Creates a new treemap trace.
The MAIDR layer carrying the nodes
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 ReadonlylayerProtected ReadonlysupportsThe go-to-extrema dialog -- the list of named targets a trace offers
under g -- which a tree has none of. Every node is already one step
from its parent and its siblings, and the largest leaf is named in the
description.
It has to be false rather than merely unimplemented. getExtremaTargets
defaults to [] while the toggle command gates only on this flag, so a
true here switches the reader into the GO_TO_EXTREMA scope, renders an
empty dialog, and leaves the arrow keys answering to a keymap that is no
longer the tree's -- a keyboard trap whose only exit is a binding the
help menu does not list. navigateToExtrema throws in the same case.
Unrelated to moveToExtreme, the Ctrl+arrow jump out to the branch root
or in to the deepest descendant: that runs through the movable and is
unaffected by this flag.
Protected ReadonlymovableProtected ReadonlyhighlighthighlightValues[row][col], or null for the whole trace when it
highlights nothing.
A single cell may also be null, meaning the chart drew no element
there. That is a narrower claim than the trace-wide null: the rest of
the grid still highlights, and only this position falls back to the
out-of-bounds state. A Google Charts calendar is the case it exists for
-- its first and last columns are ragged, so a handful of grid positions
have no rect at all while every other day does (#1174).
ProtectedxThe x axis's name, falling back to a generic one the layer authored none.
A getter rather than a field set in the constructor: the fallback is a translated word, and a trace outlives a language change — a name resolved once at construction would keep the language the chart was built in.
ProtectedyThe y axis's name, or a generic one. See xAxis.
ProtectedzThe z axis's name, or a generic one. See xAxis.
ProtectedisWhether 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
Gets the current state of the trace including audio, braille, text, and highlight information.
The current TraceState
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.
ProtectedhighlightProtectedautoplayProtectedhasHow this layer names itself in the description dialog's layer tabs.
The producer's name when there is one, and the chart-type label
otherwise — the same fallback order TextService.layerIdentity uses for
the spoken layer-switch announcement, so a tab and the announcement single
out the same layer by the same name. The two differ only in register: the
announcement says "point plot" where the dialog says "Scatter Plot",
because that written form is what the dialog's own Chart Type line has
always shown and a tab sitting above it should agree with it.
A plain-language introduction to this layer's chart type, for the description dialog. See chartGuide.
Which way this chart is drawn, or undefined for a type that has no orientation to speak of.
Entering the chart already announces it -- "This is a maidr plot of type: horizontal bar" -- but the description dialog said only "Chart Type: Bar Chart", and for the box, violin and boxen families the orientation also silently reverses the order of the rows in the table underneath, because their constructors reverse the groups when the chart is horizontal. A reader comparing the table with what they walked had no way to know why the two disagreed.
Exposed here, and read once by the description service, rather than pushed
as a stat by each of the thirty-odd traces that has one. Named apart from
the bar and distribution families' own orientation fields, which hold the
declared* value and default it to vertical for every type -- including the
ones that have no orientation at all.
horizontal or vertical, or undefined when the type has no
orientation to report.
The 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.
ProtectedvaluesProtectedaudioProtectedbrailleProtectedtextProtecteddimensionRuns action with this element's observers muted.
A cursor move normally is the announcement -- moveToIndex notifies, and
everything downstream of it speaks, brailles and highlights. That is wrong
for a move the reader did not make and is not waiting to hear: the
description dialog's layer tabs relocate the reader in the chart while the
modal is open, and the trace's announcement would land in the same live
region the dialog is using, so one of the two is dropped. The caller
announces afterwards, once, when the reader is back on the chart.
Nesting is safe and the flag is restored on every path, including a throw, because a flag left raised would silence the chart for good.
The moves to make in silence
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.
Base implementation of navigation in HIGHER and LOWER modes of ROTOR, default is no-op Needs to be implemented in Line, Bar, Heatmap, Candlestick
Utility function to compare point values for rotor functionality
boolean value
ProtectedcompareRotor compare search along one row of numeric values.
Steps from the current column in the given direction and moves to the first value that satisfies the comparison; reports the rotor boundary when nothing further qualifies. For the traces whose values are a plain numeric grid indexed [row][col]; a trace with a richer layout (the bar's orientation-normalised rows, the candlestick's segments) keeps its own.
The values of the row being searched
Which way to search
Whether a lower or a higher value is sought
True when a matching value was found and moved to
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").
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.
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, carrying only the axes the layer actually authored a label for. Subclasses should call this instead of constructing the axes object inline so charts without a real z dimension don't surface the placeholder default.
