private void RaiseLineArranged()
{
var realizationRect = RealizationRect;
if (realizationRect.Width != 0.0 || realizationRect.Height != 0.0)
{
int realizedElementCount = m_elementManager.GetRealizedElementCount();
if (realizedElementCount > 0)
{
Debug.Assert(m_firstRealizedDataIndexInsideRealizationWindow != -1 && m_lastRealizedDataIndexInsideRealizationWindow != -1);
int countInLine = 0;
var previousElementBounds = m_elementManager.GetLayoutBoundsForDataIndex(m_firstRealizedDataIndexInsideRealizationWindow);
var currentLineOffset = OM.MajorStart(previousElementBounds);
var currentLineSize = OM.MajorSize(previousElementBounds);
for (int currentDataIndex = m_firstRealizedDataIndexInsideRealizationWindow; currentDataIndex <= m_lastRealizedDataIndexInsideRealizationWindow; currentDataIndex++)
{
var currentBounds = m_elementManager.GetLayoutBoundsForDataIndex(currentDataIndex);
if (OM.MajorStart(currentBounds) != currentLineOffset)
{
// Staring a new line
m_algorithmCallbacks.Algorithm_OnLineArranged(currentDataIndex - countInLine, countInLine, currentLineSize, m_context);
countInLine = 0;
currentLineOffset = OM.MajorStart(currentBounds);
currentLineSize = 0;
}
currentLineSize = Math.Max(currentLineSize, OM.MajorSize(currentBounds));
countInLine++;
}
// Raise for the last line.
m_algorithmCallbacks.Algorithm_OnLineArranged(m_lastRealizedDataIndexInsideRealizationWindow - countInLine + 1, countInLine, currentLineSize, m_context);
}
}
}
private bool ShouldContinueFillingUpSpace(
int index,
GenerateDirection direction)
{
bool shouldContinue;
if (!IsVirtualizingContext)
{
shouldContinue = true;
}
else
{
var realizationRect = m_context.RealizationRect;
var elementBounds = m_elementManager.GetLayoutBoundsForDataIndex(index);
var elementMajorStart = OM.MajorStart(elementBounds);
var elementMajorEnd = OM.MajorEnd(elementBounds);
var rectMajorStart = OM.MajorStart(realizationRect);
var rectMajorEnd = OM.MajorEnd(realizationRect);
var elementMinorStart = OM.MinorStart(elementBounds);
var elementMinorEnd = OM.MinorEnd(elementBounds);
var rectMinorStart = OM.MinorStart(realizationRect);
var rectMinorEnd = OM.MinorEnd(realizationRect);
// Ensure that both minor and major directions are taken into consideration so that if the scrolling direction
// is the same as the flow direction we still stop at the end of the viewport rectangle.
shouldContinue =
(direction == GenerateDirection.Forward && elementMajorStart < rectMajorEnd && elementMinorStart < rectMinorEnd) ||
(direction == GenerateDirection.Backward && elementMajorEnd > rectMajorStart && elementMinorEnd > rectMinorStart);
}
return(shouldContinue);
}
private void ArrangeVirtualizingLayout(
Size finalSize,
LineAlignment lineAlignment,
bool isWrapping,
string layoutId)
{
// Walk through the realized elements one line at a time and
// align them, Then call element.Arrange with the arranged bounds.
int realizedElementCount = m_elementManager.GetRealizedElementCount();
if (realizedElementCount > 0)
{
int countInLine = 1;
var previousElementBounds = m_elementManager.GetLayoutBoundsForRealizedIndex(0);
var currentLineOffset = OM.MajorStart(previousElementBounds);
var spaceAtLineStart = OM.MinorStart(previousElementBounds);
double spaceAtLineEnd = 0;
double currentLineSize = OM.MajorSize(previousElementBounds);
for (int i = 1; i < realizedElementCount; i++)
{
var currentBounds = m_elementManager.GetLayoutBoundsForRealizedIndex(i);
if (OM.MajorStart(currentBounds) != currentLineOffset)
{
spaceAtLineEnd = OM.Minor(finalSize) - OM.MinorStart(previousElementBounds) - OM.MinorSize(previousElementBounds);
PerformLineAlignment(i - countInLine, countInLine, spaceAtLineStart, spaceAtLineEnd, currentLineSize, lineAlignment, isWrapping, finalSize, layoutId);
spaceAtLineStart = OM.MinorStart(currentBounds);
countInLine = 0;
currentLineOffset = OM.MajorStart(currentBounds);
currentLineSize = 0;
}
countInLine++; // for current element
currentLineSize = Math.Max(currentLineSize, OM.MajorSize(currentBounds));
previousElementBounds = currentBounds;
}
// Last line - potentially have a property to customize
// aligning the last line or not.
