Changelog

All notable changes to Visualize are recorded here, following Keep a Changelog and Semantic Versioning.

Note. This file is written for a consumer of the library, so it says what changed in the surface and in behaviour, not what changed in the repository. What the library is, module by module, lives in spec/, which is the source of truth for that and is not restated here.

0.4.0 — 2026-10-12

One units vocabulary for every host: UCUM coverage with aliases, 25 quantities with their facts, exact conversion, currency, and unit systems (system: :us) chosen per viewer at render, with axis ticks picked in the unit shown. A feed schema's unit and quantity are now checked against it.

Breaking

• B, kB, MB, pt and kt are now valid UCUM codes (#590, D-155). They are the bel, the kilobel, the megabel, the picotonne and the kilotonne, as UCUM defines them. Affects code that relied on Visualize.Unit.parse/1 refusing them. Before: Unit.parse("B") was {:error, {:unknown_atom, "B"}}. After: it reads as the bel. Instead: read a person's input with Visualize.Unit.parse_alias/1. It reads B as By and refuses MB and pt as ambiguous.
• Visualize.Unit.factor/1 answers {n, d, k} for a code that holds the degree (#590, D-155). The value is n/d·πᵏ. Every other code still answers {n, d}, or nil.
• Visualize.Data.Schema.new/1 checks a field's unit and quantity (#595, D-157). Affects feeds whose schema names a unit visualize does not read, a quantity outside Visualize.Quantity.all/0, or a unit that does not measure its quantity. Before: any non-empty string was a unit and any atom a quantity. After: such a schema is refused with {:unit, code, reason} at [field, :unit], {:unknown_quantity, q} at [field, :quantity], or {:quantity, q, code} at [field, :quantity], each worded by format_error/1. A symbol such as "KB" or "°C" is refused too. Instead: describe a field with a UCUM code; read a person's symbol with Visualize.Unit.parse_alias/1 first.
• Some units now imply a quantity, and some display families have grown (#591, D-155). Affects designs and code that read Visualize.Quantity.of_unit/1, resolve/1, family/2 or an axis's measure.
  • g, m2, l, deg, V and the other units of the new quantities now imply that quantity. They used to imply nil. A measure pairing one of them with :count is still refused, as before.
  • Lengths now scale through cm: a domain of 0–0.5 m is shown in cm, not mm.
  • Information and data rates now scale up to TBy, TiBy and Tbit, so a domain of 1,500 GBy is shown in TB.
  • A unit outside its quantity's families is no longer rescaled. It is shown as it is given: mbar, [nmi_i], m/s, K and W.s.
  • Visualize.Quantity.base_unit(:currency) is nil, because the currency comes from the data.
  • Visualize.Data.Schema.attributes/0 lists twelve keys, with :metric_kind and :bounds at the end.
• Visualize.Unit.convert/3 now converts between unit systems, and words its refusals (#592, D-155). Before: convert(20, "Cel", "[degF]") raised that conversion was out of scope. After: it is 68.0. Different dimensions, levels against linear units, and two currencies still raise ArgumentError, and the message now gives the reason. Instead: to check without raising, call Visualize.Unit.conversion/2.
• An axis shown in another unit ticks at round numbers in that unit (#594, D-156). Affects every axis with a measure whose display unit is not the data's unit, such as seconds shown in minutes. Before: the ticks were round in the data's unit, so 0–100 s read 0.166667 min, 0.333333 min, …. After: the ticks are round in the display unit, 0 min, 0.2 min, … 1.6 min, placed at 0, 12, … 96 s. The labels and the tick positions both change, and the grid follows them. Instead: to keep ticks in the data's unit, give the axis an explicit format or explicit tick values.

Added

Units

• Wider UCUM coverage (#590, D-155). Visualize.Unit now reads these codes, each with UCUM's own definition:
  • SI and derived units: l, L, t, ar (har, the hectare), V, A, C, lx, mol, bar, deg and rad.
  • US and imperial units: [in_i], [ft_i], [yd_i], [mi_i], [nmi_i], [kn_i], [acr_us], [oz_av], [lb_av], [stone_av], [foz_us], [pt_us], [gal_us], [foz_br], [pt_br], [gal_br], [psi], mm[Hg], [in_i'Hg] and [HP].
  • Calories and ratios: cal, [Cal] (the food Calorie), [ppm] and [ppb].
  • The logarithmic bel, B, dB and dB[SPL]. Each kind of level has a dimension of its own, so a decibel converts to a bel and never to a linear unit.
  • The prefixes c, d, h, da, T, Ti and p, as in cm, dl, hPa, TBy and TiBy.
• Visualize.Unit.parse_alias/1 reads the symbols people type, such as °C, lb, mph, inHg and kWh, as codes. It refuses an ambiguous symbol and names the codes it could mean. KB could be kBy (1,000 bytes) or KiBy (1,024 bytes), and gal could be [gal_us] or [gal_br]. Visualize.Unit.format_error/1 words a refusal for a person.
• Visualize.Unit.kind/1 says whether a code is :linear, :affine (Cel, [degF]) or :logarithmic (B, dB[SPL]).
• Visualize.Unit.conversion/2 (#592, D-155) converts between any two codes of one dimension. It returns an exact {:ok, {scale, offset}}, where the converted value is value × scale + offset. One such pair converts stored rows in place.
  • Cel, [degF] and K convert with their offsets: Cel to [degF] is exactly {{9, 5}, {32, 1}}.
  • B converts to dB, but a level never converts to a linear unit.
  • Two currencies never convert.
  • Every refusal names its reason: :dimension, :logarithmic, :currency or :affine_in_term.

Quantities

• Thirteen new quantities (#591, D-155): area, volume, mass, pace, angle, currency, electric_potential, electric_current, electric_charge, illuminance, sound_level (dB[SPL]), mass_concentration and amount_concentration.
• The facts a host needs, for every quantity.
  • Visualize.Quantity.kind/1 is :linear, :affine, :logarithmic or :cyclic.
  • bounds/1 and bounds/2 give where values physically lie. They are a hint for an axis, never a check, so a negative difference is never refused.
  • additivity/1,2 gives %{across: …, over_time: …}, refined by the field's metric kind.
• Unit systems (:metric, :us, :uk, :as_posted).
  • Visualize.Quantity.display_unit/3 and formatter/3 take system: and show a quantity in that system's family: 80 kg in lb for :us, and in stones for :uk.
  • family/3 gives a system's family.
  • :as_posted, the default, is the existing behaviour.
• Two new optional description keys in Visualize.Data.Schema.
  • metric_kind is :gauge, :counter or :rate.
  • bounds is [min, max]. It overrides the quantity's bounds and is a display hint.
• The feed conformance kit names a field whose measure is refused (#595, D-157). The :describe check reports {:measure, field, reason} for each field whose unit or quantity Visualize.Data.Schema.new/1 refuses, apart from {:schema_invalid, errors}.

Currency and value formats

• Currency as a marked extension to UCUM (#593, D-155).
  • {iso4217:USD} is a currency. Each code of the fixed ISO 4217 table has its own dimension, with its minor units.
  • Two currencies never convert, and an unknown code is refused as {:unknown_currency, code}.
  • Codes compose. Write an energy price as {iso4217:EUR}/kW/h: UCUM's / is left-associative, so {iso4217:EUR}/kW.h means euro-hours per kilowatt.
  • Visualize.Unit.currency/1 gives a unit's currency and minor_units/1 its decimals.
  • parse_alias/1 reads USD, € and £, and names the choices for $ and ¥.
  • Caveat: any other UCUM reader sees every {iso4217:…} code as the dimensionless 1.
• Visualize.Format.currency/2 takes code: and locale:. The code's minor units set the decimals, and the locale gives the symbol or else the code: $1,240.00, ¥1,240, 1,240.00 CHF. Currency axes write money with one SI prefix for the whole axis: $1.5k.
• Visualize.Format.duration/2 with style: :compound writes 1h 24m and 840ms for labels and tooltips. Axes keep a single scaled unit.
• Visualize.Quantity.format/3 formats one value of a measure for a label or a tooltip: a compound duration, money in its code, a grouped count, or fixed decimals with the unit. It writes what metresis's views wrote, apart from the differences the parity test names.
• An angle's ° sits against its number: 350°. A temperature keeps its space: 20 °C.

Axes in another unit

• system: shows a chart in the viewer's unit system (#594, D-156). Visualize.Chart.apply/2 and compile/2 take system: (:metric, :us, :uk or :as_posted, the default). Every axis with a measure is then shown in that system: 0–40 kg under :us reads 0 lb … 80 lb. The system is the viewer's choice, so a design never stores one. Boards pass it through: Visualize.Board.realise/4, Visualize.Board.Server (to every cell), Visualize.Board.Snapshot.views/2 and the board exports take system: too. A value outside the four raises ArgumentError.
• Visualize.Quantity.ticks/3 gives the ticks of an axis whose display unit differs from its data's unit. The ticks are round numbers in the display unit, converted back into the data's unit for placement. Visualize.Quantity.formatter/3 labels each one with its round number.

0.3.0 — 2026-10-12

Upgrading from 0.2.35. Visualize grows from a chart library into a dashboard library. Feeds describe their fields by meaning, and a design states what it needs of them. A board lays designs on a grid, runs them live under supervision, exports and prints them, and carries them between hosts. Themes carry meaning as ramps and roles, so a status reads the same on every theme, and every chart is named, described, reachable from the keyboard and calm under reduced motion. The imperative pipeline is unchanged, but some designs draw differently: axes derive their own ticks and formats, sequential colour scales follow the theme, and a chart's accessible markup changes, so read Breaking before you upgrade.

Breaking

• A design from a newer release is refused as {:newer_schema, needs, this} (#550, #541, D-137). Affects code that matched the error for a newer document from Visualize.Chart.from_map/1, from_map!/1, from_json/1 or Visualize.Chart.Migration.migrate/1. Before: {:error, [{[:version], {:unsupported_version, 3}}]}. After: {:error, [{[:version], {:newer_schema, 3, 2}}]}, worded version: needs schema v3, this is v2, and the refusal comes before any other key is read. {:unsupported_version, v} now means a version below 1 only. Instead: match {:newer_schema, _, _} where you matched {:unsupported_version, v} for a newer version.

• Every design reader applies sanity limits (#550, #541, D-137). Affects a design with more than 100,000 entries in one list or map, nesting deeper than 64, more than 1,000 axis ticks, more than 10,000 force iterations, or a count over 1,000,000. Before: it read. After: from_map/1, from_map!/1, from_json/1 and Fragment.from_json/1 refuse it with {path, {:limit, name, max, given}}. No gallery design comes near a limit. Instead: pass limits: [items: 500_000] (or whichever limit you need) to from_map/2, from_json/2 or Fragment.from_json/2.

• An axis with no format or tick count derives them (#532, D-134). Affects every design axis that gives neither. Before: ten ticks, and the scale's default label (2024-03-05 03:00:00Z on a time axis, 90000 on a number axis). After: the count comes from the axis's length (one tick per 80 px across, per 35 px down, between 2 and

  10. and the format from the domain: 03:00 or Mar 05, 90,000, 1.5M. Instead:
  • set ticks: 10 to keep ten ticks on an axis shorter than 800 px across or 350 px down;
  • set format: "d" on a numeric axis over years, which now reads 1,990 where it read 1990;
  • check an axis with unit: "M" over values from 1,000, which now reads 1,200M, and give it a format.

