability - this is going to limit the acceptable development strategies for regular content, and on top of that there are questions about the support for this in mobile browsers and in mobile apps - how achievable is this today?

alastc commented 7 years ago

Elements which cannot reflow such as image can still 'fit', it is easy to use something like img { max-width:100%;} like this test page, as an author or user-script.

Tables are the only group-container that is 2D and contains text. I suggest we rely on 1.3.1 for requiring a data-table for data, and say that they are exempt (under the 'spatial layout') but that layout tables should be linearisable.

The user-side script I started with included:

// Wrap data tables in a div that allows for horizontal scrolling
var dataTables = $('table:has(th)');
$(dataTables).wrapAll( "<div style='width: 100%; overflow:auto; outline:3px grey solid;padding:3px' />");

// Reflow presentational tables
var layoutTableCells = $('table[role=presentation] td');
$(layoutTableCells).css('display', 'block');

That could be more robust and elegant, but it worked as a starting point.

I can't think of anything else that isn't either a text element that linearises easily, or an image/svg/object type thing that would be exempt?

For Implementability, arguably it isn't asking for more that 1.3.1, except that SC (crucially) hasn't been interpreted as making sure the user could linearise the page. The initial test-script works pretty well on quite a few sites, e.g. BBC, Wikipedia, Microsoft. Any responsive site starts from a linearised point of view so that is fairly easy, but there methods that people use that really disrupt user-driven linearisation.

The things that are currently difficult tend to be the really aggressive layouts, where scripting is used to position things (or we haven't found the right CSS to nullify the layout yet).

For mobile, arguably some devices have that built in already (with the Reader view in Safari for example), but no-one tests against that and the rules/heuristics behind it are a mystery. You can use bookmarklets (like the example) on mobile, so it is possible.

jnurthen commented 7 years ago

You are going to need to allow aria grids and treegrids not to wrap too [role=grid] , [role=treegrid]

alastc commented 7 years ago

Yep, presumably at the same level, so exempt anything within that block.

alastc commented 7 years ago

Noting another comment about the mechanism language:

this requirement sounds like it's asking for websites to place a "linearize" button on the page.

joshueoconnor commented 7 years ago

@alastc Could people who needed content linearised or single-column formatted - like this, not have a plug in etc that did this? So the dev has to code things in a way that just facilitates this functionality? That to me is reasonable, rather then the dev themselves having to have a 'mechanism'?

alastc commented 7 years ago

@joshueoconnor Yep, that's the primary aim. It is in the same category (in customisation levels) as adapting text - let the user do it. Maybe we can import the note from adapting text.

joshueoconnor commented 7 years ago

@alastc Sounds good to me :-)

jake-abma commented 7 years ago

Trying to get grip on this SC here some small remarks:

At “Relevant Guidelines and Success Criteria” I’m wondering if guideline 1.3 will be renamed as I see “Guideline 1.3 (Flexible Date) is essential for reflow.” I didn’t think 2.0 text would be changed and the current name is “Adaptable”.

textual corrections: “Flexible Date” should be “Flexible Data” and “(Meaningful Sequences)” should be “(Meaningful Sequence)”

jake-abma commented 7 years ago

About raising the level of SC 1.4.8(2) to Level A: I do understand there is a relation between 1.4.8(2) and Reflow to Single Column but restricting column size seems not appropriate. It could be that I do want to make a very wide column with big text for a web application shown on a large screen. So I’m wondering if 1.4.8(2) is relevant here as restricting to 80 characters for a Level A seems too strict.

jake-abma commented 7 years ago

The most appropriate location to me seems Principle 1, Guideline 1.3 (Adaptable) and not as suggested Principle 1, Guideline 1.4 (Distinguishable). This because 1.3 is about “Create content that can be presented in different ways (for example simpler layout) without losing information or structure.” Especially if we expect user to linearize content themselves. Guideline 1.4 is concerned with making the default presentation as easy to perceive as possible although I realize SC 1.4.4 Resize Text sits in 1.4.

Extending on this (Adaptable) I see we need to fix the concerns as Leonie mentioned when she brings on a valid issue when tables are used for layout: https://github.com/w3c/wcag21/issues/58#issuecomment-273804060 This must be addressed.

And also Fiona has a point https://github.com/w3c/wcag21/issues/58#issuecomment-284159623 for show/hide content and turning off CSS but this is inherent if we take the comment of Alastair into account at: https://github.com/w3c/wcag21/issues/58#issuecomment-273935955 nr.2

So when Linearization is about adaptable content as Alastair says “but to make sure that if someone does forcibly reflow the content, the reading order makes sense.” It seems to me the content author only needs to be sure there is meaningful sequence in the DOM for web (HTML) .

jake-abma commented 7 years ago

The suggestion that reflow if covered by SC 1.3.2. seems valid especially when reading the text in the thread https://lists.w3.org/Archives/Public/w3c-wai-gl/2017JanMar/0202.html “2. Reflow to single column [2] is to enable people to go beyond 400% and have a correct reading order. It is NOT intended to be the authors responsibility to make the reflow happen (in HMTL), but to make sure that if someone does forcibly reflow the content, the reading order makes sense.”

In SC 1.3.2 we also have “For clarity: Providing a particular linear order is only required where it affects meaning.” And this covers linearization, not?

