Elements

33 elements, and the 15 methods every one of them has. This page is written from elements.toml, the one table go run ./tools/gen writes the Go an app calls from — elements.go, one type per element and one method per keyword — together with the interpreter's view of the package and the numbers both sides of the engine's C face count with. A method that is not here is one an app cannot write, and Go itself says so: a call to it is a type error, in gomamochi check and in go build alike.

Types on this page are Go's: string, float64, int and bool; a list of strings or of numbers is written as a variadic argument, ...string or ...float64, a list of lists as [][]float64, and the closure that builds row i as func(int) Element. A handler is a closure handed to the method the element names for it, taking what the event carries: func(), func(string), func(bool), func(int) or func(float64); see Handlers.

The methods every element has

These fifteen are methods on every element, under one name and one meaning. They are written once, on the box every element is built over, rather than repeated on thirty of them — which is why an element that owns one of the names under its own meaning keeps it: a Text's .Width is the text's own method, and it shadows the shared one.

Method	Type	Default
`.Width`	`float64`	—
`.Height`	`float64`	—
`.MinWidth`	`float64`	—
`.MaxWidth`	`float64`	—
`.Disabled`	`bool`	`false`
`.Theme`	`string`	`""`
`.Animate`	`float64`	`0`
`.Easing`	`string`	`""`
`.Enter`	`bool`	`false`
`.Exit`	`bool`	`false`
`.ColSpan`	`int`	`1`
`.RowSpan`	`int`	`1`
`.Role`	`string`	`""`
`.A11yLabel`	`string`	`""`
`.Tooltip`	`string`	`""`

Text, buttons, links

Text

A run of text. wrap is "", "nowrap" or "ellipsis"; a background with padding and a radius makes a pill.

Written as Text(text string).

Sizes itself with its own .Width: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Size`	`float64`	`0`
`.Color`	`string`	`""`
`.Align`	`string`	`""`
`.Grow`	`float64`	`0`
`.Bold`	`bool`	`false`
`.Italic`	`bool`	`false`
`.Mono`	`bool`	`false`
`.Underline`	`bool`	`false`
`.Wrap`	`string`	`""`
`.MaxLines`	`int`	`0`
`.Width`	`float64`	`0`
`.Background`	`string`	`""`
`.Padding`	`float64`	`0`
`.BorderRadius`	`float64`	`0`
`.BorderWidth`	`float64`	`0`
`.BorderColor`	`string`	`""`

Button

A button. The block runs when it is pressed.

Written as Button(label string).

Sizes itself with its own .Width / .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.OnClick`	`func()`	—
`.Width`	`float64`	`0`
`.Height`	`float64`	`0`
`.Size`	`float64`	`0`
`.Background`	`string`	`""`
`.Grow`	`float64`	`0`
`.Color`	`string`	`""`
`.HoverBackground`	`string`	`""`
`.ActiveBackground`	`string`	`""`
`.BorderRadius`	`float64`	`0`
`.BorderWidth`	`float64`	`0`
`.BorderColor`	`string`	`""`
`.Basis`	`float64`	`0`

Link

Text that opens a page when clicked. There is no handler: opening a page is not the app's state.

Written as Link(label string, url string).

Method	Type	Default
`.Size`	`float64`	`0`

The boxes that arrange

Column

Its children down the page.

Written as Column(kids ...Element).

Takes elements as its children, written as its last arguments.

Method	Type	Default
`.Spacing`	`float64`	`-1`
`.Padding`	`float64`	`0`
`.Background`	`string`	`""`
`.Grow`	`float64`	`0`
`.BorderRadius`	`float64`	`0`
`.BorderWidth`	`float64`	`0`
`.BorderColor`	`string`	`""`

Row

Its children across the page.

Written as Row(kids ...Element).

Takes elements as its children, written as its last arguments.

Method	Type	Default
`.Spacing`	`float64`	`-1`
`.Padding`	`float64`	`0`
`.Background`	`string`	`""`
`.Grow`	`float64`	`0`
`.BorderRadius`	`float64`	`0`
`.BorderWidth`	`float64`	`0`
`.BorderColor`	`string`	`""`

Grid

Its children on tracks. columns counts the tracks; col_span on a child covers more than one.

Written as Grid(kids ...Element).

Takes elements as its children, written as its last arguments.

Method	Type	Default
`.Columns`	`int`	`2`
`.Rows`	`int`	`0`
`.Spacing`	`float64`	`-1`
`.Padding`	`float64`	`0`
`.Background`	`string`	`""`
`.Grow`	`float64`	`0`
`.BorderRadius`	`float64`	`0`
`.BorderWidth`	`float64`	`0`
`.BorderColor`	`string`	`""`

GridCell

The span written out: this and col_span: on the child itself are the same tree.

