[MarkusNeusinger]

Summary

• Bumps the shared R setup action to R 4.6.1 and the Posit Package Manager snapshot to 2026-10-20, which moves ggplot2 from 3.5.1 to 4.0.3. All 42 packages (the list plus dependencies) install as noble binaries for R 4.6.1 from that snapshot.
• Adds a "ggplot2 4.0 notes" section and an **API level:** ggplot2 4. line to prompts/library/ggplot2.md. The displayed versions follow the pins since refactor: derive library versions from pins, install from uv.lock #12240: the setup-r note # Snapshot 2026-10-20 ships ggplot2 4.0.3. and the r-version default give ggplot2 4.0.3 and R 4.6, and core/constants.py is unchanged.
• Changes no plots/ file. Catalogue images stay as rendered until an implementation is regenerated.

Rebased on #12240

The branch is rebased on main after #12240. core/constants.py keeps main's version-free entries, and the setup-r action carries #12240's snapshot-note paragraph with the new date and version. tests/unit/core/test_version_sources.py passes, including the ggplot2 API level check, and pinned_versions() returns ggplot2 4.0.3 and R 4.6 with no errors.

Plan

N/A

Before and after renders

Both environments are Ubuntu 24.04 containers built like the action: R from the Posit builds through rig (what r-lib/actions/setup-r installs), the action's apt list plus fonts-dejavu-core and fonts-liberation, and the action's install.packages() call against the snapshot with the binary user agent. Each implementation ran the way impl-generate runs it: cd plots/<spec>/implementations/r && ANYPLOT_THEME=<light|dark> Rscript ggplot2.R. All 325 implementations ran, so no sample was needed.

	Before	After
R	4.4.1	4.6.1
Snapshot	2025-01-15	2026-10-20
ggplot2	3.5.1	4.0.3
ragg, systemfonts, textshaping	1.3.3, 1.1.0, 0.4.1	1.5.2, 1.3.2, 1.0.5
scales, patchwork, dplyr	1.3.0, 1.3.0, 1.1.4	1.4.0, 1.3.2, 1.2.1
Renders (325 specs, 2 themes)	650 ok, 0 failed	650 ok, 0 failed
Wall time, 16 in parallel	95 s	101 s
Specs with deprecation warnings	0	15

Pixel comparison of the 650 pairs (every pair has the same size):

Class	Renders	Specs
Identical	242	121 (both themes)
Layout shift only	345	171
Content-level change	63	33
Failed	0	0

A changed pair counts as a layout shift when under 0.01 % of its pixels lack a colour match (per-channel tolerance 24) within a 20 px window of the other render. Every pair above that threshold was inspected by eye. Most shifts come from one 4.0 change: guide_axis() no longer reserves space for blank ticks, and theme_minimal() and theme_void() blank them, so panels grow by about 11 px per axis (2 pt at 400 dpi).

The ten largest raw diffs (share of pixels with a channel delta above 32) are all layout shifts of unchanged content: horizon-basic 14.5 %, scatter-matrix 13.9 %, psychrometric-basic 13.2 %, parallel-basic 10.5 %, scatter-pitch-events 10.2 %, parallel-categories-basic 9.3 %, indicator-ichimoku 9.2 %, scatter-embedding 9.0 %, column-stratigraphic 8.8 % and line-timeseries-rolling 7.6 %.

Content-level changes, none of them a failure:

Cause	Specs	Verdict
Default bin edges moved in binning stats	histogram-2d, histogram-kde, histogram-basic, histogram-density, subplot-grid, scatter-marginal	Default drift; different bins, still correct
Default legend order changed	bubble-basic, bubble-map-geographic, map-marker-clustered, swimmer-clinical-timeline, campbell-basic, timeseries-forecast-uncertainty, indicator-macd, precision-recall, line-confidence, genome-track-multi, band-basic	Default drift
theme_void() root rect now has linewidth = 0, so the legend frame disappears	network-directed, donut-nested, bar-3d-categorical	Default drift, visible
Rotated top-axis labels run into the title	heatmap-annotated	Visible defect; vjust = 0 restores the 3.5.1 layout exactly (tested)
annotate("label", label.size = 0) is ignored, so 0.25 mm borders appear	spectrum-nmr	Visible change
Violin quantiles computed from the data, not the density	violin-basic	Documented 4.0 breaking change
geom_qq_line() is now an abline across the panel	qq-basic	Default drift
Residual shift or antialiasing, same content	count-basic, polar-scatter, line-reaction-coordinate, raincloud-basic, pictogram-basic, bar-pareto, area-stacked-percent, line-training-load-pmc, upset-basic	Default drift

No implementation broke: every render succeeded, and the only new log lines are deprecation warnings and Ignoring unknown parameters: label.size.

