ListItems going out of view

[AnthonyTschirhard]

Hello everyone,

I'm posting this question here because I've read the documentation multiple times (EXCELLENT doc and code docstrings by the way, it's a pleasure to read the friendly manual) but I'm having a problem I can't get my head around.

I have a custom TaskList widget class that inherits from ListView. And when I scroll down (with "j"), at some point the ListItem object goes out of view.

from textual.app import App, ComposeResult
from textual.screen import Screen
from textual.widgets import Header, Footer, Static, ListView, ListItem

class TaskList(ListView):
    def __init__(self):
        self.items = [ListItem(Static(f"task {i}")) for i in range(100)]
        super().__init__(*self.items)
        self.index = 0

    def next_task(self):
        self.index += 1

class MyScreen(Screen):
    widgets: list

    def __init__(self):
        self.widgets = []
        self.index_widgets = -1

        super().__init__()

    def compose(self) -> ComposeResult:
        sprint = TaskList()
        self.widgets.append(sprint)
        yield sprint

    def next_task(self):
        self.widgets[self.index_widgets].next_task()


class LazyJiraApp(App):
    CSS = """
        MyScreen {
            layout: grid;
        }
    """

    BINDINGS = [
        ("q", "quit", "Quit the app"),
        ("j", "next_task", "Next Task"),
    ]

    def __init__(self):
        super().__init__()
        self.my_screen = MyScreen()

    def compose(self) -> ComposeResult:
        yield self.my_screen

    def action_next_task(self) -> None:
        self.my_screen.next_task()
        self.refresh()

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

Would you have an idea what I'm missing? If you need more context about the code (work in progress, you can't run it presently): LazyJira.
Thanks a lot!
Anthony

[TomJGooding]

The docs for the refresh method includes this warning:

It is rarely necessary to call this method explicitly. Updating styles or reactive attributes will do this automatically.

I'm not sure exactly what you are trying to achieve here with your custom ListView?

[AnthonyTschirhard]

Also, would you mind telling me why my css was wrong? I've read the documentation you've sent me quite a few times but I must have missed something.

I've also updated the title and content of the discussion accordingly.

[TomJGooding]

Also, I absolutely love the binding:
("h", "app.focus_previous", "Previous Group"),
The reason I didn't choose this approach is that I only want to circle between certain widgets only.

Thanks for clarifying, perhaps instead you could use Screen.focus_next which you can filter by a selector?

class KanbanScreen(Screen):
    BINDINGS = [
        ("l", "focus_next_group", "Next Group"),
    ]

    def action_focus_next_group(self) -> None:
        self.focus_next(TaskListView)

[AnthonyTschirhard]

Oh yes that's absolutely perfect (and elegant).

Still, now I see this light version of the code, I understand even less why my ListItems are going out of view... Even if I completely remove the css, I still have the problem. I don't seen between your first code example and this, why your listitems stay in view and mine don't.

[TomJGooding]

I've only skimmed your trimmed down example, but you shouldn't be yielding screens. making lists of widgets, or explicitly calling refresh.
Hopefully I've shown that Textual has better ways of handling all of this?

[AnthonyTschirhard]

Hey,
Thanks a lot, you've definitely shown me a better way of using textual ;-) My code is so much cleaner now.
As soon as I stopped yielding the screen, everything was fixed. I wonder why an exception is not raised when you try to yield a screen but I guess there's probably a very good reason for that!
Thanks again!!