/// <summary>
/// 计算 from，to，并返回总长度。
///
/// 如果在虚拟化模式下，总长度返回 0.
/// </summary>
/// <param name="columns"></param>
/// <returns></returns>
private double CalcVisibleRange(TreeGridColumnCollection columns)
{
this._from = 0;
this._to = columns.Count - 1;
if (!this._isVirtualizing)
{
return(0);
}
double allWidth = 0.0; //所有列的宽度总和
double hOffset = this._rowsPanel.HorizontalOffset; //水平滚动条位置
double viewPortWidth = this._rowsPanel.ViewportWidth; //视窗宽度
double leftInvisibleSum = 0.0; //左边不可见的宽度，逐列累加，直到超过 xOffset
double visibleSum = 0.0; //当前可见的宽度，逐列累加，直到超过 viewPortWidth
bool isVisible = false; //是否当前正在统计不可见的宽度
bool stop = false; //是否停止计算可见列，而开始统计所有宽度。
for (int i = 0, c = columns.Count; i < c; i++)
{
var column = columns[i];
var width = column.CalculateActualWidth();
allWidth += width;
if (stop)
{
continue;
}
if (!isVisible)
{
if (leftInvisibleSum + width > hOffset)
{
this._from = i;
visibleSum = leftInvisibleSum + width - hOffset;
isVisible = true;
}
else
{
leftInvisibleSum += width;
}
}
else
{
visibleSum += width;
if (visibleSum > viewPortWidth)
{
this._to = i;
stop = true;
}
}
}
return(allWidth);
}
/// <summary>
/// 子类在 Measure 时，调用此方法来连接到 TreeGrid，并同步一些必要的属性。
/// </summary>
internal void ConnectToGrid()
{
if (_treeGrid == null)
{
_treeGrid = this.GetVisualParent <TreeGrid>();
if (_treeGrid != null)
{
_columns = _treeGrid.Columns;
InternalCollectionChangedEventManager.AddListener(_columns, this);
}
}
}
public static void RemoveListener(TreeGridColumnCollection source, IWeakEventListener listener)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
if (listener == null)
{
throw new ArgumentNullException("listener");
}
InternalCollectionChangedEventManager.CurrentManager.ProtectedRemoveListener(source, listener);
}
/// <summary>
/// 保证 desiredList 与 columns 长度一致。
/// </summary>
internal static void EnsureDesiredWidthList(ref List <double> desiredList, TreeGridColumnCollection columns)
{
if (columns != null)
{
int count = columns.Count;
if (desiredList == null)
{
desiredList = new List <double>(count);
}
//对于还没有在 _desiredWidthList 添加对应值的列，都添加相应的数据，
int num = count - desiredList.Count;
for (int i = 0; i < num; i++)
{
desiredList.Add(double.NaN);
}
}
}
/// <summary>
/// 测量所有已经生成的单元格。
/// </summary>
/// <param name="columns"></param>
/// <param name="availableSize"></param>
/// <returns></returns>
private Size MeasureChild(TreeGridColumnCollection columns, Size availableSize)
{
double maxWidth = availableSize.Width;
double maxHeight = availableSize.Height;
double rowDesiredHeight = 0.0; //行最终需要的高度
double rowDesiredWidth = 0.0; //行最终需要的宽度
bool firstTime = true; //是否在 Init 状态下还没有初始化过 DesiredWidthList。
var cells = this.InternalChildren;
for (int i = this._from, j = 0; i <= this._to; i++, j++)
{
var column = columns[i];
//当前行还可用的宽度
double rowAvaiableWidth = Math.Max(0, maxWidth - rowDesiredWidth);
//第一列额外元素需要的宽度
double headersDesiredWidth = 0;
#region 测量第一列额外元素需要的宽度
if (i == 0)
{
//测量 RowHeader
if (this.ShowRowHeader)
{
headersDesiredWidth += this.RowHeaderWidth;
rowAvaiableWidth -= this.RowHeaderWidth;
//this._rowHeaderContainer.Measure(new Size(columnWidth, maxHeight));
//x += this._rowHeaderContainer.DesiredSize.Width;
//columnWidth -= this._rowHeaderContainer.DesiredSize.Width;
}
//留下 FirstColumnIndent
var firstColumnIndent = Math.Min(this.FirstColumnIndent, rowAvaiableWidth);
headersDesiredWidth += firstColumnIndent;
rowAvaiableWidth -= firstColumnIndent;
//测量 Expander
if (this.ShowExpander)
{
var expander = this.Expander;
expander.Measure(new Size(rowAvaiableWidth, maxHeight));
headersDesiredWidth += expander.DesiredSize.Width;
rowAvaiableWidth -= expander.DesiredSize.Width;
}
}
#endregion
var cell = cells[j];
//测量单元格
var state = column.State;
if (state == ColumnMeasureState.Init || state == ColumnMeasureState.Headered)
{
if (firstTime)
{
TreeGridHelper.EnsureDesiredWidthList(ref this._desiredWidthList, this._treeGrid.Columns);
this.LayoutUpdated += this.OnMeasureLayoutUpdated;
firstTime = false;
}
cell.Measure(new Size(rowAvaiableWidth, maxHeight));
//只有在虚拟化后的当前页面时，才影响动态宽度。
if (this._cellsPresenter.IsOnCurrentPage)
{
//当前列需要的宽度应该是列的宽度加额外元素的宽度。
column.EnsureDataWidth(cell.DesiredSize.Width + headersDesiredWidth);
}
this._desiredWidthList[column.StableIndex] = column.DesiredDataWidth;
rowDesiredWidth += column.DesiredDataWidth;
}
else
{
var actualWidth = column.CalculateActualWidth();
rowAvaiableWidth = Math.Min(rowAvaiableWidth, actualWidth - headersDesiredWidth);
cell.Measure(new Size(rowAvaiableWidth, maxHeight));
rowDesiredWidth += actualWidth;
}
rowDesiredHeight = Math.Max(rowDesiredHeight, cell.DesiredSize.Height);
}
rowDesiredWidth += TreeGridHeaderRowPresenter.c_EndPadding;
this._cellsPresenter.IsOnCurrentPageValid = false;
return(new Size(rowDesiredWidth, rowDesiredHeight));
}