  An explicit format, count or list of values still wins. The hand-built Visualize.Axis is unchanged.

• A :sequential or :diverging colour scale left at range: :auto draws the theme's ramp (#533, D-135). Affects heatmaps, contours, hexbins, radial bars and any design with such a scale and no range. Before: a sequential scale ran from the theme's background to its first series colour in RGB (white → #3b6fa8 on the light theme), and a diverging one from the second series colour through the background to the first. After: it reads the theme's sequential or diverging ramp, Lab-interpolated: close on the light theme, the dark theme's own ramp on the dark one. Instead: to keep the old colours, give the range, for example range: ["#ffffff", "#3b6fa8"].

• Visualize.Color.to_lab/1 is the inverse of Visualize.Color.lab/4 (D-135). It used the D65 sRGB matrix against the D50 white point. Affects every Lab and LCh value of a chromatic colour, and so brighter/2, darker/2, interpolate_lab/3 and interpolate_hcl/3. Before: a grey had a chroma of about 12, and #808080 came back from a Lab round trip as #758194. After: #808080 comes back as #808080. Instead: nothing to call differently, but colours you stored or asserted from these functions change.

• A mark's renamed colour scale reaches the colours its style binds (#565, D-143). The 0.2.35 spec said a style's {:field, f} colour read the frame's color scale "whatever the mark's scales say". Affects a mark with scales: %{color: name} and a {:field, f} fill or stroke in its style. Before: the style read the frame's color scale. After: it reads name, as the mark's series channel already did. Instead: to colour the style through the frame's color scale, don't rename color on that mark.

• A chart's accessible markup changes (#557, D-142). Affects tests or CSS that match the root <svg>'s ARIA attributes, and pages that rely on a design with no meta.name rendering unnamed.

  • Before: aria-labelledby="<title-id> <desc-id>". After: aria-labelledby="<title-id>" and aria-describedby="<desc-id>". This applies to Visualize.IR.Element.root/3 and every component.
  • Visualize.Chart.render/2 and generate/2 with root: true now title a design with no meta.name by its kind (Line chart), and write a generated summary after meta.description in the <desc>. Instead: to keep 0.2.35's root, pass summary: false and your own title:.
  • A component with animate gains the class vis-animated and a <style> beside its <desc>.

Added

Charts and axes

• Visualize.Format.Auto (#532, D-134): tick formats derived from a scale's domain. time_format/2 picks a Visualize.Format.time/2 specifier from a time domain's span and the interval its ticks use: %H:%M within a day, %a %H:%M or %a %d within a week, %b %d within 92 days, and %b %Y (or %Y) beyond. notation/2 reads a numeric domain's magnitude: :plain below 1,000, :grouped below a million, and {:si, 6} and up beyond. number/2 turns a notation into a formatter (90,000; 0.5M, 1M, 1.5M, one prefix for the whole axis). formatter/2 does both for a realised scale. Every function takes locale:, which is "en" by default and the only locale for now; another raises.
• Visualize.Axis.tick_count/2 (#532): the tick count an axis of a given length asks for, one per 80 px across or per 35 px down, between 2 and 10.
• Units by UCUM code: Visualize.Unit (#536, D-138). parse/1 and valid?/1 check a UCUM code (ms, kBy, MiBy, %, Cel, kW.h, {request}/s) against a fixed table of prefixes and atoms, and refuse typos such as sec or kmin with a reason. symbol/2 writes a code for a reader (B/s, µs, °C, kW·h). convert/3 scales a value between codes of one dimension (1,500 ms is 1.5 s) and refuses °C to °F, which is out of scope. from_telemetry/1 maps a Telemetry.Metrics unit (:millisecond, :kilobyte, {:native, :millisecond}) to its code, without depending on telemetry_metrics.
• Quantities and display scaling: Visualize.Quantity (#536, D-138). A fixed list of twelve quantities (:duration, :information, :data_rate, :frequency, :ratio, :count, :temperature, :length, :speed, :power, :energy, :pressure), each with a base unit and a family to scale in. display_unit/2 picks the unit that fits a domain. formatter/3 writes a scale's ticks in it with its symbol (0.5 s, 1 s, 1.5 s for 0–1,500 ms). label/1 is the axis-label rule: the unit, else the quantity, else nothing. Information scales in decimal units (kB, MB) unless your unit is binary (MiBy) or in bits, which keep their own family.
• An axis measure (#536, D-138): measure: %{unit: "ms", quantity: :duration} (either key alone is enough) says what the axis's values are. With no format, a numeric axis's ticks are scaled into the unit that fits and carry its symbol. When the ticks cannot say the unit (a count, an explicit format), the axis draws a title by the label rule unless you anchor your own label there. The validator refuses a code it cannot read and a unit that does not measure its quantity. The existing unit key is unchanged: it is still a literal suffix.
• Overlays are marks (#565, D-143). What a host drew around a chart (event markers, thresholds, the brush) is now part of the design, so every host that applies it draws the same overlays on SVG, the canvas, the binary stream and the hybrid page.
  • A :rule at y in a cartesian frame is a horizontal rule across the plot, labelled at its left end: a threshold (channels: %{y: :value} over a source of thresholds) or a feed's target (y: fact(:primary, :latency, :target) over take(1) of the feed).
  • A colour scale's range may be a map of colours on an :ordinal scale, pinning each category by name: range: %{"info" => :info, "critical" => :bad}, or a feed's own meaning, range: fact(:events, :severity, :status). A category the map does not name draws the theme's neutral :axis colour. In JSON it is a "$colours" list of pairs.
  • polarity on a colour scale over a ramp (:higher_is_better, :lower_is_better, :neutral, or fact(:primary, :latency, :polarity)) places the ramp's good end at the better end of the domain. With kind: :threshold, domain: [fact(…, :target)] and range: {:ramp, :status}, a reading beyond the feed's target is :bad whichever way the feed says is better.
  • A variable or a fact may stand for one member of a domain list, as the threshold above does.
  • interaction: %{brush: :x}: the design's own brush. The chart writes its plot area and its x mapping (Visualize.Chart.Frame.brush_attrs/1), and BrushHook on a container around it pushes brush_select with "domain" => [lo, hi] (milliseconds for a time x). Your handler reads the window and needs no margins and no scale to invert. The element's own data-brush-type and data-brush-extent still win.
• Sanity limits on every design reader (#550, #541, D-137): Visualize.Chart.from_map/2, from_map!/2, from_json/2 and Visualize.Chart.Fragment.from_json/2 take limits: [depth: …, items: …, ticks: …, iterations: …, counts: …]. The defaults (Visualize.Chart.Limits.defaults/0) are nesting 64, 100,000 entries in one list or map, 1,000 axis ticks, 10,000 force iterations, and 1,000,000 for bins, samples, n, width and a grid's dimensions. A host reading designs or boards from elsewhere tightens them. A value over a limit is {path, {:limit, name, max, given}}, worded by Validator.format/1 as frames.main.axes[0].ticks: asks for 5000 ticks; the limit ticks is 1000. From JSON, the nesting and sizes are checked before the document is decoded, so an oversized document makes no atoms. Visualize.Chart.Limits.check/2 gives the verdict on a map without reading it. See spec/14 §9.2.
• Visualize.Chart.Migration.readable/1: the version gate alone, for a reader that holds a version before it holds a design.

Themes

• Themes carry meaning: four ramps and five roles (#533, D-135). A Visualize.Theme now has ramps, each a list of anchor colours interpolated in CIE Lab: status (good → caution → bad), thermal (cold → neutral → hot), diverging (below → at → above a midpoint) and sequential (less → more). It also has the roles :good, :warning and :bad (the status ramp at 0, 0.5 and 1), :info and :neutral. A design colours by meaning with a role (fill: :bad) or a ramp position (fill: {:ramp, :thermal, 0.8}), wherever a colour is accepted, and every theme renders it in its own tones. Visualize.Theme.ramp/3 reads a position. Roles are slots, so stylesheet/1 declares --vis-good and the rest.
• Ramp and role contracts are checked when a theme is built. Theme.new/1, Theme.merge/2 and an inline design theme refuse a ramp whose hues are out of order, whose lightness is not monotonic, or whose midpoint is not neutral. The ArgumentError names the theme, the ramp and what is broken. Theme.check/1 returns the same answer without raising, and the validator reports it as {:contract, message}. The tolerances are in spec/08 §7.5. Visualize.Theme.violations/1 (#563) lists every broken ramp and role, where check/1 gives the first.
• Visualize.Theme.colour_safe/0 (theme: :colour_safe): the light theme with its status ramp blue → orange → red, so status reads under the commonest colour-vision deficiencies. Theme.builtin/1 resolves the built-in names.
• Colour scales range over a theme ramp. range: {:ramp, :status} on an ordinal colour scale spreads its domain end to end (three states draw as :good, :warning, :bad). On a threshold scale it spreads its buckets, and on a sequential or diverging scale it interpolates the ramp. JSON writes a ramp as {"$ramp": "status"} and a position as {"$ramp": ["status", 0.5]}.
• A theme is a stored, versioned value (#561, D-139). Visualize.Chart.Theme writes a theme as a document: to_map/1 is %{version: 2, theme: node}, and to_json/1 the stamped {"$version": 2, "theme": {…}}. from_map/2 and from_json/2 read one back to a %Visualize.Theme{} under the same rules as a design. A newer theme is refused by name before a key is read, limits: bound it, an older one migrates, and a broken ramp or role is the validator's {:contract, message} at its path. A document that only names a theme that is not built-in is the new fault {:unknown_theme, name}.
• Colour-vision simulation (#563): Visualize.Color.Vision.simulate/2 shows a colour as a person with protanopia, deuteranopia or tritanopia sees it (Machado, Oliveira and Fernandes 2009, severity 1.0, in linear sRGB). recolour/2 applies it to every colour literal of an SVG.
• Visualize.Theme.print/0 (theme: :print, #578, D-150): white with dark ink and the colour-safe status ramp, for paper.

Data and feeds

• A feed can describe its fields: Visualize.Data.Schema (#551, D-136). new/1 takes a map from field name to a description of what the field means: type (required), unit, quantity, label, order, status (a state to a role such as :good, :warning or :bad), polarity, target, continuity and window (#586). attributes/0 lists the ten keys. A schema never names a colour: color, colors, palette, fill and the like are refused, because a theme chooses colour from the meaning. Each schema has a version, a SHA-256 content hash that is the same on every node and under every release, so a version can cross a wire.

• A :time field holds instants, and a feed names its window field (#585, #586, D-154). A :time field's values are DateTime, NaiveDateTime or Date (or ISO 8601 strings, for a field that is not the window field). A count, tick, sequence number or offset is :number. A feed's windows are over its window field:

  • the field described window: true, which may be :time or :number (%{tick: %{type: :number, window: true}}), else the schema's one :time field;
  • with more than one :time field, mark the one your windows are over window: true, and window: false makes a schema's only :time field not the window field;
  • a numeric field your rows are ordered by, or that continuity is measured along, is the window field too;
  • Schema.new/1 reports window on a :category or :text field ({:invalid_for, type}), a value that is not a boolean ({:type, :boolean}), and two window: true fields ({:duplicate_window, other}).

  Visualize.Feed.window_field/1 returns the window field and window_type/1 its type. Visualize.Feed.Window.applies?/2 says whether a window's bounds are of a window field's kind, and instant?/1 whether a value is an instant. A feed stamped with DateTimes that has one :time field, as Visualize.Feed.Telemetry is, needs nothing more.

