nicegui/main.py

#!/usr/bin/env python3
import asyncio
import inspect
import re
from contextlib import contextmanager
from typing import Callable, Union

import docutils.core

from nicegui import ui
from nicegui.elements.html import Html
from nicegui.elements.markdown import Markdown
from nicegui.globals import page_stack

# add docutils css to webpage
page_stack[0].head_html += docutils.core.publish_parts('', writer_name='html')['stylesheet']

# avoid display:block for PyPI/Docker/GitHub badges
page_stack[0].head_html += '<style>p a img {display: inline; vertical-align: baseline}</style>'


@contextmanager
def example(content: Union[Callable, type, str]):
    callFrame = inspect.currentframe().f_back.f_back
    begin = callFrame.f_lineno

    def add_html_anchor(element: Html):
        html = element.content
        match = re.search(r'<h3.*?>(.*?)</h3>', html)
        if not match:
            return

        headline_id = re.sub('[^(a-z)(A-Z)(0-9)-]', '_', match.groups()[0].strip()).lower()
        if not headline_id:
            return

        icon = '<span class="material-icons">link</span>'
        anchor = f'<a href="#{headline_id}" class="text-gray-300 hover:text-black">{icon}</a>'
        html = html.replace('<h3', f'<h3 id="{headline_id}"', 1)
        html = html.replace('</h3>', f' {anchor}</h3>', 1)
        element.view.inner_html = html

    with ui.row().classes('flex w-full'):
        if isinstance(content, str):
            add_html_anchor(ui.markdown(content).classes('mr-8 w-4/12'))
        else:
            doc = content.__doc__ or content.__init__.__doc__
            html = docutils.core.publish_parts(doc, writer_name='html')['html_body']
            html = html.replace('<p>', '<h3>', 1)
            html = html.replace('</p>', '</h3>', 1)
            html = Markdown.apply_tailwind(html)
            add_html_anchor(ui.html(html).classes('mr-8 w-4/12'))

        try:
            with ui.card().classes('mt-12 w-2/12'):
                with ui.column().classes('flex w-full'):
                    yield
        finally:
            code = inspect.getsource(callFrame)
            end = begin + 1
            lines = code.splitlines()
            while True:
                end += 1
                if end >= len(lines):
                    break
                if inspect.indentsize(lines[end]) < inspect.indentsize(lines[begin]) and lines[end]:
                    break
            code = lines[begin:end]
            code = [l[4:] for l in code]
            code.insert(0, '```python')
            code.insert(1, 'from nicegui import ui')
            if code[2].split()[0] not in ['from', 'import']:
                code.insert(2, '')
            code.append('ui.run()')
            code.append('```')
            code = '\n'.join(code)
            ui.markdown(code).classes('mt-12 w-5/12 overflow-auto')


ui.html(
    '<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/github-fork-ribbon-css/0.2.3/gh-fork-ribbon.min.css" />'
    '<style>.github-fork-ribbon:before { background-color: #999; }</style>'
    '<a class="github-fork-ribbon" href="https://github.com/zauberzeug/nicegui" data-ribbon="Fork me on GitHub" title="Fork me on GitHub">Fork me on GitHub</a>'
)

with ui.row().classes('flex w-full'):
    with open('README.md', 'r') as file:
        content = file.read()
        content = re.sub(r'(?m)^\<img.*\n?', '', content)
        ui.markdown(content).classes('w-6/12')

    with ui.card().classes('mx-auto mt-24'):
        with ui.row():
            with ui.column():
                ui.button('Click me!', on_click=lambda: output.set_text('Click'))
                ui.checkbox('Check me!', on_change=lambda e: output.set_text('Checked' if e.value else 'Unchecked'))
                ui.switch('Switch me!', on_change=lambda e: output.set_text('Switched' if e.value else 'Unswitched'))
                ui.input('Text', value='abc', on_change=lambda e: output.set_text(e.value))
                ui.number('Number', value=3.1415927, format='%.2f', on_change=lambda e: output.set_text(e.value))

