Two measured root causes on the headless engine, both silent:
1. page_setup_apply wrote PLOTSETTINGS group 147 (unit_factor) as 1.0 for
every scale. Under USE_STANDARD_SCALE AutoCAD's plot engine scales by
group 147 alone (a 1:10 sheet with code 21 and 147 = 1.0 plotted a
100-unit line at 99.99 mm while the row, `applied` and 142/143 said
1:10; patching 147 to 0.1 alone gave 9.99 mm). AutoCAD writes 147 as
numerator / denominator (measured live on AutoCAD 2026 for fit, 1:1,
1:2, 1:10, 1:50, 2:1, 10:1: 1.0, 1.0, 0.5, 0.1, 0.02, 2.0, 10.0). The
writer now stores 75, 142/143 and 147 from the one resolved ratio on
every route, so no reader can disagree with the plot.
2. DXF_STANDARD_SCALE_TYPE and _plot_scale followed ezdxf's STD_SCALES,
which has no 19 = 1:5 and numbers everything above 18 one lower than
the ObjectARX StdScaleType enum AutoCAD actually writes (1:10 = 21,
1:20 = 23, 1:50 = 26, 1:100 = 27, 2:1 = 28, 10:1 = 31 — measured via COM
SaveAs DXF). An AutoCAD-authored 1:50 sheet listed as "1:100" and a
1:10 sheet rendered at 1:16. papers.py now authors the full file enum
(DXF_STD_SCALES, codes 1-33 with AutoCAD's imperial names), the writer
uses the same codes ActiveX uses, and nothing goes through ezdxf's
table. 1:5 stays on the custom route on both engines (the live setter
refuses 19) while the reader knows code 19 for files AutoCAD wrote.
Tests: the plan's `1:50 -> 25` assertion was the stale numbering and now
pins 26; a pure-data test pins the enum against the measured codes and the
ActiveX numbering; a parametrised writer test checks 75/142/143/147 for
every catalogue scale; a reader test stores the scale exactly as AutoCAD
saves it (including codes 19 and 22 the writer never emits) and checks
page_setup_list and _paper_frame report and render it at its own scale.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
Finding 1: page_setup_list swapped size_mm for plot_rotation 1/3 but
reported the margins un-turned, so a 297 x 210 sheet carried its portrait
margins ([20, 20, 7.5, 7.5], printable 282 x 170) while ezdxf's Page and
_paper_frame plotted [7.5, 7.5, 20, 20] (257 x 195). The mapping now lives
once in papers.turned_sheet (cross-checked against Page.from_dxf_layout
for all four rotations) and is used by the ezdxf row, _paper_frame and the
COM row. page_setup_apply resets plot_rotation to 0; headlessly it now
re-writes the turned margins un-turned so the sheet keeps the margins it
had (nothing moves, changed says nothing), and on COM, where margins come
from the .pc3, the ones that moved show up in changed.
Finding 2: both engines forced plot paper units to millimetres with no
units field in the row, so an inch-authored ANSI sheet was rescaled 25.4x
with ok: True and changed naming only the media. Rows now carry
paper_units (mm | inches | pixels, DXF group 72 / AcPlotPaperUnits);
resolve_page_setup takes paper_units="mm" (default) | "inches" | None
(keep the layout's units, as AutoCAD's own Page Setup does); a move is
reported in changed and, with its 25.4x consequence and the way back, in
the new warnings list (papers.page_setup_warnings, identical on both
engines).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
Three live-measured behaviours of AutoCAD 2026 that the fake did not replay:
* GetPaperSize / GetPaperMargins answer in millimetres whatever PaperUnits
says; the 25.4 factor listed every imperial layout as [10668.0, 7543.8]
and lost the paper name. No factor now; the fake pins PaperUnits=0.
* Layout.StandardScale = 19 (ac1_5) is refused with "Invalid input" in every
condition; '1:5' is dropped from ACTIVEX_PLOT_SCALE so it goes through
SetCustomScale(1, 5) like 5:1 already did.
* Writing ConfigName replaces CanonicalMediaName with the new device's
default, and writing the old device back does not bring the media back —
the unknown-media refusal and a late refusal both left the layout on the
old device's default paper while the error claimed it was restored. The
device write now snapshots media / units / rotation and journals one
combined undo; the read-back after every unwind is compared to the
read-back before the first write and the message names what did not go
back instead of asserting it did.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
The ActiveX Reference (CenterPlot Property, acadauto.chm, AutoCAD 2026):
"This property cannot be set to True on a layout object whose PlotType
property is set to acLayout." The shipped sequence wrote PlotType=5 and
then CenterPlot=True for the *default* call, so page_setup_apply(layout,
resolve_page_setup("ISO_A3")) could not succeed live — either COM raised
with nine writes landed and nothing put back, or the result claimed
applied.center=True over a read-back of False.
- resolve_page_setup resolves `center` to None for plot_area="layout"
(validated as a bool first; kept as the bool for "extents"), and
`center_applies(plot_type)` carries the rule for both read-backs.
- Both engines: page_setup_list reports `center: None` under acLayout
instead of a stored flag nothing honours; apply never sets the centre
bit / CenterPlot for a layout plot (ezdxf clears bit 4, the state
AutoCAD stores for acLayout; COM clears a stale CenterPlot=True *before*
PlotType moves to acLayout, and writes CenterPlot for an extents plot
only *after* PlotType=acExtents).
- COM: every write is journaled and unwound in reverse when AutoCAD
refuses one; the ValueError names the refused property and says the
layout was restored (or what could not be). The old device-only
rollback is the same mechanism now.
- tests: the fake enforces the documented CenterPlot rule (the shipped
sequence fails under it, which is the reviewer's repro), and can refuse
a named property; new cases pin the no-write, the ordering both ways,
the reverse unwind including SetCustomScale, and the None read-backs.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
