- Emit coincident belt_brim_by_layer bands even when the leading object layer
has no InstanceVisit (zero-extrusion lead-in / no coinciding support), so the
brim at first belt contact is no longer dropped.
- Register each coincident band's brim filament in ToolOrdering and emit each
band exactly once, in its brim-filament pass; emit ordinary-layer aprons in
the brim pass before object extrusion (correct tool, brim-first) instead of
with whatever tool was active.
- has_belt_brim(): inner-only brims need brim_width>0 (leading/extra produce no
inner geometry), fixing spurious prime-tower/spiral rejection; mirror in
wants_brim. Single-extruder/single-object output is unchanged except
previously-dropped bands now print.
Prime towers reserved depth from the prime volume alone, ignoring the flush
matrix: rib-wall towers in both the engine and the preview, and rectangle and
cone towers in the preview, which never carried the flush-aware estimate the
engine already used. The preview also read the print preset, which does not
carry the printer- and filament-scope keys the estimate needs and so silently
fell back to defaults. On multi-nozzle printers the flush matrix, which holds
one block per nozzle, was additionally read as a single block. The tower could
come out too small for the purge it has to hold.
The flush-based estimate also skipped the height-based minimum depth that the
prime-volume one applies, so low-flush prints could estimate a tower shallower
than the one that actually gets built.
The placement clamps and the tower-approach router both stood in the bed's
bounding box for the bed itself, so on a delta or hexagonal bed the prime tower
could be parked in a corner that does not exist and the nozzle could be routed
across it. Both now test the real printable outline, slicing reports a tower
that does not fit instead of printing it off the bed, and a tower parked near an
edge is routed along the clamped side rather than falling back to a straight
line across the tower.
Also fixes the placement validation rotating the tower hull by degrees read as
radians about the plate origin, and never rotating the generated tower footprint
at all.
Six issues found by reviewing the previous commit against belt-printer, two of
them release-blocking.
Data race (high). Print::process() runs generate_support_material() for all
objects in a tbb::parallel_for, and make_belt_brim() runs at its tail, but
belt_brim_obstacles() read every OTHER object's support_layers() - which a
concurrent task may be inside clear_support_layers() deleting. That is a
use-after-free, and even when it survives, the obstacle set depends on which
object finishes first. Only this object's own supports are consulted now; they
are complete at that point. Foreign objects still contribute their slices,
which are finished and immutable before the support phase.
Apron bands dropped (high), two separate causes. An apron band prints below
its own object's first layer, but another object can already be printing at
that print_z, in which case process_layer() takes the ordinary path and never
emitted the band - the emission is now shared by both paths. Separately, a
band whose print_z matched a support layer of the SAME object was overwritten
in the print-wide merge, which keeps one record per object per z and could not
detect the collision because LayerToPrint::layer() is null for a band. The
per-object pairing loop is now a three-way merge over object, support and apron
streams, so each object contributes at most one record per z.
Multi-instance was far too strict (medium). It refused belt brim for every
multi-instance object, killing plain brim width and inner brim too, and only
warned when a leading length was set. Only movement ALONG the belt changes an
instance's belt-floor Z, so copies side by side ACROSS the belt share one set of
bands perfectly well; belt_brim_instances_compatible() now tests just that, and
the warning fires whenever the brim is actually suppressed.
Apron layer bookkeeping (medium). Apron layers count toward m_layer_count and
advance m_layer_index, but emitted no Z/height tags, left m_last_layer_z,
m_max_layer_z and m_last_height stale - so the first object layer computed its
height against a pre-apron Z - and skipped before_layer_change_gcode and
layer_change_gcode entirely. All of that now matches the ordinary path.
Obstacle cost (low). belt_brim_obstacles() ran a full-plate union per band.
A bounding-box pre-filter drops non-overlapping objects before materialising any
polygon, and the union is skipped for trivial inputs.
Deliberately unchanged: every apron band still reports cooling layer_id 0.
CoolingBuffer uses it for the initial_layer_fan_speed override and the
close_fan_the_first_x_layers gate, and every band lies on the belt plane itself,
so it is all first-layer material by the only definition that means anything on
a belt. Numbering the bands would ramp the fan up while still printing on the
belt. Now documented at the assignment rather than left implicit.