            with ui.column():
                ui.slider(min=0, max=100, value=50, step=0.1, on_change=lambda e: output.set_text(e.value))
                ui.radio(['A', 'B', 'C'], value='A', on_change=lambda e: output.set_text(e.value)).props('inline')
                ui.toggle(['1', '2', '3'], value='1', on_change=lambda e: output.set_text(e.value)).classes('mx-auto')
                ui.select({1: 'One', 2: 'Two', 3: 'Three'}, value=1,
                          on_change=lambda e: output.set_text(e.value)).classes('mx-auto')

            with ui.column().classes('w-24'):
                ui.label('Output:')
                output = ui.label('').classes('text-bold')

ui.markdown('## API Documentation and Examples')

with example(ui.label):
    ui.label('some label')

with example(ui.image):
    ui.image('http://placeimg.com/640/360/tech')
    base64 = 'data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAASABIAAD/4QCMRXhpZgAATU0AKgAAAAgABQESAAMAAAABAAEAAAEaAAUAAAABAAAASgEbAAUAAAABAAAAUgEoAAMAAAABAAIAAIdpAAQAAAABAAAAWgAAAAAAAABIAAAAAQAAAEgAAAABAAOgAQADAAAAAQABAACgAgAEAAAAAQAAACKgAwAEAAAAAQAAACMAAAAA/8IAEQgAIwAiAwEiAAIRAQMRAf/EAB8AAAEFAQEBAQEBAAAAAAAAAAMCBAEFAAYHCAkKC//EAMMQAAEDAwIEAwQGBAcGBAgGcwECAAMRBBIhBTETIhAGQVEyFGFxIweBIJFCFaFSM7EkYjAWwXLRQ5I0ggjhU0AlYxc18JNzolBEsoPxJlQ2ZJR0wmDShKMYcOInRTdls1V1pJXDhfLTRnaA40dWZrQJChkaKCkqODk6SElKV1hZWmdoaWp3eHl6hoeIiYqQlpeYmZqgpaanqKmqsLW2t7i5usDExcbHyMnK0NTV1tfY2drg5OXm5+jp6vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAQIAAwQFBgcICQoL/8QAwxEAAgIBAwMDAgMFAgUCBASHAQACEQMQEiEEIDFBEwUwIjJRFEAGMyNhQhVxUjSBUCSRoUOxFgdiNVPw0SVgwUThcvEXgmM2cCZFVJInotIICQoYGRooKSo3ODk6RkdISUpVVldYWVpkZWZnaGlqc3R1dnd4eXqAg4SFhoeIiYqQk5SVlpeYmZqgo6SlpqeoqaqwsrO0tba3uLm6wMLDxMXGx8jJytDT1NXW19jZ2uDi4+Tl5ufo6ery8/T19vf4+fr/2wBDAAwMDAwMDBUMDBUeFRUVHikeHh4eKTQpKSkpKTQ+NDQ0NDQ0Pj4+Pj4+Pj5LS0tLS0tXV1dXV2JiYmJiYmJiYmL/2wBDAQ8QEBkXGSsXFytnRjlGZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2f/2gAMAwEAAhEDEQAAAeqBgCIareozvbaK3avBqa52teT6He3z0TqCUZa22r//2gAIAQEAAQUCaVVKTjGnLFqSqqlGuciX+87YgM8ScWhAx5KWUJUdJClKadMye6O//9oACAEDEQE/AUxI86A0ynfb/9oACAECEQE/ASaYZBLxpKNinFh2dv8A/9oACAEBAAY/AmUniHVXxfVx7ZIP9x0GlOJdfa+BeVentkSWR66jsI1HUfF+f4l1UykiqR/CypAorg6n/hvuH5nv/8QAMxABAAMAAgICAgIDAQEAAAILAREAITFBUWFxgZGhscHw0RDh8SAwQFBgcICQoLDA0OD/2gAIAQEAAT8hrchP08Nlp8V+7MHK/wCcEXw8q94vkT4K5DD0fpsJBFkwYvy/8cJBuuX7l82UhL9HmlzVKCOfi+3/ADe6Z2jgePxcMYN/xxYQtAu8UCj/ALXDvn/sBxRB/g3/AL//2gAMAwEAAhEDEQAAEE5gPHEUEAP/xAAzEQEBAQADAAECBQUBAQABAQkBABEhMRBBUWEgcfCRgaGx0cHh8TBAUGBwgJCgsMDQ4P/aAAgBAxEBPxAN4PZaNJuOW/g//9oACAECEQE/EAGt2fwmfzBp3X8P/9oACAEBAAE/ELGubg74j5M+RuAgxMrE4g5c4qAjQh1Oh9GL3/xggJDuHs5H2fY1rQIGDISTZ3KuGYzkk8dSkh4Ah8TJ8c0SsIco+yPRD76/486QSwOdnIpjvmvjAQ8pEx4ixlVcDldAdtawTzP5CSqs1wAPeJDMz0nwvHVlRSYTI1ic6b58RUC4kuSTXmFOJuxknJgsgDQMkjQgj/gCBHee6QjzflUA4/5//9k='
    ui.image(base64).style('width:30px')

