FastBlocks UI

FastBlocks UI is a modern HTML/CSS-first UI layer with a stable ui-* namespace, Jinja/FastBlocks helpers, and optional enhancement JavaScript. It is the successor to the archived fastbulma project and is built as a clean-slate system with no compatibility bridge and no Sass/build-tool requirement.

Features

• HTML/CSS First: Uses semantic markup, CSS variables, and cascade layers as the foundation
• Template Helpers: Ships Python helpers for Jinja, async Jinja, and FastBlocks rendering
• htmx Safe: Keeps IDs, form fields, and interaction state in normal light DOM markup
• Optional Enhancement JS: Keeps behavior light and progressive-enhancement friendly
• Modern Styling: Uses a Tailwind-inspired semantic token baseline with custom visuals
• Permissive License: BSD-3-Clause for commercial and open-source use

Component Model

FastBlocks UI components are standard HTML patterns with ui-* classes and helper-backed server rendering. The v1 runtime does not register Custom Elements and does not use shadow DOM by default. htmx targets, triggers, and swapped regions should remain normal light DOM nodes so the server stays authoritative for selected tabs, open menus, form state, and validation state.

The optional light-DOM Custom Element <ui-tabs> is available as an opt-in wrapper around the canonical helper output and are tracked in docs/light-dom-custom-elements-spec.md.

Installation

Install using pip:

pip install fastblocks-ui

Then copy the assets to your project:

fastblocks-ui copy-assets --dest ./static

Usage

Once installed, you can use the ui-* classes and Python helpers with server-rendered HTML:

<div class="ui-card">
  <div class="ui-card__header">Card Title</div>
  <div class="ui-card__body">
    This is a FastBlocks UI card styled with semantic tokens.
  </div>
  <footer class="ui-card__footer">
    <button class="ui-button is-primary" type="button">Action</button>
  </footer>
</div>

For full examples covering sync Jinja, async Jinja, and htmx fragments, see docs/usage.md. The component manifest is documented in docs/components.md. PWA-friendly app integration notes live in docs/pwa.md. Theming recipes live in docs/theming-recipes.md.

Template Examples

Sync Jinja

{{ button("Save changes", variant="primary", type="submit") }}

Async Jinja

template = env.get_template("profile.html")
html = await template.render_async(user=user, button=button)

htmx Fragment

<form id="profile-form" hx-post="/profile" hx-target="#profile-form" hx-swap="outerHTML">
  {{ field(
    label="Email address",
    control_html=ui_input(id="profile-email", name="email", type="email", value=user.email)
  ) }}
  {{ button("Save", variant="primary", type="submit") }}
</form>

App Shell

A full-bleed page with a sticky bar and a navigation column that becomes an off-canvas drawer below 1024px:

from fastblocks_ui import burger, drawer, nav_list, navbar, shell

aside = drawer(
    nav_list([("Overview", "#overview"), ("Usage", "#usage")], aria_current="location"),
    id="site-nav",
    label="Section navigation",
    tag="nav",
    class_="ui-shell__aside",
    data_ui_drawer_breakpoint="1024",
)

html = navbar(
    brand="My App",
    end=burger(controls="site-nav", class_="is-shell-toggle"),
    class_="is-sticky",
) + shell(page_body, aside=aside, main_id="content")

See docs/usage.md for the annotated version.

Demo

A self-contained showcase of every component (light + dark) is generated from the Python helpers:

python scripts/build_demo.py        # writes demo/index.html
open demo/index.html                # or serve the demo/ directory

The page inlines the CSS bundle and the enhance.js behavior layer, so it runs as a single file with no build step or server required.

Theming

FastBlocks UI enables flexible theming through CSS variables:

:root {
  --ui-color-primary: #e040fb;
  --ui-radius-md: 8px;
  --ui-color-success: #00c853;
}

FastBlocks UI components automatically inherit these changes through semantic token mapping.

Components

FastBlocks UI centers its public surface on ui-* classes and helper APIs:

Layout Components

• ui-shell / shell() - Full-bleed page shell with an optional aside column
• ui-container / container() - Centered max-width container
• ui-columns / columns() - 12-column responsive grid
• ui-column / column() - Individual column in grid
• ui-section / section() - Vertical spacing container
• ui-footer / footer() - Page footer
• ui-level / level() - Horizontal toolbar/nav
• ui-hero / hero() - Full-width banner section
• ui-title / title() - Typography title
• ui-media / media() - Image + text pair
• ui-tile / tile() - Hierarchical tile layout
• ui-nav-list / nav_list() - Vertical navigation list for sidebars and drawers
• ui-nav-groups / nav_groups() - Labelled groups of vertical navigation links

UI Components

• ui-button / button() - Buttons
• ui-card / card() - Cards
• ui-field / field() - Form groups
• ui-input / input() - Form inputs
• ui-select / select() - Select dropdowns
• ui-checkbox / checkbox() - Checkboxes
• ui-switch / switch() - Toggle switches
• ui-dialog / dialog() - Modal dialogs
• ui-drawer / drawer() - Off-canvas panel built on the Popover API
• ui-burger / burger() - Burger button that toggles a drawer. Add is-shell-toggle when it opens the shell's aside, so it hides above 1024px where that aside becomes a column
• ui-tabs / tabs() - Tabbed interfaces
• ui-dropdown / dropdown() - Dropdowns
• ui-alert / alert() - Alerts

.ui-navbar.is-sticky is a modifier on navbar(), not a separate component: it fixes the bar to the top of the viewport. Above 1024px, and only when the page has a top-level .ui-hero and the visitor has not asked for reduced motion, the bar is revealed by a scroll-driven animation as the hero scrolls out; everywhere else it is simply always visible.

The full table, including the ui-* utility classes, lives in docs/components.md.

License

BSD-3-Clause