XFA: one script thread per event, and the live form kept up to date in place (#1355)

* XFA: one script thread per event, and the live form kept up to date in place

A form with hundreds of calculate scripts used to spend its open-time
budget on set-up: every script got a thread of its own, and the engine
dropped its live form after every value a script settled, rebuilding
the whole tree for the next script.

The js crate gains xfa_session::XfaSession: the scripts of one event
run on one thread (with the script stack), each in a fresh JavaScript
context or FormCalc interpreter on a copy of the form as the engine
holds it then, so scripts share nothing, a script that fails halfway
leaves nothing behind, and what a script changed reaches the next one
only through the engine. A script past its time limit is abandoned on
the thread and the session is dead from then on; a fault in the engine
(a panic) loses only that script, the thread is replaced. On wasm the
scripts run inline, as before.

The engine's runner keeps one session per event and, for a value, now
refreshes the one field in its live form in place (xfa::refresh_value,
computing the value as the tree builder would: saved values, template
defaults) instead of rebuilding the tree; rows, presence, access,
resets, relayouts and data rewrites still rebuild it. Under test, the
live form is compared with a fresh build before every script and at
the end of every event, and a difference ends the test binary (a panic
would be caught by the engine's guard and turned into a script error).

210 calculate scripts (one per row of 10 sections x 20 rows, plus a sum
per section), debug build, instrumented inside the engine: the script
event on open 495 ms -> 204 ms (of which live-form rebuilds 217 ms ->
0), on a change 300 ms -> 172 ms; through the tools, layout included,
open 1.27 s -> 0.97 s and a change 0.44 s -> 0.22 s. The rebuild cost
removed grew with form size times script count.

* CI: the GoToR tests' case lists are only grown on Unix, so Windows must not warn on their mut

parity/acrobat-features.toml

@@ -5185,7 +5185,7 @@ status = "partial"
 commands = ["file.open"]
 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/ui_group/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/ui_group/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/ui-egui/tests/ui_group/xfa.rs::a_form_whose_scripts_were_turned_off_at_open_says_so", "crates/ui-egui/tests/ui_group/xfa.rs::scripts_turned_off_by_a_click_bring_a_closed_notice_bar_back", "crates/automation/tests/automation.rs::doc_info_says_when_a_runaway_script_turned_the_forms_scripts_off", "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", "crates/xfa/src/tests.rs::choice_lists_signatures_passwords_and_pictures_become_fields_and_images", "crates/xfa/src/tests.rs::choice_values_come_from_the_data_as_saved_values_and_several_for_lists", "crates/xfa/src/tests.rs::pictures_are_sized_from_their_headers_and_hostile_ones_are_refused_unallocated", "crates/engine/src/tests.rs::xfa_choice_lists_signature_and_picture_fields_open_fill_script_and_save", "crates/xfa/src/tests.rs::repeating_subforms_inside_positioned_content_get_their_instances", "crates/engine/src/tests.rs::xfa_rows_in_areas_are_laid_out_read_calculated_and_written_where_adobe_binds_them"]
-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/PNG/GIF images) into real pages and AcroForm fields (text, password, date with AFDate formats, check boxes, radio groups, drop-downs and list boxes with shown/saved item pairs and multi-select, signature fields, image fields showing their picture (pictures decoded once per document, at most 20 million pixels, and reused across re-layouts), 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 and FormCalc (form.xfa-formcalc) run 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, which the app says in a toast and on the notice bar, with a button to the JavaScript console, and doc_info reports as xfa_scripts_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; the change event per keystroke; xfa.template, connections and data descriptions; a hidden instance of a repeating subform hides them all; choosing a new picture for an image field; barcodes are drawn as their text, not bars; keep rules; metrics are approximate and Acrobat fidelity is eyeballed on real forms, not measured (#60)"
+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/PNG/GIF images) into real pages and AcroForm fields (text, password, date with AFDate formats, check boxes, radio groups, drop-downs and list boxes with shown/saved item pairs and multi-select, signature fields, image fields showing their picture (pictures decoded once per document, at most 20 million pixels, and reused across re-layouts), 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 and FormCalc (form.xfa-formcalc) run 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. All the scripts of one event run on one thread, each in a fresh context on the form as the engine holds it then (nothing shared between scripts; the live form kept up to date in place for values, rebuilt only when the structure changed), so hundreds of calculations run within the open budget. 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, which the app says in a toast and on the notice bar, with a button to the JavaScript console, and doc_info reports as xfa_scripts_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; the change event per keystroke; xfa.template, connections and data descriptions; a hidden instance of a repeating subform hides them all; choosing a new picture for an image field; barcodes are drawn as their text, not bars; keep rules; metrics are approximate and Acrobat fidelity is eyeballed on real forms, not measured (#60)"
 
 [[feature]]
 id = "form.xfa-formcalc"