Written as GridCell(kids ...Element).

Takes elements as its children, written as its last arguments.

No methods of its own.

Stack

Its children on top of one another.

Written as Stack(kids ...Element).

Takes elements as its children, written as its last arguments.

No methods of its own.

ScrollView

A pane that scrolls when its children do not fit.

Written as ScrollView(kids ...Element).

Takes elements as its children, written as its last arguments.

Sizes itself with its own .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Height`	`float64`	`0`

HScrollView

A pane that scrolls sideways.

Written as HScrollView(kids ...Element).

Takes elements as its children, written as its last arguments.

No methods of its own.

A panel over the rest of the window while open.

Written as Modal(kids ...Element).

Takes elements as its children, written as its last arguments.

Method	Type	Default
`.Open`	`bool`	`true`

Fields and choosers

TextField

A line a person types into. on_change fires per keystroke, on_submit when they press enter; multiline makes it a paragraph field.

Written as TextField(value string).

Method	Type	Default
`.Placeholder`	`string`	`""`
`.OnChange`	`func(string)`	—
`.OnSubmit`	`func(string)`	—
`.Multiline`	`bool`	`false`
`.Rows`	`float64`	`0`

NumberField

A field for a number: enter or leaving it commits, text that is not a number is dropped. min/max both 0 is unbounded, step 0 is free.

Written as NumberField(value float64).

Method	Type	Default
`.Min`	`float64`	`0`
`.Max`	`float64`	`0`
`.Step`	`float64`	`0`
`.Placeholder`	`string`	`""`
`.OnChange`	`func(float64)`	—

IntField

The same field for a whole number.

Written as IntField(value int).

Method	Type	Default
`.Min`	`int`	`0`
`.Max`	`int`	`0`
`.Step`	`int`	`1`
`.Placeholder`	`string`	`""`
`.OnChange`	`func(int)`	—

Checkbox

A box a person ticks. The block receives the new state.

Written as Checkbox(label string).

Its own label is what a screen reader reads; .A11yLabel is refused on it, and stops the app with that reason.

Method	Type	Default
`.Checked`	`bool`	`false`
`.OnChange`	`func(bool)`	—

Switch

A switch a person flips. The block receives the new state.

Written as Switch(label string).

Its own label is what a screen reader reads; .A11yLabel is refused on it, and stops the app with that reason.

Method	Type	Default
`.Checked`	`bool`	`false`
`.OnChange`	`func(bool)`	—

Slider

A track a person drags. The block receives the new number.

Written as Slider().

Method	Type	Default
`.Value`	`float64`	`0`
`.Min`	`float64`	`0`
`.Max`	`float64`	`1`
`.Step`	`float64`	`0`
`.OnChange`	`func(float64)`	—

Select

A drop-down. The block receives the chosen index.

Written as Select().

Method	Type	Default
`.Options`	`...string`	—
`.Selected`	`int`	`0`
`.OnChange`	`func(int)`	—

RadioGroup

A column of radio buttons. The block receives the chosen index.

Written as RadioGroup().

Method	Type	Default
`.Options`	`...string`	—
`.Selected`	`int`	`0`
`.OnChange`	`func(int)`	—

Segmented

A row of joined toggle buttons. The block receives the chosen index.

Written as Segmented().

Method	Type	Default
`.Options`	`...string`	—
`.Selected`	`int`	`0`
`.OnChange`	`func(int)`	—

TabBar

A row of tabs. The block receives the chosen index.

Written as TabBar().

Method	Type	Default
`.Labels`	`...string`	—
`.Active`	`int`	`0`
`.OnChange`	`func(int)`	—

Lists and tables

ListView

Rows built on demand: the builder is called for the rows in view, not for all of them.

Written as ListView(count int, row func(int) Element).

Sizes itself with its own .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.ItemHeight`	`float64`	`24`
`.Height`	`float64`	`0`
`.Virtualized`	`bool`	`true`
`.Grow`	`float64`	`0`

Table

A table whose rows are built on demand, laid on tracks whose shares are widths. on_select receives the row clicked, on_sort the header.

Written as Table(columns []string, count int, row func(int) Element).

Sizes itself with its own .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Widths`	`...float64`	—
`.ItemHeight`	`float64`	`24`
`.Height`	`float64`	`0`
`.Grow`	`float64`	`0`
`.Selected`	`int`	`-1`
`.OnSelect`	`func(int)`	—
`.Sort`	`int`	`-1`
`.Descending`	`bool`	`false`
`.OnSort`	`func(int)`	—

DataTable

The first row child is the header; the later ones are data rows, shaded in alternation, in a frame that comes with the element.

