[xslt] Starting Over - No user context available when apply stylesheet loads an external entity

[Rush Manbert <rush manbert com>]

Hi all,

I'm sorry for this. My second post on this subject was incorrect, so I 
am starting the whole thing again.

I have an application that uses libxml2 to parse an XHTML file, then 
uses libxslt to apply one or more XSL stylesheet transformations to the 
document. The result of this is then extracted as a HTML string and 
given to a web browser control to display.

I have registered an external entity loader with libxml by calling 
xmlSetExternalEntityLoader(). I have a set of search paths that are 
registered with my code, and the loader function handles searching them 
in the proper order.

The problem that I have is that I need to have multiple windows open, 
each of which displays a different XHTML document (after parsing and 
applying stylesheet transformations). Each window can have its own set 
of search paths for file loading. This means that when my external 
entity loader is called, I need to have enough context so that I can 
find the proper set of search paths.

For parsing the XML file, I discovered and started using 
xmlCtxtReadFile(). I allocate a parser context, use the _private data 
member to store my context, then retrieve it in the entity loader.

However, when I apply a XSL stylesheet transformation to my document, 
using xsltApplyStylesheetUser(), it often loads other XHTML source 
files. This calls the loader, but the parser context that is passed in 
has no context information that I can use to find the correct path set. 
The myDoc member has a value of 0, and there is no pointer to the 
xsltTransformContext, so I can't get at its _private data member. I also 
tried setting the _private data member in the transform context, hoping 
that it might be propagated to the parser context, but that doesn't happen.

I tried writing my own XSLT loader function, assuming that it would 
always be passed a transform context pointer (even if it was cast as 
void *) and I could copy its _private data member to the new parser 
context. I registered my loader function by calling xsltSetLoaderFunc() 
and I see it get called. (My previous post said this didn't happen, but 
that was a build problem.) The problem with this approach is that the 
XSLT loader function can get called with a NULL context pointer, so that 
puts me back in the original position. When the XML external entity 
loader function gets called, I need information that lets me pick the 
proper path set to search.

Is this achievable without resorting to some nasty semaphore hack?

Thanks,
Rush