The default trace listener

The library provides one descendant of XM_XSLT_TRACE_LISTENER, namely XM_XSLT_DEFAULT_TRACE_LISTENER. This class writes trace records as XML text, optionally with timing information added, to the info_file: KI_TEXT_OUTPUT_STREAM of an UT_ERROR_HANDLER. A suitable UT_ERROR_HANDLER is available in XM_XSLT_CONFIGURATION as error_reporter.

This trace listener generates a large quantity of data for long-running transforms.

Writing your own trace listener

If you wish to write your own trace listener, then you need to look at XM_XSLT_TRACE_DETAILS. In particular the feature properties. To find out what properties can be present in the trace details, you can search the library source code, and inspect XM_XSLT_DEFAULT_TRACE_LISTENER.

TODO: document these properties.

Suspending tracing

It may be desirable to trace only parts of the execution path. In which case a mechanism is needed to turn tracing on and off. No such mechanism is available right now. One possibility is to use XPath extension functions to pause and resume tracing (this is what Saxon does). Another possibility would be to use extension attributes, or extension instructions.