A belt printer slices in a rotated frame, so the belt surface is a tilted
plane rather than the Z=0 bed plane. Each slicing layer touches the belt
only along a narrow strip at its leading edge - about 0.2mm at 45 degrees -
so a part's first layer is really a first line, with almost no contact patch
to hold it down while the belt drags it forward. Brim was hard-disabled on
belt printers, leaving no remedy at all.
Generate the brim on the belt plane instead. The object's belt footprint is
the union over layers of each slice clipped to that layer's contact band; the
brim is offset from it in a "flattened" frame where the shear axis is
stretched by 1/cos(tilt), so ordinary Clipper offsets measure true on-belt
distance. It is emitted as cross-belt lines, one per layer band, anchored to
a fixed fraction of the band so every line shares a nozzle-to-belt clearance
and therefore comes out the same width; flow is matched to the resulting band
pitch, keeping the sheet uniform and gap-free.
Three new controls, all belt-only:
* Leading brim length - extends the brim ahead of the part along the belt,
on every downhill-facing edge of its contact area. This apron necessarily
prints BELOW the object's first layer, since layer 0 is the part's leading
contact, so it needs brim-only bands of its own.
* Extra brim width - widens the brim sideways across the belt only.
* Brim type "Leading edge only" - brim at the part's first belt contact and
nothing after it. Appended last in BrimType so no existing value shifts;
degrades to an outer brim off belt printers, with a warning.
The apron bands are lightweight records rather than a Layer subclass, so no
fabricated Layer::id() can leak into initial-layer temperature selection, the
spiral vase probe, cooling or gradual interpolation. They are generated in
posSupportMaterial because their print_z values must exist before ToolOrdering
is built at psWipeTower, and they are emitted from a short dedicated branch in
process_layer that runs before any layer pointer is dereferenced.
The footprint is closed before offsetting outwards: a belt contact patch is
often a broken-up strip, and the merged offset rings of two islands closer
than 2 x brim_width would otherwise fill the space between them - space that
lies under the part.
Also fixes a pre-existing bug where PrintObject::get_first_layer_bbox()
overwrote a valid bbox with an unassigned one on any belt printer with a brim
configured, because has_brim() was true while make_brim() returned early.
Belt brim is refused alongside the prime tower and spiral vase, and requires
one instance per PrintObject - translating an instance along the belt axis
changes its physical belt-floor Z. Untilted belt printers are unchanged: they
still get no brim, since the plate brim is emitted out of skirt_brim_groups(),
which _make_skirt() never builds for a belt printer.
Adds a printer option that picks up the new tool without a blocking temperature
wait, travels to the wipe tower, and waits there right before purging, parked
beside the tower so the ooze from the heat-up lands next to it rather than on the
model. The incoming filament's target is raised ahead of the tool change, so the
heat-up overlaps both the change itself and the travel to the tower.
Off by default, and only offered for multi-extruder printers using a Type 2 wipe
tower; the generic toolchanger profile enables it.
Brings the belt-printer work up to date with 591 upstream commits.
Conflict resolutions (12 files, 42 hunks):
- GCode.cpp: adopted upstream's per-filament/per-nozzle config refactor
(get_filament_config_index, NOZZLE_CONFIG), the extracted
generate_timelapse_gcode + farthest-point timelapse, and the
ConfigOptionFloatsNullable calibration options. Re-applied the belt
hooks on top: init_belt_writer / axis remap / FirstLayerPlane setup,
on_set_origin, the belt-corrected calib_z for the volumetric speed
tower, and path_on_first_layer (belt's per-path first-layer test) in
place of upstream's layer-index on_first_layer() in the acceleration,
jerk and overhang-detection paths. Swept upstream's new m_writer.
uses to m_writer-> since belt holds the writer by unique_ptr.
- interpolate_value_across_layers: kept upstream's banded stepping and
belt's object-Z-span ratio; dropped upstream's duplicate ratio decl.
- Plater.cpp: took upstream's guarded add_model(...) early-returns and
the VFA vfa_layer_height plumbing; kept the belt temp-tower path,
_calib_apply_belt_mode and belt_calib_flip_ringing_tower. Dropped the
VFA "cut upper" block, superseded upstream by model scaling.
- Brim.cpp: upstream's ObjectInstanceID-keyed brimAreaMap, keeping the
belt early-return.
- 3DScene.cpp: kept both the belt build-plate tilt up_direction and
upstream's per-extruder printable-height shading.