• Visualize.Data.Schema.Cache: schemas held by {feed, version} as a plain value you keep in your own state. resolve/4 answers a cached version without calling anything, and calls the describe function you give it once for a version it has not seen.

• %Visualize.Data.Delivery{}: one answer of a feed, holding its rows, the window served, the resolution, capped, reduced_by and the schema version (never the schema). Visualize.Data.Table.rows/1 reads it, so it goes wherever a source goes: Visualize.Chart.apply/2's pool and a compiled chart's tick/3, step/3, render/2 and svg/2.

• A design can require and read its feed's schema (#552, D-136). A source slot can state requires: %{latency: [:unit, :label]}, the attributes its feed's schema must describe. Visualize.Chart.fact(:primary, :latency, :label) reads one of them anywhere a value goes, and inside a text as #{fact(:primary, :latency, :unit)}. So an axis title can come from the field's label and unit, and an ordinal domain from its order. Visualize.Chart.apply/2 takes the schema cache as schemas: and a describe: function, and resolves the schema each delivery names. It fails with the slot, the field and the missing attribute named ({:missing_attribute, slot, field, key}) instead of drawing a blank label. The applied chart returns schemas, versions and the grown cache. Visualize.Chart.contract/1 lists what a design requires, for a picker.

• A bound field's type is checked against its scale (#584, #582, #586, D-153, D-154). Each field a mark reads through a scale is checked against what the scale's kind needs: a time scale needs :time, band and ordinal need :category (or :text), and every other kind needs :number. A mismatch is the fault {:type_mismatch, slot, field, expected, given}, at the channel, style or offset that reads the field. A :time field read through a linear, log, power, sqrt, symlog or other numeric scale is {:type_mismatch, slot, field, :number, :time}.

  • Visualize.Chart.apply/2 reports it wherever a schema is bound. A slot with no contract has its delivery's schema resolved for the check, and a schema it cannot resolve is no fault. Rows with no schema still raise from the frame, as before.
  • The pure checks are Visualize.Chart.check_types/2 and Visualize.Board.Binding.check_types/3. Each takes a schema or a plain map of types, such as Visualize.Data.Table.column_types/1 reads from rows.

• Visualize.Chart.Compiled.stale?/2: whether a delivery names a schema version other than the one the chart was compiled with. A schema change needs a recompile, as a resize does: tick/3, step/3, render/2 and svg/2 raise ArgumentError for a stale delivery, so compile again and carry/2 the state across.

• The feed behaviour: Visualize.Feed (#537, D-140). A feed is a struct whose module implements describe/1 ({version, schema, supports}, where supports is any of [:window, :budget, :push]) and fetch(feed, window, budget) (a %Visualize.Data.Delivery{}), and optionally subscribe/2 and unsubscribe/2. Only rows are required. A window and a budget are requests. When your feed does not honour them, Visualize.Feed.finish/3 trims to the window along the window field and reduces to the budget with LTTB or M4, one series per category value and every number field's peaks kept, and records reduced_by: :visualize. It never reduces the window field itself. A push feed sends {:visualize_feed, ref, {:schema, version, schema}} before {:visualize_feed, ref, {:delivery, delivery}}, where each delivery holds the rows new since the last. A version the subscriber does not hold is asked of describe once. Callbacks answer {:error, reason} and never raise.

• Visualize.Feed.Monitor: the loop over your feeds, as a value you keep in your process's state (a LiveView, or a board). Call tick/2 each frame and handle_message/2 from handle_info/2. It describes and subscribes your feeds, polls pull feeds every every: ms, buffers pushes until the next tick and merges them once, and deduplicates a push that overlaps a fetch. Pass deliveries/1 and cache/1 to Visualize.Chart.apply/2 as sources: and schemas:. status/1 reports each feed as :loading, :live, :stale (with stale_after:) or {:down, reason}, and the last delivery is still handed out while a feed is down. window/2 moves the window: a push feed is fetched again only for older data. Each feed is asked for the window that applies to it: a feed over ticks under a window of instants is asked for its own span (nil), and is neither trimmed nor refetched as that window moves. The monitor keeps each holding in time order and keeps a late pushed row instead of dropping it (#574), and Monitor.refetch/1 asks every feed again.

• Visualize.Feed.Combine: one slot over several feeds, freshest first, for example the last hour from :telemetry and older data from a history store. Each feed is asked for the part of the window the fresher ones did not serve, and the seams are deduplicated. Every part must describe the same schema version, and the window may be over instants or numbers. describe/1 answers {:error, :combine_window_field} when the shared schema has no window field.

• Visualize.Feed.Signals: a Visualize.Signals signal as a pull feed, honouring a window of ticks, with a fixed tick (at/2) or a clock (every:). It describes its tick as %{type: :number, window: true, label: "Tick"}, so bind the tick to a linear scale, not a time scale. It comes with Visualize.Signals.rows/3, the rows from one tick to another.

• Visualize.Feed.Telemetry: an in-process :telemetry collector over a list of Telemetry.Metrics definitions. Start it in your supervision tree with {Visualize.Feed.Telemetry, metrics: metrics}. Each metric is a push feed (feeds/1) with rows %{t: DateTime, value: v} plus its tags, and a schema giving the label, the UCUM unit and the quantity. A counter's value is the running count, a sum's the running total.

• A conformance kit for your feeds: Visualize.Feed.Conformance (#538, D-145). Add use Visualize.Feed.Conformance, feed: …, windows: […] to an ExUnit.Case module and it writes six tests:

  • describe answers a valid schema under its content hash, and the same one each time;
  • every delivery is well formed and names that version, its window covers its rows and every row the feed holds there, and capped, reduced_by and resolution are true;
  • the capabilities in supports are honoured, and an undeclared :push is refused;
  • a push feed sends the schema before any delivery naming it (give push:, a function that makes it push);
  • a window the feed cannot read is an error value, never a raise (give down: to check a feed whose provider is gone as well);
  • unsubscribing stops pushes.

  The kit also checks the window field (#586): :no_window_field for a feed that supports :window with no window field, :window_value for a row whose window field is not of its type, and :not_an_instant for a :time value that is not an instant. Visualize.Feed.Conformance.check/2 runs the same checks outside a test and returns the findings as values, [] for a feed that passes. Each callback runs in its own process with you in $callers, so a sandboxed repository works and a raise is reported as a finding. The kit calls no ExUnit function itself, so it compiles in every environment of your app. Visualize.Feed.Signals and Visualize.Feed.Telemetry pass it. The LiveView guide has a new section, Writing a feed.

Boards

• Visualize.Board: a dashboard as data (#539, D-141). A board lays designs out on a 12-column grid (metresis's, so a panel maps to a cell field for field). Each cell is {x, y, w, h} and a {:composite, n} reference to a component in your store, which may be a composite or a flat design. The cells share a UTC window (%{last: seconds} or %{from, to}), a display zone, board vars and a sync group, but never geometry: a board never flattens.

  • Below layout.breakpoint (768 px) the cells stack full width in reading order (arrange/2, boxes/2).
  • Board variables are the defaults of every cell's component variables, and a cell may override one.
  • to_map/from_map and to_json/from_json round-trip a board. The JSON is stamped "$version", and a newer board is refused as {:newer_schema, needs, this} before anything is read. limits: applies, and the defaults apply when it is not given.
  • validate/1 reports off-grid and overlapping cells, a bad window and wrong-kind refs. validate/3, given a store (a fetch function or an id map), adds dangling refs, cycles, components that are not designs, undeclared cell variables, and cells whose component cannot join the board's sync group (set sync: false on those).
  • required_sources/3 lists every slot keyed {cell, slot} with its fields, types, reads and requires contract, so one design in two cells binds to two feeds.
  • realise/4 applies every cell at its box's size, purely. components/3 prepares each cell's component, writing in the board's group and zone (a time scale with no zone takes the board's).
  • The UTC window applies to feeds whose window field is :time. A feed over ticks keeps its own span, and its continuity is in its own units. To put ticks on the board's clock, map them to instants in your connector and describe them as :time.

• Visualize.Board.Binding (#539): which feed fills each {cell, slot}, supplied by your connector and never stored in the board. check/3 reports every unbound slot, every contract a feed's schema cannot meet (with apply/2's reasons), every type mismatch per cell, and every binding to a slot no cell declares. pools/2 builds one pool per cell from your sources.

• A board runs live (#574, D-146). Add {Visualize.Board.Supervisor, name: MyApp.Boards} to your tree and start a board under it with Visualize.Board.Server.start/2, passing board:, store:, binding: and feeds:.

  • The board process owns the window (UTC), the zone, the variables, the sync group and one "now". It drives the feeds through a Visualize.Feed.Monitor. window/2 sets the window and re-asks every feed, and vars/2, resize/2, tick/1, info/1 and stop/1 do what they say.
  • A board that does not validate given its store, or whose binding names a missing feed, is refused before anything starts.
  • Each cell is its own process (Visualize.Board.Cell) under a heap limit (max_heap:, words). A cell that blows its heap or raises shows "Crashed, restarting" and is restarted with a backoff, and the board and the other cells carry on. A slow cell skips to the newest data instead of drawing a backlog.
  • subscribe/1 delivers {:visualize_board, board, {:cell, name, %Visualize.Board.View{}}} straight from each cell: its SVG frame, its drawn state, and the crosshair and keyboard hooks' attributes.

• Every cell state is drawn (#574). Visualize.Board.State decides and draws loading, no data yet, stale, feed down, capped, crashed and wrong binding ({:invalid, errors}, #584) from the board's theme. Each state uses a role colour and its glyph, so it reads in greyscale. Where there is no chart the state fills the whole cell, and over a chart it is a banner. The board gains the key stale_after (seconds). Visualize.Board.Rows.place/2 breaks a line where two readings are further apart than the field's continuity.

• A live board in LiveView (#575, D-146). Render a board with <.live_component module={Visualize.Components.Board} id="ops" server={pid} board={board} />. Add one clause to your page: def handle_info({:visualize_board, _, _} = m, s), do: (Visualize.Components.Board.forward("ops", m); {:noreply, s}). The component subscribes your page to the board when it connects. It lays the cells on the 12-column grid, reflows them below the breakpoint, and shows the window in the board's zone. Each cell is its own LiveComponent (Visualize.Components.Board.Cell), so a frame's diff is that cell's alone. A cell carries data-vis-cell, is one tab stop, and wraps its chart in CrosshairHook, BrushHook and KeyboardHook.

• BoardHook (#575), the twelfth hook in the bundle. It pushes the board's width to its component and moves focus between cells with the arrow keys, Home and End. Enter moves focus into a cell's chart, and Escape (KeyboardHook's) brings it back. Escape also clears a board's selection (#581).

• BrushHook takes data-brush-target (#575). With it set, the brush pushes its events to that LiveComponent instead of the LiveView. On updated() the hook also re-attaches its overlay to a chart the server has redrawn, so a brush keeps working over a live chart.

• A board's cells interact (#581, #545, D-151). The board process holds each interaction as shared state.

