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using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Xamarin.Forms.Internals;
namespace Xamarin.Forms
{
public class FlexLayout : Layout<View>
{
public static readonly BindableProperty DirectionProperty =
BindableProperty.Create(nameof(Direction), typeof(FlexDirection), typeof(FlexLayout), FlexDirection.Row,
propertyChanged: OnDirectionPropertyChanged);
public static readonly BindableProperty JustifyContentProperty =
BindableProperty.Create(nameof(JustifyContent), typeof(FlexJustify), typeof(FlexLayout), FlexJustify.Start,
propertyChanged: OnJustifyContentPropertyChanged);
public static readonly BindableProperty AlignContentProperty =
BindableProperty.Create(nameof(AlignContent), typeof(FlexAlignContent), typeof(FlexLayout), FlexAlignContent.Stretch,
propertyChanged: OnAlignContentPropertyChanged);
public static readonly BindableProperty AlignItemsProperty =
BindableProperty.Create(nameof(AlignItems), typeof(FlexAlignItems), typeof(FlexLayout), FlexAlignItems.Stretch,
propertyChanged: OnAlignItemsPropertyChanged);
public static readonly BindableProperty PositionProperty =
BindableProperty.Create(nameof(Position), typeof(FlexPosition), typeof(FlexLayout), FlexPosition.Relative,
propertyChanged: OnPositionPropertyChanged);
public static readonly BindableProperty WrapProperty =
BindableProperty.Create(nameof(Wrap), typeof(FlexWrap), typeof(FlexLayout), FlexWrap.NoWrap,
propertyChanged: OnWrapPropertyChanged);
static readonly BindableProperty FlexItemProperty =
BindableProperty.CreateAttached("FlexItem", typeof(Flex.Item), typeof(FlexLayout), null);
public static readonly BindableProperty OrderProperty =
BindableProperty.CreateAttached("Order", typeof(int), typeof(FlexLayout), default(int),
propertyChanged: OnOrderPropertyChanged);
public static readonly BindableProperty GrowProperty =
BindableProperty.CreateAttached("Grow", typeof(float), typeof(FlexLayout), default(float),
propertyChanged: OnGrowPropertyChanged, validateValue: (bindable, value) => (float)value >= 0);
public static readonly BindableProperty ShrinkProperty =
BindableProperty.CreateAttached("Shrink", typeof(float), typeof(FlexLayout), 1f,
propertyChanged: OnShrinkPropertyChanged, validateValue: (bindable, value) => (float)value >= 0);
public static readonly BindableProperty AlignSelfProperty =
BindableProperty.CreateAttached("AlignSelf", typeof(FlexAlignSelf), typeof(FlexLayout), FlexAlignSelf.Auto,
propertyChanged: OnAlignSelfPropertyChanged);
public static readonly BindableProperty BasisProperty =
BindableProperty.CreateAttached("Basis", typeof(FlexBasis), typeof(FlexLayout), FlexBasis.Auto,
propertyChanged: OnBasisPropertyChanged);
public FlexDirection Direction {
get => (FlexDirection)GetValue(DirectionProperty);
set => SetValue(DirectionProperty, value);
}
public FlexJustify JustifyContent {
get => (FlexJustify)GetValue(JustifyContentProperty);
set => SetValue(JustifyContentProperty, value);
}
public FlexAlignContent AlignContent {
get => (FlexAlignContent)GetValue(AlignContentProperty);
set => SetValue(AlignContentProperty, value);
}
public FlexAlignItems AlignItems {
get => (FlexAlignItems)GetValue(AlignItemsProperty);
set => SetValue(AlignItemsProperty, value);
}
public FlexPosition Position {
get => (FlexPosition)GetValue(PositionProperty);
set => SetValue(PositionProperty, value);
}
public FlexWrap Wrap {
get => (FlexWrap)GetValue(WrapProperty);
set => SetValue(WrapProperty, value);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static Flex.Item GetFlexItem(BindableObject bindable)
=> (Flex.Item)bindable.GetValue(FlexItemProperty);
static void SetFlexItem(BindableObject bindable, Flex.Item node)
=> bindable.SetValue(FlexItemProperty, node);
public static int GetOrder(BindableObject bindable)
=> (int)bindable.GetValue(OrderProperty);
public static void SetOrder(BindableObject bindable, int value)
=> bindable.SetValue(OrderProperty, value);
public static float GetGrow(BindableObject bindable)
=> (float)bindable.GetValue(GrowProperty);
