Block Reference

Every building block an object may be composed of, with its properties, their types, defaults and ranges. This page is generated from the live registry, so it cannot drift from what the compiler will accept.

How to read this page

• Primitives and modifiers and behaviours list properties; a node sets them as constants under properties, or as bindings under bindings for the same names. A binding always wins.
• Components list parameters; a node sets them under parameters, each one a constant or a binding.
• A default written "token:stroke.accent" is read through the design tokens, so it follows the board's preset rather than being a fixed colour.
• A range column reading min 0, max 1 clamps the value; one listing alternatives is the set the value must come from.
• Every drawing block also carries fill, stroke, strokeWidth, strokeDash, strokeLinecap, opacity and visible.

The same catalogue is available to an agent at runtime through list_building_blocks, search_building_blocks and get_building_block_schema, which read the registry directly.

Limits

Primitives

The blocks that draw. A node names one as its type, and sets these under properties as constants or under bindings as declarative values.

arc circle clip-box ellipse freehand group image line path polygon polyline rect ring text

arc — Arc

Circular arc or annular sector measured clockwise from the start angle.

Capabilities: fillable strokable radial angular

circle — Circle

Circle defined by a centre point and a radius.

Capabilities: fillable strokable radial

clip-box — Clip box

Container showing only the part of its children that falls inside it.

Capabilities: container sizable

Accepts children.

ellipse — Ellipse

Ellipse defined by a centre point and two radii.

Capabilities: fillable strokable radial

freehand — Freehand

Strokes drawn by hand, each a list of [across, down] points given as fractions of the box, smoothed into curves. A pencil texture roughens the line like graphite, and a multiply blend lets ink underneath show through, as a highlighter does.

Capabilities: strokable sizable

group — Group

Container that positions, rotates and scales its children as one unit.

Capabilities: container

Accepts children.

image — Image

Bitmap or SVG image placed in a box. Only https:, data: and same-origin relative sources are allowed.

Capabilities: sizable media

line — Line

Straight line segment between two points.

Capabilities: strokable linear

path — Path

Raw SVG path data. Commands are restricted to the standard path grammar.

Capabilities: fillable strokable

polygon — Polygon

Closed sequence of connected points.

Capabilities: fillable strokable

polyline — Polyline

Open sequence of connected points.

Capabilities: strokable linear

rect — Rectangle

Axis-aligned rectangle with optional corner radius.

Capabilities: fillable strokable sizable

ring — Ring

Full annulus between an inner and an outer radius.

Capabilities: fillable strokable radial

text — Text

Single line of text anchored at a point.

Capabilities: fillable textual

Modifiers

Applied to a node and everything under it, in the order the modifiers array lists them.

along-path fill mirror opacity repeat rotate scale stroke translate visibility z-order

along-path — Along path

Moves a node to a point a fraction of the way along the route a connector is drawn on, optionally turned the way the route runs there.

Capabilities: transform

fill — Fill

Overrides the fill colour of a node.

Capabilities: style

mirror — Mirror

Mirrors a node about a horizontal or vertical axis through an anchor point.

Capabilities: transform

opacity — Opacity

Sets the opacity of a node or group.

Capabilities: style

repeat — Repeat

Repeats the node it is applied to, offsetting each copy by an angle step, a translation or a scale. The copy index is available to bindings as the parameter $index.

Capabilities: layout structural

rotate — Rotate

Rotates a node clockwise around an anchor point, in degrees.

Capabilities: transform angular

scale — Scale

Scales a node around an anchor point.

Capabilities: transform

stroke — Stroke

Overrides the stroke colour, width and dash pattern of a node.

Capabilities: style

translate — Translate

Moves a node or group by an offset.

Capabilities: transform

visibility — Visibility

Shows or hides a node, typically bound to a model condition.

Capabilities: style conditional

z-order — Z order

Sorts siblings; higher values are drawn on top.

Capabilities: layout

Behaviours

What the reader can do to a node, and what that writes. Listed on the node under behaviours.

clickable drag-along-route drag-angle drag-axis-tick drag-circle-point drag-in-frame drag-rotate drag-value draggable edit-text edit-value follow-pointer forget hoverable keep-time play-note press-and-slide remember resizable respond-to-simulation rotatable selectable tooltip track-pointer

clickable — Clickable

Writes a value into a model variable or into a component parameter when the node is clicked. The value is a binding like any other, so a key can write what the model or the object itself currently holds rather than only a constant.

