Creates a new step trace instance.
The MAIDR layer containing step plot data
Protected ReadonlyobserversProtectedisProtectedisTrue while AbstractTrace.getStateAt computes state at a temporarily moved cursor. Enforces (structurally, not just by documentation) that state getters never notify observers.
Protected ReadonlyidProtected ReadonlytypeProtected ReadonlytitleProtected ReadonlynameWhat this layer is, when the producer named it. See MaidrLayer.name.
Protected ReadonlyxProtected ReadonlyyProtected ReadonlyzProtected ReadonlynavigationProtected ReadonlylayerProtected ReadonlysupportsAbstract property that subclasses must implement to indicate extrema support
Protected ReadonlyrotorProtected ReadonlymovableProtected ReadonlypointsProtected ReadonlylineProtected ReadonlyhighlightProtectedhighlightProtected ReadonlyminProtected ReadonlymaxProtectedisWhether the cursor has no point to report.
Read from dimension rather than from any one trace's data,
because that is the one shape every trace already answers in. It is also
evaluated at the cursor — LineTrace returns the current series'
length as cols — so this covers a ragged layer, where one series has
points and another has none, and not only a layer that is empty
throughout.
True when there is nothing at (row, col) to describe
ProtectedoutThe state pushed to observers when navigation leaves the data.
Declared as TraceEmptyState rather than the whole TraceState union
because that is what every implementation actually returns — the accessor
exists so AbstractPlot.notifyOutOfBounds has an empty state to
push. Narrowing it here is what lets the braille and highlight callers
hand the value straight on: those states accept the empty trace shape but
not a populated one, so a wider declaration would force each of them to
cast, and a cast is exactly what stops the compiler from noticing if an
override ever starts returning a populated state.
The empty trace state, positioned for out-of-bounds audio panning.
ProtectedhighlightProtectedautoplayProtectedhasThe trace's chart type. Lightweight alternative to reading
state.traceType, which eagerly computes the full audio/braille/text/
highlight state just to expose this one string.
ProtectedvaluesProtectedgroupWhat this chart calls one of its series, when the layer names no z axis.
Overridable for the reason LineTrace.seriesLabels is: a subclass navigates the same grid but draws something else, and this label is announced literally beside the series' own name. A chart that named its own noun everywhere else and then said "Group is Honda Civic" -- or "Group is Ash" -- would use two words for one referent in a single sentence.
The fallback label
ProtectedseriesWhat this chart calls its series and its samples, in the description.
A subclass navigates the same grid but draws something else, and the description dialog renders these labels literally -- so a radar inheriting "Number of lines" tells a reader they are on a chart they are not, which is the same problem the spoken plot type is overridden to avoid.
Defaulted to the line's own wording, so nothing changes for the chart this class is named after.
The four labels the description uses
ProtectedaudioProtectedbrailleProtectedtextProtecteddimensionAnnounces this trace as a step plot in the instruction text, layer-switch cue and subplot entry cue, rather than falling back to the raw layer type.
The trace state with plotType set to 'step'
Describes the step chart in terms of its runs rather than its points: how many times the level changes, which levels occur, and how long the longest unbroken run is. That is the shape of the data a step chart encodes, and it is what the point-by-point data table cannot show at a glance.
The description state containing chart metadata and data table
ProtectedgetGets safe row and column indices to prevent accessing undefined values
Object with safe row and column indices
Registers an observer to receive state updates.
The observer to add
Removes an observer from receiving state updates.
The observer to remove
Notifies all registered observers with the current state.
Notifies observers that an out-of-bounds condition occurred.
Utility function to compare point values for rotor functionality
boolean value
Returns true if this trace supports compare (lower/higher value) navigation. Override to false for trace types that don't use compare modes (e.g., scatter, which is all we currently have).
Returns the display name for the default data navigation mode. Override to provide a trace-specific name (e.g., "ROW AND COLUMN NAVIGATION" for scatter).
Returns the rotor's compare-mode labels and boundary-message nouns. Override to rename the two compare units for a trace-specific semantic (e.g., the candlestick delta layer uses "above line" / "below line").
Get all highlight SVG elements for this trace Used by HighlightService for high contrast mode
Array of all SVG elements, or empty array if none
Get all original (visible) SVG elements for this trace. These are the actual rendered elements, not the hidden clones used for highlighting. Used by HighlightService for high contrast mode color changes.