- GCodeViewer.cpp: kept upstream's dim-previous-layers setup and belt's
exemption from the same-result early return.
- TreeSupport.cpp: upstream's >= 0 roof-layer fix inside belt's
belt-floor branch.
- calib.cpp / GCode.hpp / GCodeWriter.{cpp,hpp} / Print.hpp: upstream's
additions adapted to belt's pointer-held writer and helpers.
- Custom.json: kept profile version 02.04.00.03 (belt) over upstream's
02.04.00.01; both bumped from 02.04.00.00.
Building this tree needs the wxInspector dependency, which upstream
added in the interim (python3 and wxWidgets 3.3.2 were already present
in the shared deps prefix).
The rib tower is now always square (prime_tower_width is ignored, as the
GUI already implies), carries the rib origin offset like the BBL tower so
the rib tips sit inside the configured position, clamps the rib length to
the tower diagonal, and extends the ribs for short towers.
# Description
Changing a slicing plugin's configuration had no effect on the sliced
result until you forced a re-slice some other way; it now applies
immediately. Print, printer and filament presets also keep their plugin
configuration separately, so configuring a plugin on one no longer wipes
out what you set on another.
A plugin's custom configuration page gets the same round of improvements
in both the Plugins dialog and the per-preset dialog: it follows the
app's light/dark theme, keeps its state while you edit instead of
resetting under the cursor, and can tell whether it is being edited
globally or for a preset, so "Restore defaults" can be labeled for what
it will actually do. The two bundled examples show this off — Twistify
now ships a custom configuration UI, and Inspector is themed, groups
# Screenshots/Recordings/Graphs
https://github.com/user-attachments/assets/02ca062a-5143-49a3-abe0-a2a040b3a928
## Tests
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## Problem
On H2C (carousel) printers, the wipe tower purge volume calculation in
`_make_wipe_tower()` tracks filament state **per-extruder** (2 slots).
Since H2C has up to 7 carousel nozzle slots on a single extruder, all
filaments sharing that extruder are collapsed into one tracking slot.
This causes:
Test:
[5cubes.3mf.zip](https://github.com/user-attachments/files/30092551/5cubes.3mf.zip)
- **Massive redundant AMS flushing** every filament change on the
carousel triggers a full purge against the "previous" filament, even
when the target nozzle slot already has the correct filament loaded
- **60.9g total weight** instead of ~17g (**3.5× material waste**)
- **3h09m print time** instead of ~1h57m (**60% longer**)
## Root Cause
The code uses `nozzle_cur_filament_ids[extruder_id]` (a 2-element array)
to track which filament was last used for each extruder. BambuStudio
uses `NozzleStatusRecorder`, which tracks per `group_id` (physical
carousel slot 0..6).
## Changes
| File | Change |
|---|---|
| `Print.cpp` | Replace `nozzle_cur_filament_ids` with
`NozzleStatusRecorder`. Use `get_nozzle_for_filament()` to resolve the
physical carousel slot per layer. Select `filament_prime_volume_nc` for
nozzle changes, `filament_prime_volume` for filament changes. |
| `PrintConfig.hpp` | Add `ConfigOptionFloats filament_prime_volume`
(per-filament EC prime volume, missing from upstream but present in BBS
and H2C profiles) |
| `PrintConfig.cpp` | Register `filament_prime_volume` with default
45mm³ (matching BBS) |
| `Preset.cpp` | Add `filament_prime_volume` to preset keys |
Also includes `tests/compare_analyzer/` - two standalone Python tools
for G-code slice comparison and temperature timeline analysis (stdlib
only, no dependencies).