if (countInLine > 0)
{
double spaceAtEnd = OM.Minor(finalSize) - OM.MinorStart(previousElementBounds) - OM.MinorSize(previousElementBounds);
PerformLineAlignment(realizedElementCount - countInLine, countInLine, spaceAtLineStart, spaceAtEnd, currentLineSize, lineAlignment, isWrapping, finalSize, layoutId);
}
}
}
private void Generate(
GenerateDirection direction,
int anchorIndex,
Size availableSize,
double minItemSpacing,
double lineSpacing,
uint maxItemsPerLine,
bool disableVirtualization,
string layoutId)
{
if (anchorIndex != -1)
{
int step = (direction == GenerateDirection.Forward) ? 1 : -1;
int previousIndex = anchorIndex;
int currentIndex = anchorIndex + step;
var anchorBounds = m_elementManager.GetLayoutBoundsForDataIndex(anchorIndex);
double lineOffset = OM.MajorStart(anchorBounds);
double lineMajorSize = OM.MajorSize(anchorBounds);
uint countInLine = 1;
bool lineNeedsReposition = false;
while (m_elementManager.IsIndexValidInData(currentIndex) &&
(disableVirtualization || ShouldContinueFillingUpSpace(previousIndex, direction)))
{
// Ensure layout element.
m_elementManager.EnsureElementRealized(direction == GenerateDirection.Forward, currentIndex, layoutId);
var currentElement = m_elementManager.GetRealizedElement(currentIndex);
var desiredSize = MeasureElement(currentElement, currentIndex, availableSize, m_context);
// Lay it out.
var previousElement = m_elementManager.GetRealizedElement(previousIndex);
Rect currentBounds = new Rect(0, 0, desiredSize.Width, desiredSize.Height);
var previousElementBounds = m_elementManager.GetLayoutBoundsForDataIndex(previousIndex);
if (direction == GenerateDirection.Forward)
{
double remainingSpace = OM.Minor(availableSize) - (OM.MinorStart(previousElementBounds) + OM.MinorSize(previousElementBounds) + minItemSpacing + OM.Minor(desiredSize));
if (countInLine >= maxItemsPerLine || m_algorithmCallbacks.Algorithm_ShouldBreakLine(currentIndex, remainingSpace))
{
// No more space in this row. wrap to next row.
OM.SetMinorStart(ref currentBounds, 0);
OM.SetMajorStart(ref currentBounds, OM.MajorStart(previousElementBounds) + lineMajorSize + lineSpacing);
if (lineNeedsReposition)
{
// reposition the previous line (countInLine items)
for (uint i = 0; i < countInLine; i++)
{
var dataIndex = currentIndex - 1 - i;
var bounds = m_elementManager.GetLayoutBoundsForDataIndex((int)dataIndex);
OM.SetMajorSize(ref bounds, lineMajorSize);
m_elementManager.SetLayoutBoundsForDataIndex((int)dataIndex, bounds);
}
}
// Setup for next line.
lineMajorSize = OM.MajorSize(currentBounds);
lineOffset = OM.MajorStart(currentBounds);
lineNeedsReposition = false;
countInLine = 1;
}
else
{
// More space is available in this row.
