Style value types

Every style property accepts several value forms. This page documents each one.

Literal

A fixed value applied to all elements.

{ color: "#e22653", size: 10, label: "Hello" }

Attribute binding

Reads a value from the element’s graphology attributes.

{ color: { attribute: "color", defaultValue: "#666" } }

Field	Type	Required	Description
attribute	string	Yes	Graphology attribute name to read
defaultValue	T	No	Fallback if attribute is missing

Categorical binding

Maps discrete attribute values to outputs via a dictionary.

{
  color: {
    attribute: "community",
    dict: { science: "#e22653", art: "#277da1", tech: "#666" },
    defaultValue: "#ccc",
  },
}

Field	Type	Required	Description
attribute	string	Yes	Attribute name to read
dict	Record<string, T>	Yes	Mapping from attribute values to outputs
defaultValue	T	No	Fallback if attribute value is not in dict

Numerical binding

Maps a numeric attribute to a min/max output range.

{
  size: {
    attribute: "degree",
    min: 3,
    max: 20,
    minValue: 0,
    maxValue: 100,
    easing: "quadraticOut",
  },
}

Field	Type	Required	Description
attribute	string	Yes	Numeric attribute to read
min	number	No	Output minimum
max	number	No	Output maximum
minValue	number	No	Input minimum (values below are clamped)
maxValue	number	No	Input maximum (values above are clamped)
defaultValue	number	No	Fallback if the attribute is missing.
easing	Easing	No	Interpolation curve (see below)

Easing functions

Named: "linear", "quadraticIn", "quadraticOut", "quadraticInOut", "cubicIn", "cubicOut", "cubicInOut", "exponentialIn", "exponentialOut", "exponentialInOut"

Custom easing: any (t: number) => number function where t goes from 0 to 1.

Function

Full control via a callback. Receives the element’s attributes, state, graph state, and the graph instance.

{
  color: (attributes, state, graphState, graph) => {
    return state.isHovered ? "#e22653" : attributes.color;
  },
}

Signature: (attributes: A, state: S, graphState: GS, graph: AbstractGraph) => T

Note

Sigma does static analysis on the styles declaration, to identify dependencies between items, attributes and state fields. Using these custom functions instead prevents this static analysis, and will cause styles to be reevaluated much more often.

In performance oriented applications that handle large graphs, you should try as much as possible to avoid those.

Inline conditional

A concise conditional within a single property.

{
  size: {
    whenState: "isHovered",
    then: 15,
    else: { attribute: "size", defaultValue: 10 },
  },
}

Field	Type	Required	Description
whenState / whenData / when	predicate	Yes	Condition to test (see Predicates below)
then	GraphicValue<T>	Yes	Value when condition is true
else	GraphicValue<T>	No	Value when condition is false

Rule-level conditionals

When you need to change multiple properties based on the same condition, use a rule-level conditional instead of inline conditionals on each property:

styles: {
  nodes: [
    { color: { attribute: "color" }, size: { attribute: "size" } },
    {
      whenState: "isHovered",
      then: { size: 15, labelVisibility: "visible" },
    },
  ],
}

Rules are evaluated in order. Later rules override earlier ones for any properties they set.

Rule-level match

When you need to apply different styles based on a categorical attribute (e.g. node type, edge kind), use a matchData/cases rule. It selects a style block based on the value of a graph attribute:

styles: {
  edges: [
    { color: "#ccc", size: 1 },
    {
      matchData: "type",
      cases: {
        citation: { color: "#0f0", head: "arrow" },
        coauthorship: { color: "#f00", size: 3 },
      },
    },
  ],
}

Field	Type	Required	Description
matchData	string	Yes	Attribute name to read from the element
cases	Record<string, StyleProperties>	Yes	Mapping from attribute values to style blocks

If the attribute value doesn’t match any case, the rule is skipped. Attribute values are coerced to strings for lookup (so a numeric attribute 2 matches the key "2").

Unlike function-based when predicates, matchData/cases only reads graph attributes, so sigma can skip re-evaluation when only the interaction state changes (e.g. hovering). This makes it the preferred approach for attribute-based branching on large graphs.

There is also matchState for branching on a custom state field. It takes a single state key (matchState: "status") and looks up the value of that field in cases. It’s intended for categorical values you add via the state generics (the built-in state flags are booleans and are better expressed with whenState).

Predicates

Predicates drive whenState/whenData/when (inline and rule-level conditionals) and the match* rule variants.

whenState matches against element state flags:

Form	Example	Matches when
String	"isHovered"	The named state flag is true
Array	["isHovered", "isActive"]	ALL named flags are true (AND)
Object	{ isHovered: true, isActive: false }	All specified values match

whenData matches against graph attributes (same forms, but for attribute names/values). Re-evaluated only when graph data changes, not on interaction state changes.

when takes a function for full control:

Form	Example	Matches when
Function	(attrs, state, graphState, graph) => ...	The function returns true

Note

As stated above for style functions, using the when function predicates prevents static analysis, and will negatively impact performances.

matchData / matchState branch to a case block by attribute or state value:

Form	Example	Picks the case where
matchData	{ matchData: "type", cases: { a: {...}, b: {...} } }	attributes[type] matches the case key
matchState	{ matchState: "status", cases: { ok: {...}, ko: {...} } }	state[status] matches the case key

Case keys are strings, and attribute/state values are coerced to strings for lookup. If no case matches, the rule is skipped.