Mojo struct 🡭

StepStyle

@memory_only
struct StepStyle

Where the vertical riser sits between two consecutive samples of a Mark.LINE plot, set via Plot.mark_line(step=...) or line(step=...).

A straight segment between two samples says the value moved gradually from one to the other. Plenty of series never do that: a price that ticks, a count that increments, a state machine, a survival curve, a histogram outline. Drawing those with straight interpolation asserts intermediate values that were never measured, which is a statement about the data rather than a style choice – hence a mark-level setting rather than something on Theme, which holds what a theme is allowed to restyle.

The three non-NONE styles draw exactly the same plateaus and the same risers; they differ only in which x a riser is drawn at, which is the one thing the data itself cannot tell you. That ambiguity is why they are named rather than left to a Bool: “held since the last reading” (POST), “held until this reading” (PRE) and “changed somewhere in between” (MID) are three different claims about when the value changed, and only the caller knows which one is true.

Mutually exclusive with Theme.line_smoothing: a smoothed staircase rounds off the corners that carry the whole meaning, and the risers – two points at the same x – would pick up horizontal Catmull-Rom tangents and bow sideways. Asking for both raises at render time (_check_step_smoothing, validate.mojo) rather than silently winning one way or the other.

Aliases

• NONE = StepStyle(Int(0)): Straight interpolation between consecutive samples – the default, and what every line drew before this setting existed.
• PRE = StepStyle(Int(1)): The riser sits at the earlier sample’s x: the interval (x[i - 1], x[i]] is drawn at y[i]. Read as “the value had already reached y[i] by the time x[i] was reached” – the right choice when a reading reports what happened over the interval leading up to it.
• MID = StepStyle(Int(2)): The riser sits halfway between the two samples. Read as “the value changed somewhere between these two readings, and we do not know where” – the honest choice for regular sampling with no reason to attribute the change to either endpoint, and the one that keeps the drawn plateau centered on its own sample.
• POST = StepStyle(Int(3)): The riser sits at the later sample’s x: the interval [x[i], x[i + 1]) is drawn at y[i]. Read as “the value held at y[i] from x[i] until it changed” – the usual choice for a price, a counter, or any quantity that stays put between events.

Implemented traits

AnyType, Copyable, Deinitable, ImplicitlyCopyable, Movable

Methods

__init__

fn def __init__(out self, value: Int)

Prefer the NONE/PRE/MID/POST comptime constants over constructing one directly.

Args:

• value (Int): 0 for NONE, 1 for PRE, 2 for MID, 3 for POST.
• self (Self)

Returns:

Self

__eq__

fn def __eq__(self, other: Self) -> Bool

Args:

• self (Self)
• other (Self)

Returns:

Bool

__ne__

fn def __ne__(self, other: Self) -> Bool

Args:

• self (Self)
• other (Self)

Returns:

Bool

name

fn def name(self) -> String

This style’s constant name, for error messages that have to say which one was asked for.

Args:

• self (Self)

Returns:

String: “NONE”, “PRE”, “MID”, “POST”, or “StepStyle()” for a value outside the four constants.