It used to be that things like InsetFlex, InsetCaption, and the like used the default...

It used to be that things like InsetFlex, InsetCaption, and the like used the default layout, whatever that is---usually Standard. That gave rise to bug 2178, the solution to which is to define a new empty layout, which insets like these use instead of the default. See r22966.

So, when we have an older LyX file, it will look like this:
\begin_inset ERT
status open

\begin_layout Standard

this that
\end_layout

\end_inset
which is now invalid, because ERT uses only PlainLayout. So I had put some code into Text::readParToken, where the layout for a paragraph gets set as it is read:
       if (par.forceEmptyLayout()) {
           // in this case only the empty layout is allowed
           layoutname = tclass.emptyLayoutName();
       } else if (par.useEmptyLayout()) {
           // in this case, default layout maps to empty layout
           if (layoutname == tclass.defaultLayoutName())
               layoutname = tclass.emptyLayoutName();
       } else {
           // otherwise, the empty layout maps to the default
           if (layoutname == tclass.emptyLayoutName())
               layoutname = tclass.defaultLayoutName();
       }
This turns out not to work, because par.forceEmptyLayout() and par.useEmptyLayout() always return false here, because par.inInset() always returns a null pointer, because the paragraph's inset hasn't yet been set when Text::readParagraph() gets called from Text::read() gets called from InsetText::read(). The solution is to set the paragraph's inset when it is created, which means passing a pointer to the various read() routines along the way.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@23057 a592a061-630c-0410-9148-cb99ea01b6c8