Per the upstream review of the XDATA-based storage: the host no longer writes
its own state into the saved file. The marker record under the host-owned OCS
APPID, the on-first-use APPID registration and the verbatim-EED rewrite
handling are removed; the single source of truth is a scene-scoped in-memory
set of entity handles (Scene::reference_only) that dies with the drawing tab,
so a reopened file starts undesignated and the owning plugin re-marks on the
document-opened notification.
All behaviour sites are unchanged, driven by the set: the wire stamp moves
from an XDATA read to a set lookup threaded through the tessellation
pipelines (tessellate_entity and the dimension text path take the handle set
as a plain parameter), and the pick filters, selection retains and
update/erase refusals read Scene::is_reference_only.
Undo keeps the entity-write contract: set mutations are recorded as explicit
first-touch before/after values on each history delta (the parametric-
constraints channel pattern). A designation inside a plugin push_undo scope
joins it, a scope-less change is one step of its own, an idempotent re-mark
records nothing, erasing a designated entity drops the set entry with the
entity, and undo/redo restores entity and designation together.
The round-trip test is inverted: reference_only_designation_is_not_written_
to_dwg_or_dxf now asserts the marker appears in neither format's bytes, that
no OCS APPID or marker record survives a reload, and that the designation
stays live in memory.
Host side of HostApi::set_reference_only: plugin-owned display geometry that
renders and snaps normally but must not be edited or picked by the person at
the screen, while the owning plugin keeps full write access through the host.
- Storage: a human-readable marker value in an XDATA record under the
host-owned OCS APPID (registered on first use; foreign values survive
verbatim; stale verbatim DWG EED is dropped on rewrite), so the flag
round-trips DWG and DXF with the entity and cannot collide with plugin
APPID namespaces.
- Grips: refresh_selected_grips yields none for a reference-only entity and
an active grip edit on a newly designated target is cancelled like a
locked-layer one.
- Picking: a reference-only wire flag extends the snap_only skips in every
hit test, so a click passes through to the editable entity underneath, and
box, window, lasso, fence and select-all gathers skip the designation;
fills, solids and instanced meshes are excluded through the shared
candidate handle set.
- Write policy: built-in user paths treat a reference-only entity like a
locked-layer one (Scene::update_entity / update_entities refuse,
erase_entities skips), while the plugin-owned variants
(update_entity_plugin / erase_entities_plugin, mirroring the
remove_entities editor split) and the whole HostSession surface write
through. The MCP entities read exposes a top-level reference_only boolean
and set_properties refuses with the reference_only failure code.
- Undo: the entity-write contract - a change joins a plugin-opened push_undo
scope, a scope-less change is one undo step of its own, refusals and
idempotent re-marks record nothing.
- Known limit: entities nested inside block instances (the block cache
rebuilds instance wires without the flag).
Evidence: marking_flags_and_unmarking_clears,
foreign_values_under_the_host_app_id_survive, other_apps_are_untouched,
reference_only_refusals_record_no_undo_step,
reference_only_designation_composes_undo_like_entity_writes,
reference_only_survives_dxf_and_dwg_round_trips,
user_paths_refuse_and_plugin_paths_write_reference_only_entities,
select_all_visible_skips_reference_only_entities,
clicks_pass_through_reference_only_wires,
box_selections_skip_reference_only_wires,
entities_records_expose_the_reference_only_designation.
Sebastian