OM.SetMinorStart(ref currentBounds, OM.MinorStart(previousElementBounds) + OM.MinorSize(previousElementBounds) + (minItemSpacing));
OM.SetMajorStart(ref currentBounds, lineOffset);
lineMajorSize = Math.Max(lineMajorSize, OM.MajorSize(currentBounds));
lineNeedsReposition = OM.MajorSize(previousElementBounds) != OM.MajorSize(currentBounds);
countInLine++;
}
}
else
{
// Backward
double remainingSpace = OM.MinorStart(previousElementBounds) - (OM.Minor(desiredSize) + minItemSpacing);
if (countInLine >= maxItemsPerLine || m_algorithmCallbacks.Algorithm_ShouldBreakLine(currentIndex, remainingSpace))
{
// Does not fit, wrap to the previous row
var availableSizeMinor = OM.Minor(availableSize);
OM.SetMinorStart(ref currentBounds, !double.IsInfinity(availableSizeMinor) ? availableSizeMinor - OM.Minor(desiredSize) : 0.0);
OM.SetMajorStart(ref currentBounds, lineOffset - OM.Major(desiredSize) - lineSpacing);
if (lineNeedsReposition)
{
var previousLineOffset = OM.MajorStart(m_elementManager.GetLayoutBoundsForDataIndex((int)(currentIndex + countInLine + 1)));
// reposition the previous line (countInLine items)
for (uint i = 0; i < countInLine; i++)
{
var dataIndex = currentIndex + 1 + (int)i;
if (dataIndex != anchorIndex)
{
var bounds = m_elementManager.GetLayoutBoundsForDataIndex(dataIndex);
OM.SetMajorStart(ref bounds, previousLineOffset - lineMajorSize - lineSpacing);
OM.SetMajorSize(ref bounds, lineMajorSize);
m_elementManager.SetLayoutBoundsForDataIndex(dataIndex, bounds);
}
}
}
// Setup for next line.
lineMajorSize = OM.MajorSize(currentBounds);
lineOffset = OM.MajorStart(currentBounds);
lineNeedsReposition = false;
countInLine = 1;
}
else
{
// Fits in this row. put it in the previous position
OM.SetMinorStart(ref currentBounds, OM.MinorStart(previousElementBounds) - OM.Minor(desiredSize) - minItemSpacing);
OM.SetMajorStart(ref currentBounds, lineOffset);
lineMajorSize = Math.Max(lineMajorSize, OM.MajorSize(currentBounds));
lineNeedsReposition = OM.MajorSize(previousElementBounds) != OM.MajorSize(currentBounds);
countInLine++;
}
}
m_elementManager.SetLayoutBoundsForDataIndex(currentIndex, currentBounds);
previousIndex = currentIndex;
currentIndex += step;
}
// If we did not reach the top or bottom of the extent, we realized one
// extra item before we knew we were outside the realization window. Do not
// account for that element in the indicies inside the realization window.
if (direction == GenerateDirection.Forward)
{
int dataCount = m_context.ItemCount;
m_lastRealizedDataIndexInsideRealizationWindow = previousIndex == dataCount - 1 ? dataCount - 1 : previousIndex - 1;
m_lastRealizedDataIndexInsideRealizationWindow = Math.Max(0, m_lastRealizedDataIndexInsideRealizationWindow);
}
else
{
int dataCount = m_context.ItemCount;
m_firstRealizedDataIndexInsideRealizationWindow = previousIndex == 0 ? 0 : previousIndex + 1;
m_firstRealizedDataIndexInsideRealizationWindow = Math.Min(dataCount - 1, m_firstRealizedDataIndexInsideRealizationWindow);
}
m_elementManager.DiscardElementsOutsideWindow(direction == GenerateDirection.Forward, currentIndex);
}
}
private int GetAnchorIndex(
Size availableSize,
bool isWrapping,
double minItemSpacing,
string layoutId)
{
int anchorIndex = -1;
Point anchorPosition = default;
if (!IsVirtualizingContext)
{
// Non virtualizing host, start generating from the element 0
anchorIndex = ((IVirtualizingLayoutContextOverrides)m_context).ItemCountCore() > 0 ? 0 : -1;
}
else
{
bool isRealizationWindowConnected = m_elementManager.IsWindowConnected(RealizationRect, OM.ScrollOrientation, m_scrollOrientationSameAsFlow);
// Item spacing and size in non-virtualizing direction change can cause elements to reflow
// and get a new column position. In that case we need the anchor to be positioned in the
// correct column.