public static void SetGrow(BindableObject bindable, float value)
=> bindable.SetValue(GrowProperty, value);
public static float GetShrink(BindableObject bindable)
=> (float)bindable.GetValue(ShrinkProperty);
public static void SetShrink(BindableObject bindable, float value)
=> bindable.SetValue(ShrinkProperty, value);
public static FlexAlignSelf GetAlignSelf(BindableObject bindable)
=> (FlexAlignSelf)bindable.GetValue(AlignSelfProperty);
public static void SetAlignSelf(BindableObject bindable, FlexAlignSelf value)
=> bindable.SetValue(AlignSelfProperty, value);
public static FlexBasis GetBasis(BindableObject bindable)
=> (FlexBasis)bindable.GetValue(BasisProperty);
public static void SetBasis(BindableObject bindable, FlexBasis value)
=> bindable.SetValue(BasisProperty, value);
static void OnOrderPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
if (!bindable.IsSet(FlexItemProperty))
return;
GetFlexItem(bindable).Order = (int)newValue;
((VisualElement)bindable).InvalidateMeasureInternal(InvalidationTrigger.Undefined);
}
static void OnGrowPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
if (!bindable.IsSet(FlexItemProperty))
return;
GetFlexItem(bindable).Grow = (float)newValue;
((VisualElement)bindable).InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
}
static void OnShrinkPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
if (!bindable.IsSet(FlexItemProperty))
return;
GetFlexItem(bindable).Shrink = (float)newValue;
((VisualElement)bindable).InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
}
static void OnAlignSelfPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
if (!bindable.IsSet(FlexItemProperty))
return;
GetFlexItem(bindable).AlignSelf = (Flex.AlignSelf)(FlexAlignSelf)newValue;
((VisualElement)bindable).InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
}
static void OnBasisPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
if (!bindable.IsSet(FlexItemProperty))
return;
GetFlexItem(bindable).Basis = ((FlexBasis)newValue).ToFlexBasis();
((VisualElement)bindable).InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
}
static void OnDirectionPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var flexLayout = bindable as FlexLayout;
if (flexLayout._root == null)
return;
flexLayout._root.Direction = (Flex.Direction)(FlexDirection)newValue;
flexLayout.InvalidateLayout();
}
static void OnJustifyContentPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var flexLayout = bindable as FlexLayout;
if (flexLayout._root == null)
return;
flexLayout._root.JustifyContent = (Flex.Justify)(FlexJustify)newValue;
flexLayout.InvalidateLayout();
}
static void OnAlignContentPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var flexLayout = bindable as FlexLayout;
if (flexLayout._root == null)
return;
flexLayout._root.AlignContent = (Flex.AlignContent)(FlexAlignContent)newValue;
flexLayout.InvalidateLayout();
}
static void OnAlignItemsPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var flexLayout = (FlexLayout)bindable;
if (flexLayout._root == null)
return;
flexLayout._root.AlignItems = (Flex.AlignItems)(FlexAlignItems)newValue;
flexLayout.InvalidateLayout();
}
static void OnPositionPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var flexLayout = (FlexLayout)bindable;
if (flexLayout._root == null)
return;
flexLayout._root.Position = (Flex.Position)(FlexPosition)newValue;
flexLayout.InvalidateLayout();
}
static void OnWrapPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var flexLayout = bindable as FlexLayout;
if (flexLayout._root == null)
return;
flexLayout._root.Wrap = (Flex.Wrap)(FlexWrap)newValue;
flexLayout.InvalidateLayout();
}
Flex.Item _root;
//this should only be used in unitTests. layout creation will normally happen on OnParentSet
internal override void OnIsPlatformEnabledChanged()
{
base.OnIsPlatformEnabledChanged();
if (IsPlatformEnabled && _root == null)
PopulateLayout();
else if(!IsPlatformEnabled && _root != null)
ClearLayout();
}
protected override void OnParentSet()
{
base.OnParentSet();
if (Parent != null && _root == null)
PopulateLayout();
