Schema view lockup from per-type Cytoscape style selectors in useGraphStyles

[kmcginnes]

Symptom

With very large label sets (repro: ~10k node labels + ~10k edge labels), the schema view pins the main thread and never renders — even after the icon fan-out fix (#2103). A performance trace attributes 87.6% self-time to Cytoscape's style engine (getPropertiesDiff + getContextStyle); the layout is never reached (0.3 ms).

Root cause

createGraphStyles (useGraphStyles.ts) emits one selector per type — node[type="…"] and edge[type="…"] — so ~20k style contexts. Cytoscape resolves each element's style by scanning all contexts, making style application O(elements × contexts) ≈ 4×10⁸. Compounding it, useManageStyles's effect is keyed on a styles object with fresh identity every render, so the multi-second recompute can re-fire and never settle.

Evidence

Headless benchmark, per-type selectors vs. a single data() mapper rule, forcing per-element resolution:

n (each of node + edge types)	contexts	resolve
1,000	2,002	437 ms
3,000	6,002	3,622 ms
10,000	20,002	~100 min
10,000 (data-mapper)	2	324 ms

Fix

Two independently shippable phases:

1. Stabilize the effect — memoize the styles object identity so useManageStyles applies once instead of re-firing the recompute.
2. Data-mapper conversion — precompute each element's resolved style values onto ele.data() (ge_*) at the element-enrichment seam and emit one node rule + one edge rule using data(...), mirroring the existing node[__iconUrl] mapper. Contexts drop ~20k → ~2; cy.style() becomes O(elements). Extends Push node background-color to Cytoscape ele.data() with styled type atoms #1725 (which validates the architecture for background-color) to all per-type properties.

Per-element logic that must move out of the style loop into precompute: the isDark() label text-color pick, the line-dash-pattern/lineStyle remap, and shape coercion (ADR 20260710-coerce-retired-round-polygon-shapes).

Regression guard: assert style-context count stays O(1) regardless of type count.

Related

Umbrella #2091 · caused-with #2103 · architecture #1725 · epic #1677 · spike #1797

Important

Internal only — this issue is maintained by the core team and is not accepting external contributions.