这是一个 WrapPanel，它可以选择使用 FFDH algorithm 重新排列元素，也可以选择拉伸它们以删除空白区域 (example)。
public class StretchyWrapPanel : Panel {
public static readonly DependencyProperty ItemWidthProperty = DependencyProperty.Register(nameof(ItemWidth), typeof(double),
typeof(StretchyWrapPanel), new FrameworkPropertyMetadata(double.NaN, FrameworkPropertyMetadataOptions.AffectsMeasure, (o, e) => {
((StretchyWrapPanel)o)._itemWidth = (double)e.NewValue;
}));
private double _itemWidth = double.NaN;
[TypeConverter(typeof(LengthConverter))]
public double ItemWidth {
get => _itemWidth;
set => SetValue(ItemWidthProperty, value);
}
public static readonly DependencyProperty ItemHeightProperty = DependencyProperty.Register(nameof(ItemHeight), typeof(double),
typeof(StretchyWrapPanel), new FrameworkPropertyMetadata(double.NaN, FrameworkPropertyMetadataOptions.AffectsMeasure, (o, e) => {
((StretchyWrapPanel)o)._itemHeight = (double)e.NewValue;
}));
private double _itemHeight = double.NaN;
[TypeConverter(typeof(LengthConverter))]
public double ItemHeight {
get => _itemHeight;
set => SetValue(ItemHeightProperty, value);
}
public static readonly DependencyProperty OrientationProperty = DependencyProperty.Register(nameof(Orientation), typeof(Orientation),
typeof(StretchyWrapPanel), new FrameworkPropertyMetadata(Orientation.Horizontal, FrameworkPropertyMetadataOptions.AffectsArrange, (o, e) => {
((StretchyWrapPanel)o)._orientation = (Orientation)e.NewValue;
}));
private Orientation _orientation = Orientation.Horizontal;
public Orientation Orientation {
get => _orientation;
set => SetValue(OrientationProperty, value);
}
public static readonly DependencyProperty StretchToFillProperty = DependencyProperty.Register(nameof(StretchToFill), typeof(bool),
typeof(StretchyWrapPanel), new FrameworkPropertyMetadata(true, FrameworkPropertyMetadataOptions.AffectsArrange, (o, e) => {
((StretchyWrapPanel)o)._stretchToFill = (bool)e.NewValue;
}));
private bool _stretchToFill = true;
public bool StretchToFill {
get => _stretchToFill;
set => SetValue(StretchToFillProperty, value);
}
public static readonly DependencyProperty StretchProportionallyProperty = DependencyProperty.Register(nameof(StretchProportionally), typeof(bool),
typeof(StretchyWrapPanel), new FrameworkPropertyMetadata(true, FrameworkPropertyMetadataOptions.AffectsArrange, (o, e) => {
((StretchyWrapPanel)o)._stretchProportionally = (bool)e.NewValue;
}));
private bool _stretchProportionally = true;
public bool StretchProportionally {
get => _stretchProportionally;
set => SetValue(StretchProportionallyProperty, value);
}
public static readonly DependencyProperty RearrangeForBestFitProperty = DependencyProperty.Register(nameof(RearrangeForBestFit), typeof(bool),
typeof(StretchyWrapPanel), new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.AffectsMeasure, (o, e) => {
((StretchyWrapPanel)o)._rearrangeForBestFit = (bool)e.NewValue;
}));
private bool _rearrangeForBestFit;
public bool RearrangeForBestFit {
get => _rearrangeForBestFit;
set => SetValue(RearrangeForBestFitProperty, value);
}
private struct UVSize {
internal UVSize(Orientation orientation, Size size) {
U = V = 0d;
_isHorizontal = orientation == Orientation.Horizontal;
Width = size.Width;
Height = size.Height;
}
internal UVSize(Orientation orientation, double width, double height) {
U = V = 0d;
_isHorizontal = orientation == Orientation.Horizontal;
Width = width;
Height = height;
}
internal UVSize(Orientation orientation) {
U = V = 0d;
_isHorizontal = orientation == Orientation.Horizontal;
}
internal double U;
