A theme gives names to colours. Use them in styles and stylesheets as
"$name", e.g. style(background = "$primary"). Built-in widgets use
theme colours, so a theme restyles a whole app:
app(ui, theme = "dark") or app$theme <- termr_theme("light", accent = "purple").
Details
Named termr_theme() so that it does not mask ggplot2::theme().
Colour names: foreground, background (screen background), surface
(headers, panels), muted (secondary text, guides, disabled widgets),
primary and on_primary (primary buttons, cursors), accent (focus),
success, warning, error, information, stripe (zebra rows).
Extra names can be added.
Built-in themes: "default" (the terminal's own 16-colour palette),
"dark" and "light" (24-bit colours) and "high-contrast" (black and
white with saturated yellow / cyan highlights and a heavier border around the
focused widget).
On a terminal without colour (NO_COLOR, TERM=dumb) selections and
cursors are drawn in reverse video, errors in bold underline and
secondary text dimmed, so nothing depends on colour alone.