with example(ui.svg):
    svg_content = '''
        <svg viewBox="0 0 200 200" width="100" height="100" xmlns="http://www.w3.org/2000/svg">
        <circle cx="100" cy="100" r="78" fill="yellow" stroke="black" stroke-width="3" />
        <circle cx="61" cy="82" r="12" />
        <circle cx="127" cy="82" r="12" />
        <path d="m136.81 116.53c.69 36.17-74.11 42-81.52-.73" style="fill:none; stroke: black; stroke-width: 5;" />
        </svg>'''
    ui.svg(svg_content)

overlay = '''### Captions and Overlays

By nesting elements inside a `ui.image` you can create augmentations.

Use [Quasar classes](https://quasar.dev/vue-components/img) for positioning and styling captions.
To overlay an svg, make the `viewBox` exactly the size of the image and provide `100%` width/height to match the actual rendered size.
'''
with example(overlay):
    with ui.image('http://placeimg.com/640/360/nature'):
        ui.label('nice').classes('absolute-bottom text-subtitle2 text-center')

    with ui.image('https://cdn.pixabay.com/photo/2020/07/13/12/56/mute-swan-5400675__340.jpg'):
        svg_content = '''
            <svg viewBox="0 0 510 340" width="100%" height="100%" xmlns="http://www.w3.org/2000/svg">
            <circle cx="200" cy="200" r="100" fill="none" stroke="red" stroke-width="10" />
            </svg>'''
        ui.svg(svg_content).style('background:transparent')

with example(ui.interactive_image):
    from nicegui.events import MouseEventArguments

    def mouse_handler(e: MouseEventArguments):
        color = 'green' if e.type == 'mousedown' else 'orange'
        ii.svg_content += f'<circle cx="{e.image_x}" cy="{e.image_y}" r="10" fill="{color}"/>'
        ui.notify(f'{e.type} at ({e.image_x:.1f}, {e.image_y:.1f})')

    ii = ui.interactive_image('http://placeimg.com/640/360/arch',
                              on_mouse=mouse_handler,
                              events=['mousedown', 'mouseup'], cross=True)

with example(ui.markdown):
    ui.markdown('### Headline\nWith hyperlink to [GitHub](https://github.com/zauberzeug/nicegui).')

with example(ui.html):
    ui.html('<p>demo paragraph in <strong>html</strong></p>')

with example(ui.button):
    def button_increment():
        global button_count
        button_count += 1
        button_result.set_text(f'pressed: {button_count}')

    button_count = 0
    ui.button('Button', on_click=button_increment)
    button_result = ui.label('pressed: 0')

async_button = '''### Button with asynchronous action
The button element does also support asynchronous action.

