XFA: run the forms' JavaScript: calculations, validation, rows, visibility (#60) (#230)

* M12: run XFA forms' JavaScript: calculations, validation, rows, visibility (#60)

Laid-out XFA forms had their fields but none of their behaviour: totals
didn't compute, "Add row" buttons did nothing, and subforms a check box
should reveal stayed hidden.

The js crate gains the XFA scripting object model as native boa objects
over a snapshot of the form tree: xfa.form navigation by name, SOM
resolution (absolute, relative with the containing-subform search,
descendants, indexes and wildcards), rawValue/presence/access, instance
managers (_name, addInstance, removeInstance, setInstances, count),
xfa.host (messageBox, resetData, print, setFocus, gotoURL), xfa.layout
page numbers, xfa.event, app, console and util, plus unqualified sibling
names as XFA resolves them. Scripts run with `this` bound to the node and
yield their completion value; everything they change or ask for comes
back as effects.

The xfa crate builds the live form tree (instances from the data, values,
presence and access with overrides) and the event table from the
template, keeps presence and access overrides on the AcroForm
(/PCXfaOverrides) so undo and reopening preserve them, adds and removes
row instances in the datasets packet through the existing merge
pipeline, and lays the form out again on demand.

The engine runs initialize and calculate scripts on open (an appended
revision, nothing dirty), exit, validate and calculate after a field
changes (a failing validate shows its message and keeps the value, as
Acrobat does), and click scripts for buttons through run_javascript, so
the app's buttons and the js_run tool work unchanged. Values a script
sets go to the fields and the data at once; rows and visibility changes
re-lay the form out. All of it is one undo step. JavaScript off turns it
off. FormCalc scripts are recognised and reported, not run.

Bounds: script length and nesting as before, loop and recursion limits,
at most 1000 instances added per run, 2000 scripts and 50 re-layouts per
event; a calculate script that adds rows, or a click script looping on
addInstance/setInstances, ends quickly with a bounded form (tested).

Checked on IRCC's IMM 5669: opens with its page-number scripts, the Print
button's xfa.host.print runs through js_run, fill and save keep the
original bytes.

* M12: Save and SaveAs named actions run the file commands (#60)

XFA forms' Save buttons are app.execMenuItem("SaveAs"), which the layout
turns into a SaveAs named action; the shell answered it with "the SaveAs
action isn't supported yet". Named Save and SaveAs now run file.save and
file.save_as, like Named Print opens the print dialog.

The buttons test covers Save against a file on disk (SaveAs opens the
native dialog, which a headless test must not).

* M12: bound XFA form scripts against hostile forms (#60)

Review fixes for the XFA scripting PR (#230):

- Effects: values, presence and access set again on the same object merge
  (last wins, behind order-dependent effects); 10k effects, 100 message boxes
  and 1000 console lines per script and per event, reported when hit. An
  event's data writes are kept in memory and written as one rewrite of the
  datasets packet; later writes in the same edit replace that stream in place.
- form_tree stops at 200k objects and says so; forms without scripts build no
  live form and run nothing.
- Only click scripts may print, save, open links or move the focus; others are
  noted in the console. Open-time messages and errors show right after open.
- Lower loop limits for initialize/calculate/validate, a time budget per event
  after which remaining scripts are skipped and reported, and a per-script time
  limit after which a runaway script is abandoned and the document's scripts
  turned off.
- What open-time scripts change is noted in the XFA warnings.
- A document's Named /Save no longer writes the file on click (SaveAs opens
  the Save As dialog, as a script's execMenuItem does).
- XFA click scripts are no longer written as /S /JavaScript actions: the
  button carries /PCXfaClick and runs by SOM path. Private keys documented.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

