Trying to run the textual.app example on Windows 10 with Python 3.9.5:

➜ python -m textual.app
Traceback (most recent call last):
 File "C:\Program Files\Python39\lib\runpy.py", line 197, in _run_module_as_main
   return _run_code(code, main_globals, None,
 File "C:\Program Files\Python39\lib\runpy.py", line 87, in _run_code
   exec(code, run_globals)
 File "C:\CodeProjects\Python\Manim\manimvenv\lib\site-packages\textual\app.py", line 19, in <module>
   from .driver import Driver
 File "C:\CodeProjects\Python\Manim\manimvenv\lib\site-packages\textual\driver.py", line 8, in <module>
   import curses
 File "C:\Program Files\Python39\lib\curses\__init__.py", line 13, in <module>
   from _curses import *
ModuleNotFoundError: No module named '_curses'

i installed textual with pip and i tried to run the first example in the readme with python3 filename.py but i get the error TypeError: on_key() takes 1 positional argument but 2 were given when i press a key. got a similiar error with another example. sorry if im being dumb : p

There are a number of 'easing functions' used by the animation system. At the top of _animator.py you will see the following:

EASING = {
    "none": lambda x: 1.0,
    "round": lambda x: 0.0 if x < 0.5 else 1.0,
    "linear": lambda x: x,
    "in_cubic": lambda x: x * x * x,
    "in_out_cubic": lambda x: 4 * x * x * x if x < 0.5 else 1 - pow(-2 * x + 2, 3) / 2,
    "out_cubic": lambda x: 1 - pow(1 - x, 3),
}

These function have been copied from https://easings.net/ and translated from Javascript to Python. I would like to add the remaining functions to the EASING dict above.

See the animation.py example as a way of testing the above functions.

I noticed this when adding semantic style variants for Button.

When I hover over the warning button, the border is being set to tall $primary-lighten-3. I would expect it to be set to tall $warning-lighten-3 given Button.-warning has higher specificity.

Relevant CSS

    Button {
        border: tall $primary-lighten-3;
    }
    Button.-warning {
        background: $warning;
        color: $text-warning;
        border: tall $warning-lighten-3;  
    }
    
    Button.-warning :hover {
        background: $warning-darken-1;
        color: $text-warning-darken-1; 
    }

(hope you don't mind me opening an issue to ask a question, I've tried hard to get to the bottom of this myself)

I'm trying to get horizontal scrolling working with textual and a rich table, but no luck

Below is what I have so far.

It seems like the table is refusing to exceed the width of the terminal, thus the horizontal scroll bar of ScrollView is not coming into play.

Vertical scrolling is working great.

What am I doing wrong?

(ref: https://twitter.com/samuel_colvin/status/1426289617632960515)

from rich.table import Table

from textual import events
from textual.app import App
from textual.widgets import Header, Footer, ScrollView


class MyApp(App):
    """An example of a very simple Textual App"""

    async def on_load(self, event: events.Load) -> None:
        await self.bind("q", "quit", "Quit")

    async def on_mount(self, event: events.Mount) -> None:

        self.body = body = ScrollView()
        body.virtual_size.width = 300

        await self.view.dock(body)

        async def add_content():
            table = Table(title="Demo", width=300, min_width=300)

            for i in range(40):
                table.add_column(f'Col {i + 1}', style='magenta')

            for i in range(40):
                table.add_row(*[f'cell {i},{j}' for j in range(40)])

            await body.update(table)

        await self.call_later(add_content)


MyApp.run(title="Simple App", log="textual.log")

Versions:

python 3.9.5
textual==0.1.10
rich==10.7.0
OS: Ubuntu 21.04 with standard terminal

PyCharm gives me typing error with Reactive, see screenshot:

I'm unsure why this is the case given that mypy doesn't yield such error.

Side question: now that I have found myself a project to use Textual while fully understanding that this is WIP, I'll likely come across many little things like this one you may already be aware of. Should I keep opening issues? Or should I use some other, less formal avenue to keep the noise low and only open ticket when you request it? I'm thinking of Twitter DMs, or possibly some discord server and/or DM. Let me know what works best for you at this stage.

I was trying to add e.g. a new row to a layout after it was created in on_startup(), but it looks like it has no effect (I tried refresh() and require_layout()). Just asking as I know it might be early for that. Keep up the great work anyway!

With this PR we can now use a "mini-language" to inject event-related data into the key bindings' handlers e.g. self.bind("1,2,3", "digit_pressed('$event.key')")

• My first implementation was using the Python "Format Specification Mini-Language", so the syntax was the following:

   self.bind("1,2,3", "digit_pressed('{event.key}')") # <-- uses curly brackets for interpolation
  

  But as I was writing some integration tests with various kinds of Python primitives passed to the key bindings handlers I realised that using this syntax was causing an issue: as it's based on curly brackets we could not use Python dicts or sets in the parameters we inject.

• This is why I ended up opting for a dedicated SDL that doesn't conflict with Python syntax for dicts or set literals. As I don't want to create fancy SDLs out of thin air that users have to learn, I simply based it on the Python Template strings' one.
  So our previous expression becomes this:

   self.bind("1,2,3", "digit_pressed('$event.key')") # <-- uses a "dollar" syntax for interpolation
  
   # ...which enables this kind of things:
   self.bind("1,2,3", "digit_pressed('$event.key', {'sender_name': 'sidebar'})") # <-- injects a Python dict
  

Limits of this "action binding mini-language"

As explained in one of my comments on the GitHub diff, I also realised that this "action binding mini-language" has some strong limits, which can be a good thing for security but also has limits. We can pass $event.key to the action method for example, but we cannot pass the instance of the Event itself, or the sender instance - because this SDL is based on ast.literal_eval, which intentionally doesn't allow using custom objects.

