XFA Specification
Chapter 24, Picture Clause Specification
Picture Clause Reference
932
Null-category picture clauses are especially useful when there is a
difference between null-data and non-null data. In the example at right,
the field labeled "Tax withheld" remains blank until the person filling out
the form supplies a value.
The illustrated behavior is specified by the picture clause
null{}|num{$z,zz9.99}
.
Zero-Category Picture Clauses
Zero-category picture clauses specify output formatting for zero values associated with non-image
content types. They are always expressed with the "
zero
" category designator and may use any of the
symbols defined for numeric picture clauses.
zero{numeric
picture clause symbols}
See also
“Compound Picture Clauses” on page 907
and
“Numeric Pictures” on page 926.
As with null-category picture clauses, zero-category picture clauses are typically used in alternate picture
clause expressions, such as the following:
zero{9} | num{$z,zz9.99}
See also
“Alternate Picture Clauses” on page 909.
Examples of Input Parsing Against Null- and Zero-Category Picture Clauses
The following table illustrates the affect of input parsing against a set of alternate picture clauses that
include null-category and zero-category picture clauses.
Picture clause
null{’n/a’} |
zero {9} |
num{z,zz9.9}
Input value
""
Parsed result
null
null
"0"
"0"
"1234.5"
"n/a"
"0"
"0.0"
"1,234.5"
Note:
Order is important in expressions that use alternative picture clauses. If the picture clause
num{z,zz9.9}
is the first picture clause in the expression, the
zero{9}
picture clause is never
considered.
Examples of Output Formatting Against Null- and Zero-Category Picture
Clauses
The following table illustrates the affect of output formatting against a set of alternate picture clauses that
include null-category and zero-category picture clauses.