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://dmurdoch.github.io/rgl/dev/articles/rgl.html
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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