D14655: Reimplement signature form field and related utility classes in poppler generator

[Chinmoy Ranjan Pradhan]

chinmoyr added a dependent revision: D12901: Add unit test for 
SignatureFormField.

REPOSITORY
  R223 Okular

REVISION DETAIL
  https://phabricator.kde.org/D14655

To: chinmoyr, aacid
Cc: okular-devel, ngraham, aacid