Three changes to make paper-space viewports render correctly on
UTM-scale drawings whose viewports were saved with default
view_target=(0, 0, 0) and a view_center pointing at empty WCS:
1. **Auto-fit fallback.** When the saved view's WCS rect doesn't
overlap the IQR-bounded content cluster (`world_offset ±
local_extent_max`), override `view_center` with `world_offset` and
recompute `view_height` to fit the cluster into the paper viewport.
Matches AutoCAD's silent auto-fit-on-open for stale / uninitialized
viewports; without it those viewports rendered blank.
2. **f64 projection inner loop.** The previous f32 path computed
`(wire_offset_rel - target_offset_rel).dot(view_right) -
view_center` by subtracting values at ~5e6 magnitude (f32 ULP
~0.5 m) to land on a small paper offset. The cancellation produced
centimetre-scale jitter on paper output even when the model was
clean. Reconstruct the wire WCS coord, subtract the display center,
and dot-project in f64; cast to f32 only at the final paper
position where magnitudes are bounded by the viewport rect.
3. **examples/inspect_viewports.rs** — diagnostic that dumps every
viewport's saved view fields (view_target, view_center, view_height
vs paper height, custom_scale, status flags) plus drawing-level
insertion_units and model-space extents. Used to verify that
acadrust's DWG reader reads view_height correctly; the
`view_height == vp.height` patterns observed on real files turn out
to be genuine "default 1:1" file content rather than a reader bug
(a round-trip test through DwgWriter / DwgReader survives all
per-viewport values).
Also: switch the `acadrust` patch from `HakanSeven12/acadrust@feat/
expose-blockrecord-is-loaded` (a stale branch with the abandoned
is_loaded experiment) to `hakanaktt/acadrust@main`. Upstream main
now carries the layout paper-dimensions and mirrored-arc fixes that
this branch used to add — plus PR #20's DXF reading fixes that the
old branch was missing.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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