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DynaPDF Manual - Page 52

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Interactive Forms
Page 52 of 750
Field Names
Interactive Form Fields are identified over the field name in a viewer application. A field name
is an Ansi string that should be human readable. Beginning with PDF 1.5 field names can also
be defined as Unicode string. However, all functions to create new fields in DynaPDF support
Ansi strings only. All characters within the Ansi character set (code page 1252) can be used with
exception of the period character (.) and characters below index 32 .
A field name should also not end with a space character because Adobe's Acrobat is then
sometimes unable to access such a field with a JavaScript Action or function.
The period (.) is a reserved character because it is used to build the fully qualified field name in
a viewer application. The fully qualified field name is constructed from the partial field name of
the field and all of its ancestors.
For a field with no parent group field, the partial and fully qualified names are the same. For a
field that is the child of another field, the fully qualified name is formed by appending the child
field’s partial name to the parent’s fully qualified name, separated by a period, e.g.
Fields with identical names
It is possible to create two or more fields of the same type which use all the same name. Such
fields contain always the same value if the value of one field of the group is changed.
Fields with identical names are internally represented as a special type of field group, which is
automatically created by DynaPDF. This makes the handling more complicated because the
children of such a group do not contain a field name. The name is set to the parent's group field
but not to the children of the group. This can normally be ignored but when enumerating fields
with GetField() or GetPageField() you must consider that not all fields contain a name, the
parent field's handle is set instead.
However, with the exception described above, field names must be unique within the hierarchy
in which they appear. This is especially important when multiple Interactive Forms are
When importing multiple Interactive Forms it is highly recommended to check for invalid
duplicate field names. This can be done with the function CheckFieldNames(). The function
returns the handle of the first field which contains a field name that is already in use. You can
then change the field name with SetFieldName() and execute CheckFieldNames() again until all
invalid field names are changed.
After changing a field name you must also check whether the field is used within a JavaScript
Action or function. Such scripts must be changed so that they do not become invalid. Due to the
possible references of fields within JavaScript functions and Actions, merging of Interactive
Forms is very complicated and should be avoided whenever possible.

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