Capabilities: interaction writes-model

drag-along-route — Drag along the route

Lets the reader slide the node along the route of the connector it is drawn in: the point of the route nearest the pointer is written into the component property as the fraction of the way along it, from 0 at the start to 1 at the end. It is what moves a connector's label.

Capabilities: interaction linear

drag-angle — Drag angle

Lets the user drag the node around an anchor point and writes the resulting angle back into a model variable, using the same angle-to-value mapping the node was bound with. Naming a length as well makes the node reach the pointer rather than only point at it: how far the pointer stands from the anchor is written as the length, in the units the node is drawn in, so one drag both turns the thing and stretches it.

Capabilities: interaction angular writes-model

drag-axis-tick — Drag axis tick

Rescales an axis by dragging one of its ticks: the tick follows the pointer and the far end of the axis moves with it, writing the object's own maximum. An axis standing on zero is pulled from the middle, naming no minimum property and handing nought over as the minimum value, so what it writes is how far the drawing reaches from the origin. The same interaction, and the same arithmetic, the chart's axes have. An axis whose ticks are placed by the logarithm of their value is dragged in decades rather than in values, and one that says how many parts it is cut into rather than how much one part is worth keeps the part and writes the count, so its numbers stay the same distance apart and there are more or fewer of them.

Capabilities: interaction

drag-circle-point — Drag a point round a circle

Drags a point round a circle and writes back everything the circle is read for at once: the angle the point stands at, how far out it stands, the cosine and the sine of that angle, its tangent and its cotangent, and the length of the arc it has swept. Each of them goes into the term its row names, or into the object's own parameter when that row holds a plain number instead, and a row the model works out for itself is left alone — so a circle whose angle a definition gives is still dragged where it writes the point. Asking for a number of divisions makes the angle land on one of them: the point follows the pointer while it is held and lands on the nearest division, exactly, the moment it is let go. The whole drag is one edit.

Capabilities: interaction angular writes-model

drag-in-frame — Drag in the frame

Lets the reader drag a figure held in a referential by a node of its drawing, the pointer read in the referential's own units. As a point it writes where the pointer stands, less the origin, into the across and up variables, keeping the distance between the pointer and the point it was pressed on, and landing on the referential's ticks when it snaps to them; as an angle it writes the way the pointer stands from the origin, anticlockwise from the across axis in the model's angle unit; as a distance it writes how far the pointer stands from the origin. Each variable is written into the model, or into the component parameter when it holds a plain number.

Capabilities: interaction planar writes-model

drag-rotate — Drag rotate

Lets the user turn the node around an anchor point by dragging it. The variable moves by the angle the pointer travels, so the grabbed point follows the pointer instead of jumping to it, which is what a rose, a bezel or a dial ring needs.

Capabilities: interaction angular writes-model

drag-value — Drag value

Lets the reader set a value by where they press along a line and drag: the pointer's place between the two ends of the scale is the value written, into the model variable or into the component parameter when the variable holds a plain number. It is what a slider's handle needs. The value can be made to land on whole steps, and it never leaves the scale.

Capabilities: interaction linear writes-model

draggable — Draggable

The object can be moved with the move handle. Provided by the host shape for every component.

Capabilities: interaction

edit-text — Edit text

Lets the reader write the text a component property holds: double-clicking the node, or the object when it is selected, opens a box over the place the text stands in where it can be written over several lines. Leaving the box, or Ctrl+Enter, writes what is in it into the property, and Escape leaves the text as it was.

Capabilities: interaction

edit-value — Edit value

Lets the reader type a new value over the node: double-clicking it opens a number box where it stands, Enter or leaving the box writes the number into the model variable, or into the component parameter when the variable holds a plain number, and Escape leaves it as it was. A variable the model works out for itself cannot be typed into.

Capabilities: interaction writes-model

follow-pointer — Follow pointer

Reports where the pointer is over the node, in the units the node is scaled in, so a drawing can show the value under the cursor. What is reported is not kept: it lasts as long as the pointer is over the node, and the model is not touched.

Capabilities: interaction

forget — Forget

Empties one of the object's memories when the node is clicked.

Capabilities: interaction memory

hoverable — Hoverable

The node reacts to pointer hover with the standard highlight cursor.

Capabilities: interaction

keep-time — Keep time

A transport key for a reading of the clock: play sets it counting real time from wherever it stands, pause holds it there, and stop ends the run and clears it. A key set to toggle is both — it starts a clock standing still and holds a clock that is counting, so one key does the work of two. What is counted is written into the four parts of the reading — the hours, the minutes, the seconds and the thousandths — each into the term that part names, or into the object's own property when it names a plain number instead. The whole run is one edit.