Note: You can also pass a `functools.partial` into the `on_click` property to wrap async functions with parameters.
'''
with example(async_button):
    async def async_task():
        ui.notify('Asynchronous task started')
        await asyncio.sleep(5)
        ui.notify('Asynchronous task finished')

    ui.button('start async task', on_click=async_task)

with example(ui.checkbox):
    ui.checkbox('check me', on_change=lambda e: checkbox_state.set_text(e.value))
    with ui.row():
        ui.label('the checkbox is:')
        checkbox_state = ui.label('False')

with example(ui.switch):
    ui.switch('switch me', on_change=lambda e: switch_state.set_text('ON' if e.value else'OFF'))
    with ui.row():
        ui.label('the switch is:')
        switch_state = ui.label('OFF')

with example(ui.slider):
    slider = ui.slider(min=0, max=100, value=50).props('label')
    ui.label().bind_text_from(slider, 'value')

with example(ui.input):
    ui.input(
        label='Text',
        placeholder='press ENTER to apply',
        on_change=lambda e: result.set_text('you typed: ' + e.value),
    ).classes('w-full')
    result = ui.label('')

with example(ui.number):
    number_input = ui.number(label='Number', value=3.1415927, format='%.2f')
    with ui.row():
        ui.label('underlying value: ')
        ui.label().bind_text_from(number_input, 'value')

with example(ui.color_input):
    color_label = ui.label('Change my color!')
    ui.color_input(label='Color', value='#000000',
                   on_change=lambda e: color_label.style(f'color:{e.value}'))

with example(ui.color_picker):
    picker = ui.color_picker(on_pick=lambda e: button.style(f'background-color:{e.color}!important'))
    button = ui.button(on_click=picker.open).props('icon=colorize')

with example(ui.radio):
    radio = ui.radio([1, 2, 3], value=1).props('inline')
    ui.radio({1: 'A', 2: 'B', 3: 'C'}, value=1).props('inline').bind_value(radio, 'value')

with example(ui.toggle):
    toggle = ui.toggle([1, 2, 3], value=1)
    ui.toggle({1: 'A', 2: 'B', 3: 'C'}, value=1).bind_value(toggle, 'value')

with example(ui.select):
    with ui.row():
        select = ui.select([1, 2, 3], value=1).props('inline')
        ui.select({1: 'One', 2: 'Two', 3: 'Three'}, value=1).props('inline').bind_value(select, 'value')

with example(ui.upload):
    ui.upload(on_upload=lambda files: content.set_text(files))
    content = ui.label()

with example(ui.plot):
    import numpy as np
    from matplotlib import pyplot as plt

    with ui.plot(figsize=(2.5, 1.8)):
        x = np.linspace(0.0, 5.0)
        y = np.cos(2 * np.pi * x) * np.exp(-x)
        plt.plot(x, y, '-')
        plt.xlabel('time (s)')
        plt.ylabel('Damped oscillation')

with example(ui.line_plot):
    lines = ui.line_plot(n=2, limit=20, figsize=(2.5, 1.8)).with_legend(['sin', 'cos'], loc='upper center', ncol=2)
    line_updates = ui.timer(0.1, lambda: lines.push([datetime.now()], [
        [np.sin(datetime.now().timestamp()) + 0.02 * np.random.randn()],
        [np.cos(datetime.now().timestamp()) + 0.02 * np.random.randn()],
    ]), active=False)
    ui.checkbox('active').bind_value(line_updates, 'active')

with example(ui.log):
    from datetime import datetime

    log = ui.log(max_lines=10).classes('h-16')
    ui.button('Log time', on_click=lambda: log.push(datetime.now().strftime("%X.%f")[:-5]))

with example(ui.scene):
    with ui.scene(width=200, height=200) as scene:
        scene.sphere().material('#4488ff')
        scene.cylinder(1, 0.5, 2, 20).material('#ff8800', opacity=0.5).move(-2, 1)
        scene.extrusion([[0, 0], [0, 1], [1, 0.5]], 0.1).material('#ff8888').move(-2, -2)

