inconsistent behavior Select Widged

[dominikhoebert]

Getting very inconsistent behavior with the new Select Widged when using their .set_options. Often after the options stay empty, depending on if the Select was used before, an item was selected before or not, or the options before where empy ([]).

from textual import on
from textual.app import App, ComposeResult
from textual.widgets import Select, Button


class SelectBug(App):

    def compose(self) -> ComposeResult:
        self.select = Select(options=[("empty", 0)])
        yield self.select
        yield Button("Change Options", id="change_options")

    @on(Button.Pressed, "#change_options")
    def change_options(self, event):
        self.select.set_options([("Four", 4), ("Five", 5), ("Six", 6)])


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

Keep the great work up!

[github-actions]

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

• How do I center a widget in a screen?

Feel free to close this issue if you found an answer in the FAQ. Otherwise, please give us a little time to review.

This is an automated reply, generated by FAQtory

[willmcgugan]

@davep Suspect this is an issue with virtual_size in OptionList (but far from certain).

[willmcgugan]

The following diff fixes it. AFAICT.

@@ -631,7 +631,7 @@ class OptionList(ScrollView, can_focus=True):
         self.highlighted = None
         self._mouse_hovering_over = None
         self.virtual_size = Size(self.scrollable_content_region.width, 0)
-        self.refresh()
+        self._request_content_tracking_refresh()
         return self

     def _set_option_disabled(self, index: int, disabled: bool) -> Self:

If this is the fix, it just needs tests.

[davep]

Yup, looks good here.

[willmcgugan]

@rodrigogiraoserrao I think Dave is doing this.

[davep]

While looking at adding some useful testing for this, I've realised that the suggested fix, while it works, is slightly puzzling.

The change sets up a call to _refresh_content_tracking via _on_idle, which is fine; but beforehand in the code there's already a forced call to _refresh_content_tracking. On the surface this would seem to be the same thing, albeit a delayed refresh of the content tracking, rather than an immediate one.

[davep]

Tracing it through so far, I'm starting to suspect it's tied in with the use of overlay: screen. The code that builds the contract tracking data for OptionList can't reasonably do this until its size.width is greater than 0 (or rather, it doesn't bother attempting to calculate any of that data until it is greater than 0).

If I'm reading things correctly the OptionList within Select has a size.width of 0 until it's expanded; upshot being that clearing and then rebuilding the OptionList as part of setting the options up doesn't result in the full rebuild because it can't happen.

An alternative fix (that I'm not proposing, just making a note of to explain things), would be this:

diff --git a/src/textual/widgets/_select.py b/src/textual/widgets/_select.py
index 25564af9..b9b5d0d4 100644
--- a/src/textual/widgets/_select.py
+++ b/src/textual/widgets/_select.py
@@ -329,6 +329,7 @@ class Select(Generic[SelectType], Vertical, can_focus=True):
         overlay = self.query_one(SelectOverlay)
         self.set_class(expanded, "-expanded")
         if expanded:
+            overlay._refresh_content_tracking(force=True)
             overlay.focus()
             if self.value is None:
                 overlay.select(None)

by this time the widget has width and so the underlying content data can be worked out.

[willmcgugan]

You could compare what happens if you remove overlay: screen from the select.

[davep]

@willmcgugan Good call! Okay, it's not that. And now I look at it it's possibly more obvious: I suspect the problem is that the clear/add is happening while it's display: none, which presumably means it has no size at that point.

[davep]

Makes me wonder if what's needed here (likely needed anyway) is a Show handler on OptionList that does:

self._request_content_tracking_refresh()

much like how Resize gets handled. Curiously though I'm not seeing _on_show or on_show get fired when SelectOverlay does from display: none to display: block. I think I would have expected that.

[davep]

Not directly related, but while trying to work out why the SelectOverlay doesn't seem to get a Show event, I found that Hide never seems to happen: #2574.

[github-actions]

Don't forget to star the repository!

Follow @textualizeio for Textual updates.