internal double V;
private bool _isHorizontal;
internal double Width {
get => _isHorizontal ? U : V;
set {
if (_isHorizontal) {
U = value;
} else {
V = value;
}
}
}
internal double Height {
get => _isHorizontal ? V : U;
set {
if (_isHorizontal) {
V = value;
} else {
U = value;
}
}
}
}
protected override Size MeasureOverride(Size constraint) {
return RearrangeForBestFit ? MeasureBestFit(constraint) : MeasureKeepInOrder(constraint);
}
private Size MeasureKeepInOrder(Size constraint) {
var orientation = Orientation;
var uLimit = new UVSize(orientation, constraint.Width, constraint.Height).U;
var curLineSize = new UVSize(orientation);
var panelSize = new UVSize(orientation);
var itemWidth = ItemWidth;
var itemHeight = ItemHeight;
var itemWidthSet = !double.IsNaN(itemWidth);
var itemHeightSet = !double.IsNaN(itemHeight);
var childConstraint = new Size(
itemWidthSet ? itemWidth : constraint.Width,
itemHeightSet ? itemHeight : constraint.Height);
var children = InternalChildren;
for (int i = 0, count = children.Count; i < count; i++) {
var child = children[i];
if (child == null) continue;
// Flow passes its own constrint to children
child.Measure(childConstraint);
// This is the size of the child in UV space
var sz = new UVSize(orientation,
itemWidthSet ? itemWidth : child.DesiredSize.Width,
itemHeightSet ? itemHeight : child.DesiredSize.Height);
if (curLineSize.U + sz.U > uLimit) {
// Need to switch to another line
panelSize.U = Math.Max(curLineSize.U, panelSize.U);
panelSize.V += curLineSize.V;
curLineSize = sz;
if (sz.U > uLimit) {
// The element is wider then the constrint - give it a separate line
panelSize.U = Math.Max(sz.U, panelSize.U);
panelSize.V += sz.V;
curLineSize = new UVSize(orientation);
}
} else {
// Continue to accumulate a line
curLineSize.U += sz.U;
curLineSize.V = Math.Max(sz.V, curLineSize.V);
}
}
// The last line size, if any should be added
panelSize.U = Math.Max(curLineSize.U, panelSize.U);
panelSize.V += curLineSize.V;
// Go from UV space to W/H space
return new Size(panelSize.Width, panelSize.Height);
}
private Size MeasureBestFit(Size constraint) {
var orientation = Orientation;
var uLimit = new UVSize(orientation, constraint.Width, constraint.Height).U;
var itemWidth = ItemWidth;
var itemHeight = ItemHeight;
var itemWidthSet = !double.IsNaN(itemWidth);
var itemHeightSet = !double.IsNaN(itemHeight);
var childConstraint = new Size(
itemWidthSet ? itemWidth : constraint.Width,
itemHeightSet ? itemHeight : constraint.Height);
var children = InternalChildren;
// First-Fit Decreasing Height (FFDH) algorithm
var lines = new List<UVSize>();
for (int i = 0, count = children.Count; i < count; i++) {
var child = children[i];
if (child == null) continue;
// Flow passes its own constrint to children
child.Measure(childConstraint);
// This is the size of the child in UV space
var childSize = new UVSize(orientation,
itemWidthSet ? itemWidth : child.DesiredSize.Width,
itemHeightSet ? itemHeight : child.DesiredSize.Height);
for (var j = 0; j < lines.Count; j++) {
var line = lines[j];
if (line.U + childSize.U <= uLimit) {
lines[j] = new UVSize(orientation) { U = childSize.U, V = Math.Max(childSize.V, line.V) };
goto Next;
}
}
lines.Add(childSize);
Next:
{ }
}
var panelSize = new UVSize(orientation);
for (var i = 0; i < lines.Count; i++) {
var line = lines[i];
panelSize.U = Math.Max(line.U, panelSize.U);
panelSize.V += line.V;
}
// Go from UV space to W/H space
return new Size(panelSize.Width, panelSize.Height);
}
protected override Size ArrangeOverride(Size finalSize) {
