The new parameter allows more flexibility when encoding some elements that have a poor mapping in DocBook, like theorems. The major use is to wrap the environment in a generic container, figure, which requires a title (but none is available).
Before this patch, LyX would forcibly create an <abstract> tag even when there was no abstract in the document; this behaviour is sometimes desirable, but not when the abstract only contains comments (that's not valid DocBook: there must be a paragraph or assimilated within the abstract).
Includes a fix when wrappers are used with empty paragraphs. The logic is probably wrong if two legit wrapped paragraphs have one empty paragraph in the middle. This is only for slightly convoluted cases... Wrapping decisions should rather be taken for a series of paragraphs at once, but it would be more complex to implement and would only solve very peculiar cases like these ones.
In one paragraph, there was both a float and a list of floats in a paragraph: the list of floats has no DocBook output, so that there should be no surrounding <para>.
These paragraphs will simply have no output (no enclosing DocBook tag, no content). This change is as backward-compatible as possible: without this commit, the paragraphs will be output, but in an <IGNORE> tag (not much more can be achieved without this). It is mostly made for metadata and formatting instructions. (As opposed to NONE, which corresponds to outputting the paragraph without enclosing DocBook tag.)
More generally, ensures that paragraphs in abstracts do not have something else configured.
A major problem in making the layout more useful is that article titles are not supposed to be in TOC.
For elements that should behave like sections (for now, mostly prefaces).
A second paragraph of PartBacktext can only wreak havok: it should start a section, and nothing else (otherwise, it's a real nightmare to implement).
This will catch cases where there are multiple listings in a single paragraph, for instance.
The new code is also less brittle (checks on lyxCode instead of generated LaTeX or names).
It's invalid to have an <inlineequation> outside a paragraph. Another solution would have been to change InsetMathHull::docbook to generate an <informalequation>, but that function would have required more knowledge about its context than now.
Need more tests to determine if <inlineequation> should only be output for hullSimple or in more cases like:
const static std::set<HullType> inlineHulls = {
hullUnknown,
hullNone,
hullSimple,
hullEquation,
hullMultline,
hullGather,
hullRegexp
};