Write chart styling so PowerPoint draws DeckCraft charts as DeckCraft does by Harrison-Booth · Pull Request #1494 · storytold/deckcraft

Harrison-Booth · 2026-10-28T14:54:39Z

Charts written by DeckCraft had no c:spPr/c:txPr, so PowerPoint drew black gridlines and axis lines and 10 pt labels, while DeckCraft draws light-grey gridlines, no axis line and grey labels scaled to the frame.

The writer now emits:

c:majorGridlines/c:minorGridlines with an a:ln in D9D9D9 / F2F2F2 at 0.75 pt
a:ln with a:noFill on the axes
for new charts (not imported ones kept as-is), the default text colour (tx1 at 65 %) and the frame-scaled label and title sizes in c:txPr and the title runs

Checked

cargo test -p deckcraft-pptx: passes, with new tests for the gridline/axis XML and the text defaults.
Real PowerPoint (COM, temp copy of the sample deck saved by deckcraft-cli run --sample --save): gridline colour 14277081 (D9D9D9) at 0.75 pt, axis lines not visible, tick labels 16.35 pt in 595959, for the 800x360 pt frame (360/22, DeckCraft's own size). Before, the evidence was black at 0.75 pt and 10 pt.

Not run: macOS and Windows builds of the app, other PowerPoint versions.

Review follow-up checks

Linux (WSL2): cargo fmt --check and the focused chart serialization tests chart_title_sizes_are_bounded_and_axis_titles_use_text_size and pie_data_label_default_white_does_not_become_chart_text_color passed.
Windows (GNU toolchain): both focused chart serialization tests passed.
Not run locally: full workspace CI or macOS build/tests.

Summary by CodeRabbit

New Features
- Charts support configurable text and title sizes, with automatic sizes applied when values are not specified.
Improvements
- Missing chart text styling receives defaults, while existing custom formatting is preserved.
- Pie and doughnut data labels use white text when no chart text color is specified.
- Chart axes no longer show axis lines. Enabled major and minor gridlines use distinct light-gray shades.

Gridlines are written light grey and axis lines off, and text colour and sizes are written when a new chart has none, so PowerPoint no longer falls back to black lines and 10 pt labels.

coderabbitai · 2026-10-28T14:54:56Z

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Files selected for processing: 3

crates/pptx/src/write.rs
crates/pptx/src/write/chart.rs
crates/pptx/src/write/shapes.rs

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Walkthrough

Chart export fills missing text defaults for charts without raw XML. It writes configured text and title sizes, applies white text properties to pie and doughnut data labels when chart text color is not explicit, and styles generated axes and gridlines.

Changes: Chart formatting

Layer / File(s)	Summary
Plain chart text defaults `crates/pptx/src/write/shapes.rs`, `crates/pptx/src/write.rs`	Charts without raw XML receive defaults for missing text color, text size, and title size. Existing values are preserved. Export passes explicit-color state to chart XML generation.
Chart text and data-label serialization `crates/pptx/src/write/chart.rs`	Chart text and titles serialize font sizes in hundredths of a point after clamping. Pie and doughnut data labels use white text properties when chart text color is not explicit.
Axis and gridline formatting `crates/pptx/src/write/chart.rs`	Generated axes omit visible axis lines. Enabled major and minor gridlines use `D9D9D9` and `F2F2F2`. Tests cover gridline styling, axis lines, text sizes, and label colors.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Possibly related issues

storytold/deckcraft#1366: This change updates gridline and axis-line styling, title sizing, and chart text properties. The issue also describes other behaviors not covered here.

Suggested reviewers: nikitkara, dylanmtaylor

Merge Risk: Low · up to e0fdb

Pie labels can become harder to read after export and reimport. This bounded issue should be addressed or accepted before release.

Security architecture risk: Minimal · up to e0fdb

The inspected changes remain within chart export. They add presentation styling without exposing a new external entrypoint, increasing privileges, or weakening the existing XML-writing controls. No material security risk was identified in the changed paths.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

inferred — The inspected change affects chart presentation XML within an exported document through existing chart-shape callers. It does not introduce a new externally callable surface or grant additional filesystem, network, or credential authority.