Array of all original SVG elements, or empty array if none
ProtectedgetComputes the trace state at an arbitrary position without moving the user's cursor or notifying observers. Used by monitor mode to sonify and announce a newly appended point while the user stays put.
The state getters read this.row/this.col internally, so the cursor
is moved temporarily and always restored in a finally block — this
method is the single owner of that pattern.
Re-entrancy hazard: this is only safe because the entire call chain is synchronous (no await points), so timers (e.g. autoplay ticks) cannot interleave before the finally-restore, and state getters never notify observers. If a getter ever becomes async or triggers notifications, callers could observe the temporary cursor.
The row of the position to compute state for
The column of the position to compute state for
The trace state at the requested position
Resets the trace to initial entry state
ProtectedgetReturns a human-readable label for this trace's chart type (e.g., 'Bar Chart', 'Scatter Plot') for display in the description modal. Falls back to the raw layer type if no mapping is registered.
ProtectedgetBuilds the axes object for the description state, including z only when the layer explicitly provides a z-axis label. Subclasses should call this instead of constructing the axes object inline so charts without a real z dimension don't surface the placeholder default.
ProtectedfinalizeCommon post-navigation cleanup that should be called by subclasses after they update their internal state
Returns true if this trace supports point-by-point navigation mode. Opt-in per trace type: override to return true for traces that expose individual data points navigable in reading order (left/right) and column-major order (up/down). Currently only ScatterTrace.
Notifies the trace that the rotor is entering or leaving INTERSECTION_MODE. Default is a no-op; line-style traces don't need to track mode state because their state output is unchanged by the rotor mode. Traces whose audio/text output differs in intersection mode (e.g. ScatterTrace, which normally plays the whole x-column as a chord and must instead focus a single point) override this to flip an internal flag.
True when entering intersection mode, false when leaving.
Checks if this plot supports extrema navigation.
True if extrema navigation is supported
Base implementation for getting current X value Subclasses can override if they have different data structures
Gets the unique identifier for this trace.
The trace ID
Moves the active point to the pointer location and returns directional guidance toward the nearest data geometry in a single call.
Combining both operations avoids running findNearestPoint twice per
pointermove event — important on dense plots where the scan is the
hot path.
Screen-space x position of the pointer/finger
Screen-space y position of the pointer/finger
Guidance state relative to nearest point, or null when unavailable
ProtectedmoveMoves the trace to the nearest point when the pointer is within its bounds and the trace is not already focused on that point.
onCurve is intentionally non-optional: the caller has already paid
the cost of isPointInBounds to assemble guidance state, and
forcing subclasses to accept the value makes the contract explicit so a
future override cannot silently recompute (or worse, ignore) it.
Subclasses override this to customise hover-driven navigation:
Checks if the specified coordinates are within bounds of the element.
The x-coordinate
The y-coordinate
Object containing the SVG element and its position
True if the point is in bounds, false otherwise
ProtectedauthoredName a line carries in the spec, or undefined when the data authors
none. Consumers that have nothing meaningful to say without a real name
(e.g. the position announcement) can then stay silent about groups.
Protected for the same reason LineTrace.groupNameAt is: a subclass
that names its series from its own data -- a contour from its level --
still has to answer for a series the layer named and nothing else did, and
calling groupNameAt for that would recurse.
ProtectedgroupHuman-readable name of a single line: the authored name when the spec provides one, otherwise a positional fallback ("Line 2").
Protected rather than private because a subclass naming a series in its
own description -- which competitor led, which observation is an outlier
-- has to name it the way every other announcement does, and reaching for
points[row][0].z directly would skip the fallback and report
undefined for an unnamed series.
Gets the line series with human-readable labels. Used by the candlestick delta feature to list reference-line candidates (e.g., moving averages).
One entry per series with its label and points
Cleans up trace resources including values and highlighted SVG elements.
Only removes elements MAIDR created (hidden clones, synthetic markers); traces that highlight the chart's original live elements in place (e.g. heatmap cells, line dots) merely drop their references so the visible chart geometry survives focusout and live-data rebuilds.
ProtectedpanningWhere a cell sits in the stereo field.
