protected override Size MeasureOverride(Size availableSize)
{
if (this.OwningGrid == null)
{
return(base.MeasureOverride(availableSize));
}
if (!this.OwningGrid.AreColumnHeadersVisible)
{
return(Size.Empty);
}
double height = this.OwningGrid.ColumnHeaderHeight;
bool autoSizeHeight;
if (double.IsNaN(height))
{
// No explicit height values were set so we can autosize
height = 0;
autoSizeHeight = true;
}
else
{
autoSizeHeight = false;
}
DataGridColumn lastVisibleColumn = this.OwningGrid.ColumnsInternal.LastVisibleColumn;
DataGridColumn column = this.OwningGrid.ColumnsInternal.FirstVisibleColumn;
double measureWidth;
while (column != null)
{
DataGridLength columnWidth = column.EffectiveWidth;
measureWidth = columnWidth.IsAbsolute ? column.ActualWidth : column.ActualMaxWidth;
bool autoGrowWidth = columnWidth.IsAuto || columnWidth.IsSizeToHeader;
DataGridColumnHeader columnHeader = column.HeaderCell;
if (column != lastVisibleColumn)
{
columnHeader.UpdateSeparatorVisibility(lastVisibleColumn);
}
columnHeader.Measure(new Size(measureWidth, double.PositiveInfinity));
if (autoSizeHeight)
{
height = Math.Max(height, columnHeader.DesiredSize.Height);
}
if (autoGrowWidth && columnHeader.DesiredSize.Width > column.DesiredWidth)
{
column.DesiredWidth = columnHeader.DesiredSize.Width;
}
column = this.OwningGrid.ColumnsInternal.GetNextVisibleColumn(column);
}
// Add the filler column if it's not represented. We won't know whether we need it or not until Arrange
DataGridFillerColumn fillerColumn = this.OwningGrid.ColumnsInternal.FillerColumn;
if (!fillerColumn.IsRepresented)
{
Debug.Assert(!this.Children.Contains(fillerColumn.HeaderCell));
fillerColumn.HeaderCell.SeparatorVisibility = Visibility.Collapsed;
this.Children.Insert(this.OwningGrid.ColumnsInternal.Count, fillerColumn.HeaderCell);
fillerColumn.IsRepresented = true;
this.OwningGrid.OnFillerColumnRepresentationChanged();
// Optimize for the case where we don't need the filler cell
fillerColumn.HeaderCell.Visibility = Visibility.Collapsed;
}
fillerColumn.HeaderCell.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
return(new Size(this.OwningGrid.ColumnsInternal.VisibleEdgedColumnsWidth, height));
}
/// <summary>
/// Measures the children of a <see cref="T:System.Windows.Controls.Primitives.DataGridColumnHeadersPresenter" /> to
/// prepare for arranging them during the <see cref="M:System.Windows.FrameworkElement.ArrangeOverride(System.Windows.Size)" /> pass.
/// </summary>
/// <param name="availableSize">
/// The available size that this element can give to child elements. Indicates an upper limit that child elements should not exceed.
/// </param>
/// <returns>
/// The size that the <see cref="T:System.Windows.Controls.Primitives.DataGridColumnHeadersPresenter" /> determines it needs during layout, based on its calculations of child object allocated sizes.
/// </returns>
protected override Size MeasureOverride(Size availableSize)
{
if (this.OwningGrid == null)
{
return(base.MeasureOverride(availableSize));
}
if (!this.OwningGrid.AreColumnHeadersVisible)
{
return(Size.Empty);
}
double height = this.OwningGrid.ColumnHeaderHeight;
bool autoSizeHeight;
if (double.IsNaN(height))
{
// No explicit height values were set so we can autosize
height = 0;
autoSizeHeight = true;
}
else
{
autoSizeHeight = false;
}
double totalDisplayWidth = 0;
this.OwningGrid.ColumnsInternal.EnsureVisibleEdgedColumnsWidth();
DataGridColumn lastVisibleColumn = this.OwningGrid.ColumnsInternal.LastVisibleColumn;
foreach (DataGridColumn column in this.OwningGrid.ColumnsInternal.GetVisibleColumns())
{
// Measure each column header
bool autoGrowWidth = column.Width.IsAuto || column.Width.IsSizeToHeader;
DataGridColumnHeader columnHeader = column.HeaderCell;
if (column != lastVisibleColumn)
{
columnHeader.UpdateSeparatorVisibility(lastVisibleColumn);
}
// If we're not using star sizing or the current column can't be resized,
// then just set the display width according to the column's desired width
if (!this.OwningGrid.UsesStarSizing || (!column.ActualCanUserResize && !column.Width.IsStar))
{
// In the edge-case where we're given infinite width and we have star columns, the
// star columns grow to their predefined limit of 10,000 (or their MaxWidth)
double newDisplayWidth = column.Width.IsStar ?