parity/acrobat-features.toml

@@ -5129,9 +5129,9 @@ tier = "P1"
 milestone = "M12"
 status = "partial"
 commands = ["file.open"]
-tools = ["doc_open", "doc_info", "form_fields", "form_fill"]
-evidence = ["crates/xfa/src/tests.rs::layout_places_captions_fields_and_sizes_containers_to_their_content", "crates/xfa/src/tests.rs::tables_break_across_pages_and_repeat_their_header_row", "crates/xfa/src/tests.rs::rendering_into_the_pdf_replaces_the_placeholder_page_and_adds_fields", "crates/engine/src/tests.rs::dynamic_xfa_forms_are_laid_out_on_open_filled_and_saved_incrementally", "crates/automation/tests/automation.rs::dynamic_xfa_forms_open_render_fill_and_save_through_tools", "crates/ui-egui/tests/xfa.rs::a_dynamic_xfa_form_is_laid_out_and_filled", "crates/xfa/src/tests.rs::nested_width_less_subforms_lay_out_in_polynomial_time"]
-notes = "laid out from the template on open by the xfa crate (positioned, tb, lr-tb, table/row, page masters, breaks, repeated header rows, captions, rich text, JPEG images) into real pages and AcroForm fields (text, date with AFDate formats, check boxes, radio groups, buttons with reset/print/save/URL), filled from the datasets packet (including rows another viewer added), saved as an incremental revision with the values merged into the datasets so Adobe's viewers show them; doc_info reports xfa_layout. Missing: no FormCalc or XFA JavaScript, so rows don't grow by button and calculations don't run; choice lists are text fields; signature, image and barcode fields are blank; PNG images; keep rules; metrics are approximate and Acrobat fidelity is eyeballed on real forms, not measured (#60)"
+tools = ["doc_open", "doc_info", "form_fields", "form_fill", "js_run"]
+evidence = ["crates/xfa/src/tests.rs::layout_places_captions_fields_and_sizes_containers_to_their_content", "crates/xfa/src/tests.rs::tables_break_across_pages_and_repeat_their_header_row", "crates/xfa/src/tests.rs::rendering_into_the_pdf_replaces_the_placeholder_page_and_adds_fields", "crates/engine/src/tests.rs::dynamic_xfa_forms_are_laid_out_on_open_filled_and_saved_incrementally", "crates/automation/tests/automation.rs::dynamic_xfa_forms_open_render_fill_and_save_through_tools", "crates/ui-egui/tests/xfa.rs::a_dynamic_xfa_form_is_laid_out_and_filled", "crates/xfa/src/tests.rs::nested_width_less_subforms_lay_out_in_polynomial_time", "crates/js/src/tests.rs::instance_managers_add_remove_and_count", "crates/xfa/src/tests.rs::the_form_tree_carries_values_presence_instances_and_the_events", "crates/engine/src/tests.rs::xfa_scripts_initialize_calculate_validate_toggle_and_add_rows", "crates/automation/tests/automation.rs::xfa_scripts_run_for_buttons_and_field_changes_through_tools", "crates/ui-egui/tests/xfa.rs::xfa_buttons_run_their_scripts_in_the_app", "crates/engine/src/tests.rs::hostile_xfa_open_scripts_are_merged_capped_kept_from_printing_and_noted", "crates/engine/src/tests.rs::runaway_xfa_calculations_at_open_end_quickly_with_a_report", "crates/xfa/src/tests.rs::the_live_form_of_nested_repeating_subforms_stops_at_its_node_budget", "crates/xfa/src/tests.rs::data_ops_of_one_event_are_one_datasets_rewrite"]
+notes = "laid out from the template on open by the xfa crate (positioned, tb, lr-tb, table/row, page masters, breaks, repeated header rows, captions, rich text, JPEG images) into real pages and AcroForm fields (text, date with AFDate formats, check boxes, radio groups, buttons with reset/print/save/URL), filled from the datasets packet (including rows another viewer added), saved as an incremental revision with the values merged into the datasets so Adobe's viewers show them; doc_info reports xfa_layout. XFA JavaScript runs in the js crate's XFA object model (xfa.form, SOM resolution, rawValue, presence, access, instance managers, xfa.host, xfa.layout, xfa.event): initialize and calculate on open, exit, validate and calculate after a field changes, click for buttons (through js_run and the app), with rows added and removed, subforms shown and hidden, and the form laid out again, all as one undo step and kept in the file. Hostile scripts are bounded per event (merged and capped effects, messages and console lines, lower loop limits and a time budget on open and calculate, one datasets rewrite per event, print/save/links/focus from clicks only, a runaway script abandoned and the form's scripts turned off) and what open-time scripts changed is noted. Missing: loops inside nested calls are only stopped by abandoning their thread, and script memory is not capped; FormCalc (reported, not run); the change event per keystroke; xfa.template, connections and data descriptions; a hidden instance of a repeating subform hides them all; choice lists are text fields; signature, image and barcode fields are blank; PNG images; keep rules; metrics are approximate and Acrobat fidelity is eyeballed on real forms, not measured (#60)"
 
 [[feature]]
 id = "form.xfa-formcalc"