SelectionList with long lines throws an exception when the window is too small

[valberg]

Textual Diagnostics

Versions

Name	Value
Textual	0.29.0
Rich	13.4.2

Python

Name	Value
Version	3.11.3
Implementation	CPython
Compiler	GCC 13.1.1 20230429
Executable	/home/valberg/.pyenv/versions/textual-dev/bin/python

Operating System

Name	Value
System	Linux
Release	6.4.1-arch2-1
Version	#1 SMP PREEMPT_DYNAMIC Tue, 04 Jul 2023 08:39:40 +0000

Terminal

Name	Value
Terminal Application	Unknown
TERM	xterm-256color
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=62, height=34
legacy_windows	False
min_width	1
max_width	62
is_terminal	True
encoding	utf-8
max_height	34
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

Bug report

Running the following in a smallish window, or resizing below the length of the selection length:

from textual.app import App, ComposeResult
from textual.widgets import Header, Footer, SelectionList


class TestApp(App):

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

        yield SelectionList(
            ("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", 1),
        )

        yield Footer()


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

results in the following exception:

OptionDoesNotExist: There is no option with an index of 1

[github-actions]

We found the following entry in the FAQ which you may find helpful:

• How do I center a widget in a screen?

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[davep]

Good catch; some work should either be done to truncate options longer than the width, or OptioinList needs to be improved to handle the underlying selection list's wrapping of long options. If I quickly hack Textual to eat the error you can see how the underlying lines and the check boxes get out of sync too.

[valberg]

I have worked around it by simply having shorter labels - for now :)

If you have any pointers on how this could be solved, and where to solve it, I might be able to put in the grunt work. But as everybody else I'm short for time, so it's a big maybe :)

[davep]

It's all down to how SelectionList sits on top of OptionList, and how the former has been done with "each thing only takes up one line" in mind, but the latter is super flexible and can have one option spanning many lines. So really I guess the first thing for us to do is to decide if we should restrict the prompts for SelectionList (that was the intention: to have it act like a CheckBox-adjacent take on RadioSet) so they never "wrap", or if we relax that and then how and where the checks go when a prompt spans multiple lines.

I sense it's a quick design chat we'll need internally first before fixing this.

[zdovcj]

I have also tried to size my content upon resize event, but it doesn't solve the issue. In this case, it will even crash on increasing the terminal size. I assume that the function that sets the content length might be called before the the code that crashes.

Code to reproduce the crash upon increasing:

import textual.widgets
import textual.app
import textual.events
import textual  

class App(textual.app.App):

    @textual.on(textual.events.Resize)
    def resize_handler(self):
        width = self.size.width
        text = 'a' * (width - 4)
        widget = self.query_one(textual.widgets.SelectionList)
        widget.clear_options()
        widget.add_option((text, 0, None))

    def compose(self):
        yield textual.widgets.SelectionList (('random_text', 0), id='widget_id')

if __name__ == '__main__':
    App().run()

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