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GtkColumnView: bad fast scrolling performance

Fedora 33, Wayland, GNOME, GTK4 3.99.4 from org.gnome.Sdk//master.

I have a GtkColumnView with a few label columns and ~1500 rows.

image

Fast scrolling brings it down to below 20 FPS whereas a Qt5 app with 4-5 times as many columns scrolls much smoother.

out

(apologies for a phone recording; something broke obs-xdg-portal a few days ago and gnome-shell screencast is also broken)

The .ui file for the column view: table.ui

The closures bound to list items directly fetch properties, they all look something along this:

    [GtkCallback]
    private string? format_vert_speed (Row? row) {
        if (row == null)
            return null;

        var frame = row.command_frame;
        if (frame == null)
            return null;

        var state = frame.pre_player_move;
        if (state == null)
            return null;

        var vel = state.velocity;
        if (vel[2] == 0)
            return null;

        return "%.1f".printf (vel[2]);
    }

I did a perf record of fast scrolling and got a flame graph. Open in browser to be able to zoom in on sub-trees.

perf.svg