Written as DataTable(kids ...Element).

Takes elements as its children, written as its last arguments.

No methods of its own.

Charts and progress

BarChart

Bars. min/max both 0 take the range from the data; axis draws ticks and gridlines; series draws several groups.

Written as BarChart(data []float64).

Sizes itself with its own .Width / .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Labels`	`...string`	—
`.Width`	`float64`	`0`
`.Height`	`float64`	`0`
`.Min`	`float64`	`0`
`.Max`	`float64`	`0`
`.Axis`	`bool`	`false`
`.Color`	`string`	`""`
`.Series`	`[][]float64`	—
`.Colors`	`...string`	—

LineChart

A line. Same arguments as the bars, and series draws several lines.

Written as LineChart(data []float64).

Sizes itself with its own .Width / .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Labels`	`...string`	—
`.Width`	`float64`	`0`
`.Height`	`float64`	`0`
`.Min`	`float64`	`0`
`.Max`	`float64`	`0`
`.Axis`	`bool`	`false`
`.Color`	`string`	`""`
`.Series`	`[][]float64`	—
`.Colors`	`...string`	—

Progress

A track filled to value (0 to 1); indeterminate sweeps instead, for work with no known length.

Written as Progress(value float64).

Sizes itself with its own .Width / .Height: those are the element's, and the shared methods leave them alone.

Its own label is what a screen reader reads; .A11yLabel is refused on it, and stops the app with that reason.

Method	Type	Default
`.Width`	`float64`	`0`
`.Height`	`float64`	`0`
`.Label`	`string`	`""`
`.Indeterminate`	`bool`	`false`

Pictures and the canvas

Image

A picture from a file.

Written as Image(source string).

Sizes itself with its own .Width / .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Width`	`float64`	`0`
`.Height`	`float64`	`0`

Svg

A drawing from an SVG file, painted at any size.

Written as Svg(source string).

Sizes itself with its own .Width / .Height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Width`	`float64`	`0`
`.Height`	`float64`	`0`

Canvas

A grid of virtual pixels, painted by the commands written in its block. A color here is a NUMBER: the index of a color in palette, which is how drawing code written for a pixel machine ports line for line. scale is how many logical pixels one virtual pixel takes.

Written as Canvas(width int, height int).

Sizes itself with its own width / height: those are the element's, and the shared methods leave them alone.

Method	Type	Default
`.Scale`	`int`	`1`
`.Background`	`int`	`0`
`.Palette`	`...string`	—
`.Paint`	`func(*Painter)`	—

The small pieces

Spacer

Takes the space its parent has left over; 0 is one share.

Written as Spacer().

Method	Type	Default
`.Grow`	`float64`	`0`

Divider

A rule across its parent: level in a column, upright in a row.

Written as Divider().

Method	Type	Default
`.Color`	`string`	`""`
`.Thickness`	`float64`	`0`

Spinner

A turning ring, for work with no known length.

Written as Spinner().

Method	Type	Default
`.Size`	`float64`	`0`

The canvas's drawing commands

The 10 commands below are methods on the *Painter a Canvas's .Paint closure is handed. They are not elements: they have none of the methods above, nothing can click them, and they mean nothing outside the canvas they are written in. Every coordinate is a whole virtual pixel and every color is a number, the index of a color in the canvas's palette. Go has no optional argument, so a value the table gives a default to is written all the same.

Command	Written as
`Pixel`	`p.Pixel(x int, y int, color int)`
`Line`	`p.Line(x1 int, y1 int, x2 int, y2 int, color int)`
`Rect`	`p.Rect(x int, y int, w int, h int, color int)`
`RectOutline`	`p.RectOutline(x int, y int, w int, h int, color int)`
`Circle`	`p.Circle(x int, y int, r int, color int)`
`CircleOutline`	`p.CircleOutline(x int, y int, r int, color int)`
`Triangle`	`p.Triangle(x1 int, y1 int, x2 int, y2 int, x3 int, y3 int, color int)`
`TriangleOutline`	`p.TriangleOutline(x1 int, y1 int, x2 int, y2 int, x3 int, y3 int, color int)`
`Sprite`	`p.Sprite(x int, y int, source string, u int, v int, w int, h int, colkey int, flipX bool, flipY bool)`
`PixelText`	`p.PixelText(x int, y int, text string, color int)`

Adding one

An element is a row in elements.toml and an arm in the engine's materialize. go run ./tools/gen writes elements.go and internal/symbols/symbols.go from it — one type per element, one method per keyword, and the interpreter's view of the package — and the sweep fails when either is behind the table, so an element cannot come to mean one thing in Go and another where it is drawn. The same table is read by the other three languages on this engine.