  • Brush to window. A brush in any cell sets the window of every cell. The component calls Visualize.Board.Server.brush/2, which waits debounce: milliseconds (250) for the next brush, so a burst of brushes re-asks each feed once. Visualize.Board.Server.reset_window/1 restores the window the board was started with. The component shows a Reset window button while the window is moved, and the board's info reports moved. A cleared brush does not restore the window, because a click on a chart is a cleared brush; Reset window is the undo.
  • Linked selection. A click on a chart, or Enter on a point the keyboard reached, selects {field, value} across the board. The field is the series field, else a :category field of the schema. Every cell whose rows hold the selection dims the other data with opacity 0.25, bound per datum through the style grammar. A cell that does not hold it is drawn unchanged. The board key links: %{name: :service} joins fields of different names. Escape or Clear selection clears it. The functions are Visualize.Board.Server.select/2 and pick/4, and Visualize.Board.link/2 and linked/2.
  • Drill-down. A cell's drill: %{board: ref, vars: %{var => {:datum, field}}} opens another board, or :self, with variables taken from the clicked datum. Visualize.Board.validate/3 and Visualize.Board.Server.start/2 take boards: and refuse a target the host does not hold ({:no_board, ref}) or a variable it does not declare. The component sends your page {:visualize_board_drill, id, %{cell, board, vars}}, and you follow it, for example with push_navigate/2. Visualize.Board.drill/3 resolves a target from a row.

  KeyboardHook gains data-keyboard-pick-event and data-keyboard-target. A board's JSON gains {"$datum": field}.

• A board leaves the screen (#578, D-150). Visualize.Board.Server.snapshot/1 freezes a running board as a Visualize.Board.Snapshot: the board, its now and window, the theme, and each cell's component and the data it showed. Visualize.Board.Snapshot.realise/4 makes one purely, as Visualize.Board.realise/4 does.

  • A snapshot needs no store, feed or process. to_json/1 writes it (stamped "$version", rows column by column), and from_json/2 reads it back under the same version policy and limits as a board.
  • Visualize.Board.Export.svg/2 draws a snapshot as one SVG document: the header with the window in the board's zone, and every cell at its grid box with its title, its state banner, and its chart embedded byte for byte as the cell draws it, or its state's panel when it has no chart. png/2 rasterises that through resvg.
  • For paper, Export.pages/2 lays the board on A4 or Letter, portrait or landscape, never splitting a cell, as one SVG per page. Export.html/2 puts the pages in one HTML document a browser prints as a PDF. Use it with theme: :print.
  • Visualize.Board.window_text/2 writes a window in a zone as the board's header does.

• A board travels to another host in a bundle (#542, D-147). Visualize.Chart.Builder.Bundle.export_board/3 bundles a %Visualize.Board{} with every component its cells reference, the library entries those use, and every stored theme the board or its components name (a theme the design's theme names, read through the cell's variables). import_board/3 checks the whole bundle before it puts anything:

  • a newer schema or board version is refused;
  • limits: bound the board, the entries and the components;
  • a cell whose component the bundle does not carry is {:not_carried, id} at that cell;
  • a carried theme whose name the store already gives a different theme is {:theme_taken, name}.

  It then imports the entries through the store's own import/2 and returns %{board: board, ids: table, outside: ids}, the board's cell refs rewritten to the new ids. Bindings never travel: bind the imported board's required_sources/3 to your own feeds. %Bundle{} gains a board key, nil for a bundle export/3 makes.

• A worked live board (#576). The examples site's /board page is a complete host. It puts Visualize.Board.Supervisor in its tree, starts a board of five cells over Visualize.Feed.Signals and in-process Visualize.Feed.Telemetry feeds, and renders it with Visualize.Components.Board and the one forwarding clause. One component sits in two cells bound to different metrics, and one cell is bound to a feed that is always down, so its drawn state is on the page. Copy it as the starting point for your own board.

Accessibility

• Every chart describes itself (#557, D-142). Visualize.Chart.Summary.new/1 reads an applied chart into a text alternative: its name, its kind (a line chart, a gauge, a treemap…), its series, each axis's range or categories, and the highest and lowest value it draws, each with where it is. text/1 writes it as sentences, values written as their axis writes them (its measure's display unit, prefix and unit) to four significant digits. table/2 is the data-table fallback: an HTML <table> per mark, visually hidden and still read, for a page to place beside the chart. attrs/2 and description/2 name and describe whatever element stands for the chart, such as a canvas or the wrapper of a hybrid chart's layers. Visualize.Chart.render/2 and generate/2 take summary: (true, false, or your own string), and Visualize.IR.Element.root/3 takes hidden: true for aria-hidden.
• A chart's points from the keyboard (#558, D-142). KeyboardHook, the bundle's eleventh hook, makes a chart one tab stop. The arrow keys move between its points and its series, and Home and End go to a series' ends. A polite live region reads each point (y, 3 of 51: x 2, y 54.3), and a ring marks it over the SVG or the canvas. Escape hands focus back to an enclosing data-vis-cell, so a board can navigate its cells around charts. Visualize.Hooks.Keyboard.attrs/1 writes the points once on the server from an applied chart. A series of more than 1,000 points is sampled evenly.
• Reduced motion (#559, D-142). Visualize.Chart.compile/2 takes motion: :reduce, and Compiled.tick/3 and step/3 take motion: per tick. Every scale transition and mark motion is then drawn at its target on the tick it changes, its state kept, so turning motion back on eases on from where the chart stands. ResizeHook now pushes reduced_motion (prefers-reduced-motion: reduce) with every size, and again when the reader changes it, so the page that sizes a chart can compile it to match. A component with animate stops its transition under that media query.
• Status beyond hue (#560, D-142). Every role carries a glyph and a dash besides its hue, fixed by the library in Visualize.Theme.cue/1: :good a circle and solid, :warning a triangle and "6 3", :bad a cross and "2 3", :info a square and "8 3 2 3", :neutral a diamond and "1 4". A {:field, f} binding on a :symbol mark's symbol or on stroke_dasharray reads through the frame's colour scale to the role and draws its cue, so a status chart reads in greyscale. The gallery's Gauge marks its zones with their glyphs.

Builder

• The builder has a theme mode (#562, D-139). Opening a theme entry, New → theme, or the Theme button on a chart's bar puts Visualize.Chart.Builder in the theme mode.
  • The inspector edits the theme's series colours, chrome (background, surface, text, axis, grid) and fonts, and can derive from a built-in or stored theme.
  • The main column is a sheet of sample charts (series, the five roles, thermal, diverging, axes and text) drawn in the theme being edited. You can add designs from the store to it.
  • Save to library keeps the theme and refuses one that is not valid. Store.theme_entry/2 finds the entry a stored theme name stands for.
• The theme mode edits ramps and roles and checks them live (#563, D-139). Each ramp is drawn as the theme interpolates it, with a lightness strip and its anchors (change, add by resampling, remove). The status roles are marked at their fixed positions and set by the colour there, and :info and :neutral are colours of their own. Every edit runs the meaning contracts: a broken ramp or role is outlined and named in the contract's words, and Save to library refuses the theme. The seen with select draws the ramps and the preview sheet under each colour-vision deficiency.
• A host ships a theme through the builder's store (#561). Visualize.Chart.Builder.Store.theme/2 loads a stored theme by the name it gives itself, and the builder's preview draws a design whose theme: names a stored theme in it. Visualize.Chart.Builder.Store.theme_name/1 is the name a stored theme entry answers to. Visualize.Chart.Fragment.read_json/2 is from_json/2 with the version the document was stamped with.
• Build a board in the builder (#579, D-152). A board is a library kind: a store entry %{board: map} holding Visualize.Board.to_map/1, read back with Visualize.Board.from_map/2. Fragment.kinds/0 includes :board, so your store issues {:board, n} ids. Fragment.to_json/1 and from_json/2 round-trip a board, and Bundle.export/3 of a board entry carries its cells' components. A store whose put/2 derives the kind with Fragment.kind/1 needs no change.
  • Opening a board entry, or New → board, puts Visualize.Chart.Builder in its board mode.
  • Drag a cell to place it and drag its edges to resize it. The arrow keys do the same on a focused cell. The server refuses an overlap or a cell off the grid.
  • You can pick each cell's component, title, sync and variables. You can set the board's name, window (none, last N seconds, or a fixed UTC span), display zone, sync group, stale_after, layout and variables.
  • A narrow view shows how the board stacks below its breakpoint.
  • Each cell previews through Visualize.Board.realise/4 over your sources, its slots bound by name.
  • Edit component opens a cell's composite, and Back to board returns.
  • A board entry cannot be dropped into a chart.
• Bind a board's slots in the builder (#580, D-152). Give Visualize.Chart.Builder a catalog: a map from each feed you offer to its Visualize.Data.Schema, for example the schema Visualize.Feed.describe/1 answers. In the board mode, each cell's sources are then bound to those feeds. Without a catalog they are bound to your sources.
  • The mode shows every unbound slot and every unmet contract (Visualize.Board.Binding.check/3) before any data flows.
  • The binding is never stored in the board. Each change is sent to your LiveView as {on_bind, id, board_id, binding} (on_bind defaults to :visualize_board_bound). Hand it back through board_bindings, keyed by the board entry's id, when the board opens again.
  • A slot with no binding starts bound to the feed of its own name, if there is one.
  • The preview binds through the binding. A catalog feed previews over your sources entry of that name, or else over rows made from its schema (Visualize.Chart.Builder.Boards.sample/2, which gives a :number window field its row's place, 0 to 59).
• A wrong binding in the builder is a fault panel, not a crash (#584, D-153). The single-chart preview, the inspector and the board mode's cells check types before they apply. A wrong binding is drawn as a fault panel in the board runtime's cell-state style, with every fault listed beneath it.

Changed

• A component with animate carries the class vis-animated and a <style> that stops its transition under prefers-reduced-motion: reduce (#559).
• A canvas names itself, and a hybrid chart's SVG layers are hidden (#557). The root wrapper of Visualize.Backend.Canvas and Visualize.Backend.Hybrid.render/1 take title: and description: and put them on the <canvas> (role="img", aria-label, and the description as its fallback content). Hybrid.render_static/1, and so a compiled chart's static, dynamic and backdrop documents, is aria-hidden="true": one layer of a picture the page names.
• In a cartesian frame a :rule and an :x_band are cut to the plot area (#565, D-143). A rule outside it, or a band wholly outside it, draws nothing, and a band that crosses an edge is clamped to it. An event that began before the window no longer draws across the axis.
• BrushHook sends domain whenever it can map the selection: in a sync group, as before, and now under a design's brush too (#565).
• A compiled chart's SVG carries its frame's sync and brush attributes (#574, D-146). Visualize.Chart.Compiled.svg/2 and step/3 now write data-vis-sync, data-vis-sync-x and data-vis-brush on the frame group, as Visualize.Chart.render/2 already did. A compiled chart in a sync group therefore joins the group's bus from its SVG alone. A design with no group and no brush renders exactly as before.
• A :symbol mark in a polar frame keeps its glyph (#560). Only its position bends around the arc. Before, the glyph itself was bent and drew as a sliver.
• A retargeted easing is shown where it starts on the tick it is retargeted (#559). This is unchanged for any easing with a duration. An easing of no duration now reaches its target on that tick instead of the next.
• ramps and roles merge key by key in Theme.new/1 and Theme.merge/2, and a theme lacking one takes the default theme's, never a series colour (#533).
• Theme.slots/1 and Theme.colour_slots/1 include the five roles, after surface (#533). Code that pairs the slot list with a fixed list sees five more entries.
• Visualize.Chart.Fragment.to_json/1 stamps the document with "$version" (#550, D-137). from_json/2 reads and drops it, refusing a newer one as {:error, {:newer_schema, …}} and an oversized document as {:error, {:limits, errors}}. Documents written before the stamp read as they always did, and from_json(to_json(f)) is still f.
• A bundle's provenance carries schema, the version it was exported at, and Visualize.Chart.Builder.Store.relocate/3 refuses a newer bundle before it puts an entry (#541).
• The Visualize.Chart.Validator.path type may hold strings: the path of a limit fault in a JSON document refused before decoding uses the document's own keys (#550).
• The builder is split into modules by area, with no change in behaviour (#568). Visualize.Chart.Builder keeps its assigns, its messages, css/0, styles/1 and tick/2 exactly as before. What moved is internal (Visualize.Chart.Builder.Events.*, Editing, Tree, Selection, Writes, Workspace, Modes, ThemeMode, none of them public). A test that calls the component's handle_event/3 directly sees the same results, and an event the builder does not handle still raises FunctionClauseError.
• Visualize now starts :crypto (extra_applications), for the schema version's hash.
• :telemetry is an optional dependency (#537), for Visualize.Feed.Telemetry. If your app lacks it, everything else builds as before. Visualize does not depend on telemetry_metrics.
• The repository's lock moves decimal to 3.2.0, past CVE-2026-97853 (#583). Visualize does not require decimal; it reaches the lock through the test-only Explorer and the optional Jason. Your app's own lock decides its version, so run mix deps.update decimal if it holds 3.1.1.
• The README says where visualize is going (#587): designs, feeds, boards and themes as layers a host composes, and how a host integrates them. It is titled README in the docs sidebar (#530).

