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Elements

33 elements, and the 15 keywords every one of them takes. This page is written from elements.toml, the one table the Perl subs an app calls, the numbers both sides of the engine's C face count with, and the engine's own constants are generated from. A keyword that is not here is one an app cannot write, and rakugan check says so by name.

Types on this page: text is a string, number a float, whole number an integer, true/false a boolean, and a list of either. A handler is an anonymous sub written on the keyword the element names for it, taking what the event carries; see Handlers.

The keywords every element takes

These fifteen ride on every element under one name and one meaning. They are wrappers around the element rather than fields 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, and the box leaves it alone.

Keyword Type Default
width number —
height number —
min_width number —
max_width number —
disabled true/false false
theme text ""
animate number 0
easing text ""
enter true/false false
exit true/false false
col_span whole number 1
row_span whole number 1
role text ""
a11y_label text ""
tooltip text ""

Text, buttons, links

text

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

Sizes its own width: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
text text written first, in order
size number 0
color text ""
align text ""
grow number 0
bold true/false false
italic true/false false
mono true/false false
underline true/false false
wrap text ""
max_lines whole number 0
width number 0
background text ""
padding number 0
border_radius number 0
border_width number 0
border_color text ""

button

A button. The block runs when it is pressed.

Sizes its own width / height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
label text written first, in order
on_click a handler —
width number 0
height number 0
size number 0
background text ""
grow number 0
color text ""
hover_background text ""
active_background text ""
border_radius number 0
border_width number 0
border_color text ""
basis number 0

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

Keyword Type Default
label text written first, in order
url text written first, in order
size number 0

The boxes that arrange

column

Its children down the page.

Takes elements as its children, written as its arguments.

Keyword Type Default
spacing number -1
padding number 0
background text ""
grow number 0
border_radius number 0
border_width number 0
border_color text ""

row

Its children across the page.

Takes elements as its children, written as its arguments.

Keyword Type Default
spacing number -1
padding number 0
background text ""
grow number 0
border_radius number 0
border_width number 0
border_color text ""

grid

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

Takes elements as its children, written as its arguments.

Keyword Type Default
columns whole number 2
rows whole number 0
spacing number -1
padding number 0
background text ""
grow number 0
border_radius number 0
border_width number 0
border_color text ""

grid_cell

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

Takes elements as its children, written as its arguments.

No keywords of its own.

stack

Its children on top of one another.

Takes elements as its children, written as its arguments.

No keywords of its own.

scroll_view

A pane that scrolls when its children do not fit.

Takes elements as its children, written as its arguments.

Sizes its own height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
height number 0

h_scroll_view

A pane that scrolls sideways.

Takes elements as its children, written as its arguments.

No keywords of its own.

A panel over the rest of the window while open.

Takes elements as its children, written as its arguments.

Keyword Type Default
open true/false true

Fields and choosers

text_field

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

Keyword Type Default
value text written first, in order
placeholder text ""
on_change a handler —
on_submit a handler —
multiline true/false false
rows number 0

number_field

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.

Keyword Type Default
value number written first, in order
min number 0
max number 0
step number 0
placeholder text ""
on_change a handler —

int_field

The same field for a whole number.

Keyword Type Default
value whole number written first, in order
min whole number 0
max whole number 0
step whole number 1
placeholder text ""
on_change a handler —

checkbox

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

Its own label is what a screen reader reads, so the shared a11y_label is not offered here.

Keyword Type Default
label text written first, in order
checked true/false false
on_change a handler —

switch

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

Its own label is what a screen reader reads, so the shared a11y_label is not offered here.

Keyword Type Default
label text written first, in order
checked true/false false
on_change a handler —

slider

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

Keyword Type Default
value number 0
min number 0
max number 1
step number 0
on_change a handler —

select

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

Keyword Type Default
options list of text []
selected whole number 0
on_change a handler —

radio_group

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

Keyword Type Default
options list of text []
selected whole number 0
on_change a handler —

segmented

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

Keyword Type Default
options list of text []
selected whole number 0
on_change a handler —

tab_bar

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

Keyword Type Default
labels list of text []
active whole number 0
on_change a handler —

Lists and tables

list_view

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

Sizes its own height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
count whole number written first, in order
row a count, and the sub building row i written first, in order
item_height number 24
height number 0
virtualized true/false true
grow number 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.

Sizes its own height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
columns list of text written first, in order
count whole number written first, in order
row a count, and the sub building row i written first, in order
widths list of numbers []
item_height number 24
height number 0
grow number 0
selected whole number -1
on_select a handler —
sort whole number -1
descending true/false false
on_sort a handler —

data_table

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

Takes elements as its children, written as its arguments.

No keywords of its own.

Charts and progress

bar_chart

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

Sizes its own width / height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
data list of numbers written first, in order
labels list of text []
width number 0
height number 0
min number 0
max number 0
axis true/false false
color text ""
series list of lists of numbers []
colors list of text []

line_chart

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

Sizes its own width / height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
data list of numbers written first, in order
labels list of text []
width number 0
height number 0
min number 0
max number 0
axis true/false false
color text ""
series list of lists of numbers []
colors list of text []

progress

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

Sizes its own width / height: those are the element's, and the shared keyword leaves them alone.

Its own label is what a screen reader reads, so the shared a11y_label is not offered here.

Keyword Type Default
value number written first, in order
width number 0
height number 0
label text ""
indeterminate true/false false

Pictures and the canvas

image

A picture from a file.

Sizes its own width / height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
source text written first, in order
width number 0
height number 0

svg

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

Sizes its own width / height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
source text written first, in order
width number 0
height number 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.

Sizes its own width / height: those are the element's, and the shared keyword leaves them alone.

Keyword Type Default
width whole number written first, in order
height whole number written first, in order
scale whole number 1
background whole number 0
palette list of text []

The small pieces

spacer

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

Keyword Type Default
grow number 0

divider

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

Keyword Type Default
color text ""
thickness number 0

spinner

A turning ring, for work with no known length.

Keyword Type Default
size number 0

The canvas's drawing commands

The 10 commands below are written inside a canvas's paint sub. They are not elements: they take none of the keywords 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. A value with a default may be left out, and is then given by name.

Command Written as
pixel pixel(x, y, color)
line line(x1, y1, x2, y2, color)
rect rect(x, y, w, h, color)
rect_outline rect_outline(x, y, w, h, color)
circle circle(x, y, r, color)
circle_outline circle_outline(x, y, r, color)
triangle triangle(x1, y1, x2, y2, x3, y3, color)
triangle_outline triangle_outline(x1, y1, x2, y2, x3, y3, color)
sprite sprite(x, y, source, u, v, w, h, colkey => -1, flip_x => false, flip_y => false)
pixel_text pixel_text(x, y, text, color)

Adding one

An element is a row in elements.toml and an arm in the engine's materialize. tools/gen.pl writes the Perl subs and the table as Perl data from it, and the sweep fails when either is behind the table, so an element cannot come to mean one thing in Perl and another where it is drawn. The same table is read by the other three languages on this engine.