Strange behavior of scrolling up a list in Ubuntu

[tarachom]

Good day.
I noticed a strange behavior of ColumnView scrolling in Ubuntu 22. There is no such problem on Windows.
When scrolling a large list from bottom to top, the slider reaches a certain limit and flies to the bottom again. If you hover the cursor over the slider itself and scroll, then it does not fly away. When scrolling from top to bottom, there is no such problem.

Thanks for the new release of GirCore!

zapis-z-260626-14-20-27_WQ9Ilwob.mp4

[badcel]

Thanks for the report. Are you sure it's not related to your code? I would assume if this is a real bug it's in GTK.

Either way, can you provide a minimal C# sample?

Then we can check if it is GirCore related. If not you can open an issue for GTK.

[tarachom]

Here is a minimal example. It turns out that if you select an item in the list and then scroll up, the slider does not jump down, but if the selected item is somewhere far down, the slider falls down. This is probably somehow related to the widget factory.

ColumnView example

1_tRrm5EpL.mp4

using Gtk;

namespace Program;

class Program
{
    private static void Main()
    {
        var app = Application.New("ua.org.accounting.test", Gio.ApplicationFlags.FlagsNone);
        app.OnActivate += (_, _) =>
        {
            var window = Window.New();
            window.SetDefaultSize(300, 500);
            window.Application = app;

            ColumnView grid = ColumnView.New(MultiSelection.New(StringList.New([.. Enumerable.Range(0, 500).Select(i => $"Text {i + 1}")])));

            SignalListItemFactory factory = SignalListItemFactory.New();
            factory.OnSetup += (_, args) =>
            {
                ListItem listItem = (ListItem)args.Object;
                listItem.Child = Label.New(null);
            };
            factory.OnBind += (_, args) =>
            {
                ListItem listItem = (ListItem)args.Object;
                if (listItem.Item is StringObject strobj && listItem.Child is Label label)
                    label.SetText(strobj.GetString());
            };
            ColumnViewColumn column = ColumnViewColumn.New("Text", factory);
            grid.AppendColumn(column);

            ScrolledWindow scroll = ScrolledWindow.New();
            scroll.SetChild(grid);

            window.Child = scroll;
            window.Show();
        };

        app.RunWithSynchronizationContext(null);
    }
}

[badcel]

See issue #1541