PolylinePlot - implement "area under curve" fill

[mathesoncalum]

Providing "area under curve" coloring for polylines. This is expressed as a vector of colors so that each region can be colored independently.

[coderabbitai]

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• framework/uicomponents/qml/Muse/UiComponents/polylineplot.cpp

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📝 Walkthrough

Walkthrough

PolylinePlot now exposes the QML colorsUnderLine property with matching accessors, storage, change notification, and repainting. The plot clears configured colors when point data changes and excludes synthetic points outside the normalized range from the visible polyline. A new helper draws line segments and fills each segment area to the baseline when a configured color is available. paint() uses this helper for rendering.

Merge Risk: 🟡 Moderate · up to d8fd4

Area-under-curve colors may be assigned to the wrong segments or omitted when boundary points are present, which can make plotted data visually misleading. Merge should wait for this mapping issue to be fixed or explicitly accepted by the owner.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description states the feature and motivation but omits the issue reference and all required checklist sections from the repository template.	Add the required issue reference, complete each checklist item, and include any relevant testing or implementation details.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: adding area-under-curve fill to PolylinePlot.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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🧪 Generate unit tests (beta)

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[coderabbitai]

Actionable comments posted: 1

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Inline comments:
In `@framework/uicomponents/qml/Muse/UiComponents/polylineplot.cpp`:
- Around line 1097-1121: Update the polyline rendering flow around polylinePx()
so each rendered segment retains its source data-segment index through sorting
and cropping. Use that index when reading m_colorsUnderLine, and skip left/right
horizontal extension segments rather than assigning them colors; add coverage
for interior segments and cropped points.

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

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📥 Commits

Reviewing files that changed from the base of the PR and between 9b124d2 and 8eb7dec.

📒 Files selected for processing (2)

• framework/uicomponents/qml/Muse/UiComponents/polylineplot.cpp
• framework/uicomponents/qml/Muse/UiComponents/polylineplot.h

[mathesoncalum]

/build

[github-actions]

Build dispatched: https://github.com/musescore/muse_framework/actions/runs/32023554115