Esempio n. 1
0
 public bool IsWithin(VerticalArea area)
 {
     return
         ((area.Top >= Top && area.Top <= Bottom)
          ||
          (area.Bottom >= Top && area.Bottom <= Bottom)
          ||
          (area.Top <= Top && area.Bottom >= Bottom));
 }
        /// <summary>
        /// Measure the children
        /// </summary>
        /// <param name="availableSize">Size available</param>
        /// <returns>Size desired</returns>
        protected override Size MeasureOverride(Size availableSize)
        {
            if (ScrollOwner != null)
            {
                if (ScrollOwner.ScrollableWidth < HorizontalOffset)
                {
                    SetHorizontalOffset(ScrollOwner.ScrollableWidth);
                }
                if (ScrollOwner.ScrollableHeight < VerticalOffset)
                {
                    SetVerticalOffset(ScrollOwner.ScrollableHeight);
                }
            }

            // We need to access InternalChildren before the generator to work around a bug
            UIElementCollection     children     = InternalChildren;
            IItemContainerGenerator generator    = ItemContainerGenerator;
            ItemsControl            itemsControl = ItemsControl.GetItemsOwner(this);
            TreeViewExItem          treeViewItem = itemsControl as TreeViewExItem;
            TreeViewEx treeView = itemsControl as TreeViewEx ?? treeViewItem.ParentTreeView;

            Debug(treeViewItem, "Measuring");
            double maxWidth             = 0;
            double currentYinItemSystem = 0;

            if (treeView.IsVirtualizing)
            {
                // never forget: virtualization of a tree is an approximation. there are some use cases which theoretically work and others
                // we try to get it working by estimations. See GetCachedOrEstimatedHeight for more infos.

                int itemCount             = itemsControl.Items.Count;
                int firstVisibleItemIndex = 0;
                int lastVisibleItemIndex  = itemCount;

                double itemTop;
                if (treeViewItem != null)
                {
                    itemTop = treeViewItem.itemTopInTreeSystem + GetHeightOfHeader(itemsControl);
                }
                else
                {
                    // get the area where items have to be visualized. This is from top to bottom of the visible space in tree system.
                    // We add a little of offset. It seems like it improves estimation of heights.
                    double predictionOffset = 50;
                    double top = VerticalOffset - predictionOffset;
                    if (top < 0)
                    {
                        top = 0;
                    }
                    treeView.realizationSpace.Top    = top;
                    treeView.realizationSpace.Bottom = VerticalOffset + availableSize.Height + predictionOffset;

                    itemTop = GetHeightOfHeader(itemsControl);
                }

                int         itemGeneratorIndex    = 0;
                bool        isPreviousItemVisible = false;
                IDisposable generatorRun          = null;
                currentYinItemSystem = 0;
                int childHierarchyLevel = 0;
                if (treeViewItem != null)
                {
                    childHierarchyLevel = treeViewItem.hierachyLevel + 1;
                }
                try
                {
                    // iterate child items
                    for (int i = 0; i < itemCount; i++)
                    {
                        double       estimatedHeight = GetCachedOrEstimatedHeight(treeView, childHierarchyLevel);
                        VerticalArea childSpace      = new VerticalArea();
                        childSpace.Top    = itemTop + currentYinItemSystem;
                        childSpace.Bottom = childSpace.Top + estimatedHeight;

                        // check if item is possibly visible or could become visible if someone changes expanding of siblings
                        bool isVisibleItem = treeView.realizationSpace.IsWithin(childSpace);

                        if (isVisibleItem)
                        {
                            // we have found a visible item, lets check if its the first visible item.
                            if (!isPreviousItemVisible)
                            {
                                // we found a visible item, lets initialize the visible item section of the loop
                                isPreviousItemVisible = true;
                                firstVisibleItemIndex = i;
                                GeneratorPosition startPos = generator.GeneratorPositionFromIndex(i);
                                itemGeneratorIndex = (startPos.Offset == 0) ? startPos.Index : startPos.Index + 1;
                                generatorRun       = generator.StartAt(startPos, GeneratorDirection.Forward, true);
                            }
                            else
                            {
                                itemGeneratorIndex++;
                            }