bool needAnchorColumnRevaluation = isWrapping && (
OM.Minor(m_lastAvailableSize) != OM.Minor(availableSize) ||
m_lastItemSpacing != minItemSpacing ||
m_collectionChangePending);
var suggestedAnchorIndex = m_context.RecommendedAnchorIndex;
bool isAnchorSuggestionValid = suggestedAnchorIndex >= 0 &&
m_elementManager.IsDataIndexRealized(suggestedAnchorIndex);
if (isAnchorSuggestionValid)
{
anchorIndex = m_algorithmCallbacks.Algorithm_GetAnchorForTargetElement(
suggestedAnchorIndex,
availableSize,
m_context).Index;
if (m_elementManager.IsDataIndexRealized(anchorIndex))
{
var anchorBounds = m_elementManager.GetLayoutBoundsForDataIndex(anchorIndex);
if (needAnchorColumnRevaluation)
{
// We were provided a valid anchor, but its position might be incorrect because for example it is in
// the wrong column. We do know that the anchor is the first element in the row, so we can force the minor position
// to start at 0.
anchorPosition = OM.MinorMajorPoint(0, OM.MajorStart(anchorBounds));
}
else
{
anchorPosition = new Point(anchorBounds.X, anchorBounds.Y);
}
}
else
{
// It is possible to end up in a situation during a collection change where GetAnchorForTargetElement returns an index
// which is not in the realized range. Eg. insert one item at index 0 for a grid layout.
// SuggestedAnchor will be 1 (used to be 0) and GetAnchorForTargetElement will return 0 (left most item in row). However 0 is not in the
// realized range yet. In this case we realize the gap between the target anchor and the suggested anchor.
int firstRealizedDataIndex = m_elementManager.GetDataIndexFromRealizedRangeIndex(0);
Debug.Assert(anchorIndex < firstRealizedDataIndex);
for (int i = firstRealizedDataIndex - 1; i >= anchorIndex; --i)
{
m_elementManager.EnsureElementRealized(false /*forward*/, i, layoutId);
}
var anchorBounds = m_elementManager.GetLayoutBoundsForDataIndex(suggestedAnchorIndex);
anchorPosition = OM.MinorMajorPoint(0, OM.MajorStart(anchorBounds));
}
}
else if (needAnchorColumnRevaluation || !isRealizationWindowConnected)
{
// The anchor is based on the realization window because a connected ItemsRepeater might intersect the realization window
// but not the visible window. In that situation, we still need to produce a valid anchor.
var anchorInfo = m_algorithmCallbacks.Algorithm_GetAnchorForRealizationRect(availableSize, m_context);
anchorIndex = anchorInfo.Index;
anchorPosition = OM.MinorMajorPoint(0, anchorInfo.Offset);
}
else
{
// No suggestion - just pick first in realized range
anchorIndex = m_elementManager.GetDataIndexFromRealizedRangeIndex(0);
var firstElementBounds = m_elementManager.GetLayoutBoundsForRealizedIndex(0);
anchorPosition = new Point(firstElementBounds.X, firstElementBounds.Y);
}
}
Debug.Assert(anchorIndex == -1 || m_elementManager.IsIndexValidInData(anchorIndex));
m_firstRealizedDataIndexInsideRealizationWindow = m_lastRealizedDataIndexInsideRealizationWindow = anchorIndex;
if (m_elementManager.IsIndexValidInData(anchorIndex))
{
if (!m_elementManager.IsDataIndexRealized(anchorIndex))
{
// Disconnected, throw everything and create new anchor
m_elementManager.ClearRealizedRange();
var anchor = m_context.GetOrCreateElementAt(anchorIndex, ElementRealizationOptions.ForceCreate | ElementRealizationOptions.SuppressAutoRecycle);
m_elementManager.Add(anchor, anchorIndex);
}
var anchorElement = m_elementManager.GetRealizedElement(anchorIndex);
var desiredSize = MeasureElement(anchorElement, anchorIndex, availableSize, m_context);
var layoutBounds = new Rect(anchorPosition.X, anchorPosition.Y, desiredSize.Width, desiredSize.Height);
m_elementManager.SetLayoutBoundsForDataIndex(anchorIndex, layoutBounds);
}
else
{
// Throw everything away
m_elementManager.ClearRealizedRange();
}
// TODO: Perhaps we can track changes in the property setter
m_lastAvailableSize = availableSize;
m_lastItemSpacing = minItemSpacing;
return(anchorIndex);
}