        with scene.group().move(z=2):
            box1 = scene.box().move(x=2)
            scene.box().move(y=2).rotate(0.25, 0.5, 0.75)
            scene.box(wireframe=True).material('#888888').move(x=2, y=2)

        scene.line([-4, 0, 0], [-4, 2, 0]).material('#ff0000')
        scene.curve([-4, -2, 0], [-4, -1, 0], [-3, -1, 0], [-3, 0, 0]).material('#008800')

        logo = "https://avatars.githubusercontent.com/u/2843826"
        scene.texture(logo, [[[0, 3, 0], [3, 3, 0]], [[0, 0, 0], [3, 0, 0]]]).move(1, -2)

        teapot = 'https://upload.wikimedia.org/wikipedia/commons/9/93/Utah_teapot_(solid).stl'
        scene.stl(teapot).scale(0.2).move(-3, 4)

with example(ui.chart):
    from numpy.random import random

    def update():
        chart.options.series[0].data[:] = random(2)

    chart = ui.chart({
        'title': False,
        'chart': {'type': 'bar'},
        'xAxis': {'categories': ['A', 'B']},
        'series': [
            {'name': 'Alpha', 'data': [0.1, 0.2]},
            {'name': 'Beta', 'data': [0.3, 0.4]},
        ],
    }).classes('max-w-full h-64')
    ui.button('Update', on_click=update)

with example(ui.table):
    def update():
        table.options.rowData[0].age += 1

    table = ui.table({
        'columnDefs': [
            {'headerName': 'Name', 'field': 'name'},
            {'headerName': 'Age', 'field': 'age'},
        ],
        'rowData': [
            {'name': 'Alice', 'age': 18},
            {'name': 'Bob', 'age': 21},
            {'name': 'Carol', 'age': 42},
        ],
    }).classes('max-h-40')
    ui.button('Update', on_click=update)

with example(ui.joystick):
    ui.joystick(
        color='blue',
        size=50,
        on_move=lambda msg: coordinates.set_text(f'{msg.data.vector.x:.3f}, {msg.data.vector.y:.3f}'),
        on_end=lambda _: coordinates.set_text('0, 0'))
    coordinates = ui.label('0, 0')

with example(ui.dialog):
    with ui.dialog() as dialog, ui.card():
        ui.label('Hello world!')
        ui.button('Close', on_click=dialog.close)

    ui.button('Open a dialog', on_click=dialog.open)

async_dialog = '''### Awaitable dialog
Dialogs can be awaited.
Use the `submit` method to close the dialog and return a result.
Canceling the dialog by clicking in the background or pressing the escape key yields `None`.
'''
with example(async_dialog):
    with ui.dialog() as dialog, ui.card():
        ui.label('Are you sure?')
        with ui.row():
            ui.button('Yes', on_click=lambda: dialog.submit('Yes'))
            ui.button('No', on_click=lambda: dialog.submit('No'))

    async def show():
        result = await dialog
        await ui.notify(f'You chose {result}')

    ui.button('Await a dialog', on_click=show)

tooltip = '''### Tooltips
Simply call the `tooltip(text:str)` method on UI elements to provide a tooltip.
'''
with example(tooltip):
    with ui.row():
        ui.button().props('icon=thumb_up').tooltip('I like this')
        ui.label('tooltips').classes('q-mt-sm').tooltip('tooltips are shown on mouse over')

with example(ui.menu):
    choice = ui.label('Try the menu.')
    with ui.menu() as menu:
        ui.menu_item('Menu item 1', lambda: choice.set_text('Selected item 1.'))
        ui.menu_item('Menu item 2', lambda: choice.set_text('Selected item 2.'))
        ui.menu_item('Menu item 3 (keep open)', lambda: choice.set_text('Selected item 3.'), auto_close=False)
        ui.menu_separator()
        ui.menu_item('Close', on_click=menu.close)