Every axis is gated, not just z. xAxis and yAxis fall back to the
literal 'X' and 'Y' when the JSON authors no label -- legal, and
common in adapter-generated specs -- and the dialog rendered that as
"X: X", a line that says nothing twice. The figure-level branch of the
description already showed only authored labels
(DescriptionService.getFigureAxes), so gating here is what makes
the two levels of the same dialog follow one rule.
Blankness is tested with trim(), the same rule named applies
when it decides whether to substitute the fallback in the first place. A
whitespace-only z label is truthy but blank, so the untrimmed guard used
to pass it through and then print the 'Level' placeholder the guard
existed to keep out.
Get available extrema targets for the current navigation context
Array of extrema targets that can be navigated to Default implementation returns empty array (no extrema support)
Base implementation for navigateToExtrema Subclasses must override to provide actual implementation
The extrema target to navigate to
ProtectedfinalizeCommon post-navigation cleanup that should be called by subclasses after they update their internal state
Returns true if this trace supports intersection navigation mode. Opt-in per trace type: override to return true (possibly conditionally, e.g. based on data shape) for trace types that expose point intersections between series. Intersection navigation is a trace-level capability — it has no meaning at the figure or subplot level, which is why it lives on AbstractTrace rather than AbstractPlot.
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.
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.
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.
ProtectedupdateDefault implementation for updating visual point position Subclasses can override if they need custom positioning logic
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
Moves to a specific X value in the trace.
The X value to navigate to
True if the move was successful, false otherwise
Whether a mark of this trace sits at exactly this X, as moveToXValue finds one before it falls back to the nearest.
A layer switch asks this to choose between the two X values a position
can offer (see Trace.getAlternateXValue). Reads the x of each point;
a trace that keeps its X some other way answers false unless it says
otherwise, and the switch then carries what it always carried.
The X a layer switch would carry
True when some point's x is exactly xValue
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
Offers a walk along the whole level, across parents.
The arrow keys stay the tree: left and right are siblings, and a step past the last child of a parent is refused rather than landing in a cousin's subtree unannounced. That is the right default and it is what makes this a hierarchy rather than a grid -- but it is not the only reading anyone wants. An icicle is drawn as depth-ordered bands, a whole row of blocks per level, and "everything at this depth, in layout order" is a question that reading asks directly.
So the band goes on the rotor rather than on the arrows. One data model with two different arrow semantics, chosen by which layout the producer happened to pick, would be worse for a reader who meets both than one semantics plus an explicit mode.
Withheld on a level of one, where it could only ever answer "none found".
The level unit alongside whatever else is offered
Moves within an active rotor filter unit along the filtered axis.
Called by RotorNavigationService when the current rotor mode is
one of this trace's getRotorFilterUnits. Filter units navigate a
single axis, so only left/right are dispatched here — the service
announces up/down as unavailable without calling the model (matching
intersection mode). Implementations should move to the nearest point
matching the unit identified by key and notify observers, returning
true; when no such point exists they should call notifyRotorBounds
and return false.
Default is a no-op that reports bounds, so a trace advertising a filter unit but forgetting to implement movement fails safe (announces "no point found") rather than moving unexpectedly.
True if the cursor moved, false otherwise
Protectedfind
Trace implementation for treemaps and any other hierarchy laid out as area.
A treemap encodes a tree as nested rectangles whose area is a magnitude. Every other trace in MAIDR is a flat grid, and a tree read as one loses the only thing the chart is drawn to show: a list of thirty leaves says nothing about which three of them make up most of Europe.
The tree navigates as a tree, on the arrow keys that already exist. Up returns to the parent, down enters the first child, left and right walk the siblings -- the file-manager interaction, which is the one a reader already has. No new command, no new keybinding: a node's address is
(depth, index-at-that-depth), and MovableGraph already navigates an arbitrary graph over such addresses. Siblings are linked to each other and nothing else, so left and right stay inside one parent; a cousin is reached by going up, across and back down, which is what the tree structure means.This is a chart a non-visual reading can do better than a visual one. A sighted reader compares areas by eye and is poor at it -- that is the standing criticism of the form. A reader given the tree is told each node's exact share of its parent, which is the comparison the rectangles are drawn to support and the one the eye estimates worst.
The hierarchy is declared as a path, never as a parent pointer. A path is acyclic by construction and cannot be orphaned: a node whose ancestors are named is placed, and there is no id to dangle. Producers all have it -- a
d3.hierarchywalk yields it directly, and Plotly'slabels/parentspair resolves to it -- and it is also the breadcrumb, so the reader is told where they are out of the same field that put them there.Interior nodes need not be declared. A layer that emits only its leaves -- which is what a treemap draws -- gets its interior nodes and their totals derived. A layer that declares them keeps the declared numbers, since a parent may carry mass of its own that no child accounts for, and a total that disagrees with the sum of its children is a fact about the data rather than an error to correct.