Fixed

• Visualize.Chart.to_json/1 raised on a channel at its scale's own end (#554): a {:scale, :min} or {:scale, :max} channel, such as an area's y0, had no JSON form. It is now written {"$scale": "min"} and read back as the tuple.
• An axis's format: :duration read back from JSON as the string "duration" (#554, D-144), so the axis printed that word as a format specifier instead of durations. Where a key may be a string or an enumerated atom, a string naming a member of the enumeration now reads back as the atom. Every gallery design now round-trips through to_json/1 and from_json/1.
• A projection no longer raises ArithmeticError at the edge of its domain (#566, #577, D-149). Rounding carried a value that is exactly ±1 at a pole or the antimeridian a few ulps past it. Projection.invert/3 of :collignon's own south pole raised asin(-1.0000000000000004), and so did a rotation that carried a point onto that pole. :albers, :conic_equal_area, :mollweide, :eckert2, :eckert3, :eckert6, :wagner4 and :loximuthal failed the same way at a pole, and :mollweide's project/3 at a latitude one ulp inside one. Every inverse sine and cosine in Visualize.Geo is now d3's clamped one, so invert/3 of a point just outside a map's outline returns a point, as d3 does, where it raised. Points inside the domain project and invert exactly as before.
• Binding a feed of the wrong type no longer takes the builder down (#584, #582, D-153). It raised from the frame inside the builder's previews. The type check above reports it instead.
• The builder no longer raises while rendering a design whose inline theme breaks a contract (#563). Its colour wells draw the theme unchecked.
• A non-composite chart in the builder (a style, a theme) no longer reports its own version stamp as a fault of its kind (#561).
• The examples' performance drawer test failed under load (#567, D-148). A tick's elapsed time came from the real clock, so a strip meant to scroll two columns scrolled a hundred on a busy machine and crossed its byte budget. The chart page reads every instant of a run through a run_clock it holds, and its tests drive that clock exactly. Nothing a person sees changes.
• The suite no longer waits on the clock (#520, D-148). Every test that waited on wall time now waits on a message or a count with a bound of at least five seconds. A check beside D-114's fails the gate on a shorter assert_receive, ExUnit's 100 ms default, a refute_receive that waits, a short receive … after or a sleep, unless the site is allow-listed with its reason. The examples' per-chart size test, which ran 51.6 s of its 60 s timeout, is one test per chart that renders each chart once instead of three times.

0.2.35 — 2026-10-10

Changed

• The documentation is the README, the guides and the changelog (#529, D-133). The specification, API_SURFACE.md and usage-rules.md are no longer hexdocs pages; they still ship in the package and are read on GitHub. Every link to them from the README, the guides and this changelog is now an absolute GitHub URL, and a link to a section of the specification uses GitHub's heading anchor, so it opens at that section there.

0.2.25 — 2026-10-10

Added

• Visualize.Geo.Circle (#525): d3-geo's geoCircle. polygon/1 returns the circle of radius degrees (default 90) about a center [lon, lat] (default [0, 0]), every precision degrees (default 6), as a GeoJSON Polygon — d3-geo 3.1.1's ring point for point, in d3's winding, so Visualize.Geo.Path fills the cap about the centre under any projection, cut and closed at the antimeridian. A night side is polygon(center: antisolar_point).
• alpha and ticks on the :force step (#527, D-132): the temperature a compiled chart reheats the layout to each tick (0.3) and the iterations it runs (3).
• Visualize.Layout.Force.run/1 takes :alpha and :alpha_decay (#527): a run can continue a layout, from nodes that carry their x, y, vx and vy, as a reheated d3 simulation does. The defaults are unchanged.
• Visualize.Chart.Frame.new/2 takes warm: (#527, D-132): the force layouts a compiled chart carries between ticks.

Changed

• The cheatsheet links open its rendered page on HexDocs (#528). guides/cheatsheet.cheatmd is ExDoc's cheatsheet format, so GitHub and GitLab show it as plain text. The README and the guides now link https://hexdocs.pm/visualize/cheatsheet.html.
• A projection's clip hides a row; it no longer drops it (#522, D-130). A :projection step keeps every row it is given. A point the projection clips keeps its row with x and y set to nil. A geometry that projects to nothing keeps its row with path, x and y set to nil. Marks draw nothing for these rows on every backend. Domains are now inferred over every row, whatever the viewpoint. Before, a turning globe coloured through an inferred ordinal_scale(:color) changed its land colours as it turned, and a bubble map's size domain depended on what was in view. Rows with a missing or non-numeric coordinate, or a geometry that is not a map, are still dropped. If you count or read the step's output rows, expect the clipped ones, with nil positions.
• A :line or :area path that places no point draws no element (D-130). This applies to a whole series a projection clips, and to a line with no rows. Before, it drew an empty <path d="">.
• A compiled chart's force layout is warm (#527, D-132). Visualize.Chart.Compiled keeps each :force step's last layout, every node's position and velocity by id, and each tick/3 or step/3 moves the graph on from it instead of laying it out again from scratch. A change to the step's distance or strength now perturbs the graph rather than replacing it with a new one, often a reflection or rotation of the last. A node new to the graph starts near its linked neighbours, and a node that has gone is forgotten. Compiled.carry/2 carries the layout across a recompilation, so a caller that compiles again because a tick's marks differ keeps the graph where it was. Visualize.Chart.apply/2 and render are unchanged: the same input lays out the same graph, cold.
• The marks of one graph share one layout (#527, D-132). Visualize.Chart.Frame.new/2 lays out each distinct :force step once and holds it in the frame's new forces field, so a links mark and a nodes mark over the same step agree exactly and the simulation runs once per realisation, not once per mark and pass. Compiling a graph is about eight times cheaper.
• A :force node source's x and y seed the layout (#527). A node whose row has numeric x and y starts there, as d3 honours a given position.

0.2.4 — 2026-10-10

Changed

• Visualize is on Hex (#516): depend on {:visualize, "~> 0.2"} rather than a git tag. The documentation is on HexDocs. The source, and issues and feedback, are at github.com/dcoai/Visualize.

0.2.0 — 2026-10-10

Upgrading from 0.1.0. This is the first minor since the first tag, and the breaks are in the declarative layer and the builder. The imperative pipeline (Scale → Shape → IR.Element → Render) removes nothing. A design now holds its frames by name and records no size: the host gives size: at Visualize.Chart.apply/2, and Visualize.Chart.compile/2 returns one compiled chart per frame. Stored version-1 designs still read, because from_map/1 and from_json/1 migrate them, but code that builds designs, reads a compiled chart, or implements Visualize.Chart.Builder.Store needs the edits listed under Breaking. Three d3-conformance fixes in geo and stacking also move output for the same input. Read those if you draw globes, rotate projections, or stack :insideout.

Breaking

• A design holds its frames by name, and the schema is version 2 (#383, #428). The design's frame: key is frames: %{main: …}, %Visualize.Chart{} has frames where it had frame, and to_map/1 writes version: 2 (Visualize.Chart.Migration.current/0). Affects code that writes design maps or fragments by hand, or matches on the struct. Instead: write frames: %{main: %{kind: :cartesian, …}}, and use Visualize.Chart.Build.in_frame/2 to put fragments under another frame. A whole design that says version: 1 still works: from_map/1, from_json/1, apply/2 and compile/2 migrate it first (#479). A fragment carries no version, so it is not migrated, and a fragment written with frame: is an unknown key. Visualize.Chart.Applied gains frames. Its frame is the first frame by name.
• A design records no size (#427). A frame has no size key and the :size node kind is gone. Instead: pass the host's container as size: {width, height} to Visualize.Chart.apply/2 or Visualize.Chart.compile/2 (or Visualize.Chart.Frame.new/2). The default is {600, 400}. Migration drops a version-1 design's frame.size. Such a design now draws at 600×400 unless you pass size:. A version-2 design that still says size fails validation as an unknown key.
• Build's frame functions take a name, not a size (#427, #383). Build.cartesian(width, height, opts) and the same three-argument forms of polar, geo and facet are removed. The two-argument forms now mean (name, opts), so cartesian(600, 400) raises. Instead: Visualize.Chart.Build.cartesian/0, cartesian(opts) or cartesian(:name, opts), and the size at apply. Visualize.Chart.Build.scale/3, axis/3 and legend/2 now write into frames.main.
• Visualize.Chart.compile/2 returns one compiled chart per frame (#431, #385). It returns {:ok, %{main: compiled}} where it returned {:ok, compiled}. Instead: match the frame you want ({:ok, %{main: compiled}} = Chart.compile(design, opts)), or map over the result for a design of several frames.
• A compiled chart no longer carries its sources (#412). The sources field is gone from %Visualize.Chart.Compiled{}. Affects code that read compiled.sources or matched on it. Instead: keep the rows you passed. Compiled.render/2, svg/2 and tick/3 take the tick's sources as before.
• Visualize.Chart.Builder.Store is version 2 (#173, D-99, D-100, D-103). The 0.1.0 callbacks were list/0, get(name) and put(name, map) returning :ok. Now:
  • Every callback takes a context, and an entry has an id. The callbacks are list(context), which returns [%{id, name, kind}], then get(id, context), put(entry, context), which returns {:ok, id}, delete(id, context), and import(bundle, context).

  • An entry is %{id: nil | id, name, kind, fragment}. The store issues ids as {kind, n} and never reuses one. The name is a "group:sub-group:name" label.

