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

[Rush Manbert <rush manbert com>]

Hi,

I have an application that uses libxml2 to parse an XML 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, 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 separate XHTML document. 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.

Have I missed something here? How am I supposed to know my application 
context when I am in the entity loader? I suppose I could guard the XSL 
transformation with a semaphore, and set the context info into some 
global location that the loader can retrieve from, but that seems like a 
nasty hack.

I am using libxml2-2.6.19 and libxslt-1.1.14.

Thanks,
Rush