[jowr]

Addresses #39: three optional additions to property diagrams, and one changed default.

Summary

Critical and triple points (diagram.marked_points = ("critical", "triple"))

• A dot in the colour and casing of the saturation curve; it follows set_line_style("saturation", ...).
• "triple" marks both ends of the saturation curve at the triple temperature (saturated liquid and vapour).
• A point is drawn only inside the chart's T-p box. The default region "DEF" starts 1 % above the triple point, so the triple point needs tp_limits=[None, None, None, None]. When a point is drawn, the axes widen by 1.5 % of the span so the dot is not cut off at the frame.
• Mixtures and pseudo-pure blends (R407C) mark the critical point only.
• The dots draw at z 3.5: above the dome and the single lines of Highlighting single isolines #32 (z 3.0), below the labels.

Saturation scale (diagram.saturation_scale = True, or {"step": 10, "Q": 0})

• A scale just inside the frame, right of the vertical axis: saturation temperatures next to a pressure axis (p-h, p-s, p-rho), saturation pressures next to a temperature axis (T-s, T-rho). The h-s and p-T charts have none; asking for one raises an error that says why.
• Ticks sit on round values in the chart's units, up to the critical point: a given step, or chosen by the chart (1-2-5 per decade for pressures).
• Q picks the dew point (the default) or the bubble point of a blend.
• Values that would overlap are left out, from the top down.
• It uses the colour, width and length of the axis ticks. Isoline labels, the legend and the badge keep clear of it, and it never changes the axes.

Labels inside the dome (settings.with_(labels={"dome": True}))

• Two more labels on each labelled isotherm (isobar on a T-s chart): one just right of the bubble line, one just left of the dew line. They come on top of the labels of the label mode, which do not change.
• They sit on the chord between the bubble and dew states and turn with it, so on a blend they follow the slope the glide gives the isotherms.
• They keep clear of the other labels, the legend, the badge, the scale and cycles. A label that does not fit is left out; near the critical point that leaves one label of a line, then none.

Changed default: versions in the badge

• BrandingSettings.versions is now True, so the badge of a new chart also says "CoolProp x, CoolPlot y".
• Specs saved since 1.2 hold "versions": false and keep their badge as it was.
• A chart without badge now takes {"references": "none", "versions": False}; "references": "none" alone leaves the versions line. The upgrade guide has a 1.5 to 1.6 section on this.

How it is built

• The engine computes the states that need CoolProp (the marked points, the scale ticks, the bubble and dew ends) together with the domain, and caches them per fluid.
• The composer only places items. It uses existing scene item types (Markers, Line, Text), so no renderer needed a change.
• coolplot-core 1.6 composes the same scenes from the new optional "points", "scale" and "dome" keys of the compose record. The bridge refuses these features for an older core, so the Python composer draws them, with a warning.
• The new spec fields (marked_points, saturation_scale, labels.dome) are written to the record only when set, so records of 1.5 read and draw as before.
• Master is merged in (single lines Highlighting single isolines #32, phase diagram examples Add phase diagram examples for CO2 and water #42, CI CI: test branches through their pull request, not on every push too #44). Both sides add to DiagramSpec, the composer and coolplot-core 1.6.

Tests

• New modules: tests/test_marked_points.py, tests/test_saturation_scale.py, tests/test_dome_labels.py. tests/test_native_core.py compares the Python composer with the C++ port for each feature and checks that an older core is refused.
• C++: 9 new golden cases generated by make_data.py (compose_rails_*marked_points*, *scale*, *dome_labels*). After the merge of Highlighting single isolines #32, 53 C++ test cases pass, and the JS SVG writer check reports all files identical.
• Full suite on the merge of Highlighting single isolines #32: 615 passed with the Python composer, 675 passed through coolplot-core with CoreFallbackWarning as an error. CI was green there, including core and docs.
• Parity sweep (not committed): 429 charts, with all three features on, single lines, cycles, four label modes, three plot sizes and three theme/unit combinations, composed by Python and by coolplot-core, also with previous labels. 426 match exactly. The other 3 fail the same way on master without these features: an inline-mode label with a zero direction on a blend T-rho chart. That is left to a separate fix.
• After the merge of Add phase diagram examples for CO2 and water #42 and CI: test branches through their pull request, not on every push too #44 (only CHANGELOG.md conflicted): the phase diagram examples pass both ways, the feature, branding and port tests pass through coolplot-core (120), and mypy is clean. CI is running on that head.

Docs: how_to/isolines.md (marked points, saturation scale), how_to/labels.md (labels inside the dome), how_to/branding.md, upgrade.md, reference/contracts.md, CHANGELOG.md.

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Files ignored due to path filters: 7

• cpp/tests/data/compose_rails_blend_ph_bubble_scale.svg is excluded by !**/*.svg
• cpp/tests/data/compose_rails_blend_ph_dome_labels_edge.svg is excluded by !**/*.svg
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• cpp/tests/data/compose_rails_water_ts_saturation_scale.svg is excluded by !**/*.svg

Files selected for processing: 37

• CHANGELOG.md
• cpp/include/coolplot/compose.h
• cpp/include/coolplot/layout.h
• cpp/include/coolplot/spec.h
• cpp/src/compose.cpp
• cpp/src/layout.cpp
• cpp/src/spec.cpp
• cpp/tests/data/compose_rails_blend_ph_bubble_scale.json
• cpp/tests/data/compose_rails_blend_ph_dome_labels_edge.json
• cpp/tests/data/compose_rails_r290_ph_dome_labels.json
• cpp/tests/data/compose_rails_r290_ph_saturation_scale.json
• cpp/tests/data/compose_rails_water_ts_dome_labels.json
• cpp/tests/data/compose_rails_water_ts_marked_points.json
• cpp/tests/data/compose_rails_water_ts_saturation_scale.json
• cpp/tests/data/make_data.py
• cpp/tests/test_compose.cpp
• docs/how_to/branding.md
• docs/how_to/isolines.md
• docs/how_to/labels.md
• docs/reference/contracts.md
• docs/upgrade.md
• src/coolplot/compose/builder.py
• src/coolplot/compose/layout.py
• src/coolplot/corelib.py
• src/coolplot/diagram.py
• src/coolplot/engine/engine.py
• src/coolplot/engine/planning.py
• src/coolplot/spec/__init__.py
• src/coolplot/spec/diagram.py
• src/coolplot/spec/settings.py
• src/coolplot/thermo/provider.py
• tests/test_api_vocabulary.py
• tests/test_branding.py
• tests/test_dome_labels.py
• tests/test_marked_points.py
• tests/test_native_core.py
• tests/test_saturation_scale.py

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