Math.Min(column.ActualMaxWidth, DataGrid.DATAGRID_maximumStarColumnWidth) :
Math.Max(column.ActualMinWidth, Math.Min(column.ActualMaxWidth, column.Width.DesiredValue));
column.SetWidthDisplayValue(newDisplayWidth);
}
// If we're auto-growing the column based on the header content, we want to measure it at its maximum value
if (autoGrowWidth)
{
columnHeader.Measure(new Size(column.ActualMaxWidth, double.PositiveInfinity));
this.OwningGrid.AutoSizeColumn(column, columnHeader.DesiredSize.Width);
column.ComputeLayoutRoundedWidth(totalDisplayWidth);
}
else if (!this.OwningGrid.UsesStarSizing)
{
column.ComputeLayoutRoundedWidth(totalDisplayWidth);
columnHeader.Measure(new Size(column.LayoutRoundedWidth, double.PositiveInfinity));
}
// We need to track the largest height in order to auto-size
if (autoSizeHeight)
{
height = Math.Max(height, columnHeader.DesiredSize.Height);
}
totalDisplayWidth += column.ActualWidth;
}
// If we're using star sizing (and we're not waiting for an auto-column to finish growing)
// then we will resize all the columns to fit the available space.
if (this.OwningGrid.UsesStarSizing && !this.OwningGrid.AutoSizingColumns)
{
double adjustment = Double.IsPositiveInfinity(availableSize.Width) ? this.OwningGrid.CellsWidth : availableSize.Width - totalDisplayWidth;
totalDisplayWidth += adjustment - this.OwningGrid.AdjustColumnWidths(0, adjustment, false);
// Since we didn't know the final widths of the columns until we resized,
// we waited until now to measure each header
double leftEdge = 0;
foreach (DataGridColumn column in this.OwningGrid.ColumnsInternal.GetVisibleColumns())
{
column.ComputeLayoutRoundedWidth(leftEdge);
column.HeaderCell.Measure(new Size(column.LayoutRoundedWidth, double.PositiveInfinity));
if (autoSizeHeight)
{
height = Math.Max(height, column.HeaderCell.DesiredSize.Height);
}
leftEdge += column.ActualWidth;
}
}
// Add the filler column if it's not represented. We won't know whether we need it or not until Arrange
DataGridFillerColumn fillerColumn = this.OwningGrid.ColumnsInternal.FillerColumn;
if (!fillerColumn.IsRepresented)
{
Debug.Assert(!this.Children.Contains(fillerColumn.HeaderCell));
fillerColumn.HeaderCell.SeparatorVisibility = Visibility.Collapsed;
this.Children.Insert(this.OwningGrid.ColumnsInternal.Count, fillerColumn.HeaderCell);
fillerColumn.IsRepresented = true;
// Optimize for the case where we don't need the filler cell
fillerColumn.HeaderCell.Visibility = Visibility.Collapsed;
}
fillerColumn.HeaderCell.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
if (this.DragIndicator != null)
{
this.DragIndicator.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
}
if (this.DropLocationIndicator != null)
{
this.DropLocationIndicator.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
}
this.OwningGrid.ColumnsInternal.EnsureVisibleEdgedColumnsWidth();
return(new Size(this.OwningGrid.ColumnsInternal.VisibleEdgedColumnsWidth, height));
}