return RearrangeForBestFit ? ArrangeBestFit(finalSize) : ArrangeKeepInOrder(finalSize);
}
private static UVSize GetChildSize(Orientation orientation, UIElement child, UVSize fixedChildSize) {
var childSize = new UVSize(orientation, child.DesiredSize);
if (!double.IsNaN(fixedChildSize.U)) childSize.U = fixedChildSize.U;
if (!double.IsNaN(fixedChildSize.V)) childSize.V = fixedChildSize.V;
return childSize;
}
private Size ArrangeKeepInOrder(Size finalSize) {
var orientation = Orientation;
var fixedChildSize = new UVSize(orientation, ItemWidth, ItemHeight);
var children = InternalChildren;
var firstInLine = 0;
var uLimit = new UVSize(orientation, finalSize).U;
var currentLineSize = new UVSize(orientation);
var accumulatedV = 0d;
for (int i = 0, count = children.Count; i < count; i++) {
var child = children[i];
if (child == null) continue;
var childSize = GetChildSize(orientation, child, fixedChildSize);
if (currentLineSize.U + childSize.U > uLimit) {
// Need to switch to another line
if (!double.IsNaN(fixedChildSize.U)) {
ArrangeLineFixedSize(orientation, children, accumulatedV, currentLineSize.V, firstInLine, i, fixedChildSize.U);
} else if (!StretchToFill) {
ArrangeLineDefault(orientation, children, accumulatedV, currentLineSize.V, firstInLine, i);
} else {
ArrangeLineStretch(orientation, children, accumulatedV, currentLineSize.V, firstInLine, i, uLimit, StretchProportionally);
}
accumulatedV += currentLineSize.V;
currentLineSize = childSize;
firstInLine = i;
} else {
// Continue to accumulate a line
currentLineSize.U += childSize.U;
currentLineSize.V = Math.Max(childSize.V, currentLineSize.V);
}
}
// Arrange the last line, if any
if (!double.IsNaN(fixedChildSize.U)) {
ArrangeLineFixedSize(orientation, children, accumulatedV, currentLineSize.V, firstInLine, children.Count, fixedChildSize.U);
} else if (!StretchToFill) {
ArrangeLineDefault(orientation, children, accumulatedV, currentLineSize.V, firstInLine, children.Count);
} else {
ArrangeLineStretch(orientation, children, accumulatedV, currentLineSize.V, firstInLine, children.Count, uLimit, StretchProportionally);
}
return finalSize;
}
private static void ArrangeLineDefault(Orientation orientation, UIElementCollection children, double v, double lineV, int start, int end) {
var position = new UVSize(orientation){ U = 0d, V = v };
for (var i = start; i < end; i++) {
var child = children[i];
if (child != null) {
var childSize = new UVSize(orientation, child.DesiredSize) { V = lineV };
child.Arrange(new Rect(position.Width, position.Height, childSize.Width, childSize.Height));
position.U += childSize.U;
}
}
}
private static void ArrangeLineStretch(Orientation orientation, UIElementCollection children, double v, double lineV, int start, int end,
double limitU, bool stretchProportionally) {
var totalU = 0d;
for (var i = start; i < end; i++) {
totalU += new UVSize(orientation, children[i].DesiredSize).U;
}
var position = new UVSize(orientation) { U = 0d, V = v };
var uExtra = stretchProportionally ? limitU / totalU : (limitU - totalU) / (end - start);
for (var i = start; i < end; i++) {
var child = children[i];
if (child != null) {
var childSize = new UVSize(orientation, child.DesiredSize) { V = lineV };
childSize.U = stretchProportionally ? childSize.U * uExtra : Math.Max(childSize.U + uExtra, 1d);
child.Arrange(new Rect(position.Width, position.Height, childSize.Width, childSize.Height));
position.U += childSize.U;
}
}
}
private static void ArrangeLineFixedSize(Orientation orientation, UIElementCollection children, double v, double lineV, int start, int end, double itemU) {
