Mouse hover highlighting of a `ListItem` in a `ListView` works in unexpected ways

[davep]

Given this code:

from textual.app import App, ComposeResult
from textual.containers import Horizontal
from textual.widgets import ListView, ListItem, Label

class ListViewHoverIssueApp(App[None]):

    def compose(self) -> ComposeResult:
        yield ListView(
            *[ListItem(Horizontal(Label(f"Item {n}"))) for n in range(100)]
        )

if __name__ == "__main__":
    ListViewHoverIssueApp().run()

note that the :hover highlight only appears when the mouse is hovered over the "empty" part of the item in the list, not when over the text. The reason would seem to be:

    ListItem > Widget :hover {
        background: $boost;
    }

in the code for ListItem; which means that the background boost only happens when (in the case of the example code above) the mouse is over the Horizontal, but not when it's over the Label.

[davidfokkema]

The 'inverse' seems to happen when a ListItem contains just a Label. Then only the Label is highlighted and not the empty part. The issue seems to be the same.

[davep]

Aye, for the same reason above. I just did it the above way as it's easier to see.

[davidfokkema]

Aye, for the same reason above. I just did it the above way as it's easier to see.

I got that, 😉. Sorry for not making that clear. I like your code BTW, very concise.

[TomJGooding]

I didn't even realise there was a hover highlight in ListView as the effect was so subtle!

I'm wondering if the styling should be closer to the OptionList?

from textual.app import App, ComposeResult
from textual.containers import Horizontal
from textual.widgets import Label, ListItem, ListView, OptionList
from textual.widgets.option_list import Option


class ExampleApp(App):
    def compose(self) -> ComposeResult:
        with Horizontal():
            yield ListView(
                ListItem(Label("One")),
                ListItem(Label("Two")),
                ListItem(Label("Three")),
            )
            yield OptionList(
                Option("One"),
                Option("Two"),
                Option("Three"),
            )


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

[davidfokkema]

I didn't even realise there was a hover highlight in ListView as the effect was so subtle!

I'm wondering if the styling should be closer to the OptionList?

So... is an OptionList just a fancy ListView? Do we even need a ListView?

[TomJGooding]

A ListView can contain other Textual widgets, whereas an OptionList is limited to Rich renderables.

For example a ListView could contain an OptionList item - so yes actually in hindsight it doesn't make sense to compare the styling!

[davep]

Also, further to what Tom says, each item in a ListView is going to be at least two widgets (the ListItem and at least one thing within it), which means two message queues and all that per item. ListView is great for very rich (not Rich, just rich) items but not many of them.

OptionList, on the other hand, is just a single widget no matter how many items are within it. If you've got many 100s, even 1,000s, of items to show, OptionList is a better choice.

[davep]

I'm wondering if the styling should be closer to the OptionList?

We still have #1780 kicking about which, in part, has been diluted by some of the recent style revamping @willmcgugan did, but there's still a wee bit more work to day (in part the idea of adding some more $builtin-things to say "this is a focused cursor", "this is a non-focused cursor", etc...).

Edit to add: #1704

[davidfokkema]

So, an OptionList is basically a poor-man's ListView? And very useful at that because it is much faster? Because the OptionList reference documentation really shows of the ability to render Rich elements and the ListView docs are more basic, I thought it was the other way round. Thanks both for the clarification!

[davep]

So, an OptionList is basically a poor-man's ListView?

I wouldn't personally characterise it like that as I think it misses the fact that they're very distinct classes of widget that serve very different purposes. I think it makes more sense to view ListView as a Vertical with pre-canned "let's navigate the widgets within and be told when things are selected" machinery. OptionList is a whole other thing with a different purpose, which can also serve as the bedrock for all sorts of other uses (see SelectionList, and also OptionList is designed to serve as the basis for classic bouncebar menus, etc).

[TomJGooding]

I stumbled on this old issue looking for something else. The highlighting must have been fixed at some point, as I can't reproduce this on Textual v1.0!

[davidfokkema]

Can confirm that the issue was present in 0.30.0, but is resolved in 1.0.0. And probably some time before that, ;-). Anyway, since I was the one originally asking about this on Discord, and @davep was kind enough to create the issue, I'll close it. Wait, I don't have permission to do that, haha.

[davep]

Allow me...