Atom label settings

Screen-space labels are opt-in and avoid displayed atoms and other labels. This is the exhaustive option table — for the narrative, see the dedicated Atom Labels section: activating labels, how placement works (the concepts behind the placement, repair, callout, and performance knobs below), and labels in the widget.

Option	Type	Default	Description
atomLabels.show	String or Array	"none"	none, all, non-hydrogen, or an array of atom selectors/specifications.
atomLabels.placementMode	String	"auto-omit"	auto-omit adaptively uses quality placement for ordinary visible workloads and performance placement for dense ones; quality-omit forces exact candidate evaluation with repair; performance-omit forces front-to-back, zoom-specific no-space reuse without repair; maximum-coverage searches farther and adds callouts. Omission modes reject confusing crossings.
atomLabels.text	Object	{}	Optional display-text overrides keyed by base label or symmetry-qualified atom ID.
atomLabels.fontSize	Number	14	Canvas text font size in CSS pixels.
atomLabels.fontWeight	Number	500	Canvas text font weight.
atomLabels.fontFamily	String	"system-ui, -apple-system, sans-serif"	Canvas text font family.
atomLabels.colorMode	String	"uniform"	uniform uses atomLabels.color; atom uses each atom's element colour.
atomLabels.color	Color	"#111111"	Label text colour in uniform colour mode.
atomLabels.atomColorLuminanceCeiling	Number	0.25	In atom colour mode, the element palette is scaled so its brightest colour reaches this relative-luminance ceiling without clustering colours there.
atomLabels.atomColorLuminanceFloor	Number|null	null	When set (0–1), replaces the ceiling: in atom colour mode the palette is mixed towards white so its darkest element colour reaches this relative luminance — keeps labels readable on dark backgrounds. See the default dark theme.
atomLabels.haloColor	Color	"#ffffff"	Contrast halo colour behind label text.
atomLabels.haloWidth	Number	2	Contrast halo width in CSS pixels.
atomLabels.leaderLines	String	"auto"	Controls when leader lines from a label to its atom are drawn.
atomLabels.leaderColor	Color	"rgba(17, 17, 17, 0.55)"	Leader-line colour.
atomLabels.leaderWidth	Number	1	Leader-line width in CSS pixels.
atomLabels.atomPadding	Number	3	Collision clearance around atoms in CSS pixels.
atomLabels.bondPadding	Number	2	Collision clearance around bonds in CSS pixels.
atomLabels.labelPadding	Number	2	Collision clearance between labels in CSS pixels.
atomLabels.viewportPadding	Number	4	Collision clearance to the viewport edges in CSS pixels.
atomLabels.fallbackDistance	Number	18	Farther fallback spacing when close placements are unavailable, in CSS pixels.
atomLabels.maxConnectorLength	Number	Infinity	Hard connector-length ceiling in CSS pixels. Labels which cannot fit within the ceiling are omitted rather than drawn with extreme connectors.
atomLabels.ringPenalty	Number	1000	Candidate scoring penalty for interference with ADP rings.
atomLabels.movementPenalty	Number	80	Candidate scoring penalty for movement between successive layouts.
atomLabels.repairDepth	Number	2	Maximum depth of displacement repair before a label is omitted or given a distant callout. Set to 0 to disable repair.
atomLabels.repairSearchLimit	Number	48	Maximum candidate evaluations during displacement repair. Set to 0 to disable repair.
atomLabels.autoPerformanceLabelThreshold	Number	500	Visible requested-label count above which auto-omit selects performance placement. Because this uses the current projection, zooming may switch policy.
atomLabels.performanceNoSpaceCellSize	Number	24	Screen-space tile size used by performance placement. Larger tiles reuse more front-atom no-space results but may omit more deeper labels. Tiles are rebuilt after zoom or other camera changes.
atomLabels.spatialCellSize	Number	64	Uniform screen-space collision-index cell size in CSS pixels.
atomLabels.useWorker	Boolean	true	Runs collision placement in a Web Worker after the structure's first paint. Unsupported or failed workers fall back to the main thread.
atomLabels.showLoadingIndicator	Boolean	true	Shows an accessible progress status when asynchronous layout exceeds the configured delay.
atomLabels.loadingIndicatorDelayMs	Number	120	Delay in milliseconds before the loading indicator appears.
atomLabels.layoutThrottleMs	Number	32	Minimum time between relayouts during interaction, in milliseconds.
atomLabels.interactionLabelLimit	Number	300	Label count above which relayout is deferred until interaction ends.
atomLabels.hideLabelsDuringDeferredLayout	Boolean	true	Hides stale labels while a deferred layout is recomputed after dragging, avoiding after-images.
atomLabels.calloutPlacement	String	"structure"	structure keeps maximum-coverage callouts just outside the projected structure; viewport uses the full viewport edges.
atomLabels.calloutGap	Number	12	Compact structure clearance for callouts in CSS pixels.
atomLabels.maximumCoverageDistanceSteps	Number	6	Number of local radial distance bands searched in maximum-coverage mode before callouts. More bands give repair additional moderate placements at added worker cost.
atomLabels.calloutColumns	Number	3	Callout lane count used by maximum-coverage placement.
atomLabels.calloutColumnGap	Number	8	Horizontal spacing between callout lanes in CSS pixels.
atomLabels.calloutRowGap	Number	4	Vertical spacing between callout rows in CSS pixels.
atomLabels.calloutSearchLimit	Number	64	Maximum callout candidates examined per label.
atomLabels.calloutChoiceLimit	Number	4	Maximum callout candidates retained per label.
atomLabels.leaderBondCrossingPenalty	Number	25	Candidate-score penalty for a leader line crossing a displayed bond.
atomLabels.maxVisible	Number	Infinity	Maximum labels attempted; excess labels are reported as hidden.