Charts: one combo plot-kind rule; Scale::ticks keeps ticks off the step grid #1146

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1. vangel76 commented on Oct 13, 2026

   

   vangel76

   on Oct 13, 2026

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   I'm working on this.
2. iluebbe commented on Oct 23, 2026

   

   iluebbe

   on Oct 23, 2026

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   #1150 checked

   Fixes it. Resolving and drawing now share one combo plot-kind rule, the dead fixed_scale helper is gone, and a scale whose minimum is off the step grid keeps its own ticks.

   Setup: PR head 5cf0e24, merged locally into main at a1c8454, Windows 11. Checked with the chart crate tests and by reading the diff. The PR has since merged main at a1c8454 itself (7f8ac83); that merge was not rebuilt.

   • All three points of the issue are still present on main (render.rs has its own plot_kind, axis.rs has fixed_scale, Scale::ticks snaps every tick to the step grid).
   • Scale { min: 3, max: 7, step: 4 }: main gives ticks 4 and 8, the PR gives 3 and 7. Aligned scales (0 to 1 by 0.1) still snap float error away.
   • drawing_and_resolving_agree_on_the_combo_plot_kind covers every chart kind × every series kind (or none) × series 0..3.
   • The only behaviour change is the one the PR names: a hand-built ChartData with a Combo series kind in a combo chart. resolve never produces that.

   Problems: none found.

   Merging: the checked head conflicted with main at a1c8454 only in crates/chart/src/tests.rs and ROADMAP.md, where both sides append; the updated head 7f8ac83 merges without conflicts. It also overlaps with other open chart PRs:

   • Charts: series on the secondary axis, fixed axis bounds and units, secondary axis title (#1267) #1290 changes the same snapping lines in Scale::ticks for its fixed bounds. That is the same fix done a second way, so whichever lands second should keep only one version.
   • Charts: automatic value axis leaves 0 out like Excel's #2277 still imports fixed_scale, which this PR removes.
   • Charts: work and memory are bounded by series x points; ranges are clipped before evaluation (#1147) #1155 edits the same use crate::axis::… line in render.rs.

   Tests: both new tests pass. cargo test -p gridcraft-chart passes (41, merged with main). cargo clippy -p gridcraft-chart --all-targets -- -D warnings and cargo fmt --all -- --check are clean.