Dynamic actions sharing the same keybinding

[xavierog]

Dynamic bindings/actions do not allow changing the description of a "toggle" action (e.g. dark mode / light mode, expand / collapse, lock / unlock) without also changing its key.

MRE

./DarkLight.py successfully implements a toggle action using two actual actions with different keys (d: Light mode, e: Dark mode) SAME_BINDINGS= ./DarkLight.py does the same but declares the two actual actions with the same key (d). Result: only the "quit" action is retained.

Code

#!/usr/bin/env python3
from os import environ
from textual.app import App, ComposeResult
from textual.binding import Binding
from textual.widgets import Header, Footer

class DarkLight(App):
    if 'SAME_BINDINGS' in environ:
        BINDINGS = [
            ('d', 'light', 'Light mode'),
            ('d', 'dark', 'Dark  mode'),
            ('q', 'quit', 'Quit'),
        ]
    else:
        BINDINGS = [
            ('d', 'light', 'Light mode'),
            ('e', 'dark', 'Dark  mode'),
            ('q', 'quit', 'Quit'),
        ]

    def action_light(self):
        self.dark = False
        self.refresh_bindings()

    def action_dark(self):
        self.dark = True
        self.refresh_bindings()

    def check_action(self, action, _parameters):
        if action == 'light':
            return self.dark
        if action == 'dark':
            return not self.dark
        return True

    def compose(self) -> ComposeResult:
        yield Header()
        yield Footer()

if __name__ == "__main__":
    app = DarkLight()
    app.run()

Textual Diagnostics

Versions

Name	Value
Textual	0.72.0
Rich	13.7.1

Python

Name	Value
Version	3.12.4
Implementation	CPython
Compiler	GCC 13.2.0
Executable	/path/to/venv/bin/python3

Operating System

Name	Value
System	Linux
Release	6.9.9-amd64
Version	#1 SMP PREEMPT_DYNAMIC Debian 6.9.9-1 (2024-07-13)

Terminal

Name	Value
Terminal Application	tmux (3.4)
TERM	tmux-256color
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=104, height=31
legacy_windows	False
min_width	1
max_width	104
is_terminal	False
encoding	utf-8
max_height	31
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

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[merriam]

I think this the description of your bug, but let me know if I missed it.

1. Run the program
2. Press 'd' for dark mode, then 'e' for the light mode.
3. The screen is now dark mode, but the footer says 'e Dark' meaning the footer did not update
4. Move the mouse to trigger the footer to update.

So, the issue is that request to update the footer somehow gets stuck in a queue waiting for any other event to pop it out?

[TomJGooding]

@merriam Not quite, though if the footer isn't updating for you in the first example, you might try updating your version of Textual.

This boils down to a fairly common question about how to change the description of a binding. For example, where the d key toggles dark mode, update the description to display 'Light Mode' when in dark mode and 'Dark' when in light mode.

There's not currently a way of updating the binding description AFAIK. You can't bind a key to multiple actions so trying to use check_actions as a workaround isn't going to work.

[MeadBarrel]

The issue is that you cannot change an action's description depending on the current state. For instance you can have "toggle dark mode" but not "enable dark mode" and "disable dark mode" on the same key, switching between the two depending on whether dark mode is currently active.

[willmcgugan]

I can see why this happens. The code makes the erroneous assumption that there is one binding per key.

The fix is non-trivial, but required for such dynamic bindings!

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