[R-pkg-devel] Screen reader help request

[Duncan Murdoch]

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