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