else if (Parent == null && _root != null)
ClearLayout();
}
void PopulateLayout()
{
InitLayoutProperties(_root = new Flex.Item());
foreach (var child in Children)
AddChild(child);
}
void InitLayoutProperties(Flex.Item item)
{
var values = GetValues(AlignContentProperty,
AlignItemsProperty,
DirectionProperty,
JustifyContentProperty,
WrapProperty);
item.AlignContent = (Flex.AlignContent)(FlexAlignContent)values[0];
item.AlignItems = (Flex.AlignItems)(FlexAlignItems)values[1];
item.Direction = (Flex.Direction)(FlexDirection)values[2];
item.JustifyContent = (Flex.Justify)(FlexJustify)values[3];
item.Wrap = (Flex.Wrap)(FlexWrap)values[4];
}
void ClearLayout()
{
foreach (var child in Children)
RemoveChild(child);
_root = null;
}
protected override void OnAdded(View view)
{
AddChild(view);
view.PropertyChanged += OnChildPropertyChanged;
base.OnAdded(view);
}
protected override void OnRemoved(View view)
{
view.PropertyChanged -= OnChildPropertyChanged;
RemoveChild(view);
base.OnRemoved(view);
}
void AddChild(View view)
{
if (_root == null)
return;
var item = (view as FlexLayout)?._root ?? new Flex.Item();
InitItemProperties(view, item);
if (!(view is FlexLayout)) { //inner layouts don't get measured
item.SelfSizing = (Flex.Item it, ref float w, ref float h) => {
var sizeConstrains = item.GetConstraints();
sizeConstrains.Width = (_measuring && sizeConstrains.Width == 0) ? double.PositiveInfinity : sizeConstrains.Width;
sizeConstrains.Height = (_measuring && sizeConstrains.Height == 0) ? double.PositiveInfinity : sizeConstrains.Height;
var request = view.Measure(sizeConstrains.Width, sizeConstrains.Height).Request;
w = (float)request.Width;
h = (float)request.Height;
};
}
_root.InsertAt(Children.IndexOf(view), item);
SetFlexItem(view, item);
}
void InitItemProperties(View view, Flex.Item item)
{
var values = view.GetValues(OrderProperty,
GrowProperty,
ShrinkProperty,
BasisProperty,
AlignSelfProperty,
MarginProperty,
WidthRequestProperty,
HeightRequestProperty,
IsVisibleProperty);
item.Order = (int)values[0];
item.Grow = (float)values[1];
item.Shrink = (float)values[2];
item.Basis = ((FlexBasis)values[3]).ToFlexBasis();
item.AlignSelf = (Flex.AlignSelf)(FlexAlignSelf)values[4];
item.MarginLeft = (float)((Thickness)values[5]).Left;
item.MarginTop = (float)((Thickness)values[5]).Top;
item.MarginRight = (float)((Thickness)values[5]).Right;
item.MarginBottom = (float)((Thickness)values[5]).Bottom;
item.Width = (double)values[6] < 0 ? float.NaN : (float)(double)values[6];
item.Height = (double)values[7] < 0 ? float.NaN : (float)(double)values[7];
item.IsVisible = (bool)values[8];
if (view is FlexLayout) {
var padding = view.GetValue(PaddingProperty);
item.PaddingLeft = (float)((Thickness)padding).Left;
item.PaddingTop = (float)((Thickness)padding).Top;
item.PaddingRight = (float)((Thickness)padding).Right;
item.PaddingBottom = (float)((Thickness)padding).Bottom;
}
}
void RemoveChild(View view)
{
if (_root == null)
return;
var item = GetFlexItem(view);
_root.Remove(item);
view.ClearValue(FlexItemProperty);
}
void OnChildPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if ( e.PropertyName == WidthRequestProperty.PropertyName
|| e.PropertyName == HeightRequestProperty.PropertyName) {
var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
item.Width = ((View)sender).WidthRequest < 0 ? float.NaN : (float)((View)sender).WidthRequest;
item.Height = ((View)sender).HeightRequest < 0 ? float.NaN : (float)((View)sender).HeightRequest;
InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
return;
}
if (e.PropertyName == MarginProperty.PropertyName) {
var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
if (item == null)
return;
var margin = (Thickness)((View)sender).GetValue(MarginProperty);
item.MarginLeft = (float)margin.Left;
item.MarginTop = (float)margin.Top;
item.MarginRight = (float)margin.Right;
item.MarginBottom = (float)margin.Bottom;
InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
return;
}
if (e.PropertyName == PaddingProperty.PropertyName) {
var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