  • The store assign may be {module, context}.
  • Visualize.Chart.Builder.Store.relocate/3 is a reference import/2 over your put/2.
  • The kind is Visualize.Chart.Fragment.kind/1, one of Visualize.Chart.Fragment.kinds/0, which has no :design (#187). Save a composite; a design is what deploying produces.
• The builder's save message carries structure, not a flat design (#178, #183, D-103). {on_save, id, structure} is now a composite of Visualize.Chart.Use sites holding store ids. Instead: flatten it with Visualize.Chart.flatten/2, which returns {:ok, design, report}. Or handle the new {on_deploy, id, design} message, which the builder's Deploy button sends with the flat design. The tag is the on_deploy assign, default :visualize_chart_deployed.
• The validator refuses designs 0.1.0 accepted (#368, D-113; #487, D-122). A reference into a declaring map the design never wrote is now reported. For example, data: :s with no sources is {:undeclared, :source, :s}, where 0.1.0 treated the missing map as unknown. A colour channel's constant value, or a typed column, that a declared ordinal colour domain can never hold is {:outside_domain, scale, value}. Instead: declare what you reference, and widen the domain or drop the constant.
• A stack's :insideout order is d3's stackOrderInsideOut (#496, D-125). It put the heaviest series at the bottom, where the spec said the middle. It now takes the series in order of appearance (by the index of each one's peak) and places each on whichever side has the smaller running sum, so the earliest-peaking series sits in the middle and later ones outward. Any stack ordered :insideout, or a design's :stack step ordered :inside_out, stacks in a different order. Instead: to keep a fixed order of your own, use order: {:keys, list} (#492, below).
• A projection's phi and gamma are d3's (#511, D-129). phi now tilts the globe and gamma rolls it, with d3's axes, order and sign. What 0.1.0 called phi is now gamma with its sign flipped, and 0.1.0's gamma has no equivalent. Instead: a rotation {λ, φ, 0} from 0.1.0 is {λ, 0, -φ} now. lambda keeps its opposite-to-d3 sign (D-44), so a rotation copied from d3 keeps φ and γ and negates λ.
• Projected GeoJSON is clipped on the sphere as d3-geo clips it, so winding matters (#509, #510, D-127). Visualize.Geo.Path cuts lines and polygons at the antimeridian of the rotated frame, and under a clip_angle along the small circle. It no longer drops vertices. An anticlockwise ring is the rest of the sphere, as in d3. Instead: rewind data in RFC 7946's winding before drawing it (Natural Earth as d3 ships it needs nothing). The defaults change too:
  • The azimuthal clip angles are d3's: 90 + 1e-6 for the orthographic, 180 - 1e-3 for the azimuthal equal-area and equidistant.
  • bounds/2 and centroid/2 read the clipped vertices.
  • A ring that crosses nothing keeps its vertices exactly.
• The incremental 0x60 scroll record carries its viewport (#295, D-106). Sixteen more header bytes, vx vy vw vh, follow the offset, making a fixed 27-byte header. The shipped CanvasIncrementalChart hook reads it, so this affects only a host that decodes the stream itself. Visualize.Backend.CanvasIncremental.encode_incremental/4 takes the rectangle as viewport:, the whole canvas by default.

Added

Documentation

• Guides (#515): Getting started, Charts in LiveView, Designing charts and a cheatsheet, under Guides in the docs. Every Elixir block in them and in the README runs in the test suite, so they cannot fall behind the code.
• The README is a short introduction: what visualize is, why, how to install it and run the examples, and where the documentation is.

Declarative charts

• Several frames in one design (#428, #437, #436, #438). A frame takes a box (fractions of the render's size), a z and a background. A design's layout (Visualize.Chart.Build.layout/1: columns and rows as weights, gap in pixels) places frames by cell and span instead of arithmetic. A frame can adopt another frame's scale, so two frames share a domain while each keeps its own range (Visualize.Chart.Build.adopt/2, {:frame, :main, :x}). A composite is placed as frames by its key. Visualize.Chart.generate/2 with root: true renders a whole design as an accessible <svg> document (#131).
• New marks:
  • :text (#337), with edge anchors for the rectangular types.
  • :needle (#392, Visualize.Shape.Needle).
  • :tiles (#475; see Geo).
• series is a channel of every mark that draws rows (#508, D-126). Every element and label of a series carries data-series, so a legend toggle hides a series' points with its line.
• New data steps:
  • :fold (#240): wide columns to long rows.
  • :take and :window (#426): the newest rows or a duration back from now:.
  • :spectrum (#375): a one-sided amplitude spectrum by FFT.
  • :lttb and :m4 (#448): shape-preserving downsampling.
  • :hexbin (#353).
  • :projection over a geometry column, with the Sphere (#350).
  • A graph's nodes as a second source, and strength and distance on :force (#352, D-110).
• Polar as a coordinate transform (#390–#393). An angle scale carries start and sweep. Every ordinary mark is laid out in (angle, r) and bent around the arc. A categorical angle closes its ring, which gives the radar. Labels take :outward/:inward anchors with dr, rotate in degrees or :tangent/:radial (#338), and a {:frame, :center} anchor (#489).
• Scales:
  • Offset scales, a band within a band, which gives grouped bars (#339, D-109).
  • A time scale's display zone (#447; see Data and scales).
  • {:scale, :min} and {:scale, :max} as a channel value, so an area can fill to its axis whatever the domain (#420).
  • A transition node on a scale or a mark eases a moving domain or value between ticks in a compiled chart (#360, #417). Visualize.Chart.Compiled.step/3 steps one frame, and Visualize.Chart.Compiled.carry/2 keeps the easing across a resize (#434).
• Styles:
  • Gradients in defs, used as {:paint, name}; see Visualize.Chart.Build.gradient/3 and paint/1 (#133, #219).
  • A fill style; a stroke style of single, double, inside or outside (#218); blend mode and shadow or blur effects (#220).
  • font_style and the weight words (#217).
  • Multi-line text with line_height (#221); vertical_align, margin_x, margin_y and text_angle (#222).
  • A style site takes a stack of styles (D-98).
  • :contrast as a colour (#486, D-123): the theme's text or background, whichever reads against the fill under the label, with WCAG AA guaranteed. See Visualize.Theme.ink/2.
  • A mark label's fit: :truncate or :hide (#138).
• Axes and legends: a legend outside the plot with inside: false (#347); prefix and unit on an axis or legend (#351); format: :duration on an axis (Visualize.Format.duration/1, #191).
• Typed columns (#369): a source's types declares each field as :time, :number, :category or :text. See Visualize.Chart.column_type/3 and Visualize.Data.Table.column_types/1.
• Sync groups share hover (#466, D-116). A design key, interaction: %{sync: "<group>"}, makes charts on one page share a cursor. Hovering one moves the crosshair and the tooltip of every other member to the same x in domain units, through each chart's own scale, so members may differ in width and margin. No host JavaScript is needed: the frame renders data-vis-sync and data-vis-sync-x (Visualize.Chart.Frame.sync_attrs/1, also in Visualize.Hooks.Crosshair.attrs/3), and TooltipHook and CrosshairHook exchange vis:sync:<group> events on document. Only a linear or time x can join a group. The validator refuses any other kind as {:sync, :x_scale, kind}. Visualize.Chart.Build.interaction/1 writes the key. A chart's to_map/1 and JSON now carry interaction (default %{}).
• Sync groups share the brush (#467, D-117). A window brushed on one member shows as a band on every other, and only the chart brushed pushes to its server. The bus is Visualize.Hooks.Sync.js_bus/0, bundled ahead of the hooks that use it.
• A stack order fixed by explicit keys (#492). Visualize.Shape.Stack.order/2 and a design's :stack step take {:keys, list}, the listed keys bottom first and every key the list leaves out above them in key order; a listed key the stack lacks is ignored. Every other order is computed from the data each call is given, so over an animated or streaming source :inside_out re-sorts per frame and layers swap places; a fixed order computed once does not. In JSON it is {"$keys": [...]}. A :sort step's order is still a direction alone.
• Use sites and composites (#174, #186, #188, D-101, D-102). A composite is a list of Visualize.Chart.Use sites: a reference, a local body, a mask and bindings, resolved ref → local → mask → bind. See Visualize.Chart.bind/2, mask/2 and resolve/2, and Visualize.Chart.flatten/2, which turns a composite into a flat design through a fetch. Visualize.Chart.Fragment and Visualize.Chart.Composite hold the walks. Visualize.Chart.Validator.validate/2 validates a fragment as its kind.
• A public JSON codec for fragments (#465). Visualize.Chart.Fragment.to_json/1 and from_json/1 write and read any fragment, a composite of use sites holding ids included, in the JSON form spec/14 §19.7 specifies ($use, $id). It is not validated as a design, since a fragment may be partial. A store that keeps its library in a database can now persist what Store.put/2 hands it. Chart.from_json/1 validates a whole design and so refuses a composite, and the codec under both was private.
• Node paths on request (#260, D-105). paths: true on Visualize.Chart.Frame.generate/2 stamps data-node on everything a frame draws. The default render is unchanged.

Rendering and backends

• Visualize.Render.to_png/2 and to_png!/2 (#473, #474, #481, D-121). A root IR element, or the SVG string it renders to, is rasterised to a PNG by the resvg command-line tool, run as an OS process over a port.
  • No Hex dependency. The host installs resvg 0.45 or later (apt install resvg on Debian and Ubuntu, the upstream release tarball, or cargo install resvg). Name it with config :visualize, :resvg, "/path/to/resvg", or leave it on the PATH.
  • When resvg is missing or too old. Without one, the result is {:error, :no_rasterizer}. An older one gives {:error, {:rasterizer_version, found, required}}.
  • Isolation. A render holds no BEAM scheduler, cannot crash the VM and writes no temp file.
  • Options. scale: is the device pixel ratio and background: a CSS colour. timeout: (default 30 s) bounds the render: on expiry resvg is killed and the result is {:error, :timeout}.
  • Literal colours only. Generate the SVG with resolve: :literal. A var(--…) theme reference returns {:error, :css_references}, since resvg would paint it black.
• PNG fonts and warnings (#474, #481). to_png/2 takes the font configuration: font_dirs:, system_fonts: (default true) and generic_families: (resvg's defaults, where sans-serif is Arial). font_family: covers text that names none (default "sans-serif"). resvg loads the fonts on each call, so a font added to a directory is seen by the next render.
  • The success value is {:ok, png, warnings}, resvg's own report. There is one {:missing_family, list} per font-family list no font resolves, whose text was left out, and {:rasterizer, line} for anything else resvg printed.
  • to_png!/2 raises when there is a warning.
  • The gallery has raster goldens, rendered with a bundled DejaVu Sans and no system fonts.
• A compiled chart's backdrop (#476, D-120). Visualize.Chart.Compiled.backdrop/1, and the backdrop key of render/2's map and of tick/3's payload, hold a :tiles mark's images as an SVG document. A page stacks it beneath the canvas, so a dense track drawn on the canvas sits on its basemap.
  • The attribution stays in the SVG layer over the canvas.
  • Compiled.static/1 no longer holds a static basemap's images. A page that draws tiles on the hybrid split stacks the backdrop.
  • The binary stream still drops :image and gains no record for it.
• A theme's :surface slot (#422). It is the plane a chart's data is laid on, between the background and the grid: #eef2f6 on Visualize.Theme.default/0 and #23272f on dark/0. It is a colour slot like any other. slots/1 and colour_slots/1 list it, and resolve/3 gives var(--vis-surface, …) on SVG and the literal on canvas. An inline :theme node takes a surface key. A theme from new/1 that names none takes the light value, as it does for every field it leaves out.
• A reference decoder for the binary canvas stream (Visualize.Backend.CanvasBinary.Decoder, #291).
• New IR primitives: Visualize.IR.Element.clip/3, filter/2, drop_shadow/3, gaussian_blur/1, tspan/2, put_attr/3, and Visualize.IR.Path.from_commands/1.