## Test Results (5-color H2C Hybrid print, same 3mf project)
| Metric | Upstream (broken) | **Fixed** | BBS (reference) |
|---|---|---|---|
| **Total weight** | 60.90g | **16.20g** ✅ | 17.47g |
| **Print time** | 3h09m | **1h57m** ✅ | 1h51m |
| **Filament changes** | 105 | 105 | 140 |
| **Tool changes** | 35 | 35 | 35 |
| **Critical discrepancies vs BBS** | ⚠️ YES | ✅ None | — |
## Analysis Tools (`tests/compare_analyzer/`)
Two standalone Python tools (stdlib only, no dependencies) for deep
G-code comparison:
- **`compare_slices.py`** - comprehensive .3mf slice comparison:
filament usage, nozzle mapping, tool change sequences, prime tower
analysis, temperature timeline, retract parameters, and automatic
critical discrepancy detection (weight/time anomalies)
- **`show_temp_plot.py`** - interactive HTML temperature timeline
plotter for visualising heater profiles during multi-nozzle prints
(supports single-file and side-by-side comparison)
Usage:
```bash
python3 tests/compare_analyzer/compare_slices.py file1.3mf file2.3mf --labels "Upstream" "Fixed"
python3 tests/compare_analyzer/show_temp_plot.py file1.3mf file2.3mf
```
## Screenshots
### OrcaSlicer Upstream (unfixed) - 60.90g, 3h09m
<img width="1512" height="982" alt="Screenshot 2026-07-16 at 15 22 58"
src="https://github.com/user-attachments/assets/3efb2bff-ff1e-43db-9669-feafa5921b51"
/>
### OrcaSlicer Fixed - 16.20g, 1h57m
<img width="1512" height="982" alt="Screenshot 2026-07-16 at 15 23 08"
src="https://github.com/user-attachments/assets/c1d36dc5-9b01-4691-80ef-7364540e1f4e"
/>
### BambuStudio Reference - 17.47g, 1h51m
<img width="1512" height="982" alt="Screenshot 2026-07-16 at 15 24 52"
src="https://github.com/user-attachments/assets/5c0b11e2-64f4-40e9-8c7c-3f42519786c3"
/>
### Temperature Timeline: Upstream vs Fixed
<img width="1511" height="829" alt="Screenshot 2026-07-16 at 15 23 35"
src="https://github.com/user-attachments/assets/926c2cb5-dfd4-4ce0-bb40-82e6165eb134"
/>
### Temperature Timeline: Fixed vs BBS
<img width="1512" height="825" alt="Screenshot 2026-07-16 at 15 23 51"
src="https://github.com/user-attachments/assets/85c72dda-e779-4aa6-8118-fb17e5f8482d"
/>
## Compatibility
Safe for non-carousel printers: when each extruder has a single nozzle,
`group_id == extruder_id`, so `NozzleStatusRecorder` behaves identically
to the original per-extruder tracking. The `filament_prime_volume`
default (45mm³) matches the existing global `prime_volume` default.
## Reference
BambuStudio `Print.cpp` `_make_wipe_tower()` L3341-3392 -
`NozzleStatusRecorder` pattern.
- WipeTower: use filament_ramming_volumetric_speed(_nc) for ramming, falling back to
max_vol_speed only when nil; gate precool temps on enable_pre_heating
- ToolOrderUtils: disable the inter-layer forecast in the per-nozzle base reorder so
H2D/H2C ordering is unchanged
- PrintConfig: stop stripping filament_prime_volume in handle_legacy; document that
prime_volume drives the Type2 wipe tower and filament_prime_volume the Type1 one
- GCodeProcessor: exclude post-print end-gcode M400 dwells from the M73 estimate and
drop the dead air-filtration state
- Trim verbose BambuStudio source-location comments across the port
The upstream _make_wipe_tower() tracked purge volumes per-extruder (2 slots),
which collapsed all H2C carousel filaments into one slot and caused massive
redundant AMS flushing (~40g instead of ~0.4g).
Changes:
- Print.cpp: Replace per-extruder nozzle_cur_filament_ids with BBS
NozzleStatusRecorder that tracks per group_id (carousel slot 0..6).
Use get_nozzle_for_filament() to resolve physical slot per layer.
Select filament_prime_volume_nc for nozzle changes, filament_prime_volume
for filament changes (BBS pattern).
- PrintConfig.hpp/cpp: Register filament_prime_volume (per-filament EC prime
volume, default 45mm³) matching BBS PrintConfig.
- Preset.cpp: Add filament_prime_volume to preset keys list.
Safe for non-carousel printers: group_id == extruder_id when each extruder
has one nozzle, so NozzleStatusRecorder behaves identically to the original
per-extruder tracking.
Reference to BBS: BambuStudio/src/libslic3r/Print.cpp _make_wipe_tower() L3341-3392
Resolve five conflicts, all of which needed both sides rather than a pick:
- BackgroundSlicingProcess: ours was a pure tabs->spaces reformat of base, so
keep main's per-filament volume/nozzle map read-back (its only change here).