I guess that time and dog-fooding will tell us if expressions such as $event.sender (which is the string representation of the sender, rather than the sender instance) is enough, or if we should rather start thinking of something else? :slightly_smiling_face:

Potential future improvements: dependency injection?

One potential way to solve this would be to use "a la Pytest" / "a la FastAPI" dependency injection... So if the action method declares a param named event for example we detect that and inject the Event instance for this parameter. Same with a param named sender, etc. :slightly_smiling_face:

Dependency injection would also allow users to not use error-prone "Python-syntax-in-a-string expressions" - i.e. it's easy to miss the syntax error in something like this:

self.bind("1,2,3", "digit_pressed('$event.key', {'sender_name: 'sidebar'})")

(a closing single quote is missing)

closes #496

Downstream projects get a message error: Skipping analyzing "textual": module is installed, but missing library stubs or py.typed marker when trying to use mypy. This adds the missing marker, copied from rich. tool.poetry.include is not required, though - poetry (now?) picks this up from VCS, like other files.

Tested with:

$ pip run build
...
$ unzip -l dist/textual-0.1.15-py3-none-any.whl | grep py.typed
        0  01-01-1980 00:00   textual/py.typed

I kept the primary button as is on dark mode. I think I'd prefer if it was the blue/primary background colour on both light and dark mode, but not too fussed either way.

One kind of annoying thing is the "success" button is the only one where, on hover, the text colour changes.

https://user-images.githubusercontent.com/5740731/173611944-6ff07367-60a8-4c45-98ae-a83a2e8148fc.mov

• Moved example to "old examples" directory. We can gradually start porting examples with new API.
• Copied LRUCache from Rich
• Implemented ScrollView widget
• Implemented DataTable widget

Data Table is still fairly rudimentary in terms of features. You add columns / rows and it will render it.

A future update will add a caret / selection and other features

https://user-images.githubusercontent.com/554369/174762713-acbc8491-773d-494f-906f-c87540e0f5bc.mov

Reading config files and merging them.

• Things are kept in dictionary form for now as that's how they get merged.
• We could throw the data into an immutable Pydantic object to ensure validity, but I haven't implemented any validation stuff.
• Focus here is on reading config files and merging them correctly, essentially pulling all the data together into a single structure which contains the correct merged/prioritised data.
• Supports multiple config files on a users system. Whether this will be required, I don't know yet.
• It's the responsibility of the user of this class to pass in the paths to the configuration files. Textual may user appdirs for example to get locations for user config and pass them into this class.
• Environment variable ignored for now.
• There's some missing docstrings etc but will add them later.
• App config will be prefixed with app., not done that yet though.

I used simple code:

from textual.app import App
from textual.widgets import Placeholder


class SimpleApp(App):

    async def on_mount(self) -> None:
        await self.view.dock(Placeholder(), edge="left", size=40)
        await self.view.dock(Placeholder(), Placeholder(), edge="top")


SimpleApp.run(log="textual.log")

Then, I ran the code but nothing appeared until i resized terminal

https://user-images.githubusercontent.com/40739871/177348394-7e87f1a6-0ec3-44a3-ae3c-9c57783db12a.mp4

Added some steps for setup for relevant packages that may not be installed by standard

Created documentation for the button widget, based on the current main branch (tell me if you prefer documentation to be based off the current code in the css branch)

I was trying to view messages from asyncio mqtt updated ASAP with textual and couldn't figure how to add another task in the loop. Then I found this answer which explains how to set it up.

It might seem obvious for experimented async users but I was puzzled.

I think this is a key feature for a basic usage of Textual and it should be added in the documentation.

To be added by @willmcgugan

Hi all,

being all new to Textual, but very excited to try out the new Theengs Explorer I'm only ever getting constant loops of

Task exception was never retrieved
future: <Task finished name='Task-1458' coro=<TheengsExplorerApp.detection_callback() done, defined at __init__.py:36> exception=LookupError(<ContextVar name='active_app' at 0x113b61130>)>
Traceback (most recent call last):
  File "__init__.py", line 39, in detection_callback
    await self.scroll_view.update(self.device_table.render(), home=False)
  File "/Users/me/.pyenv/versions/3.8.5/lib/python3.8/site-packages/textual/widgets/_scroll_view.py", line 89, in update
    await self.window.update(renderable)
  File "/Users/me/.pyenv/versions/3.8.5/lib/python3.8/site-packages/textual/views/_window_view.py", line 39, in update
    layout.add(self.widget)
  File "/Users/me/.pyenv/versions/3.8.5/lib/python3.8/site-packages/textual/layouts/vertical.py", line 28, in add
    self._max_widget_width = max(widget.app.measure(widget), self._max_widget_width)
  File "/Users/me/.pyenv/versions/3.8.5/lib/python3.8/site-packages/textual/message_pump.py", line 59, in app
    return active_app.get()
LookupError: <ContextVar name='active_app' at 0x113b61130>

while the Textual examples all work fine for me, and all the required dependencies/extra packages for Theengs Explorer are satisfied - TheengsDecoder doesn't exist as an installable package yet, but must be built

Unless this is an obvious older macOS version issue to you, for which I'd be happy to do some external disk newer macOS testing, any further pointers as to what might cause this would be greatly appreciated.

The creator of TheengsExplorer, @koenvervloesem, is also following this to chip in.

Many thanks