Feature Request #1267

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1. richard1912

   added 3 commits that reference this issue on Oct 14, 2026

   Combo chart with secondary axis rendered by GridCraft (storytold#1267)

   8a844f3

   storytold#1267 screenshots

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   storytold#1267 screenshots

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2. richard1912 commented on Oct 14, 2026

   

   richard1912

   on Oct 14, 2026

   Contributor

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   Hi Mike, not a maintainer, just another Excel user testing GridCraft on Windows. I tried your exact example (conductivity as columns on the primary axis 0 to 3,000, pH as a line on a secondary axis 6 to 10, titles on both).

   What already worked: GridCraft reads an Excel combo chart with a secondary axis and draws it correctly, columns on the left axis and the pH line on its own right-hand axis.

   What was missing, and what PR #1290 adds:

   1. A way to build it inside GridCraft: the Format pane's Series section now has a chart type picker and a "Secondary axis" box per series (or chart.formatSelection {series, secondary, type} for scripts).
   2. Fixed axis scales: Minimum, Maximum and Major unit for both vertical axes, plus the secondary axis title, in a new Axes section of the Format pane. They are read from and written to the XLSX, so a round trip through GridCraft no longer sends your axes back to Automatic (before the PR, Excel reopened the file with 0 to 2,500 and 0 to 9 and no pH title).

   Checked by opening the results in Excel for Microsoft 365: series types, axis groups, bounds, units and titles all come back as set. Log scale, minor units and the horizontal axis options are not in this PR.
3. iluebbe commented on Oct 23, 2026

   

   iluebbe

   on Oct 23, 2026

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   #1290 checked

   Fixes it. The reporter's chart can now be built in GridCraft: conductivity as columns on 0–3,000, pH as a line on a secondary axis 6–10 with its own title. Excel reads it back exactly as set, and a combo with fixed bounds made in Excel survives a round trip through GridCraft. There are a few problems around the edges, listed below.

   Setup: PR head 67217f7, merged locally into main at a1c8454 (the conflicts needed some resolving, see Merging), Windows 11. Checked with:

   • gridcraft-cli from the PR and from main;
   • the PR's tests and a temporary render probe;
   • Excel for Microsoft 365 through COM. A combo with fixed bounds was built in Excel and saved to a scratch folder, and the GridCraft-written files were opened in Excel.

   Case	main	PR
   chart.formatSelection {"series":1,"secondary":true,"type":"line"} on a column chart	accepted, but the chart stays a plain column chart	combo: series 1 columns on axis 1, series 2 a line on axis 2 (read back in Excel)
   chart.set {"yMin":0,"yMax":3000,"yUnit":500,"y2Min":6,"y2Max":10,"y2Title":"pH"}, saved, opened in Excel	ignored	Excel shows 0–3000 by 500 and 6–10 titled "pH"
   Excel-made combo with these bounds, opened and saved by GridCraft, reopened in Excel	bounds become automatic (0–3500 and 0–10), "pH" title lost	0–3000 by 500 and 6–10, "pH" kept
   yMin ≥ yMax, yUnit 0, a missing series	—	refused with a clear message

   Problems:

   • A fixed major unit that gives more than 50 steps only labels the first 50. apply_fixed accepts up to 1,000 steps, but Scale::ticks stops at 50. On a 0–1,000 axis, unit 1 draws labels and gridlines only from 0 to 50, and unit 10 only up to 500; the rest of the axis has none.

     gridcraft/crates/chart/src/axis.rs

     Line 25 in 67217f7

     let n = ((span / self.step + 1e-9).floor() as i64).clamp(1, 50);

     and

     gridcraft/crates/chart/src/axis.rs

     Line 149 in 67217f7

     let step = match fixed.major_unit.filter(|u| u.is_finite() && *u > 0.0 && span / *u <= 1000.0) {

   • A fixed Minimum above the automatic maximum is silently dropped. With data 100…1,000 and yMin 2000, the axis stays 0–1,200. The value is stored and saved, but has no effect on screen.

     gridcraft/crates/chart/src/axis.rs

     Line 145 in 67217f7

     if max <= min {

   • The Format pane's Minimum, Maximum and Major unit boxes strip every comma before parsing. In a decimal-comma setting, 0,5 becomes 5.

     gridcraft/crates/ui-egui/src/panes.rs

     Line 250 in 67217f7

     let t = typed.trim().replace(',', "");

   • The pane's new labels ("Axes", "Vertical axis", "Secondary vertical axis", "Minimum:", "Major unit:", "Secondary axis", …) are not passed through the translation tables. This is minor.
   • The XLSX reader change "every series of a combo keeps its group's type" is already on main (08902d9, fix(xlsx): combination-chart import loses the first group's series types #1014). The two versions conflict, and main's loop no longer has the gi variable the PR's lines use.

   Merging: conflicts with main at a1c8454 in crates/chart/src/tests.rs, crates/engine/src/cmd/insert.rs, crates/engine/src/tests.rs, crates/xlsx/src/chart.rs, crates/xlsx/src/chartex.rs, crates/xlsx/src/tests/mod.rs and docs/chart-parity.md. After resolving:

   • main's new XLSX tests (chart_book_names.rs, multilevel_category_roundtrip.rs) need the three new Chart fields;
   • the PR's axis_roundtrip.rs needs main's Series::quartiles.

   It also overlaps with other open chart PRs:

   • Charts: axis direction round-trips and renders mirrored (#1687) #1895 also adds Chart fields and edits the same <c:scaling> writer and reader, so most Chart literals conflict.
   • Charts: automatic value axis leaves 0 out like Excel's #2277 changes the same nice_scale(lo, hi, force_zero) call.
   • Charts: one combo plot-kind function, no dead scale helpers (#1146) #1150 rewrites the same Scale::ticks snapping.
   • Charts: draw every doughnut series as a ring #1827 changes the same chart.set parameter line.
   • Charts: work and memory are bounded by series x points; ranges are clipped before evaluation (#1147) #1155 and Charts: add Pareto charts #1826 touch the same use and pub use lines in render.rs and chart/src/lib.rs (trivial).

   Tests (merged with main, with the additions above): cargo test -p gridcraft-chart 42 passed. -p gridcraft-model: 23 passed. -p gridcraft-xlsx: 254 passed, including the new axis_roundtrip tests. -p gridcraft-engine --lib: 391 passed. -p gridcraft-ui-egui --lib: 151 passed. cargo clippy -p gridcraft-chart -p gridcraft-xlsx -p gridcraft-engine -p gridcraft-model -p gridcraft-ui-egui --all-targets -- -D warnings and cargo fmt --all -- --check are clean. Not run: the ui-egui integration tests.