- GUI_App: main's #12506 else-if attached to an `if` this branch deleted;
re-expressed onto the same-agent early-return path (the agent factory caches
per id, so pointer equality is the same predicate).
- MainFrame: both sides relocated Sync Presets independently; keep main's
push_notification plus the branch's Plugins menu items.
- Tab: the "TODO: Orca: Support hybrid" blocks were unchanged base, not a branch
decision; take main's enabled Hybrid to match the already auto-merged siblings.
- test_config: union of both sides' cases (6 plugin + 9 multi-nozzle).
# Description
Adds a --slice (-s) mode to the profile validator that slices a
two-colour cube through every shipped printer, expanding all custom
g-code (change_filament_gcode, machine start/end, etc.). This catches
invalid-placeholder / bad-flow / slicing errors that the static JSON
checks and unit tests can't see.
Included:
- Validator: new -s sweep mode; per-profile error attribution in the
log; resolves the synthetic 2nd-filament nozzle-mapping so multi-nozzle
BBL printers (incl. the Direct-Drive+Bowden X2D) validate cleanly.
- CI, two complementary paths:
- check_profiles.yml — runs the sweep on profile-only PRs (nightly
binary).
- build_all.yml — new parallel slice_check_linux job runs it on
engine/src PRs with the PR-built binary (build_all doesn't trigger on
resources/**, so no overlap). Runs off the build's artifact, so it
doesn't lengthen the build leg.
- Profile fixes surfaced by the sweep: Creality, FLSun, Ginger, Qidi,
RatRig, iQ.
- Engine: whitelist BBL firmware T-opcodes (T1001/T65279/T65535) in the
time estimator (log-only, no g-code change); dedupe a
per-filament/per-layer log flood in get_config_index.
# Screenshots/Recordings/Graphs
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The time estimator's speed/acceleration limits were indexed by time
mode only, reading slot 0 of the per-(extruder x volume-type) arrays
the multi-extruder profiles already carry (H2C 0.4: 8 entries, H2D
0.4: 10). Every move was therefore modelled with the first machine
slot's limits regardless of which nozzle variant was printing -
estimation fidelity only, since emitted feedrates/accelerations are
decided on the slicing side.
Now the estimator resolves the machine slot of the nozzle currently
mounted in the active extruder: the nozzle grouping context is handed
to the processor BEFORE the streaming replay (new member + setter -
deliberately separate from the post-stream result-field handover that
gates the richer change-time model, whose timing is unchanged), the
occupancy recorder is populated on every filament change (bookkeeping
decoupled from the gated time model; recorder writes have no time
effect), and get_machine_config_idx maps (volume type x extruder type
x extruder) to the slot via the printer's variant layout, newly
carried on the processor result. The feedrate/acceleration getters
gain a slot parameter indexing [slot*2 + mode]; jerk and the
print/travel/retract accelerations stay mode-only. Reloaded sliced
projects re-estimate with the result's saved grouping context;
imported bare g-code degrades to slot 0 - the historical read.
M201/M203 write the parsed value into EVERY slot's mode entry (a
firmware envelope change is global), which keeps per-slot reads in
lockstep with the mode-only reads they replace: the fleet emits
envelope lines before any motion, so estimates - hence the estimated
time header, M73 lines, and every other byte - are unchanged (20/20
pinned-slice byte gate bit-identical, incl. the sequential repro
sliced twice). Fidelity improves where envelope emission is off or a
migrating per-layer plan moves filaments across variants.
Tests: a stub-driven processor case proving the slot follows the
active nozzle through the exact production path (T..H.. commands,
fallback recorder bookkeeping, 4x time ratio on the slow variant),
that emitted M201/M203 reach every slot, and that a missing context
degrades to slot 0. Suites green (libslic3r 48998/169, fff_print
667/62).
When the per-layer filament selector (enable_filament_dynamic_map)
migrates a filament across nozzle variants (e.g. Standard -> High Flow),
the config write-back only stored the derived extruder map; every
per-variant filament value (retraction, nozzle temperature, flow,
flush...) kept the numbers resolved from the pre-slice static mapping.