var position = new UVSize(orientation) { U = 0d, V = v };
var childSize = new UVSize(orientation){ U = itemU, V = lineV };
for (var i = start; i < end; i++) {
var child = children[i];
if (child != null) {
child.Arrange(new Rect(position.Width, position.Height, childSize.Width, childSize.Height));
position.U += childSize.U;
}
}
}
private class ArrangeBestFitLine {
public UVSize Size;
public readonly List<int> ItemIndices = new List<int>();
public void ArrangeDefault(Orientation orientation, UIElementCollection children, double v) {
var position = new UVSize(orientation){ U = 0d, V = v };
for (var i = 0; i < ItemIndices.Count; i++) {
var child = children[ItemIndices[i]];
if (child != null) {
var childSize = new UVSize(orientation, child.DesiredSize) { V = Size.V };
child.Arrange(new Rect(position.Width, position.Height, childSize.Width, childSize.Height));
position.U += childSize.U;
}
}
}
public void ArrangeStretch(Orientation orientation, UIElementCollection children, double v, double limitU, bool stretchProportionally) {
var totalU = 0d;
for (var i = 0; i < ItemIndices.Count; i++) {
totalU += new UVSize(orientation, children[ItemIndices[i]].DesiredSize).U;
}
var position = new UVSize(orientation) { U = 0d, V = v };
var uExtra = stretchProportionally ? limitU / totalU : (limitU - totalU) / ItemIndices.Count;
for (var i = 0; i < ItemIndices.Count; i++) {
var child = children[ItemIndices[i]];
if (child != null) {
var childSize = new UVSize(orientation, child.DesiredSize) { V = Size.V };
childSize.U = stretchProportionally ? childSize.U * uExtra : Math.Max(childSize.U + uExtra, 1d);
child.Arrange(new Rect(position.Width, position.Height, childSize.Width, childSize.Height));
position.U += childSize.U;
}
}
}
public void ArrangeFixedSize(Orientation orientation, UIElementCollection children, double v, double itemU) {
var position = new UVSize(orientation) { U = 0d, V = v };
var childSize = new UVSize(orientation){ U = itemU, V = Size.V };
for (var i = 0; i < ItemIndices.Count; i++) {
var child = children[ItemIndices[i]];
if (child != null) {
child.Arrange(new Rect(position.Width, position.Height, childSize.Width, childSize.Height));
position.U += childSize.U;
}
}
}
}
private Size ArrangeBestFit(Size finalSize) {
var orientation = Orientation;
var fixedChildSize = new UVSize(orientation, ItemWidth, ItemHeight);
var uLimit = new UVSize(orientation, finalSize).U;
// First-Fit Decreasing Height (FFDH) algorithm
var lines = new List<ArrangeBestFitLine>();
var children = InternalChildren;
for (int i = 0, count = children.Count; i < count; i++) {
var child = children[i];
if (child == null) continue;
var childSize = GetChildSize(orientation, child, fixedChildSize);
for (var j = 0; j < lines.Count; j++) {
var line = lines[j];
if (line.Size.U + childSize.U <= uLimit) {
line.Size.U += childSize.U;
line.Size.V = Math.Max(childSize.V, line.Size.V);
line.ItemIndices.Add(i);
goto Next;
}
}
lines.Add(new ArrangeBestFitLine {
Size = childSize,
ItemIndices = { i }
});
Next:
{ }
}
var accumulatedV = 0d;
for (var i = 0; i < lines.Count; i++) {
var line = lines[i];
if (!double.IsNaN(fixedChildSize.U)) {
line.ArrangeFixedSize(orientation, children, accumulatedV, fixedChildSize.U);
} else if (!StretchToFill) {
line.ArrangeDefault(orientation, children, accumulatedV);
} else {
line.ArrangeStretch(orientation, children, accumulatedV, uLimit, StretchProportionally);
}
accumulatedV += line.Size.V;
}
return finalSize;
}
}