As Wayne already says in https://github.com/w3c/wcag21/issues/58#issuecomment-277046105 “We can already produce a linearized accessibility API. Why is that so difficult in the browser?” isn’t this already true in the case of the DOM which must have a meaningful sequence (SC 1.3.2) and thus fits the condition for linearization?

jake-abma commented 7 years ago

As John says https://github.com/w3c/wcag21/issues/58#issuecomment-273231053 “Tables can be linearized today“ and Alastair at https://github.com/w3c/wcag21/issues/58#issuecomment-273935955 and https://github.com/w3c/wcag21/issues/58#issuecomment-287919785 this is true from a CSS perspective if this is what you mean but not from an accessibility perspective as playing with the display property for a table removes the role from the accessibility API and causing screen readers to not recognize them as tables anymore. This means if you’re zoomed in and using a screen reader the tables are not read properly anymore. Also using the arrow keys cause strange behaviour skipping / jumping around.

jake-abma commented 7 years ago

For “A mechanism is available to view content…” I wonder if this is something a content author should / could provide or that it is a function of a user / user agent for instance and I see this was also mentioned by Paul and referenced by Alastair: https://github.com/w3c/wcag21/issues/58#issuecomment-288461497. And Jared at https://github.com/w3c/wcag21/issues/249 Seems like we’re steering at making it possible for users to do the linearization themselves and not providing a mechanism (to be available).

GreggVan commented 7 years ago

The difference between "“A mechanism is available” and "“A mechanism is provided” is that with “A mechanism is available” — the author can rely on the mechanism being provided on the other end and they just need to support it.
With the “A mechanism is provided” - the author would need to provide it.

This should be clear from the Understanding WCAG 2.0 document — and if it is not - it needs to be added so that it is clear.

g

On May 5, 2017, at 6:04 AM, Jake Abma notifications@github.com wrote:

For “A mechanism is available to view content…” I wonder if this is something a content author should / could provide or that it is a function of a user / user agent for instance and I see this was also mentioned by Paul and referenced by Alastair: #58 (comment) https://github.com/w3c/wcag21/issues/58#issuecomment-288461497. And Jared at #249 https://github.com/w3c/wcag21/issues/249 Seems like we’re steering at making it possible for users to do the linearization themselves and not providing a mechanism (to be available).

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/w3c/wcag21/issues/58#issuecomment-299428008, or mute the thread https://github.com/notifications/unsubscribe-auth/AJph3psFnMi_3XbuMKVuQpVJf8Pwz-IBks5r2vQmgaJpZM4K-ARo.

DavidMacDonald commented 7 years ago

Comment on linearization. I've accommodated and trained employees with low vision in banks and government for about 15 years. My experience is that once we need more than 400% (4x zoom), we are really into screen reader territory. I generally say "OK lets start thinking about migrating to learning a screen reader."

Almost all users I've worked at were extremely relieved to transition to screen reader at anything over 400%. One employee was nervouse to go to screen reader and hung onto zooming til it was 20x. (about 5 letters on a 27"screen) When we finally went to screen reader she was extremely relieved and wish she had done it sooner.

I don't think WCAG 2.1 should try to accommodate more than 400% without assistive technology. I think the ask upon the developer is disproportionate to the benefit to most end users.

I think after 400% the end user either needs AT like ZoomText's docreader app which reflows content, a screen reader, or other other means. I don't think it should be the author's responsibility at this point in history.

joshueoconnor commented 7 years ago

+1 to @DavidMacDonald

alastc commented 7 years ago

My experience is that once we need more than 400% (4x zoom), we are really into screen reader territory

Perhaps that is because there haven't been any good intermediate options? (I think Wayne and others would say magnification isn't a good option, at least for reading.)

I don't think WCAG 2.1 should try to accommodate more than 400% without assistive technology.

Do we consider user-side scripts/extensions AT? It is adapting the interface in a way that the author doesn't specify, so I would have thought so.

An important point about this SC is that we don't expect the author to provide a different interface, we expect them not to prevent the user making one.

KerstinProbiesch commented 7 years ago

I think that also in this case a note should be added, that the WG is seeking input on PDF.

alastc commented 7 years ago

I think you mean that for #77?

KerstinProbiesch commented 7 years ago

@alastc Also for this SC cause a PDF reflow is explicitly mentioned.

alastc commented 7 years ago

ok, I just meant this one hasn't gotten as far along yet, I don't think it is up for a CFC yet.

DavidMacDonald commented 7 years ago

(I think Wayne and others would say magnification isn't a good option, at least for reading.)

The docreader pulls out the content and reflows it and does anything with the text the user wants. It's not perfect. It can be heavy on the system, and doesn't pull put controls etc... But I'll stand by my experience with many low vision employees. More than 400% is getting into screen reader territory, and it's a huge ask on developers in today's wild west environment.

https://www.youtube.com/watch?v=6cbYmbeDZyQ See at around 2:30.

alastc commented 7 years ago

Hi David,

The idea of this SC is to make something like ZoomText's docreader for the web work.

So this:

Gov uk website screenshot

Becomes this (or something like it, the colours and size would be down to preference):

Gov uk website linearised and in black and white

Simply by running a user-side script (that's a real example using bookmarklets).

As I've said above the mechanism is fairly straightforward, the things devs would have to worry about are mixing in layout with JS, and checking that dynamic updates to layout work when the layout has been neutralised.

mraccess77 commented 7 years ago

Last time I checked the ZT doc read in PDF (Acrobat) it appeared that i was copying the content from the page using something like the clipboard and inserting it into the doc reader. I could be wrong and maybe on the web it is more complex than that.

alastc commented 7 years ago

According to their video the DocReader is for Word/PDF, and it does pull the text into a separate window. (AppReader they suggest for web content, but that reads it out audibly whilst highlighting the location, it doesn't try and re-format the text.)

DavidMacDonald commented 7 years ago

According to their video the DocReader is for Word/PDF, Doc Reader is for HTML also.