Split out because two places need it and they must agree: the tone for the cursor's own point, and the tones of every series a chord sounds at an intersection. A subclass that hears its columns somewhere other than a straight left-to-right sweep -- a radar's spokes go out and back around a circle -- overrides this one method and both follow, rather than one of them keeping the line's sweep and contradicting the other.
The series index
The column index
The panning for that cell
ProtectedmapOptionalselectors: string[]ProtectedmapGet extrema targets for the current line plot Returns min, max values, and intersection points within the current group
Array of extrema targets for navigation
Navigate to a specific extrema target
The extrema target to navigate to
ProtectedupdateUpdate the visual position of the current point This method should be called when navigation changes
Move the line plot to the position that matches the given X value
The X value to move to
true if the position was found and set, false otherwise
Base implementation of navigation in HIGHER and LOWER modes of ROTOR, default is no-op Needs to be implemented in Line, Bar, Heatmap, Candlestick
Intersection navigation mode is available only when the plot has
multiple lines. points is a 2-D array whose outer dimension is the line
index, so length > 1 means at least two lines exist — a prerequisite for
any crossing between sampled series to be possible.
Move to the next point intersection (right arrow in intersection rotor mode). Default is a no-op returning false; subclasses that advertise supportsIntersectionMode must override to provide real behavior.
Move to the previous point intersection (left arrow in intersection rotor mode). Default is a no-op returning false; subclasses that advertise supportsIntersectionMode must override to provide real behavior.
ProtectedreconcileMaps the vertices of a rendered step path back onto the data points.
A step chart is drawn with the corner vertices the steps introduce, so the
rendered path carries more vertices than the series has points — matplotlib
emits 2N - 1 for hv/vh and 2N for mid. The inherited
reconciliation drops the surplus from the end, which would place every
highlight on the first half of the chart. Here the surplus is interleaved
rather than trailing, so it is removed by stride instead:
2N - 1 vertices (hv/vh): the even-indexed vertices are exactly the
data points; the odd-indexed ones are the corners.2N vertices (mid): each data point owns a horizontal pair. The
first and last runs are half-width — steps-mid starts at x[0] and
ends at x[N-1] rather than at a midpoint — so those two samples sit at
the outer end of their run and are read off directly. An interior run
spans midpoint to midpoint, and its centre is the sample only when the
spacing either side is equal: in general the centre is
(x[i-1] + 2x[i] + x[i+1]) / 4, off by a quarter of the local second
difference. The highlight therefore always lands inside the sample's own
run — never on a neighbour's — but on an irregularly sampled mid chart
it is not exactly on the sample. Recovering x[i] exactly would mean
iterating x[i+1] = 2m[i] - x[i] from one end, which is numerically
unstable over a long series; a bounded sub-run offset is the better
trade.Any other count is left to the inherited handling — a library that simplifies collinear vertices (a long flat run in a hypnogram is exactly that) produces neither shape, and interpolating along the surviving segments is the right recovery there.
Vertices parsed from the path, mutated in place
Index of the series these coordinates belong to
Offers a "Transitions" rotor mode whenever the current series actually changes level. Point-by-point navigation across a long step chart — a whole night of sleep epochs, say — is unusable; jumping between the moments the level changes is the navigation this chart type calls for.
The transition rotor unit, or none when the series never changes
Jumps to the previous or next point at which the level changes, staying within the current series.
The RotorFilterUnit.key of the active unit
The direction to search
True if the cursor moved, false when no further transition exists
Trace implementation for step (stairs) charts, where the value is piecewise constant: it is held across an interval and then jumps, rather than being interpolated between samples as a line chart implies.
Everything numeric is inherited from LineTrace unchanged. In particular the audio stays one discrete tone per point, which is already the right sonification for piecewise-constant data — a run of equal levels sounds as a repeated pitch, and a transition is an audible jump. The continuous glissando that
SmoothTraceuses would interpolate between levels, which is exactly what a step chart does not do.What this class adds is what a step chart has that a line chart does not: navigation by transition rather than by sample, and a description written in terms of runs. Announcing an ordinal level by name ("REM" rather than "3") used to live here too, but a line or path over the same ordinal y needs it just as much, so
LineTracereads the point'slabeland this class inherits that unchanged.