XFA: import and export data files, and pictures for image fields (#1175)

Export Data on an XFA form writes its data as Acrobat does: XML (the
data alone, rooted at the form's root data node, its namespaces
declared) or an XDP holding the whole datasets and a reference to the
PDF (.xdp, a new format). Import Data takes an XDP, a datasets or data element, or a
data document whose root is the form's root data node, and makes it
the form's whole data, keeping data descriptions; a laid-out form is
laid out again from it (rows added and removed) and its calculations
run; XFDF, FDF and tables still go the AcroForm way. Undoable.

Image fields are now buttons marked /PCXfaImage (no PDF action): the
forms layer treats one as an image field, so clicking it (or
form_set_image) picks a picture, which is kept in the data as base64
with its xfa:contentType, as Designer saves it, and the laid-out form
shows it from there.

xfa: replace_data, write_data_image (hostile content types cleaned,
32 MB cap), export_data, import_data (64 MB cap, the parser's node
limit, self-closing data elements). engine: export routing by
document kind, import routing by the file's root element, re-layout
and calculation after the data changes outside the fields, the
picture's content type from its bytes. UI: XML and XDP in the export
dialog of an XFA form, .xdp in the import filter. Tool texts, README
and parity (form.xfa-data) updated.

Hardened after an adversarial review pass: the file's data is held as
a tree and written with the packet's own namespace prefix (never its
markup), every packet rewrite is parsed back before it is written,
files capped at 16 MB and 64 levels (a tag scan before the recursive
parser, also guarding the datasets parser), pictures at 8 MB and PNG/
JPEG/GIF only, the file's shape and root name checked, UTF-16 and
ISO-8859-1 decoded, pictures into data groups refused, cleaned names
for pictures, static forms empty the fields the file doesn't hold,
more rows than the layout cap reported, one datasets stream per edit,
and only image fields take pictures into the data.

parity/acrobat-features.toml

@@ -4639,7 +4639,7 @@ status = "shipped"
 commands = ["form.import_data"]
 tools = ["doc_import_data"]
 evidence = ["crates/xfdf/src/tests.rs::xfdf_round_trips_comments_and_values", "crates/xfdf/src/tests.rs::fdf_round_trips_values_and_comments", "crates/automation/tests/automation.rs::comments_and_form_data_travel_as_xfdf_fdf_and_text"]
-notes = "XFDF, FDF; values go through formats and validation; read-only fields take data"
+notes = "XFDF, FDF; values go through formats and validation; read-only fields take data; XFA forms also take XDP/XML data files (form.xfa-data)"
 
 [[feature]]
 id = "form.export-data"
@@ -4651,7 +4651,7 @@ status = "shipped"
 commands = ["form.export_data"]
 tools = ["doc_export_data"]
 evidence = ["crates/xfdf/src/tests.rs::xfdf_round_trips_comments_and_values", "crates/automation/tests/automation.rs::comments_and_form_data_travel_as_xfdf_fdf_and_text"]
-notes = "XFDF, FDF"
+notes = "XFDF, FDF; XFA forms also export their data as XML or XDP (form.xfa-data)"
 
 [[feature]]
 id = "form.data-xml-csv-txt"
@@ -5200,10 +5200,10 @@ area = "F"
 tier = "P2"
 milestone = "M12"
 status = "partial"
-commands = ["file.open", "file.save"]
-tools = ["doc_open", "form_fill", "doc_save"]
-evidence = ["crates/xfa/src/tests.rs::the_datasets_packet_is_written_from_the_fields_and_read_back", "crates/xfa/src/tests.rs::data_fills_the_fields_and_adds_rows", "crates/engine/src/tests.rs::dynamic_xfa_forms_are_laid_out_on_open_filled_and_saved_incrementally", "crates/xfa/src/tests.rs::data_paths_leave_areas_out", "crates/engine/src/tests.rs::xfa_rows_in_areas_are_laid_out_read_calculated_and_written_where_adobe_binds_them"]
-notes = "the datasets packet inside the PDF: read on open (values, dates in ISO form, check and radio states, extra rows for repeating subforms) and rewritten after every form edit from the fields' SOM paths (/PCSom), with areas left out of data paths as Adobe binds them. Missing: importing or exporting a standalone XML/XDP data file, explicit bind refs, data descriptions"
+commands = ["file.open", "file.save", "form.export_data", "form.import_data"]
+tools = ["doc_open", "form_fill", "doc_save", "doc_export_data", "doc_import_data", "form_set_image"]
+evidence = ["crates/xfa/src/tests.rs::the_datasets_packet_is_written_from_the_fields_and_read_back", "crates/xfa/src/tests.rs::data_fills_the_fields_and_adds_rows", "crates/engine/src/tests.rs::dynamic_xfa_forms_are_laid_out_on_open_filled_and_saved_incrementally", "crates/xfa/src/tests.rs::data_paths_leave_areas_out", "crates/engine/src/tests.rs::xfa_rows_in_areas_are_laid_out_read_calculated_and_written_where_adobe_binds_them", "crates/xfa/src/tests.rs::data_exports_as_datasets_xml_or_an_xdp_and_imports_from_any_of_them", "crates/xfa/src/tests.rs::a_picture_chosen_for_an_image_field_is_kept_in_the_data_with_its_content_type", "crates/engine/src/tests.rs::xfa_data_exports_imports_and_pictures_round_trip_through_the_session", "crates/engine/src/tests.rs::xfa_data_import_adds_and_removes_rows_of_a_dynamic_form", "crates/automation/tests/automation.rs::xfa_data_files_export_and_import_through_tools"]
+notes = "the datasets packet inside the PDF: read on open (values, dates in ISO form, check and radio states, extra rows for repeating subforms) and rewritten after every form edit from the fields' SOM paths (/PCSom), with areas left out of data paths as Adobe binds them. Export Data writes it as XML (the data alone, rooted at the form's root data node, as Acrobat does) or an XDP with the whole datasets and a reference to the PDF; Import Data takes an XDP, datasets or data XML file (or a bare data document) as the form's whole data, keeping data descriptions, lays a dynamic form out again from it (rows added and removed, more than 50 rows reported) and runs its calculations, undoable; a static form's fields take the data and the rest are emptied; the file's data is re-serialized with the packet's own prefix and every packet rewrite is parsed back before it is written; XFDF/FDF/CSV still go the AcroForm way. Files are UTF-8, UTF-16 or ISO-8859-1, at most 16 MB and 64 levels deep; pictures at most 8 MB (PNG, JPEG, GIF). Pictures chosen for image fields are kept in the data as base64 with xfa:contentType, as Designer saves them. Missing: explicit bind refs, data descriptions are kept but not checked, no data connection (WSDL/ODBC)"
 
 [[feature]]
 id = "form.xfa-flatten"