Adobe FDF Compatibility

[6C1]

Bug

The FDF files produced by fdfgen.forge_fdf are unable to be imported via Adobe Acrobat's FDF import functionality. They are compatible with PDFtk, which indicates the incompatibility lies in a discrepancy between the Adobe and PDFtk parsers. I assume that the Adobe parser is more strict than the PDFtk parser.

Causes

The causes were identified by producing identical FDF files via both fdfgen and Adobe Acrobat's Export data function, and comparing the results in hexl-mode. They were:

• Extraneous whitespace. Extra whitespace and newline characters were causing parse failure.
• Mismatched encoding. Field keys were being encoded in UTF-16 instead of UTF-8.

Fix

Whitespace characters have been removed, and the encoding of field keys has been changed to UTF-8.

Additionally, this PR explicitly spells carriage returns and newlines in hex, as cautioned by Sid Steward in the original forge_fdf.php documentation.

Testing

This fix has been tested by producing FDF files, comparing them at the hex level with Acrobat-produced FDF files, and successfully filling PDF forms with them. The filling was tested with both Adobe Acrobat and PDFtk. Test FDF files included text fields, checkboxes, and radio button groups.

[6C1]

This may resolve some of the issues reported in #9.

[thraxil]

Awesome. Thanks!