if (item == null)
return;
var padding = (Thickness)((View)sender).GetValue(PaddingProperty);
item.PaddingLeft = (float)padding.Left;
item.PaddingTop = (float)padding.Top;
item.PaddingRight = (float)padding.Right;
item.PaddingBottom = (float)padding.Bottom;
InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
return;
}
if (e.PropertyName == IsVisibleProperty.PropertyName) {
var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
if (item == null)
return;
item.IsVisible = (bool)((View)sender).GetValue(IsVisibleProperty);
InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
return;
}
}
protected override void LayoutChildren(double x, double y, double width, double height)
{
if (_root == null)
return;
Layout(x, y, width, height);
foreach (var child in Children) {
var frame = GetFlexItem(child).GetFrame();
if (double.IsNaN(frame.X)
|| double.IsNaN(frame.Y)
|| double.IsNaN(frame.Width)
|| double.IsNaN(frame.Height))
throw new Exception("something is deeply wrong");
child.Layout(GetFlexItem(child).GetFrame());
}
}
bool _measuring;
protected override SizeRequest OnMeasure(double widthConstraint, double heightConstraint)
{
//All of this is a HACK as X.Flex doesn't supports measuring
if (!double.IsPositiveInfinity(widthConstraint) && !double.IsPositiveInfinity(heightConstraint))
return new SizeRequest(new Size(widthConstraint, heightConstraint));
_measuring = true;
//1. Set Shrink to 0, set align-self to start (to avoid stretching)
// Set Image.Aspect to Fill to get the value we expect in measuring
foreach (var child in Children) {
var item = GetFlexItem(child);
item.Shrink = 0;
item.AlignSelf = Flex.AlignSelf.Start;
}
Layout(0, 0, widthConstraint, heightConstraint);
//2. look at the children location
if (double.IsPositiveInfinity(widthConstraint)) {
widthConstraint = 0;
foreach (var item in _root)
widthConstraint = Math.Max(widthConstraint, item.Frame[0] + item.Frame[2] + item.MarginRight);
}
if (double.IsPositiveInfinity(heightConstraint)) {
heightConstraint = 0;
foreach (var item in _root)
heightConstraint = Math.Max(heightConstraint, item.Frame[1] + item.Frame[3] + item.MarginBottom);
}
//3. reset Shrink, algin-self, and image.aspect
foreach (var child in Children) {
var item = GetFlexItem(child);
item.Shrink = (float)child.GetValue(ShrinkProperty);
item.AlignSelf = (Flex.AlignSelf)(FlexAlignSelf)child.GetValue(AlignSelfProperty);
}
_measuring = false;
return new SizeRequest(new Size(widthConstraint, heightConstraint));
}
void Layout(double x, double y, double width, double height)
{
if (_root.Parent != null) //Layout is only computed at root level
return;
_root.Left = (float)x;
_root.Top = (float)y;
_root.Width = !double.IsPositiveInfinity((width)) ? (float)width : 0;
_root.Height = !double.IsPositiveInfinity((height)) ? (float)height : 0;
_root.Layout();
}
}
static class FlexExtensions
{
public static int IndexOf(this Flex.Item parent, Flex.Item child)
{
var index = -1;
foreach (var it in parent) {
index++;
if (it == child)
return index;
}
return -1;
}
public static void Remove(this Flex.Item parent, Flex.Item child)
{
var index = parent.IndexOf(child);
if (index < 0)
return;
parent.RemoveAt((uint)index);
}
public static Rectangle GetFrame(this Flex.Item item)
{
return new Rectangle(item.Frame[0], item.Frame[1], item.Frame[2], item.Frame[3]);
}
public static Size GetConstraints(this Flex.Item item)
{
var widthConstraint = -1d;
var heightConstraint = -1d;
var parent = item.Parent;
do
{
if (parent == null)
break;
if (widthConstraint < 0 && !float.IsNaN(parent.Width))
widthConstraint = (double)parent.Width;
if (heightConstraint < 0 && !float.IsNaN(parent.Height))
heightConstraint = (double)parent.Height;
parent = parent.Parent;
} while (widthConstraint < 0 || heightConstraint < 0);
return new Size(widthConstraint, heightConstraint);
}
public static Flex.Basis ToFlexBasis(this FlexBasis basis)
{
if (basis.IsAuto)
return Flex.Basis.Auto;
if (basis.IsRelative)
return new Flex.Basis(basis.Length, isRelative: true);
return new Flex.Basis(basis.Length, isRelative: false);
}
}
}