    ui.button('Open menu', on_click=menu.open).props('color=secondary')

with example(ui.expansion):
    with ui.expansion('Expand!', icon='work').classes('w-full'):
        ui.label('inside the expansion')

with example(ui.notify):
    ui.button('Show notification', on_click=lambda: ui.notify('Some message', close_button='OK'))

design = '''### Styling

NiceGUI uses the [Quasar Framework](https://quasar.dev/) version 1.0 and hence has its full design power.
Each NiceGUI element provides a `props` method whose content is passed [to the Quasar component](https://justpy.io/quasar_tutorial/introduction/#props-of-quasar-components):
Have a look at [the Quasar documentation](https://quasar.dev/vue-components/button#design) for all styling props.
You can also apply [Tailwind](https://tailwindcss.com/) utility classes with the `classes` method.

If you really need to apply CSS, you can use the `styles` method. Here the delimiter is `;` instead of a blank space.

All three functions also provide `remove` and `replace` parameters in case the predefined look is not wanted in a particular styling.
'''
with example(design):
    ui.radio(['x', 'y', 'z'], value='x').props('inline color=green')
    ui.button().props('icon=touch_app outline round').classes('shadow-lg ml-14')

with example(ui.colors):
    ui.button('Gray', on_click=lambda: ui.colors(primary='#555'))
    ui.button('Default', on_click=lambda: ui.colors())
    ui.colors()

with example(ui.card):
    with ui.card().tight():
        ui.image('http://placeimg.com/640/360/nature')
        with ui.card_section():
            ui.label('Lorem ipsum dolor sit amet, consectetur adipiscing elit, ...')

with example(ui.column):
    with ui.column():
        ui.label('label 1')
        ui.label('label 2')
        ui.label('label 3')

with example(ui.row):
    with ui.row():
        ui.label('label 1')
        ui.label('label 2')
        ui.label('label 3')

clear = '''### Clear Containers

To remove all elements from a row, column or card container, use the `clear()` method.
'''
with example(clear):
    container = ui.row()

    def add_face():
        with container:
            ui.icon('face')
    add_face()

    ui.button('Add', on_click=add_face)
    ui.button('Clear', on_click=container.clear)

binding = '''### Bindings

NiceGUI is able to directly bind UI elements to models.
Binding is possible for UI element properties like text, value or visibility and for model properties that are (nested) class attributes.

Each element provides methods like `bind_value` and `bind_visibility` to create a two-way binding with the corresponding property.
To define a one-way binding use the `_from` and `_to` variants of these methods.
Just pass a property of the model as parameter to these methods to create the binding.
'''
with example(binding):
    class Demo:
        def __init__(self):
            self.number = 1

    demo = Demo()
    v = ui.checkbox('visible', value=True)
    with ui.column().bind_visibility_from(v, 'value'):
        ui.slider(min=1, max=3).bind_value(demo, 'number')
        ui.toggle({1: 'a', 2: 'b', 3: 'c'}).bind_value(demo, 'number')
        ui.number().bind_value(demo, 'number')

with example(ui.timer):
    from datetime import datetime

    with ui.row().classes('items-center'):
        clock = ui.label()
        t = ui.timer(interval=0.1, callback=lambda: clock.set_text(datetime.now().strftime("%X.%f")[:-5]))
        ui.checkbox('active').bind_value(t, 'active')

    with ui.row():
        def lazy_update():
            new_text = datetime.now().strftime('%X.%f')[:-5]
            if lazy_clock.text[:8] == new_text[:8]:
                return False
            lazy_clock.text = new_text
        lazy_clock = ui.label()
        ui.timer(interval=0.1, callback=lazy_update)

lifecycle = '''### Lifecycle

You can run a function or coroutine on startup as a parallel task by passing it to `ui.on_startup`.
If NiceGUI is shut down or restarted, the tasks will be automatically canceled (for example when you make a code change).
You can also execute cleanup code with `ui.on_shutdown`.
'''
with example(lifecycle):
    with ui.row() as row:
        ui.label('count:')
        count_label = ui.label('0')
        count = 0