Capabilities: interaction writes-model

play-note — Play a note

A key of an instrument: it sounds its own pitch for as long as it is held, and stops when it is let go. Several keys sound together, whether they are held by several fingers or by several computer keys at once, and sliding across them plays them in turn. The object reports the notes it is holding into a parameter of its own, so its drawing can show which keys are down and what it publishes can be worked out from the chord. Nothing is written down: a file remembers no note left sounding.

Capabilities: interaction sound

press-and-slide — Press and slide

A control the reader holds down: pressing keeps the value where it is, sliding the pointer up raises it and down lowers it, by however far it travelled, and letting go lets the value fall back to its resting value a step at a time. It is what a pedal or a throttle needs — nothing is written by pressing alone, and the whole gesture, the fall back included, is one edit.

Capabilities: interaction linear writes-model

remember — Remember

Appends a row to one of the object's memories when the node is clicked. A row carries a label and two numbers, all of them bindings, so a key records what the object held at the moment it was pressed.

Capabilities: interaction memory

resizable — Resizable

The object can be resized with the corner handles. Provided by the host shape for every component.

Capabilities: interaction

respond-to-simulation — Respond to simulation updates

Marks the object as redrawing on every simulation tick. Components with model bindings get this automatically.

Capabilities: simulation

rotatable — Rotatable

The object can be rotated with the rotation handle. Provided by the host shape for every component.

Capabilities: interaction

selectable — Selectable

The object can be selected on the board. Provided by the host shape for every component.

Capabilities: interaction

tooltip — Tooltip

Shows a native tooltip with a fixed or bound text when the pointer rests on the node.

Capabilities: interaction textual

track-pointer — Track pointer

Records where the pointer is while it is dragged over the node, one sample every sampling interval, into one of the object's memories. The sample is written in the units the node is scaled in, so what is recorded is a pair of values rather than a pair of pixels — and when the memory names model terms, the run becomes the values those terms take, iteration by iteration. Nothing is recorded until the pointer travels: a click that never moves leaves the memory alone, and a drag opens its run at the point the pointer went down.

Capabilities: interaction memory writes-model

Components

Ready-made assemblies. A node names one as its type and sets these under parameters.

ac-generator battery cable calculator capacitor circuit circuit-track circular-gauge clock compass dial-face electric-circuit electric-switch gauge geometry-point geometry-system key-cap label-ring light-bulb magnetic-system mechanical-anchor mechanical-ball mechanical-block mechanical-joint mechanical-pulley mechanical-rope mechanical-spring mechanical-surface mechanical-system mechanical-wave media memory-list memory-trace microphone mind-map-bubble mind-map-connector mind-map-ellipse mind-map-rectangle mouse-tracker optical-system orbit-system oscilloscope piano piano-keyboard plot-axes plot-crosshair plot-grid pointer-hand pointer-ring program protractor question resistor rich-text rotating-vector ruler seven-segment-display slider slope speedometer steering-wheel text-box thermometer tick-ring trigonometric-circle value

ac-generator — AC generator

Represents an alternating-current generator in an electric circuit, with a terminal at each end for connecting cables. Its electromotive force swings as a sine of the independent variable, A·sin(2πft + φ), from its amplitude, frequency and phase, each read from a variable or a number, and it displays the current through it and the voltage across its terminals, with an optional arrow showing the direction of the current.

Capabilities: reads-model

battery — Battery

Represents a battery cell in an electric circuit, with a terminal at each end for connecting cables. Displays the electromotive force, the current through the cell and the voltage across its terminals, each read from a variable or a number, with an optional arrow showing the direction of the current.

Capabilities: reads-model

cable — Cable

Connects a terminal of one circuit part to a terminal of another. When linked to the variable holding the loop current, it displays charges moving along the cable in the direction of the current, at a speed proportional to its magnitude, and stationary when no current flows.

Capabilities: reads-model

calculator — Calculator

Provides a calculator on the board, with basic operations and, at larger widths, a scientific keypad for powers, roots, trigonometry and logarithms. Dedicated keys load the values of model variables at the current iteration, the result can be written to a model variable, and completed operations are kept in a history.

Capabilities: interaction textual reads-model writes-model memory

capacitor — Capacitor

Represents an electrolytic capacitor in an electric circuit, with two terminals for connecting cables. Displays the capacitance, the current and the voltage, each read from a variable or a number, which makes it suitable for charging and discharging in RC circuit models.

