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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// Description: Implementation of a UniformGrid that evenly distributes
// space among its children
//
// NewsClient is defining this Panel because it wants a
// multi-row, multi-column display of news items in the Pod;
// Grid can be databound, but it does not do auto-indexing,
// meaning that all of the generated items would be laid out
// on top of each other. Rather than subclassing Grid to
// introduce this auto-indexing behavior, it seemed more
// straightforward to construct this straightforward panel.
//
namespace System.Windows.Controls.Primitives
{
/// <summary>
/// UniformGrid is used to arrange children in a grid with all equal cell sizes.
/// </summary>
public class UniformGrid : Panel
{
//-------------------------------------------------------------------
//
// Constructors
//
//-------------------------------------------------------------------
#region Constructors
/// <summary>
/// Default constructor.
/// </summary>
public UniformGrid()
: base()
{
}
#endregion Constructors
//-------------------------------------------------------------------
//
// Public Properties
//
//-------------------------------------------------------------------
#region Public Properties
/// <summary>
/// the start column to arrange children. Leave first 'FirstColumn'
/// cells blank.
/// </summary>
public int FirstColumn
{
get { return (int)GetValue(FirstColumnProperty); }
set { SetValue(FirstColumnProperty, value); }
}
/// <summary>
/// FirstColumnProperty
/// </summary>
public static readonly DependencyProperty FirstColumnProperty =
DependencyProperty.Register(
"FirstColumn",
typeof(int),
typeof(UniformGrid),
new FrameworkPropertyMetadata(
(int)0,
FrameworkPropertyMetadataOptions.AffectsMeasure),
new ValidateValueCallback(ValidateFirstColumn));
private static bool ValidateFirstColumn(object o)
{
return (int)o >= 0;
}
/// <summary>
/// Specifies the number of columns in the grid
/// A value of 0 indicates that the column count should be dynamically
/// computed based on the number of rows (if specified) and the
/// number of non-collapsed children in the grid
/// </summary>
public int Columns
{
get { return (int)GetValue(ColumnsProperty); }
set { SetValue(ColumnsProperty, value); }
}
/// <summary>
/// DependencyProperty for <see cref="Columns" /> property.
/// </summary>
public static readonly DependencyProperty ColumnsProperty =
DependencyProperty.Register(
"Columns",
typeof(int),
typeof(UniformGrid),
new FrameworkPropertyMetadata(
(int)0,
FrameworkPropertyMetadataOptions.AffectsMeasure),
new ValidateValueCallback(ValidateColumns));
private static bool ValidateColumns(object o)
{
return (int)o >= 0;
}
/// <summary>
/// Specifies the number of rows in the grid
/// A value of 0 indicates that the row count should be dynamically
/// computed based on the number of columns (if specified) and the
/// number of non-collapsed children in the grid
/// </summary>
public int Rows
{
get { return (int)GetValue(RowsProperty); }
set { SetValue(RowsProperty, value); }
}
/// <summary>
/// DependencyProperty for <see cref="Rows" /> property.
/// </summary>
public static readonly DependencyProperty RowsProperty =
DependencyProperty.Register(
"Rows",
typeof(int),
typeof(UniformGrid),
new FrameworkPropertyMetadata(
(int)0,
FrameworkPropertyMetadataOptions.AffectsMeasure),
new ValidateValueCallback(ValidateRows));
private static bool ValidateRows(object o)
{
return (int)o >= 0;
}
#endregion Public Properties
//-------------------------------------------------------------------
//
// Protected Methods
//
//-------------------------------------------------------------------
#region Protected Methods
/// <summary>
/// Compute the desired size of this UniformGrid by measuring all of the
/// children with a constraint equal to a cell's portion of the given
/// constraint (e.g. for a 2 x 4 grid, the child constraint would be
/// constraint.Width*0.5 x constraint.Height*0.25). The maximum child
/// width and maximum child height are tracked, and then the desired size
/// is computed by multiplying these maximums by the row and column count
/// (e.g. for a 2 x 4 grid, the desired size for the UniformGrid would be
/// maxChildDesiredWidth*2 x maxChildDesiredHeight*4).
