Beispiel #1
0
        private void RectangleSelection_PointerMoved(object sender, PointerRoutedEventArgs e)
        {
            if (scrollViewer == null)
            {
                return;
            }

            var currentPoint   = e.GetCurrentPoint(uiElement);
            var verticalOffset = scrollViewer.VerticalOffset;

            if (selectionState == SelectionState.Starting)
            {
                if (!HasMovedMinimalDelta(originDragPoint.X, originDragPoint.Y - verticalOffset, currentPoint.Position.X, currentPoint.Position.Y))
                {
                    return;
                }

                // Clear selected items once if the pointer is pressed and moved
                selectionStrategy.StartSelection();
                OnSelectionStarted();
                selectionState = SelectionState.Active;
            }
            if (currentPoint.Properties.IsLeftButtonPressed)
            {
                var originDragPointShifted = new Point(originDragPoint.X, originDragPoint.Y - verticalOffset); // Initial drag point relative to the topleft corner
                base.DrawRectangle(currentPoint, originDragPointShifted, uiElement);
                // Selected area considering scrolled offset
                var rect = new System.Drawing.Rectangle((int)Canvas.GetLeft(selectionRectangle), (int)Math.Min(originDragPoint.Y, currentPoint.Position.Y + verticalOffset), (int)selectionRectangle.Width, (int)Math.Abs(originDragPoint.Y - (currentPoint.Position.Y + verticalOffset)));

                foreach (var item in itemsPosition.ToList())
                {
                    try
                    {
                        if (rect.IntersectsWith(item.Value))
                        {
                            selectionStrategy.HandleIntersectionWithItem(item.Key);
                        }
                        else
                        {
                            selectionStrategy.HandleNoIntersectionWithItem(item.Key);
                        }
                    }
                    catch (ArgumentException)
                    {
                        // Item is not present in the ItemsSource
                        itemsPosition.Remove(item);
                    }
                }
                if (currentPoint.Position.Y > uiElement.ActualHeight - 20)
                {
                    // Scroll down the list if pointer is at the bottom
                    var scrollIncrement = Math.Min(currentPoint.Position.Y - (uiElement.ActualHeight - 20), 40);
                    scrollViewer.ChangeView(null, verticalOffset + scrollIncrement, null, false);
                }
                else if (currentPoint.Position.Y < 20)
                {
                    // Scroll up the list if pointer is at the top
                    var scrollIncrement = Math.Min(20 - currentPoint.Position.Y, 40);
                    scrollViewer.ChangeView(null, verticalOffset - scrollIncrement, null, false);
                }
            }
        }