Capabilities: reads-model

circuit — Circuit

Displays a closed racing track generated from a track number, with straights, bends, kerbs and a start line. It holds bodies whose position and heading are model variables, measured from the center of the track in configurable units, and indicates when a body leaves the road.

Capabilities: holds-shapes

circuit-track — Circuit track

A closed racing track laid out from a seed: the same seed always draws the same loop of straights and bends, fitted to the width and height it is given. The road is drawn as one wide stroke along the centreline, red and white kerbs stand on every bend, and a chequered line marks the start of the lap. The road is the node called "road", so whatever holds shapes on the track can tell where its edges are.

Capabilities: generated

circular-gauge — Circular gauge

Displays the value of a model variable as a ring that fills clockwise in proportion to that value between a configurable minimum and maximum. The start angle and span of the ring are adjustable, and an optional numeric readout shows the value with its unit.

Capabilities: radial angular reads-model

clock — Clock

Displays a time as an analog face or a digital readout, either from model variables for hours, minutes, seconds and milliseconds or from the independent variable taken as seconds. It can also operate as a stopwatch, with controls to start, stop and record laps.

Capabilities: radial angular reads-model textual interaction memory

compass — Compass

Displays a compass rose with cardinal directions and a needle whose heading is read from a model variable, while a second variable rotates the rose. Dragging the needle or the rim of the rose writes the corresponding value back to the model, so it also serves as a heading control.

Capabilities: radial angular reads-model interaction writes-model

dial-face — Dial face

Circular face with an optional bezel ring, used as the background of clocks, gauges and compasses.

Capabilities: radial background

electric-circuit — Electric circuit

Holds batteries, resistors, bulbs, capacitors, switches and the cables joining them, and works out the current through each part and the voltage across it. Parts and cables are added with the circuit's + button.

Capabilities: layout interaction

electric-switch — Switch

Represents a switch in an electric circuit, with two terminals for connecting cables. Clicking the switch opens or closes it, writing 0 or 1 to its variable, so the model can make or break the circuit. The current and the voltage across the switch are also displayed.

Capabilities: reads-model interaction writes-model

gauge — Gauge

Displays the value of a model variable as a needle on a numbered dial, and allows the value to be set by turning the needle. The scale can adjust automatically to the range of the run or use a fixed minimum and maximum, and up to three colored bands mark regions of the scale.

Capabilities: radial angular reads-model writes-model interaction scale

geometry-point — Geometry point

A point of a geometric construction, placed by two coordinates. Dragging it moves every segment, line, circle, polygon and angle built on it; a variable the model defines moves it instead.

Capabilities: reads-model writes-model interaction

geometry-system — Geometry

A workspace with axes for building geometric constructions as in dynamic geometry: points joined by segments, lines, rays and vectors, circles, triangles and polygons, and angles. Constructions follow their points wherever they are dragged or wherever the model moves them, and lengths, slopes, areas, perimeters and angles are shown on the drawing and can be written into model variables. Constructions are added with the system’s + button, by clicking existing points or empty places where new points are put.

Capabilities: layout interaction reads-model writes-model

key-cap — Key cap

Rounded key with a centred label. It carries no interaction of its own: put it inside a group and give that group the behaviour the key performs, so the same cap serves a keypad, a legend or a toolbar.

Capabilities: sizable textual

label-ring — Label ring

Numeric or text labels placed evenly around a centre, always drawn upright.

Capabilities: radial angular textual

light-bulb — Light bulb

Represents a light bulb in an electric circuit, with two terminals for connecting cables. Its brightness reflects the power it receives relative to its rated power, calculated from the voltage and current, or from the current and resistance when no voltage is given. Resistance, current and voltage are each read from a variable or a number.

Capabilities: reads-model

magnetic-system — Magnetic system

A space for magnetism, with axes in metres. It holds bar magnets, wires and coils carrying currents, compasses, regions of uniform field and charged particles, draws the field lines of the magnets and currents, turns each compass to the field and traces the path of each particle through the uniform fields. Parts are added with the system's + button.

Capabilities: layout interaction reads-model writes-model

mechanical-anchor — Anchor

A fixed point in a mechanical system that springs, ropes and joints are fastened to, like the support of a pendulum. Dragging it moves the point of support. Springs, ropes and joints fasten to its terminals.

Capabilities: reads-model interaction

mechanical-ball — Ball

A circular rigid body in a mechanical system that rolls and collides, with a mass, a radius, friction and restitution. Its position, angle and velocity are numbers it starts from, variables the simulation writes, or variables the model defines. Dragging it moves it and dragging the grip on its rim turns it. Springs, ropes and joints fasten to its terminals.

