[KevinH]

No spellcheck does not ignore user dictionaries that are properly specified but they do follow and use the lang and xml:lang attributes religiously to determine which dictionary to spellcheck a potential word in.

But in this plugin's case, there are no xml:lang or lang attributes on span tags on foreign words so it will default to either the xml:lang or lang attributes on the html tag or if those are not present, the first dc:language metadata tag in the opf.

So it is a bit of a catch-22 here. You need the lang attributes to know what dictionary to look a word up in but you need spellcheck to determine if a word is potentially a foreign word or just an incorrectly spelled one.

Detecting single possible foreign words is possible with only one dictionary and you can generate a word list of probable foreign words. But until spans are added and merged and xml:lang/lang attributes for the proper foreign language added, there is no way to tell which dictionary to look up a word in.

I think the best approach is multi-pass. First to use a single dictionary to create a list of single foreign words, wrap those in span tags and add proper lang and xml:lang attributes to each.

Next pass is to use the find foreign words variant of this plugin, or just search for xml:lang and visually/manually fix any intervening adjacent words that were not properly detected to add the proper span and lang info.

Final pass, merge adjacent spans with matching xml:lang attributes.

Plugins can in fact use hunspell spellchecking directly, and you could inside a plugin force lookup a word to see if it exists in both dictionaries and if adjacent to an existing span, add it.

Then the entire process would be done inside the plugin.