This patch is the first step towards implementing support for
interactive forms (AcroForms). It makes it possible to render text
widget annotations exactly like Adobe Reader/Acrobat.
Everything we implement for AcroForms is disabled by default using a
preference, mainly because it is not ready to use yet, but has to
implemented in many steps to avoid complexity. The preference allows us
to work with the code while not exposing the behavior by default. Mainly
storing entered values and printing them is still absent, which would be
minimal requirements for enabling this by default.
Most code for Popup annotations is already present for Text annotations.
This patch extracts the popup creation logic from the Text annotation
code so it can be reused for Popup annotations.
Not only does this add support for Popup annotations, the Text
annotation code is also considerably easier. If a `Popup` entry is
available for a Text annotation, it will not be more than an image. The
popup will be handled by the Popup annotation. However, it is also
possible for Text annotations to not have a separate Popup annotation,
in which case the Text annotation handles the popup creation itself.
This patch makes the naming consistent with the `TextLayerBuilder`, and also the new `AnnotationLayer`, and should thus help reduce possible confusion when working with the code.
Please note that the files were renamed using `git mv`, in order to preserve blame.
