10. Contextual commands

10. Contextual commands
	Chapter 2. Writing macro-commands

The following macro swaps the character before the caret with the character after the caret. It is useful if, like everybody, you are a bit dyslexic.

<command name="transposeChars">
  <macro undoable="true" label="Transpose Characters">
    <sequence>
      <test expression="not($selected) and not($mark) and 
                        $dotOffset &gt; 0 and 
                        $dotOffset &lt; string-length($dot)"/>
      <command name="selectTo" parameter="previousChar" />
      <command name="cut" />
      <command name="moveDotTo" parameter="nextChar" />
      <command name="paste" parameter="into" />
    </sequence>
  </macro>
</command>

The above macro uses basic commands selectTo, moveDotTo, cut and paste, but also XPath-based construct test.

As a pseudo-command of a macro, test can be executed only if its expression attribute evaluated as a boolean in the context specified by its context attribute returns true.

This construct like pass, fail and match, is only a test. When test is actually executed, it does nothing at all.

Test is used in the above macro to ensure that the macro can be executed only if:

There is no node selection: not($selected).
There is no text selection: not($mark).
The caret is not before first character of a textual node: $dotOffset > 0.
The caret is not after last character of a textual node: $dotOffset < string-length($dot).

Like selected and implicitElement seen in previous examples, mark, dot and dotOffset are predefined variables mapped to the selection in XXE.


9. Variables mapped to the selection in XXE		Part II. Reference