justinjohn0306 69709bd458 Line charts: smooth (spline) curves (issue #52) ...

Add support for Excel's "smoothed line" chart style. The smooth flag flows
model -> resolve -> chart render, persists through XLSX (<c:smooth val="1"/>),
and is toggled via the chart.addElement "smooth" element.

Rendering interpolates each gap-free run with a uniform Catmull-Rom spline
(0.5 tangent scale, 100 sub-segments per data segment), so the curve passes
through every data point and rounds the vertices — matching Excel's observed
behaviour. Long runs are still decimated before smoothing.

- model: Series.smooth (#[serde(default)], so old workbooks load unchanged)
- chart: SeriesData.smooth; smooth_run + catmull in render; wired through
  resolve and the sanitize() copy; draw_runs takes the flag (line + scatter)
- engine: chart.addElement element="smooth"
- xlsx: read/write <c:smooth val> instead of hard-coding val="0"
- tests: smooth_line_adds_interpolated_points_and_keeps_endpoints,
  smooth_line_splits_at_gaps, smooth_line_setting_round_trips
- examples/smooth_demo.rs: generates a straight+smooth side-by-side workbook

cargo xtask ci: all 7 steps pass.

2026-10-10 00:09:12 +05:30

..

perf.rs

Rename SheetCraft to GridCraft everywhere (crates, apps, bundle ids, packaging, docs)

2026-10-06 01:39:08 -04:00

smooth_demo.rs

Line charts: smooth (spline) curves (issue #52)

2026-10-10 00:09:12 +05:30