LiveView and hooks

• Frame acknowledgement (#305, #307, #322, D-107). CanvasIncrementalChart and CanvasBinaryChart acknowledge each payload's seq when their element carries data-ack. A producer can then bound frames in flight, and a hold times out rather than stall. This is opt-in, and existing uses are unchanged.
• The sync-group hover and brush above need no host JavaScript beyond the shipped hooks.

Geo

• Basemap tiles (#475, #476, D-119, D-120). A :tiles mark draws Web-Mercator tiles beneath a geo frame's other marks, at the nearest zoom, over a projection fitted without moving its centre. See Visualize.Geo.Tiles (aligned/1, zoom/2, cover/3, url/3).
• Visualize.Geo.Projection.sphere/1 (the outline of the visible globe), fit/3 and precision/2, and Visualize.Geo.Path.path/2.

Data and scales

• Time zones (#447, D-115). Visualize.Scale.Time.zone/2 (and Visualize.Scale.zone/2, or a design's zone key) ticks on local calendar boundaries across DST. It reads the zone through the host's configured Calendar.TimeZoneDatabase, so the library takes no dependency for it.
  • A zone the database cannot show raises ArgumentError at the setter, and in a design it is {:zone, name, reason}.
  • Without a zone, every tick is the UTC one byte for byte.
  • Visualize.Scale.Time.local/2 converts a value into the scale's zone.
• Downsampling: Visualize.Data.lttb/3 and Visualize.Data.m4/3 (#448).
• Visualize.Data.FFT (fft/1, spectrum/3, window/2, #375).
• Visualize.Signals (#247): deterministic sine, square, random and discrete sources over a sliding window, for a chart that moves without a host feed.
• Visualize.Format.duration/1 (#191), Visualize.Layout.Hexbin (#353), the closed curves Visualize.Shape.Curve.basis_closed/1 and cardinal_closed/2 (#393), Visualize.Shape.Arc.angles/2 and radii/2, and Visualize.Contour.cost/2 (#462).
• A force simulation's subscribers at start (#483): Visualize.Layout.Force.Simulation.start_link/1 takes subscribers:, pids registered before the first tick, so a subscriber sees every tick from the first. subscribe/2 still joins a running simulation.

Builder

• The builder became an editor of typed fragments (#142–#388, spec/14 §18–§19).
  • Layout. It ships its own stylesheet, rendered inline. styles={false} turns that off, and the host then serves Visualize.Chart.Builder.css/0 itself (D-94). The workspace holds several charts beside a library tree.
  • Library entries. A library drop arrives linked. Unlocking it copies the body into the site, and a site can mask paths and bind variables.
  • Editing. It has a Variables tab, a style form, a data page with typed columns and generated signals, axes ticked per side, and "add data / add a mark / add axes" steps.
  • Saving. Save sends structure; Deploy sends the flat design (above).
  • New assigns: on_deploy, source_defaults, tick_ms and styles.
  • Import and export. These move bundles: Visualize.Chart.Builder.Bundle.export/3, and the store's import/2.
• A referenced group expands in the builder's tree (#388). A library composite dropped linked now carries the ▸ and the count of its entry's sites. Opened, it draws them beneath its row, muted and locked, each tagged with the entry's name.
  • They are the library's, so they take no flat position of their own. A click, a drag or the menu on one acts on the group.
  • A drop into the group is refused with name is from the library — open it to edit.
  • Visualize.Chart.Builder.Stack.all/2 is new: the tree's rows, with each referenced group's inside fetched and each row naming its owner. So are inside/2 and inner_label/3.

Changed

• A colour outside its domain is the scale's unknown (#487, D-122). A color ordinal scale that gives no unknown now takes the theme's :axis colour. In 0.1.0 its unknown was nil, so the element got no fill: SVG painted it black and a canvas drew nothing. A series line outside the domain is drawn in that neutral, not in the series colour of its position. Say unknown: :none on the scale to hide such values. A missing colour is now bound as :none, which draws nothing on SVG and canvas alike.
• The pie, sunburst and treemap components ink their labels by contrast and fit them (#494, #497, D-123). Their labels are now :contrast with the gallery's fit (:hide on the pie, :truncate on the sunburst and treemap), so a label too big for its slice is hidden or cut. The markup of those labels changes. Every path and the rest of the shell are byte for byte as before.
• A labelled mark is a wrapper of two groups (#485). The elements are in a styled group and the labels in an unstyled sibling group, so labels no longer inherit the mark's stroke. The wrapper keeps the mark class, data-node, the tooltip attributes and the centring transform.
• An area's default baseline is the y scale's zero clamped to the plot (#420). An area over a domain that excludes zero no longer fills into the margin. An explicit y0 is placed as given.
• A line whose style gives a fill draws the area under it, down to the baseline (#232), where it used to fill the polygon between the curve's ends.
• A :chord step centres on the plot, as an arc mark does (#488). Its size sets the radius only.
• The builder's layers assign seeds the stack and does not control it (#144, D-95). An unrelated host render no longer resets an editing session. A changed list is adopted.
• The canvas hooks size the canvas to data-width × data-height at every draw (#456). A resize clears it, and the incremental hook draws no scroll record until a full frame follows.
• A canvas draws by the effective style (#231, D-111). A mark whose paint sits on its group draws on canvas as on SVG. The binary stream gains one style record per mark group.

Fixed

• A drop below a closed group in the builder's stack lands where it was aimed (#468). BuilderHook counted the drawn rows to name a drop's position, while every flat position the builder reads counts a closed group's rows too. So a drop between a closed group and the row after it landed inside the group, and a group dropped directly below itself moved.
  • A stack row now carries data-builder-end, the flat position past everything it holds, beside its data-builder-layer. The hook reads both instead of counting.
  • The gap before a row is its position, and the gap at the end is the last row's end.
  • A move shifts by the rows the dragged one lifts out.
• A composite exports and imports with its references (#470). Fragment.refs/1 and relocate/2 treated every struct as a leaf. A composite's sites are %Use{} structs holding ids in ref, origin, local and vars. So Bundle.export/3 of a composite left out what its uses referenced, and an import left it pointing at the source store's entries. The two id walks now read a use's parts. Every other walk still stops at a struct (D-92).
• A glyph carries no id (#471). The :linear and :radial fill-style pictures and the :blur effect drew an inline <defs> with a fixed id. The editor shows a glyph once per choice and per open row, so a page repeated the id, which LiveView refuses (Duplicate id found … vis-glyph-linear). They are now translucent bands and squares, with no paint server and no filter. The glyph test also walks the four drawn keys it had skipped (fill_style, effect, vertical_align, stroke_style).
• A version 1 design read from JSON migrates (#479). The codec typed every key by the current schema, so a v1 design's frame kept string values and failed validation once migrated to frames.main. So JSON-stored designs from before #383 couldn't be read, which contradicted §9.
  • Migration.legacy_type/2 gives a removed key its old type, and the codec reads by it, so the document is typed before it is migrated.
  • §14.4 also corrects current/0 to 2.
• An adopted scale has a JSON form (#480). A frame adopting another frame's scale ({:frame, :main, :x}, §4.3) had no JSON form, so Chart.to_json/1 raised on any design with an adoption, and the design couldn't be stored by a host or the builder's store. It now encodes as {"$adopted": ["main", "x"]} and reads back. A tagged object is never read as a node.
• The default tick label prints a float in plain decimal (#354), never 1.0e3.
• A compiled chart resolves a mark's paints and carries the design's defs (#356). A gradient fill was black on the canvas and unrenderable on the SVG layer.
• The binary canvas stream encodes line, polyline, polygon and ellipse (#290). The encoder silently dropped them, so an axis's ticks drew nothing on a binary canvas.
• A contour ring always closes (#81, D-112). A crossing never sits on a grid corner, and a ring closes on its exact start.
• compose/2 no longer merges a whole-node variable into a :union key (#120, D-92). It could produce a struct with foreign keys.
• CrosshairHook measures the chart, not its container (#507). Its markers sat a few pixels off the series under an inline <svg> or <canvas>.
• Cost:
  • Building a path is linear in its commands; it was quadratic (#414).
  • A scroll tick costs the strip and its neighbours, not the window (#333, #404, #410, #423, D-108).
  • The incremental window keeps no closure, so a scroll's cost no longer doubles every frame (#406).
  • The :natural, :basis_closed and :cardinal_closed curves are linear (D-114).
• Documented examples run (#117, #121, D-90, D-93). Every iex> example under lib/ is a doctest, and the three that were wrong are corrected.

0.1.0 — 2026-09-09

0.1.0 is the first tag. Until it, the only way to depend on this library was branch: "main", so everything below has already reached anyone tracking that branch — the sections are therefore written as they will read from the tag onwards: Added is the surface a new consumer gets, and Changed and Fixed are what moved under a consumer who was following main and now has a point to pin.

Pre-1.0. The surface can still move; a breaking change opens 0.2.0 rather than bending the meaning of a patch.

Added

• The declarative chart layer — Visualize.Chart. A chart is a design: a plain map of atoms, numbers, strings and Visualize.Chart.Var placeholders, with no functions and no structs in it, so a design can be stored, diffed, sent over the wire, versioned and edited by something other than code (D-57). The imperative pipeline — Scale → Shape → IR.Element → Render — is unchanged and remains the layer this one is written on; nothing about the chart layer is mandatory.

  • Visualize.Chart.Schema is the design's grammar as data. Every key carries a facet (:data, :geometry, :channel, :binding, :style, :meta) and a merge rule, so a validator, an editor and a composition operator all read the same description instead of each carrying their own copy of it (D-58). Schema.describe/1 is what the builder's UI is generated from.
  • Visualize.Chart.Validator checks a design against the schema and reports by path — [:marks, 2, :channels, :y] — rather than by message, so an editor can put an error next to the field that caused it.
  • Frames own the scales. A frame declares named scales whose domains may be :auto, realises them once from the whole bound column, never widens them afterwards, and renders its own furniture — axes, grid, legend, labels — with or without data (D-60).
  • Marks are the generators, named: :line, :area, :band, :rule, :x_band, :percentile_band, :rose, :symbol, :arc, :path, :rect, :circle. A mark names the scale each channel family reads through (D-61, D-67), and takes its paint from the theme's series.
  • Transforms are pure steps over rows, run by the frame before its scales are realised, so a transform can change what the domains infer from (D-62): :filter, :bin, :stack, :sum, :sort, :tree, :cluster, :pack, :partition, :treemap, :chord, :sankey, :force, :contour, :density, :delaunay, :voronoi, :projection.
  • Styles and themes. A style node resolves to two outputs — literal attributes for SVG, and CSS custom-property references for a themed page — and binds its field references per element (D-63). Visualize.Theme carries the slots; a slot renders as var(--vis-…, <literal>), its literal always present as the fallback, so a page that ships no stylesheet still draws in colour (D-55).
  • Templates: typed source slots and Visualize.Chart.Var variables, bound by Chart.apply/2. A variable's default lives in its declaration, and a stored design keeps what its author wrote rather than being rewritten with defaults (D-59).
  • Chart.compile/2 splits a chart into the regions that are static and drawn once and those that are dynamic and carry a closure, fixes each mark's render target at compilation, and gives the streaming window its own plot-area canvas (D-66).
  • Chart.to_map/1, from_map/1, to_json/1, from_json/1 — JSON carries what JSON cannot hold (dates, tuples, atoms) as tagged terms, and the round trip is the identity (D-57). JSON needs the optional :jason dependency; without it the two JSON functions return an error value rather than failing to compile.