    async def counter():
        global count
        while True:
            count_label.text = str(count)
            count += 1
            await row.view.update()
            await asyncio.sleep(1)

    ui.on_startup(counter())

with example(ui.link):
    ui.link('NiceGUI on GitHub', 'https://github.com/zauberzeug/nicegui')

with example(ui.page):
    with ui.page('/other_page'):
        ui.label('Welcome to the other side')
        ui.link('Back to main page', '#page')

    with ui.page('/dark_page', dark=True):
        ui.label('Welcome to the dark side')
        ui.link('Back to main page', '#page')

    ui.link('Visit other page', 'other_page')
    ui.link('Visit dark page', 'dark_page')

with example(ui.open):
    with ui.page('/yet_another_page') as other:
        ui.label('Welcome to yet another page')
        ui.button('RETURN', on_click=lambda e: ui.open('#open', e.socket))

    ui.button('REDIRECT', on_click=lambda e: ui.open(other, e.socket))

sessions = """### Sessions

`ui.page` provides an optional `on_connect` argument to register a callback.
It is invoked for each new connection to the page.

The optional `request` argument provides insights about the clients URL parameters etc. (see [the JustPy docs](https://justpy.io/tutorial/request_object/) for more details).
It also enables you to identify sessions over [longer time spans by configuring cookies](https://justpy.io/tutorial/sessions/).
"""
with example(sessions):
    from collections import Counter
    from datetime import datetime

    from starlette.requests import Request

    id_counter = Counter()
    creation = datetime.now().strftime('%H:%M, %d %B %Y')

    def handle_connection(request: Request):
        id_counter[request.session_id] += 1
        visits.set_text(f'{len(id_counter)} unique views ({sum(id_counter.values())} overall) since {creation}')

    with ui.page('/session_demo', on_connect=handle_connection) as page:
        visits = ui.label()

    ui.link('Visit session demo', page)

add_route = """### Route

Add a new route by calling `ui.add_route` with a starlette route including a path and a function to be called.
Routed paths must start with a `'/'`.
"""
with example(add_route):
    import starlette

    ui.add_route(starlette.routing.Route(
        '/new/route', lambda _: starlette.responses.PlainTextResponse('Response')
    ))

    ui.link('Try the new route!', 'new/route')

get_decorator = """### Get decorator

Syntactic sugar to add routes.
Decorating a function with the `@ui.get` makes it available at the specified endpoint, e.g. `'/another/route/<id>'`.

Path parameters can be passed to the request handler like with [FastAPI](https://fastapi.tiangolo.com/tutorial/path-params/).
If type-annotated, they are automatically converted to `bool`, `int`, `float` and `complex` values.
An optional `request` argument gives access to the complete request object.
"""
with example(get_decorator):
    from starlette import requests, responses

    @ui.get('/another/route/{id}')
    def produce_plain_response(id: str, request: requests.Request):
        return responses.PlainTextResponse(f'{request.client.host} asked for id={id}')

    ui.link('Try yet another route!', 'another/route/42')

with example(ui.keyboard):
    from nicegui.events import KeyEventArguments

    def handle_key(e: KeyEventArguments):
        if e.key == 'f' and not e.action.repeat:
            if e.action.keyup:
                ui.notify('f was just released')
            elif e.action.keydown:
                ui.notify('f was just pressed')
        if e.modifiers.shift and e.action.keydown:
            if e.key.arrow_left:
                ui.notify('going left')
            elif e.key.arrow_right:
                ui.notify('going right')
            elif e.key.arrow_up:
                ui.notify('going up')
            elif e.key.arrow_down:
                ui.notify('going down')

    keyboard = ui.keyboard(on_key=handle_key)
    ui.label('Key events can be caught globally by using the keyboard element.')
    ui.checkbox('Track key events').bind_value_to(keyboard, 'active')

ui.run()