`ThemePicker`¶

Render an accessible no-JavaScript form for an allowlisted theme and color-mode preference.


Import	`from hedron import ThemePicker`
Distribution	`hedron`
Backend activity	No
Normal render mode	`RenderMode.FRAGMENT`

Live demo¶

ThemePickerRender an accessible no-JavaScript form for an allowlisted theme and color-mode preference.

The preview is a local docs simulation (not a running Hedron server). Interactive demos show a “Simulated HTMX” trace when applicable.

Basic use¶

from hedron import ThemePicker, ThemePreference
component = ThemePicker(selected=ThemePreference(theme='aurora', color_mode='dark'))

Compose under Page for full documents, or return from a fragment route for HTMX swaps.

How it works¶

ThemePicker emits a native POST form. The application owns persistence and authorization; optional client boot helpers are bounded and do not replace the server-rendered selection.

This component's core behavior is server-rendered HTML and does not require a browser runtime. The preview is ordinary semantic HTML, so keyboard, form, link, and disclosure behavior comes from the platform.

Constructor and parameters¶

ThemePicker(*, themes: 'tuple[str, ...]' = ('folio', 'classic', 'aurora'), color_modes: 'tuple[ColorMode, ...]' = ('system', 'light', 'dark'), selected: 'ThemePreference | None' = None, action: 'SafeUrl | str' = '/preferences/theme', csrf_token: 'str | None' = None, compact: 'bool' = False, id: 'str | None' = None, class_: 'str | None' = None, mark: 'str | None' = None, **kwargs: 'object') -> 'None'

Parameter	Type	Meaning
`themes`	`tuple[str, ...]`	Constructor parameter. Default: `('folio', 'classic', 'aurora')`.
`color_modes`	`tuple[ColorMode, ...]`	Constructor parameter. Default: `('system', 'light', 'dark')`.
`selected`	`ThemePreference \| None`	Constructor parameter. Default: `None`.
`action`	`SafeUrl \| str`	Constructor parameter. Default: `'/preferences/theme'`.
`csrf_token`	`str \| None`	Constructor parameter. Default: `None`.
`compact`	`bool`	Constructor parameter. Default: `False`.
`id`	`str \| None`	Optional DOM `id`. Default: `None`.
`class_`	`str \| None`	Optional CSS class string (`class` in HTML). Default: `None`.
`mark`	`str \| None`	Optional stable test mark (`data-hedron-mark`). Default: `None`.

Composition and backend behavior¶

Keep ThemePicker at the smallest semantic boundary. Fragment routes should return only the replaced region and preserve stable target IDs across success, validation, empty, loading, and error responses.

ThemePicker is primarily presentational; keep any mutation on an explicit action or component route.

Accessibility¶

Keep the labels, native submit path, and selected server state available when JavaScript is disabled.

Security¶

Escaping and SafeUrl / TrustedHtml are framework concerns; authorization and data exposure remain application code. Redact secrets before rendering.

Common mistakes¶

Do not pass unregistered theme names, remote actions, CSS, or identity-bearing preference values into the picker.
Do not copy docs-preview JavaScript into an application server.

Testing¶

from hedron import RenderMode, render

result = render(component, mode=RenderMode.FRAGMENT)
assert result.html
assert not result.diagnostics

All component demos · Built-in API · Testing

ThemePicker¶