This is exactly what <xsl:message> is designed for. However, the output location is entirely dependent on the processor. I only have a Mac handy but, sadly, both Firefox and Safari suppress the <xsl:message> output. I expect MSIE will do the same.
Given that, I think your best bet is to use <xsl:comment> to generate your logs. Something like the below should do the trick:
<xsl:template match='my-element'>
<xsl:comment>Entering my-element template</xsl:comment>
<p class='my-element'><xsl:apply-templates/></p>
<xsl:comment>Leaving my-element template</xsl:comment>
</xsl:template>
That would give you something like this in the output:
<!-- Entering my-element template -->
<p class='my-element'>...</p>
<!-- Leaving my-element template -->
Clearly, you can put whatever logging you want into that that output. I would consider creating something like the following and using it to run your logging. This references a global param called 'enable-logging' to determine if logging should occur or not.
<xsl:template name='create-log'>
<xsl:param name='message'/>
<xsl:if test="$enable-logging = 'yes'">
<xsl:comment><xsl:value-of select='$message'/></xsl:comment/>
</xsl:if>
</xsl:template>
Use this in your stylesheet as:
<xsl:template match='my-element'>
<xsl:call-template name='create-log'>
<xsl:with-param name='message'/>Entering my-element template</xsl:with-param>
</xsl:call-template>
<p class='my-element'><xsl:apply-templates/></p>
<xsl:call-template name='create-log'>
<xsl:with-param name='message'/>Leaving my-element template</xsl:with-param>
</xsl:call-template>
</xsl:template>
One benefit of doing it this way is you can change that <xsl:comment> to <xsl:message> when in a more complete environment. It is more verbose but more general.
