private static void DataGridLoaded(DataGrid dataGrid)
{
if (VisualTreeExHelper.FindChildren <ScrollViewer>(dataGrid).FirstOrDefault() is ScrollViewer scrollViewer)
{
SetSenderDataGrid(scrollViewer, dataGrid);
scrollViewer.ScrollChanged += ScrollViewerOnScrollChanged;
}
}
void OnLoaded()
{
if (VisualTreeExHelper.FindItemsPanel(AssociatedObject) is not UniformGrid uniformGrid)
{
throw new Exception($"ItemsPanel must be of type {nameof(UniformGrid)}");
}
this.uniformGrid = uniformGrid;
AssociatedObject.PreviewKeyDown += AssociatedObject_PreviewKeyDown;
}
static (int, int)? ScrollViewerOnScrollChanged(ScrollViewer scrollViewer, ItemsControl dataGrid, ScrollChangedEventArgs a)
{
//AssociatedObject_ScrollChanged();
if (VisualTreeExHelper.FindVisualChildren <ScrollBar>(scrollViewer).Single(s => s.Orientation == Orientation.Vertical) is ScrollBar verticalScrollBar)
{
int totalCount = dataGrid.Items.Count;
var firstVisible = verticalScrollBar.Value;
var lastVisible = firstVisible + totalCount - verticalScrollBar.Maximum;
return((int)firstVisible, (int)lastVisible);
}
return(null);
}
private static void ScrollViewerOnScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (sender is ScrollViewer scrollViewer)
{
if (VisualTreeExHelper.FindChildren <ScrollBar>(scrollViewer).FirstOrDefault(s => s.Orientation == Orientation.Vertical) is ScrollBar verticalScrollBar)
{
DataGrid dataGrid = GetSenderDataGrid(scrollViewer);
int totalCount = dataGrid.Items.Count;
int firstVisible = (int)verticalScrollBar.Value;
int lastVisible = (int)(firstVisible + totalCount - verticalScrollBar.Maximum);
SetVisibleItems(dataGrid, GetVisibibleItems(firstVisible, lastVisible, dataGrid).ToArray());
}
}
private void DataGridIsLoadedChanges()
{
if (VisualTreeExHelper.FindVisualChildren <ScrollViewer>(AssociatedObject).FirstOrDefault() is ScrollViewer scrollViewer)
{
// N.B this doesn't work well if VerticalScrollBar is used to scroll- works for mouse-wheel.
if (MouseFactor > 1)
{
scrollViewer.ScrollChanged += AssociatedObject_ScrollChanged;
}
scrollViewer
.ScrollChanges()
.Select(a => ScrollViewerOnScrollChanged(scrollViewer, AssociatedObject, a))
.Where(a => a.HasValue)
.Select(a => a !.Value)
.Subscribe(a =>
{
var(firstVisible, lastVisible) = a;
FirstIndex = firstVisible;
LastIndex = lastVisible;
Size = lastVisible - firstVisible + 1;
});
}
void AssociatedObject_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (scrollViewer.VerticalOffset == scrollPosition)
{
return;
}
scrollPosition = scrollViewer.VerticalOffset + e.VerticalChange * MouseFactor;
if (scrollPosition >= scrollViewer.ScrollableHeight)
{
scrollViewer.ScrollToBottom();
}
else
{
scrollViewer.ScrollToVerticalOffset(scrollPosition);
}
}
