#193 area/label is not considered and alt and title are not generated for imagemaps

[Björn Kautler]

The current docbook-xsl stylesheets

• do not honour the label attribute of an <area> or <areaset> in any way
• do not generate a title attribute for an <area> in an <img> map in any way
• do only generate an alt attribute for an <area> in an <img> map from an illegal <area> subtag <alt> which must not appear there according to DocBook XML

The attached patch takes the label attribute from an <area> if present of from the parent <areaset> if present otherwise and uses it as title and if no <alt> subtag is there also as alt attribute for the resulting HTML imagemap <area>.

I have let the <alt> tag usage in there as primary source for alt text to not change the output for the user unexpectedly if he used this non-valid DocBook syntax to get an alt text. I don't know how the modus operandi is for the XSLs, should non-valid DocBook supported or not? If not, the <alt> tag usage can of course be removed, if it should just be used as fallback, then the order changed.

[Björn Kautler]

Ok, well, non-valid DocBook is maybe the wrong word, as you can extend the DTD to make the alt tag valid in this place.
So then I think using the alt tag if present is actually the right way, because if someone made the hassle of extending the DTD and setting the alt tag, this is probably what he wants as alt text.