Breaking changes handled

The new prompt section tells the generator to use linewidth/border.colour on labels instead of label.size, geom_errorbar(orientation = "y") instead of geom_errorbarh(), the part-specific line widths instead of fatten, quantiles plus quantile.linetype instead of draw_quantiles, coord_transform() and annotation_borders() instead of the renamed forms, and a two-letter facet_wrap(dir = ) instead of as.table. It also covers four silent default changes: anchor bins with boundary, give bordered rects under theme_void() an explicit linewidth, set vjust = 0 on rotated top-axis text, and fix legend order with guide_legend(order = ). Each replacement was checked in the 4.0.3 container.

First review (Gemini 3.8 Flash)

• Adopted: the section is now called notes, so the reviewer, which also reads the file, does not take it as a scoring rubric. The facet_wrap(dir = ) line now names the layout that replaces as.table = FALSE ("lb", same panel layout, checked), and the annotation_borders() rename and plot.tag inheritance were added.
• Rejected after checking: mgcv missing (it is a recommended package and is installed with R 4.6.1), libtiff5-dev missing on noble (the package exists there), geom_crossbar(middle.linewidth = ) unverified (it runs without a warning and is the replacement the 4.0.3 deprecation message names), and the template theme needing explicit border widths (it uses theme_minimal(), whose rect line width is non-zero).

Regeneration candidates

• Visible change: heatmap-annotated (labels overlap the title), spectrum-nmr (unwanted label borders), network-directed, donut-nested and bar-3d-categorical (legend frame lost).
• Deprecated API, renders fine: coefficient-confidence and bar-permutation-importance (geom_errorbarh), violin-basic (draw_quantiles), strip-basic (fatten), and label.size in line-annotated-events, bode-basic, contour-map-geographic, scatter-embedding, network-transport-static, shap-waterfall, network-force-directed, network-directed, scatter-ashby-material, ternary-basic and tree-decision.

These matter only when daily-regen or impl-repair re-renders an implementation; this PR re-renders nothing.

Pre-existing gaps, unchanged by this PR

• The action does not install hexbin, so in an environment built from the action alone hexbin-basic and hexbin-map-geographic warn and draw no hexes, before and after.
• The action does not install maps (map-projections, flowmap-origin-destination) or qrcode (qrcode-basic). Both containers added them as test-only extras.

These packages go to a separate task, not into this PR.

Verification gaps

The .github/actions/setup-r change has no live verification loop beyond the container run above. The first real check is the next impl-generate, impl-repair or daily-regen job on an R implementation after merge. No review-retest.yml arm is needed: the "ggplot2 4.0 notes" section is generation guidance, not a review rule, even though the review step also reads prompts/library/ggplot2.md.

Test plan

• Rendered all 325 ggplot2 implementations in both themes in the before and after containers and compared them pixel by pixel
• Installed every package from the 2026-10-20 snapshot as a noble binary for R 4.6.1
• ruff check, ruff format --check, mypy, pytest tests/unit tests/integration (12,331 passed after the rebase) and the changelog check
• After merge: the first R pipeline job installs through the action and renders both themes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[Copilot]

🔵 Needs a closer look

The shared rendering environment upgrade needs human sign-off because installation and rendering through the actual GitHub Actions pipeline remain unverified.

No open issues 🎉

What changed in this PR

Updates the shared R rendering environment to R 4.6.1 and ggplot2 4.0.3, with generator guidance for changed APIs and rendering defaults. Existing catalogue images remain unchanged until regeneration.

Changes:

• Advances the R runtime and Posit snapshot to 2026-10-20.
• Adds ggplot2 4.0 migration guidance for generated implementations.
• Updates displayed versions and records the upgrade, with merge coordination documented for #12240.

File	Description
prompts/​library/​ggplot2.md	Adds ggplot2 4.0 API and rendering guidance.
core/​constants.py	Updates displayed R and ggplot2 versions.
changelog.d/​r-4.6-ggplot2-4.md	Records the upgrade and catalogue impact.
.github/​actions/​setup-r/​action.yml	Pins R 4.6.1 and the newer package snapshot.

_{Review effort: Balanced}