DarkListView scrolls very slowly with small amount of items

[istir]

Hello, I encountered a weird problem, that would indicate a connection between the total amount of items in a DarkListView and the scroll speed of said control. If I'm using 20 items it takes around 5-6 "scrolls" with the wheel to scroll down by 1 item, however if I'm using 100 items it only takes around 1,5 "scrolls". This behavior doesn't occur in a standard ListView control - the scroll amount is always the same.

It obviously works as intended with more items, but I find it highly frustrating having to scroll 20 times to get down 3 items.

I downloaded the package from NuGet, but also cloned the repository and checked the Example project - the behavior is the same as in my project.

[varandas79]

Hello, In my case I've to solve this issue by adapting the UpdateThumb method into DarkScrollBar.cs

private void UpdateThumb(bool forceRefresh = false)
{
    // Calculate size ratio
    float maxsize = (float)((Minimum < Maximum) ? (Maximum - Minimum) : (Maximum - Minimum));
    if (maxsize == 0)
        _viewContentRatio = 1.0f;
    else
        _viewContentRatio = (_scrollOrientation == DarkScrollOrientation.Vertical) ? (Height / maxsize) : (Width / maxsize);

    var viewAreaSize = Math.Max(maxsize, 1);
    var positionRatio = ((float)Value - Minimum) / (float)viewAreaSize;
    if (Minimum < 0)
    {
        positionRatio = (float) ((Minimum*-1) + (float) Value)/(float) viewAreaSize;
    }

    // Update area
    if (_scrollOrientation == DarkScrollOrientation.Vertical)
    {
        var thumbSize = (int)(_trackArea.Height * _viewContentRatio);
        _thumbArea = new Rectangle(_trackArea.Left + 3, _trackArea.Top + (int)(_trackArea.Height * positionRatio),
            Consts.ScrollBarSize - 6, Math.Max(thumbSize, Consts.MinimumThumbSize));
    }
    else
    {
        var thumbSize = (int)(_trackArea.Width * _viewContentRatio);
        _thumbArea = new Rectangle(_trackArea.Left + (int)(_trackArea.Width * positionRatio), _trackArea.Top + 3, 
            Math.Max(thumbSize, Consts.MinimumThumbSize), Consts.ScrollBarSize - 6);
    }

    if (forceRefresh)
    {
        Invalidate();
        Update();
    }
}

And OnMouseWheel into DarkScrollBase.cs

protected override void OnMouseWheel(MouseEventArgs e)
{
    base.OnMouseWheel(e);
    const int offset  = 50;
    var horizontal = false;

    if (_hScrollBar.Visible && ModifierKeys == Keys.Control)
        horizontal = true;

    if (_hScrollBar.Visible && !_vScrollBar.Visible)
        horizontal = true;

    if (!horizontal)
    {
        if (e.Delta > 0)
            _vScrollBar.ScrollBy(-offset);
        else if (e.Delta < 0)
            _vScrollBar.ScrollBy(offset);
    }
    else
    {
        if (e.Delta > 0)
            _hScrollBar.ScrollBy(-offset);
        else if (e.Delta < 0)
            _hScrollBar.ScrollBy(offset);
    }
}

You can also change the scroll speed by changing the offset value.