PIs
This section contains a list of PTC ALD processing instructions (PIs), organized into groups depending upon the area of a document in which they will invoke formatting instructions or text properties.
Each PI is defined in detail according to the following criteria:
• Description: an explanation of the purpose of the PI
• Syntax: how the PI should be written
• Parameter options and associated permitted values
The syntax for a PI is written in this document with a particular arrangement of components: its name, its parameters and their values and the order in which they should be written if applicable. Some PIs, however, can take additional options which define their effect in a slightly different way to a simple assignment of value. Parameters that define measurement (such as height, length, etc.) can have the characters +, - and ? optionally included for the following effects:
+
Can be used to simply increment the current value, rather than apply a fixed value. For example <?th=+10pt will increase the current text height by 10 pt, e.g from 6pt to 16pt.
-
Can be used to force text to behave in a different way than expected. For example <?th=-6pt will reverse and invert the text whilst drawing it at 6pt height.
?
PI values can also take queries. For example <?th ?8pt=10pt> will change all text whose height is set to 8pt to 10pt.
It should also be noted that while an = character is acceptable within a PI, eg. <?th=10pt>, this syntax will make an XML document invalid. For this reason the = character is also optional within PI syntax. To maintain XML compatibility, write the PI in the form <?th 10pt>