• The fragment algebra — Visualize.Chart.Build and the operators on it. A fragment is a partial design, and the algebra is what makes designs composable rather than merely storable.

  • Visualize.Chart.Build builds fragments through one function per schema node — a function per mark type, transform op and scale kind, generated from the schema so the builder cannot drift from the grammar it builds (D-79). Every option is a key of the node the function builds (D-78).
  • Chart.compose/1,2 merges fragments key by key under the schema's merge rules. Chart.stack/1,2 is a second closed operation over the same values: a cascade, where a higher layer overrides a lower one and the result is itself a fragment, so a stack of stacks is a stack (D-81). Composition unions; a cascade overrides. They are different questions and now have different operators.
  • Element identity. A mark's or label's identity is its id, an axis's is {scale, side}, and a matched element is replaced whole rather than deep-merged (D-82) — which is what lets a layer say "this one, replaced" without saying it by list position.
  • Chart.explain/1 reports provenance: which layer each key in the result came from, computed from the layers rather than carried in the fragment (D-83).
  • Chart.free_vars/1 reports the variables a design still needs, walking exactly where application walks; a variable bound to another variable is an error reported by path (D-84).
  • extends: on a style derives it from a parent, flattened at the lookup rather than at write time, so a change to the parent reaches its children (D-80).

• Visualize.Chart.Builder — an embeddable LiveComponent for building designs. Optional in every sense: it needs LiveView, which is an optional dependency, and it is a component the host mounts rather than a route the library owns. Its only output is one message to the host, which owns the route, the storage (Builder.Store) and the meaning of saving (D-85). The editor's nodes, controls and widgets are generated from the schema's types, and a composite value is read as a literal and never evaluated (D-86). The stack panel shows the layers — disabling a layer is not deleting it — the inspector is explain/1 rendered, and the parameters form is free_vars/1 rendered, editing the builder's own copy of the bindings (D-87, D-88). Import and export move a design as JSON.

• New marks: Visualize.Shape.Band (a state timeline: one :rect per datum, index-aligned — D-26), Visualize.Shape.Rule and Visualize.Shape.XBand (annotations that take domain values and a scale, not pixels — D-27), Visualize.Shape.PercentileBand (a composition with a fixed output shape — D-28), and Visualize.Shape.Rose (Arc over a radial scale — D-31).

• New scale: Visualize.Scale.Radial, an angle scale whose ticks divide the turn and whose nice/1 is the identity, because there is no nicer boundary on a circle than the one you asked for (D-30).

• Interaction hooks — Visualize.Hooks. Zoom and Brush (with one-axis selection helpers that work on the axes they are given — D-29), Resize, and the three canvas hooks CanvasChart, CanvasBinaryChart and CanvasIncrementalChart (D-40). New in this release: Tooltip, which reads the datum's own fields from data attributes the server wrote on the element (D-75); Crosshair, which snaps to an array the server wrote once and draws in an overlay it owns rather than in the patched subtree (D-76); and Legend, where an entry and its series path carry the same data-series and toggling hides with display (D-77). The pattern throughout: data attributes are the contract, and a hook draws outside the subtree LiveView patches.

• Tabular ingestion — Visualize.Data.Table.rows/1. One door for tabular data: row lists, column maps, Nx tensors, Explorer data frames and anything else implementing Table.Reader (D-52). Every generator, compute and component reads its data through it (D-53), so a data frame is accepted wherever a list of maps is. The :table package is optional, like Nx; without it lists, column maps and tensors still work and a struct source raises at the call.

• Themes and accessibility. Visualize.Theme with a light and a dark palette and a generated stylesheet; responsive sizing as two halves — ResizeHook for the round trip and viewBox scaling for everything between (D-54); and a chart that names itself, with <title>, <desc> and role="img" on the root and aria-hidden axes (D-56).

• Ten preset chart components (Visualize.Chart.Presets): line, bar, horizontal bar, pie, scatter, area, stacked bar, tree, treemap and sunburst — each a preset design plus an assign mapping, drawn by the chart layer into the same markup the hand-written components always produced (D-64), and byte-identical to their goldens.

• The specification ships with the package (spec/), together with API_SURFACE.md, a generated golden that lists every public function the specification declares against every public function lib/ defines. A function in lib/ with no row is unspecified; a row with no function is unimplemented; either fails CI. It is the contract a consumer holds the library to, so it ships.

• LICENSE — MIT — and package/0 now declares licenses: ["MIT"]. Before this the licence was unstated to anyone who received the package.

Changed

• Visualize.Render.with_backend/2 is removed (D-2). It set a backend in the process dictionary for the duration of a function, so any render inside that function silently used a backend chosen somewhere else, and restoring the previous value needed try/after. A backend is now selected only by the :backend option at the call site or by config :visualize, default_backend:. Code that rendered inside with_backend/2 must thread backend: through instead.

• Shape.Stack returns its series in key order, not in stacking order, and each series carries index, its position in the stack (D-22). A caller that indexed the returned list by stacking position must read index instead. :diverging and :wiggle are now ports of d3's stackOffsetDiverging and stackOffsetWiggle; previously :diverging did not accumulate negatives and :wiggle was :silhouette under another name.

• A collapsed domain maps to the range midpoint in every continuous scale, and nothing raises (D-49). Linear and Time previously raised ArithmeticError on a single-datum extent or an all-zero [0, 0] domain; Power and Symlog returned the range start. All five now return the midpoint, as d3 does — a single-datum chart draws its point in the middle of the axis. Callers that widened collapsed domains by hand no longer need to.

• :top axis labels moved off the plot, and band ticks moved to the centre of the band (D-23). A :top axis's labels shift by 2·(tick_size_inner + tick_padding); every band axis's ticks shift by half a band. A caller who had added bandwidth / 2 through offset/2 to centre ticks by hand is not double-shifted, but should drop the workaround.

• Negative zero is folded in the d serialisers, so a coordinate that rounds to zero prints 0 and never -0 (D-32), and in the projection golden, where the sign of zero is not a property of the maths (D-6). Path strings that differed only in a minus sign before a zero are now stable across refactors.

• One d serialisation. There were two path serialisers producing different strings for the same path; there is now one, behind both the SVG bridge and the IR (D-12, D-34, D-71). The tree components' link paths therefore print in the comma-separated form (D-71, #79); goldens that recorded the old form were regenerated.

• Time ticks follow d3-time: boundary snapping on every interval, ratio-based interval choice, clamped month stepping and multi-year intervals (D-16). A time axis that previously produced unsnapped or wrongly-spaced ticks produces d3's.

• Format.number/2 groups the magnitude, Format.formatter/1 is a parser for d3-format specifiers, and Format.time/2 is a one-pass strftime tokenizer (D-24, D-25) — where before each was an approximation.

• The scale protocol is a behaviour, and every scale stores lists (D-15). Power, Symlog, Quantile, Quantize and Threshold implement it, so Scale.apply/2, ticks, nice, invert and bandwidth work uniformly across every scale type — which is what lets Axis stop special-casing scale kinds.

• Layout.Force's many-body force has no :theta (D-4). The option was accepted and ignored — there is no quadtree behind it — so it is removed rather than left inert. The force is exact, O(n²) per tick. Passing :theta is now a programmer error.

• Geo.Projection.clip_angle/2 clips. The value was stored and never read, so orthographic globes drew the back of the world over the front (D-3). project/3 now returns nil beyond the clip angle, and azimuthal projections take d3's per-type defaults. Callers that project points beyond the horizon now receive nil and must handle it; Geo.Path drops them.

• Phoenix is optional and stays optional (D-7, D-45). Visualize.Components, Visualize.Components.Tree, Visualize.Chart.Builder and the Phoenix.HTML.Safe implementations compile only when Phoenix.Component is loaded; a host without LiveView never fetches Phoenix. The same holds for Nx, :jason and :table, and a consumer check runs on every pipeline to prove it.

• Geo.Projection and Backend.CanvasBinary were split into family modules, which are @doc false internals rather than public API (D-9).

• The canvas binary format gained f32 path records (path32, path_cubic32), which are the encoder's default because canvas coordinates are pixels (D-73), and a compact cubic-run record with no sub-opcodes, because that is what every curve generator emits (D-74). The decoder round-trips both.

Fixed

• Visualize.Components never rendered. The component layer called a Scale API that did not exist; every component raised. It was rewritten against the real API and is now held by render goldens (#43). Visualize.Components.Tree — tree, treemap and sunburst — was rewritten the same way and now honours colors and label (#44, D-46).

• Geo.Delaunay was not a Delaunay triangulation. It is now Bowyer–Watson with an orientation-normalised in-circle test and half-edges (D-43), which also makes Geo.Voronoi correct.

• The hierarchy, sankey and pack layouts are now ports of d3's. Layout.Hierarchy gained path/2 and stratify/2; the tidy tree is Buchheim; Partition and Treemap keep zero-valued children (D-41); Sankey has d3's alignments and one link scale; Pack is d3's packSiblings/packEnclose with a deterministic fallback (D-42).

• Projection rotation now inverts in reverse order, the collision force pushes both nodes rather than one, and every computed range has a step — the 0..-1 empty-range class was swept out of the tree (D-44).

• Transverse Mercator invert/3 no longer raises. It raised ArithmeticError away from the central meridian; it is now d3's spherical inverse, returns nil outside the hemisphere, and the forward projection clips (D-5, D-51). The projection golden records the inverse instead of excluding it.

• Line and Area break into subpaths at undefined data instead of drawing through the gap (D-18); Curve.natural/1 is the natural cubic spline, solved rather than approximated (D-19); Curve.basis/1 is d3's curveBasis, which previously skipped a B-spline segment and started and ended in the wrong place (D-33); the step curves emit d3-identical paths (D-8); Line.x/1 and Line.y/1 accept constants, and LineNx honours :curve (D-20).

• Shape.Arc applies corner_radius and pad_angle (D-21). Both were accepted and ignored.

• Band, quantize, colour, ordinal, linear, log and symlog tick defects, and a crash in Data.ticks/3 (D-17, #24).

• IR.Transform.scale/2's pipeline form raised FunctionClauseError because a guard ordering made its second clause unreachable (D-1). IR.Path.transform/2 now takes a full affine matrix (D-35).

• SVG.Element.from_ir/1 renders view_box as viewBox — attribute names go through one map, so casing cannot differ between the two bridges (D-11, D-34).

• Backend.Canvas emits executable commands and group styles; the CanvasIncremental and Incremental contracts were made to match the code; Benchmark measures elapsed time with its own clock (D-37, D-38, D-39).

• Hooks.js_code/0 emitted every hook twice, as duplicate named exports, which is a syntax error in a JavaScript module (D-48); and BrushHook leaked its listeners, because it removed handlers it had never bound — it now stores the bound handlers and removes those (D-47).

• Contour.Density.compute/2 took minutes on its default grid. The grid is now an indexed structure and the ring tracing takes each segment once; a list read by index was the whole cost (D-72).

• Shape.LineNx warned at compile time in a consumer without Nx — nine warnings, not the one first reported. Both Nx-calling modules declare @compile {:no_warn_undefined, Nx} and a consumer check fails on any warning: line from the library's compile (D-50).

• Data.range/3 and a set of dead clauses across the tree; the force simulation's timer discipline — tagged ticks, restart keeps the state, alpha is clamped — under an ExTLA model that is checked in CI (D-14).