Trust Boundaries and Controls

observed — Generated chart text continues through XML text-escaping helpers, and attributes retain attribute escaping. Raw XML reuse remains a separate, pre-existing preservation path; parsing and model equality are not treated here as a general guarantee that imported XML is trustworthy.

Resilience and Maintainability Implications

inferred — Default insertion does not mutate the source chart: it operates on a clone. Each export initializes its own package and counters before returning a completed byte result, so this change does not introduce shared mutable chart state or a durable intermediate styling state requiring recovery.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 18.18% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documenta…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: writing chart styling so PowerPoint renders DeckCraft charts consistently with DeckCraft.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 18.18% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 11 functions across 3 files.

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

Finishing Touches

🧪 Generate unit tests (beta)

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Actionable comments posted: 3

🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @crates/pptx/src/write/chart.rs:
- Line 87: Clamp the point size to the 1–4000 pt range before converting it to
DrawingML hundredths in the chart font-size conversion, so exported `sz`
attributes stay within the permitted range.
- Line 140: Update title to accept the font size separately and pass c.text_size
at both axis-title call sites, while keeping c.title_size for the chart-title
call; use the supplied size in the rich call instead of always using
c.title_size.

Review comments at @crates/pptx/src/write/shapes.rs:
- Line 684: Update the c.text_color default handling so pie and doughnut data
labels without an explicit text color preserve their white default through
export and reimport, rather than acquiring an explicit grey fallback. Keep
existing default-color behavior for other chart labels unchanged.

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crates/pptx/src/write/chart.rs
crates/pptx/src/write/shapes.rs

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Inline comments:
Review comments at @crates/pptx/src/write/chart.rs:
- Around line 406-408: Track whether the chart text color was explicitly set
before chart_text_defaults applies a default, and use that state in data_labels
so pie and doughnut labels retain the white default when the color was not
explicit while respecting an explicit color. Add coverage for both direct
chart_xml calls and the shape-export path.

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crates/pptx/src/write/chart.rs

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Harrison-Booth · 2026-10-28T20:32:54Z

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FredApps

ReviewerA — source-read COMMENT (not an approval)

I read the first hunk: chart_rel now takes a text_color_explicit flag, and per the title the PPTX writer emits chart styling so PowerPoint draws DeckCraft's charts as DeckCraft does (explicit colours and text properties rather than PowerPoint's defaults, which differ from DeckCraft's). Writing the styling explicitly is the way to get the same look. I can't judge the look from the diff; please attach screenshots of one chart type in DeckCraft and in PowerPoint. I did not read the writer change. Check that a chart with preserved XML from an imported file is not restyled (the preserved result suggests that is handled), that dark and light themes both work, and the chart still opens with no repair prompt in PowerPoint. Nothing was run.

I ran nothing and have no exact-head CI result for this PR, so this is not an approval. Where a diff was long I read its code hunks rather than every generated or documentation line.

Status: waiting_author.

Write DeckCraft's chart styling so PowerPoint draws charts the same

6f18abc

Gridlines are written light grey and axis lines off, and text colour and sizes are written when a new chart has none, so PowerPoint no longer falls back to black lines and 10 pt labels.

coderabbitai Bot reviewed Oct 28, 2026

View reviewed changes

Comment thread crates/pptx/src/write/chart.rs Resolved

Comment thread crates/pptx/src/write/chart.rs Resolved

Comment thread crates/pptx/src/write/shapes.rs Resolved

Harrison-Booth added 2 commits October 28, 2026 13:28

Merge remote-tracking branch 'origin/main' into dc-chart-style

f34a1f4

M1.2: fix chart text style review findings

0bdb900

coderabbitai Bot reviewed Oct 28, 2026

View reviewed changes

Comment thread crates/pptx/src/write/chart.rs Resolved

M1.2: preserve default white pie labels

f6db3ac

This was referenced Oct 28, 2026

#1366: wrap long chart titles Harrison-Booth/deckcraft#30

Open

Charts: long titles wrap and the plot sits below them #1524

Open

Merge remote-tracking branch 'origin/main' into dc-chart-style

e0fdbda

echelon mentioned this pull request Oct 30, 2026

Charts: honor an explicit manual plot rectangle #1523

Open

FredApps reviewed Nov 1, 2026

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