                            // Get or create the child
                            bool           newlyRealized;
                            TreeViewExItem child = generator.GenerateNext(out newlyRealized) as TreeViewExItem;
                            Debug(treeViewItem, "Found visible child: " + child.DataContext);

                            if (newlyRealized)
                            {
                                // Figure out if we need to insert the child at the end or somewhere in the middle
                                AddOrInsertItemToInternalChildren(itemGeneratorIndex, child);
                                child.ParentTreeView = treeView;
                                generator.PrepareItemContainer(child);
                            }
                            else
                            {
                                // The child has already been created, let's be sure it's in the right spot
                                if (child != children[itemGeneratorIndex])
                                {
                                    throw new InvalidOperationException("Wrong child was generated");
                                }
                            }

                            if (treeViewItem != null)
                            {
                                child.itemTopInTreeSystem = currentYinItemSystem + itemTop;
                                child.hierachyLevel       = treeViewItem.hierachyLevel + 1;
                            }
                            else
                            {
                                child.itemTopInTreeSystem = currentYinItemSystem;
                                child.hierachyLevel       = 1;
                            }

                            InvalidateMeasure(child);
                            child.Measure(new Size(double.MaxValue, double.MaxValue));

                            // add real height to cache
                            double heightOfChild = child.DesiredSize.Height;
                            RegisterHeight(treeView, childHierarchyLevel, heightOfChild);
                            currentYinItemSystem += child.DesiredSize.Height;
                            // save the maximum needed width
                            maxWidth = Math.Max(maxWidth, child.DesiredSize.Width);
                        }
                        else
                        {
                            //Debug(treeViewItem, "Found invisible child: " + i);
                            if (isPreviousItemVisible)
                            {
                                // set last visible index. this is important, to cleanup not anymore used items
                                lastVisibleItemIndex  = i;
                                isPreviousItemVisible = false;
                            }

                            // dispose generator run. if we do it after the whole loop, we run in multithreading issues
                            if (generatorRun != null)
                            {
                                generatorRun.Dispose();
                                generatorRun = null;
                            }

                            currentYinItemSystem += GetCachedOrEstimatedHeight(treeView, childHierarchyLevel);
                        }
                        //Debug(treeViewItem, "Current y for " + i + ": " + currentYinItemSystem);
                    }
                }
                finally
                {
                    //just for safety
                    if (generatorRun != null)
                    {
                        generatorRun.Dispose();
                        generatorRun = null;
                    }
                }

                //Debug("Cleaning all items but " + firstVisibleItemIndex + " to " + lastVisibleItemIndex + " for element " + itemsControl.DataContext);
                CleanUpItems(firstVisibleItemIndex, lastVisibleItemIndex);
            }
            else
            {
                //Debug("Virtualization is OFF.");
                GeneratorPosition startPos = generator.GeneratorPositionFromIndex(0);
                using (generator.StartAt(startPos, GeneratorDirection.Forward, true))
                {
                    for (int i = (startPos.Offset == 0) ? startPos.Index : startPos.Index + 1; i < itemsControl.Items.Count; i++)
                    {
                        // Get or create the child
                        bool           newlyRealized;
                        TreeViewExItem child = generator.GenerateNext(out newlyRealized) as TreeViewExItem;
                        if (newlyRealized)
                        {
                            // Figure out if we need to insert the child at the end or somewhere in the middle
                            AddOrInsertItemToInternalChildren(i, child);
                            child.ParentTreeView = treeView ?? treeViewItem.ParentTreeView;
                            generator.PrepareItemContainer(child);
                        }

                        child.Measure(new Size(double.MaxValue, double.MaxValue));
                        // now get the real height
                        double height = child.DesiredSize.Height;
                        // add real height to current position
                        currentYinItemSystem += height;
                        // save the maximum needed width
                        maxWidth = Math.Max(maxWidth, child.DesiredSize.Width);
                    }
                }
            }

            if (double.IsPositiveInfinity(maxWidth) || double.IsPositiveInfinity(currentYinItemSystem))
            {
                throw new InvalidOperationException("???");
            }

            Extent   = new Size(maxWidth, currentYinItemSystem);
            Viewport = availableSize;
            Debug(treeViewItem, "Desired height: " + Extent.Height);
            return(Extent);
        }