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[xsl] XSLT-driven syntax highlighting for XPath 2.0, XSLT 2.0 and XSD 1.1

Subject: [xsl] XSLT-driven syntax highlighting for XPath 2.0, XSLT 2.0 and XSD 1.1
From: Philip Fearon <pgfearo@xxxxxxxxxxxxxx>
Date: Fri, 30 Nov 2012 09:39:04 +0000

I frequently need to publish documentation in HTML form that has code samples
which include XPath 2.0 expressions, either standalone or embedded in XSLT 2.0.
But has anyone else noticed that there aren't many syntax highlighters
for standalone
or XML-embedded XPath on the web?

To improve this choice, I've developed an XSLT 2.0 stylesheet that's a
syntax highlighter
specially for XPath 2.0, XSLT 2.0, XSD 1.1 (the assert element) and
also suitable for
generic XML. The input to the stylesheet (specfied in an XSL
parameter) is either XML
or plain-text, the output is an HTML document and a CSS file.

I'm sharing this in the hope that others may also find it useful. Note
that this is not a
'pretty-print' formatter, it is assumed that whitespace formatting is
in-place and this is
all preserved in the output (including inter/intra-attribute whitespace etc.).

One main concern with embedded languages (like XPath within XSLT) is
not to overwhelm
the reader with highlighted code colors. To alleviate this I've used
the Solarized[1] color
theme which has 8 highlight colors (+ 8 base colors) of relatively low
contrast. Cooler
colors are used for XML-based syntax and warmer colors for the XPath.
There's some
crossover though: for example, to show that an xsl:function 'name'
attribute is referenced
from XPath, a warmer color is used.

Features List:
- Open source - maintained on GitHub
- Processes plain-text or XML files
- Identifies XML coloring scheme from the root namespace (if XML)
- Just 1300 or so lines of XSLT in one file - no dependencies
- Standard XSLT 2.0. No extensions required (developed/tested on
Saxon-HE and Saxon-CE)
- Uses 'Solarized' color theme
- Light or dark color themes
- Generates the required CSS file also - depending on theme specified

- XPath 2.0 Highlighting:
          - Supports XPath Comments
          - All whitespace formatting preserved
          - No dependency on reserved keywords
          - Standalone files supported - or embedded in XML
          - Designed to be extensible to support XPath 3.0
- XML Highlighting
          - Built-in XML parser (coded in XSLT) keeps all text, as-is
          - CDATA preserved intact and highlighted
- XSLT 2.0 Highlighting
          - Scheme colors help separate instructions from expressions
          - Literal Result Elements have different coloring
          - AVTs or native XPath attributes supported
          - All whitespace formatting preserved
- XSD 1.1 Highlighting
           - Element and Attribute definition elements highlighted
           - XPath coloring for *test* attribute in *assert* element


Sample screenshot of XSLT 2.0 using dark color theme:


The stylesheet 'xmlspectrum.xsl' is on the GitHub project site along
with samples etc. at:



[1 Solarized] http://ethanschoonover.com/solarized

As ever, any feedback on color themes, missing features, issues etc
would be greatly appreciated. Details on other XSLT stylesheets that
do the same thing that would also
be useful to know.

Many thanks,

Phil Fearon

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