Fix pyplot autoscale margins and bar extents [mpl compatibility]

[sselvakumaran]

Summary

• snapshot Matplotlib's default x/y autoscale margins when each axes is created, and apply them consistently to public limits and rendered domains
• compute bar autoscale extents from the full geometry: category width, zero or explicit baseline, and cumulative stacked endpoints
• keep bar baselines and contour boundaries sticky while adding Matplotlib-style headroom, including log-coordinate padding
• add regressions for line/log margins, positive/negative/mixed/stacked/horizontal/categorical bars, and bar-label headroom

Validation

• pytest -q tests/pyplot — 623 passed, 3 skipped
• focused autoscale/layout/reference suite — 50 passed
• ruff check — passed
• ruff format --check — passed
• git diff --check — passed

The visual micro-suite also confirms line views now use the expected 5% limits and ordinary/stacked/horizontal bar labels remain inside the rendered view.

[greptile-apps]

Greptile Summary

This PR updates pyplot autoscaling and label geometry to match Matplotlib-style margins. The main changes are:

• Adds explicit x/y axis margin support in core chart axes and public components.
• Snapshots pyplot rc autoscale margins when axes are created.
• Applies consistent margin handling to public limits and rendered domains.
• Expands bar autoscale extents using full bar geometry, baselines, and stacked endpoints.
• Adjusts tick-label padding and bar-label alignment across browser, SVG, and raster rendering.
• Adds tests for line/log margins, bar layouts, twin axes, singleton data, and UI label placement.

Confidence Score: 5/5

This PR appears safe to merge with low risk.

The changes are focused on autoscale range propagation and render geometry, with broad tests for the affected pyplot, core, SVG/raster, and browser paths. No verified correctness or security issues were found in the changed code.

No files require special attention.

T-Rex Logs

What T-Rex did

• Executed the PyTest suite for pyplot-autoscale-bar-layout validation and saved a proof log detailing the command, working directory, pytest output, timestamps, and an exit code of 0.

_{Ran code and verified through T-Rex}

Important Files Changed

Filename	Overview
python/xy/pyplot/_axes.py	Snapshots rc autoscale margins, delegates render margins to core axes, and expands bar/contour autoscale extents with sticky baselines.
python/xy/_figure.py	Adds axis margin support to core autorange, including explicit log-coordinate padding and singleton handling.
python/xy/components.py	Exposes validated margin on public x/y axis components and forwards it into figure axis options.
python/xy/pyplot/_plot_types.py	Updates bar labels to use point-scaled padding and vertical alignment for positive/negative bar geometry.
python/xy/_svg.py	Adds shared tick-label offset calculation and updates SVG tick/annotation text placement.
python/xy/_raster.py	Aligns raster tick-label and bottom-aligned annotation placement with SVG/browser geometry.
js/src/50_chartview.ts	Adjusts browser tick-label placement to account for tick length, direction, and label padding.
tests/pyplot/test_autoscale_margin_bar_regressions.py	Adds focused tests for pyplot margins, log scaling, twin axes, singleton data, bars, and bar labels.

_{Reviews (7): Last reviewed commit: "Remove visual comparison asset" | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 102 untouched benchmarks
⏩ 2 skipped benchmarks¹

---

_{Comparing agent/fix-pyplot-autoscale-margins (5c7418e) with main (119a1ce)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[sselvakumaran]

Before / after renderings

These are the same pyplot gallery cases at the same normalized 640×480 output size. Before is the pre-PR behavior; after is this PR.

Horizontal bars — full value/category extents

Before, every bar is clipped to the fallback 0..1 x-domain. After, the data extent, category width, and label headroom are included.

Before	After

Rotated categorical bars — all categories remain in view

Before, the fallback category domain shows only two of four bars. After, all four categories and the outer half-bar widths fit.

Before	After

Positive bar labels — Matplotlib-style headroom

Before, the tallest value label crosses the top spine. After, the 5% autoscale margin keeps it inside the axes.

Before	After

The largest changes are in the plot limits and bar visibility. This PR does not fix the separate tick-label-to-tick spacing/chrome issue; that remains visible in both sets.

[sselvakumaran]

Correction to the earlier visual: that panel compared two XY revisions, not Matplotlib directly. This one renders the same calls in Matplotlib 3.11 and XY:

What the Matplotlib source and direct measurements show:

• General autoscaling is a transformed data-span margin (delta = span * margin), with the default axes.xmargin / axes.ymargin set to 0.05. The automatic line example therefore has the same 0.475..1.025 limits in both implementations.
• bar_label creates an Annotation in offset points; its text bbox does not enter dataLim. In the exact Matplotlib reference above, the 1.8 bbox reaches about 0.46 px past the top spine.
• XY now keeps Matplotlib's general 5% autoscale behavior, but raises the automatic value-axis reservation to 7.5% when an edge bar_label is present. That gives the label visible headroom on vertical and horizontal bars. Explicit set_xlim / set_ylim and explicit margins() still take precedence.
• The default XY PNG is intentionally high-DPI (1280x960 for this 640x480 figure). The image above normalizes it to 640x480 only for same-size viewing; the 2x scale multiplies marks, text, and gaps uniformly and is not the source of the relative margin.

The separate tick-label fix is also included: padding starts after the outward end of the tick, and the browser geometry test measures the requested 5 px gap after a 6 px tick. Validation: 710 passed, 3 skipped, plus the focused browser geometry test.

[greptile-apps]

This repository has used its 100 free open-source review credits for this billing period. An organization admin can enable additional billed reviews, or reviews resume next period.

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 49ce66aa-eac9-49e3-8a9d-de5da1aeed2b

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch agent/fix-pyplot-autoscale-margins

---

_{Comment @coderabbitai help to get the list of available commands.}