Continue on 260140b / c2d4a17 (CC #191)

This is an API-breaking change.

docs/devel/changelog_staging.md

@@ -4,3 +4,5 @@
 <!-- List character: dash (-) -->
 
 # Changelog for next release
+- On multi-page rendering, `PdfDocument` objects constructed in parallel jobs now correctly initialize a form env if the triggering `PdfDocument` has an active one. (In versions 4.1 and 4.2, a form env would never be initialized and thus forms never rendered. In v4.0, a form env would always be initialized for documents with forms.)
+- API-breaking change on `PdfDocument.init_forms()`: `config` (`FPDF_FORMFILLINFO`) parameter changed to `config_maker` (`Callable` -> `FPDF_FORMFILLINFO`), on behalf of the multi-page renderer.

src/pypdfium2/_helpers/document.py

@@ -75,6 +75,7 @@ def __init__(
         self._data_holder = []
         self._data_closer = []
         self.formenv = None
+        self._form_config_maker = None
 
         if isinstance(self._input, pdfium_c.FPDF_DOCUMENT):
             self.raw = self._input
@@ -133,7 +134,12 @@ def new(cls):
         return cls(new_pdf)
 
 
-    def init_forms(self, config=None):
+    @staticmethod
+    def _default_form_config_maker():
+        return pdfium_c.FPDF_FORMFILLINFO(version=2)
+
+
+    def init_forms(self, config_maker=None):
         """
         Initialize a form env, if the document has forms. If already initialized, nothing will be done.
         See the :attr:`formenv` attribute.
@@ -143,16 +149,23 @@ def init_forms(self, config=None):
             before getting any page handles (due to PDFium's API).
         
         Parameters:
-            config (FPDF_FORMFILLINFO):
-                Caller-provided form config interface to use. Optional for default builds.
-                Must be given if using V8 enabled PDFium (:data:`.V_PDFIUM_IS_V8`), with all required fields implemented.
+            config_maker (typing.Callable | None):
+                Callback returning a custom form config interface. Optional for default builds.
+                Must be given if using V8 enabled PDFium (:data:`.V_PDFIUM_IS_V8`), and the returned config must implement all required fields.
         """
+
         if (self.get_formtype() == pdfium_c.FORMTYPE_NONE) or self.formenv:
             return
-        if not config:
+
+        if config_maker:
+            self._form_config_maker = config_maker
+        else:
             if V_PDFIUM_IS_V8:
-                raise RuntimeError("A caller-provided form config is required with V8 enabled PDFium.")
-            config = pdfium_c.FPDF_FORMFILLINFO(version=2)
+                raise RuntimeError("A caller-provided form config maker is required with V8 enabled PDFium.")
+            else:
+                config_maker = PdfDocument._default_form_config_maker
+
+        config = config_maker()
         raw = pdfium_c.FPDFDOC_InitFormFillEnvironment(self, config)
         self.formenv = PdfFormEnv(raw, config, self)
 
@@ -540,15 +553,14 @@ def get_toc(
 
 
     @classmethod
-    def _process_page(cls, index, input_data, password, renderer, converter, pass_info, need_formenv, **kwargs):
+    def _process_page(cls, index, input_data, password, renderer, converter, pass_info, need_formenv, form_config_maker, **kwargs):
 
         pdf = cls(
             input_data,
             password = password,
         )
         if need_formenv:
-            # TODO handle custom form config - as ctypes objects can't be pickled, we can't directly pass in a form config (which recursively consists of ctypes objects), so we'll need some different mechanism, likely a callback to create the form config.
-            pdf.init_forms()
+            pdf.init_forms(config_maker=form_config_maker)
         page = pdf[index]
 
         bitmap = renderer(page, **kwargs)
@@ -617,6 +629,7 @@ def render(
             converter = converter,
             pass_info = pass_info,
             need_formenv = bool(self.formenv),
+            form_config_maker = self._form_config_maker,
             **kwargs
         )