Now both dynamic write-back sites (the by-layer branch and the
sequential stitch) branch on the result's dynamic support. Migrating
results run a mixed-filament expansion that regathers every
filament_options_with_variant key from the pristine per-variant
superset, giving a migrating filament one config slot per (extruder
type x nozzle volume type) it lands on - filament_self_index,
filament_extruder_variant, and all value arrays grow in lockstep - and
recompute the retract overrides with per-slot machine indices so a nil
slot falls back to its own variant's machine value. Non-migrating
dynamic results take the merged three-map write-back so re-applies
reproduce from the written maps. Unrouted filaments resolve from the
result's own default map, so slot resolution never depends on
filament_map round-tripping through the plate config.
Print::apply reproduces the identical expansion from the persisted
group result (shared dedupe helper, expansion function, and slot
indices on both sides): the expanded keys sit in the psWipeTower /
psGCodeExport invalidate lists, so without the reproduction every
re-apply after a selector slice would diff non-empty and permanently
invalidate. cal_non_support_filaments now resolves the extruder per
layer from the published result for dynamic groupings.
filament_map_2 keeps its apply-time static derivation; nothing on the
dynamic path reads it (the per-slot machine indices key the override
merge), and per-(extruder x volume-type) machine limits in the g-code
processor remain a documented follow-up.
Every change is gated behind is_dynamic_group_reorder() or a persisted
result with dynamic support; no profile sets the flag, so the static
fleet's instruction stream is unchanged (20/20 pinned-slice byte gate
identical, incl. the sequential repro sliced twice, deterministic).
Tests: expansion unit coverage (migrating slots, unrouted fallback via
the default map, mis-sized volume map ignored, nullable retract keys in
lockstep, slot machine index layout), an end-to-end stub-driven
write-back asserting expanded slots, per-layer config-index resolution,
the override merge incl. the nil-slot variant fallback, and re-apply
stability, plus a real selector slice staying valid across re-apply.
Suites green (libslic3r 48987/168, fff_print 633/60).
Sequential (by-object) prints were incoherent with the per-layer filament
selector (enable_filament_dynamic_map): the by-object branch published a
static grouping while each per-object ToolOrdering independently ran the
dynamic planner from an empty nozzle status and wrote its own map to the
config (one write per object, last object wins). The exported toolchange
sequences then disagreed with the published result that drives the
per-layer maps, placeholders, and selector emission.
Now the by-object branch, when the selector is enabled, plans each unique
object once — threading the physical nozzle occupancy and the previous
object's last filament into the next plan — stitches the per-object
per-layer nozzle maps into one print-wide result (gap-filled by the new
normalize_nozzle_map_per_layer so any layer index resolves a filament's
nozzle consistently), publishes it, and writes the derived extruder map
back once. The plans are cached on the Print and g-code export consumes
the cache: the ToolOrdering seed changes the plan input (dontcare
assignment, first-layer reorder), so a fresh export-time construction
could re-plan differently from the published stitch. The per-object
dynamic write-back is gated off for sequential prints.
Every change is gated behind is_dynamic_group_reorder(); no profile sets
the flag, so the static fleet's instruction stream is unchanged (20/20
pinned-slice byte gate identical, incl. the by-object repro sliced twice).
Tests: normalize unit coverage (carry-forward, back-fill, ragged input),
stitched-blocks selector detection, and an end-to-end by-object selector
slice (apply -> process -> export) asserting the published stitched
result, one cached plan per object, the config write-back, and a clean
export. Suites green (libslic3r 48958/165, fff_print 633/60).
The Print-level LayeredNozzleGroupResult had a single producer, the
by-layer branch of ToolOrdering, which is gated to non-sequential prints.
The by-object branch in Print::process computed a grouping only in auto
map modes and never stored it, so a sequential slice exported with a null
group result: the per-nozzle placeholder tables came up empty and any
start g-code indexing nozzle_diameter_at_nozzle_id[] aborted with
"Indexing an empty vector variable". A prior by-layer slice masked the
bug by leaving its (never cleared) result on the Print.
Now the by-object branch runs get_recommended_filament_maps in every
static map mode (in manual modes the result mirrors the user's
assignment, deviations throw as in by-layer) and publishes it
print-wide. The config write-back stays gated to auto modes: in manual
modes it would only re-store the pre-slice values.
Regression test: a two-object by-object print must publish a non-null
group result and resolve nozzle_diameter_at_nozzle_id[] in start g-code
(both fail without the fix). Suites green (libslic3r 48929/162,
fff_print 633/60); 18-fixture byte gate identical; the by-object repro
project goes from the export error to valid g-code, determinism x2.
harrierpigeon