Capabilities: reads-model writes-model interaction

mechanical-block — Block

A rectangular rigid body in a mechanical system, with a mass, a size, friction and restitution. Its position, angle and velocity are numbers it starts from, variables the simulation writes, or variables the model defines. Dragging it moves it and dragging the grip on its side turns it. Springs, ropes and joints fasten to its terminals.

Capabilities: reads-model writes-model interaction

mechanical-joint — Joint

A rigid connection between two parts of a mechanical system: a rod that keeps them at the same distance, a pivot that pins one to the other at a point while both turn freely, or a weld that holds them fast. It is drawn from a terminal of one part to a terminal of another.

Capabilities: reads-model writes-model

mechanical-pulley — Pulley

An ideal fixed pulley in a mechanical system, with no mass and no friction, that turns a rope round. Two ropes fastened to its left and right sides act as one rope over the wheel: the same tension pulls both bodies and the total length stays the same. Dragging it moves it.

Capabilities: reads-model interaction

mechanical-rope — Rope

A flexible rope fastened between two parts of a mechanical system. It pulls only while it is taut and goes slack when its ends come closer. It does not stretch, unless it is given a stiffness: then it stretches like a spring that only pulls, as a bungee cord does. Two ropes fastened to the sides of a pulley act as one rope over it.

Capabilities: reads-model writes-model

mechanical-spring — Spring

A coil spring fastened between two parts of a mechanical system, pulling and pushing them by Hooke’s law with damping. It is drawn from a terminal of one part to a terminal of another and follows them as they move.

Capabilities: reads-model writes-model

mechanical-surface — Surface

A fixed flat or inclined surface in a mechanical system that bodies rest on, slide along and bounce off, with friction and restitution. Dragging it moves it; dragging its right end changes its inclination and its length. Springs, ropes and joints fasten to its terminals.

Capabilities: reads-model interaction

mechanical-system — Mechanical system

A workspace with axes in metres for building mechanical systems from blocks, balls, surfaces, anchors, pulleys, springs, ropes, joints and forces. A built-in physics simulation works out their motion with gravity, friction, air drag, collisions, springs and constraints, row by row with the model; any position or velocity can instead be given by the model, and what the simulation works out can be written into model variables. Parts are added with the system’s + button.

Capabilities: layout interaction reads-model writes-model

mechanical-wave — Mechanical wave

Represents a mechanical wave as a chain of oscillators, each reproducing the motion of the source with a delay proportional to its distance. It can replay the values of a model variable over the run, or compute a wave from its amplitude, frequency, speed and damping and return the displacement of a chosen oscillator to the model.

Capabilities: reads-model writes-model oscillation

media — Media

Shows an image, a video or a sound, chosen from a file, from the catalogue or from a link to a video page. A video or a sound can follow the model, a frame for each step, or play on its own with its own controls.

Capabilities: layout interaction

memory-list — Memory list

The rows of a memory drawn as a list, newest first, with the label on the left and the number on the right. Rows can carry actions, so choosing one puts what it holds back into the object.

Capabilities: memory textual interaction

memory-trace — Memory trace

The path the rows of a memory draw, mapped from the values they hold to the pixels of a plot with the same origin and scale the recording used.

Capabilities: memory linear

microphone — Microphone

Displays the sound level picked up by the computer's microphone as a column of lights colored by configurable ranges, with readouts of the level in decibels and the dominant frequency. When linked to existing model variables, it writes the level and frequency to them at each iteration, so dependent variables follow the sound.

Capabilities: writes-model sound

mind-map-bubble — Speech bubble

Represents a speech bubble in a mind map or diagram: a rounded box with a tail pointing toward a speaker or a part of the board. Its text is edited by double-clicking, the tail position is adjustable, and connectors can be attached anywhere on its outline.

Capabilities: textual interaction

mind-map-connector — Mind map connector

Connects two objects on the board with a line or an arrow, either end attached to an object or left free. The line can be curved, straight or elbowed, solid or dashed, with a choice of end tips, and can carry a text label positioned along its length.

Capabilities: interaction textual

mind-map-ellipse — Mind map ellipse

Represents a node of a mind map as an ellipse holding text, typically used for the central idea. Its text is edited by double-clicking and wraps to fit the shape. Connectors can be attached anywhere on its outline and follow it when it moves.

Capabilities: textual interaction