engineering/understand/diff.py reads each revision once into entity
records and matches them in three stages: exact signature (type, layer,
geometry rounded to tol, text, block, rotation, scale, attributes;
handles ignored), then handle while at least half of the exact matches
kept theirs, then type + layer + nearest anchor within move_tol (default
2 % of the 1st-99th percentile diagonal). The report counts changes by
layer and type, says what changed per entity (moved by, text, attribute,
radius ... from -> to), compares named block definitions by content and
groups the changes into clusters.
drawing_diff opens group D's copy of SECTION 26. It is read-only unless
markup=True, which files revision clouds around the model-space clusters
on the current document through add_revision - refused before any read
with new_path, without a valid rev, or on an engine without revcloud.
A revision path that is neither .dxf nor .dwg is refused naming the
parameter (old_path: / new_path:), like every other path refusal.
Tests: the synthetic plant P&ID edited five ways (a move, a text, an
attribute, an add, a delete) under renumbered handles reports exactly
those five edits; renumbering alone reports nothing.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
Every track H reader is measured on this pair, never on a client drawing
(spec section 14). tests/fixtures/plant_pair.py writes pid.dxf and layout.dxf
with invented names and returns their truth, computed from the positions it
placed:
- the P&ID is room 1 of the layout stretched 1.3x and room 2 rearranged, so
21.8 % of the 55 tag pairs fall within 10 % of the median ratio (schematic)
while room 1 alone is 100 % at 1.3;
- service layers in English and Dutch, Russian supply / return words, one CIP
return drawn on the supply layer, sizes spelled as drafters do (an MTEXT
format run, %%c, \U+2205, the U+2300 sign, o-stroke, SMS, DN, 20x27), a
reducer, inline valves, an arc bend, a segment drawn twice;
- electrical texts in Russian with the power stated for all loads but one;
- a layout declaring inches over millimetre geometry, a stray line 5,000 km
out, two plan copies 100 m apart, wall outlines, room labels and wiring
callouts in four spellings.
Run lengths are the rectilinear MST of each run's tags, cable metres are
the Manhattan length rounded up after the 20 % allowance; the generator
refuses to write a pair whose own premises fail.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