/// </summary>
/// <param name="constraint">Constraint</param>
/// <returns>Desired size</returns>
protected override Size MeasureOverride(Size constraint)
{
UpdateComputedValues();
Size childConstraint = new Size(constraint.Width / _columns, constraint.Height / _rows);
double maxChildDesiredWidth = 0.0;
double maxChildDesiredHeight = 0.0;
// Measure each child, keeping track of maximum desired width and height.
for (int i = 0, count = InternalChildren.Count; i < count; ++i)
{
UIElement child = InternalChildren[i];
// Measure the child.
child.Measure(childConstraint);
Size childDesiredSize = child.DesiredSize;
if (maxChildDesiredWidth < childDesiredSize.Width)
{
maxChildDesiredWidth = childDesiredSize.Width;
}
if (maxChildDesiredHeight < childDesiredSize.Height)
{
maxChildDesiredHeight = childDesiredSize.Height;
}
}
return new Size((maxChildDesiredWidth * _columns),(maxChildDesiredHeight * _rows));
}
/// <summary>
/// Arrange the children of this UniformGrid by distributing space evenly
/// among all of the children, making each child the size equal to a cell's
/// portion of the given arrangeSize (e.g. for a 2 x 4 grid, the child size
/// would be arrangeSize*0.5 x arrangeSize*0.25)
/// </summary>
/// <param name="arrangeSize">Arrange size</param>
protected override Size ArrangeOverride(Size arrangeSize)
{
Rect childBounds = new Rect(0, 0, arrangeSize.Width / _columns, arrangeSize.Height / _rows);
double xStep = childBounds.Width;
double xBound = arrangeSize.Width - 1.0;
childBounds.X += childBounds.Width * FirstColumn;
// Arrange and Position each child to the same cell size
foreach (UIElement child in InternalChildren)
{
child.Arrange(childBounds);
// only advance to the next grid cell if the child was not collapsed
if (child.Visibility != Visibility.Collapsed)
{
childBounds.X += xStep;
if (childBounds.X >= xBound)
{
childBounds.Y += childBounds.Height;
childBounds.X = 0;
}
}
}
return arrangeSize;
}
#endregion Protected Methods
//------------------------------------------------------
//
// Private Methods
//
//------------------------------------------------------
#region Private Methods
/// <summary>
/// If either Rows or Columns are set to 0, then dynamically compute these
/// values based on the actual number of non-collapsed children.
///
/// In the case when both Rows and Columns are set to 0, then make Rows
/// and Columns be equal, thus laying out in a square grid.
/// </summary>
private void UpdateComputedValues()
{
_columns = Columns;
_rows = Rows;
//parameter checking.
if (FirstColumn >= _columns)
{
//NOTE: maybe we shall throw here. But this is somewhat out of
//the MCC itself. We need a whole new panel spec.
FirstColumn = 0;
}
if ((_rows == 0) || (_columns == 0))
{
int nonCollapsedCount = 0;
// First compute the actual # of non-collapsed children to be laid out
for (int i = 0, count = InternalChildren.Count; i < count; ++i)
{
UIElement child = InternalChildren[i];
if (child.Visibility != Visibility.Collapsed)
{
nonCollapsedCount++;
}
}
// to ensure that we have at leat one row & column, make sure
// that nonCollapsedCount is at least 1
if (nonCollapsedCount == 0)
{
nonCollapsedCount = 1;
}
if (_rows == 0)
{
if (_columns > 0)
{
// take FirstColumn into account, because it should really affect the result
_rows = (nonCollapsedCount + FirstColumn + (_columns - 1)) / _columns;
}
else
{
// both rows and columns are unset -- lay out in a square
_rows = (int)Math.Sqrt(nonCollapsedCount);
if ((_rows * _rows) < nonCollapsedCount)
{
_rows++;
}
_columns = _rows;
}
}
else if (_columns == 0)
{
// guaranteed that _rows is not 0, because we're in the else clause of the check for _rows == 0
_columns = (nonCollapsedCount + (_rows - 1)) / _rows;
}
}
}
#endregion Private Properties
private int _rows;
private int _columns;
}
}
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