Thanks very much for your response.
The two images where the tags showed up are regular figures, using
lattice and base graphics. There are also a lot of rgl figures, which
have HTML code like this in the source .html file:
<div id="rgl61108" style="width:480px;height:296.662546353523px;"
class="rglWebGL html-widget "></div>
(Looks like I should think about rounding the height value!)
All the interesting stuff (including the alt tags) is added within the
div by Javascript that runs after the page is loaded. The fact that it
didn't show up in your reader indicates to me that either it needs to be
there before the Javascript runs, or that I put the text in the wrong
place. I'll try a few variations on the code and hopefully find
something that works.
Your comments about the content of the tags was also very helpful. I am
imagining that there are at least two groups of readers who might make
use of them:
- readers who would skip over the graphics completely, but who would
be helped by knowing what they missed.
- readers who can get information from the graphics but only with an
effort, so they would want to know where to apply that effort.
For the document I posted, there might not be very many people in either
group, but I'm hoping to make the package useful to others, who would be
writing documents with different audiences.
Duncan Murdoch
On 17/03/2023 5:18 p.m., Jonathan Godfrey wrote:
Hello Duncan,
I guess a few people might expect me to contribute to your request. First I'll assure
you that two graphics do have an alt tag which my screen reader is telling me about,
so in a sense that is success. I did not check with multiple screen readers or
different browsers because I would only find fault if I used inferior software; I
expect success with JAWS or NVDA to represent the other and likewise for browsers.
These two successes are the lattice and base graphics relating to the volcano data.
Others are not showing to my screen reader (JAWS) and browser (Chrome) on my OS
(Windows). I note that these are inserted using <img> though.
What should appear in an alt tag is an area of much debate though, and the
attitude towards their creation differs widely. I believe that the context is
the primary driver for what should be communicated. In your context, where you
are obviously writing about the package (in general) and comparison of lattice
v base graphics (where I do see the alt tags), it is the main text that should
be communicating with your audience. You know what you are writing and why. If
you do not write about the differences then you leave it up to chance that your
(mostly visually-dependent) audience sees the differences that matter to you
and your efforts as an author/developer. Complementing that information
intended for the whole audience with a sensible alt tag on the graphics for the
blind part of your audience, would be fundamentally different to what you might
need to offer for the same graphics in another context, say an analysis feeding
into a business report for example. In your context, the b
lind person needs to know that the graphic does appear, and that the graphic
has a unique (enough) label to make it obvious which graphic appeared where. We
do not need a full description of every last detail of each graphic, although
in other contexts, that is exactly what we need.
Generating alt tag text automatically (no human interaction) is going to
deliver on the technical aspects, without the analytic outcomes, although our
recent efforts with the BrailleR package are trying to offer more and more
factual information that could help with the analysis of the data. Our main aim
is to assure the blind producer of a graphic that it does actually exist and
what (roughly) it shows; it would not be great text for an alt tag in most
circumstances. I've done some limited testing with AI solutions but haven't yet
been overwhelmed by positive experiences.
Anyone using an R markdown workflow can add alt text using the fig.alt option
in the header of their chunks. Without that, the fig.cap option is used, and if
neither is used, the screen reader user is victim to their personal settings.
(We choose whether to be told about unlabelled graphics which used to be
helpful for ignoring advertising.) I don't put unique alt tags in all of my
work because I just need to convey that the graphic is there, but I do make
sure there is a default bit of text that saves blind users with the wrong
settings from their decisions.
An author wishing to support blind consumers of their efforts, could spend lots
of time working out what to write, and never get it perfectly correct because
the desires of those consumers are not homogeneous. I advise people to use an
alt tag, but to make sure it does not duplicate what is already said in the
main text of their document. Authors already do this when thinking about the
right caption for their figures, but it is easy to see how varied that can be.
At least the target audience of captions is well known to the author given the
author is part of that population; in contrast, most authors are not blind and
may over or under-estimate the needs of the blind readers of their work. Before
doing everything an individual requests, please make sure that what is being
sought is in keeping with what you are hoping to communicate.
I despair at the retrospective creation of alt tags, especially if applied to
living documents. Creation of alt tags is simple for anyone using regular
markdown based insertion of their graphics because the ![]() construct embraces
them in the []. Authors using a LaTeX workflow must load an additional package
and add an optional argument to their \includegraphics{} commands. MS Word
users can label their graphics anytime but of late there is an increased use of
an automated alt tag creation for them (and messages in Outlook too for that
matter). I am loathed to fully describe the LaTeX pipeline unless the author is
also committed to producing their output in HTML as I have utter contempt for
the pdf (or post script) that is the default for most authors using any TeX
workflows.
Post hoc editing of html is perhaps the worst possible action I observe. This process has
separated the creator of the content from the creator of the access for blind people, and
is heavily reliant on the skill set of the accessibility "expert". Such editing
is common in university settings where the Disability Support Service is responsible for
the accessibility. If I was an undergraduate today, I'd be camping outside the doors of
my teaching staff to get the alt tags inserted. I spent plenty of time back then, sitting
in corridors waiting my turn, but so many of the access challenges of the dead-tree era
are thankfully behind us.
I'm curious though that a blind person is going to benefit much from your
package given so much of what I read relies on using a mouse, or having the
ability to imagine the 3d data projected into an inherently 2d
page/screen/image. In turn, that inaccessibility might heavily influence my
effort to provide comprehensive alt tags.
I'd be more than happy to continue this conversation, and to do so on list
because I think there are so many opportunities on offer today for people to
embrace; many of which will not create piles of extra work.
Jonathan
-----Original Message-----
From: R-package-devel <r-package-devel-boun...@r-project.org> On Behalf Of
Duncan Murdoch
Sent: Saturday, 18 March 2023 8:26 am
To: r-package-devel@r-project.org
Subject: [R-pkg-devel] Screen reader help request
I received a request a few days ago to add alt text to the plots in the HTML
vignettes for the rgl package.
That was easy to do, and I did it, but realized most of the graphics that rgl produces are
not in <img> format, they are WebGL canvases, and those don't support the same method
of adding alternate text. Online I've seen a variety of suggestions about how to do it for
<canvas> elements, and have implemented one of them.
Could I ask someone who is familiar with one or more screen readers to test
whether the method that I used works? A sample web page produced with the new
code is here:
https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdmurdoch.github.io%2Frgl%2Fdev%2Farticles%2Frgl.html&data=05%7C01%7Ca.j.godfrey%40massey.ac.nz%7Ccd3d6ce4f3e1439e61da08db271d7564%7C388728e1bbd0437898dcf8682e644300%7C1%7C0%7C638146779729138276%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=V0dX8tOrAEZQIVizo%2FBrdB3zEXJRfIXUqqVvPiEMcHY%3D&reserved=0
The very first graphic is a plot of the iris data, and it should have alt text reading
"rglwidget in chunk unnamed-chunk-1".
That was default text generated without user input, users could put whatever
they wanted there instead.
Some related questions:
- Could you suggest better default text to use?
- Could you suggest good custom text for this particular graphic?
- The text is inserted when some Javascript has run to initialize the page,
so if the Javascript fails, there'll be no alt text. Is that a reasonable
limitation?
Duncan Murdoch
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