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using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
namespace Xamarin.Forms
{
public partial class VisualElement
{
sealed class MergedStyle : IStyle
{
////If the base type is one of these, stop registering dynamic resources further
////The last one (typeof(Element)) is a safety guard as we might be creating VisualElement directly in internal code
static readonly IList<Type> s_stopAtTypes = new List<Type> { typeof(View), typeof(Layout<>), typeof(VisualElement), typeof(Element) };
IList<BindableProperty> _classStyleProperties;
readonly List<BindableProperty> _implicitStyles = new List<BindableProperty>();
IList<Style> _classStyles;
IStyle _implicitStyle;
IStyle _style;
IList<string> _styleClass;
public MergedStyle(Type targetType, BindableObject target)
{
Target = target;
TargetType = targetType;
RegisterImplicitStyles();
Apply(Target);
}
public IStyle Style
{
get { return _style; }
set { SetStyle(ImplicitStyle, ClassStyles, value); }
}
public IList<string> StyleClass
{
get { return _styleClass; }
set
{
if (_styleClass == value)
return;
if (_styleClass != null && _classStyles != null)
foreach (var classStyleProperty in _classStyleProperties)
Target.RemoveDynamicResource(classStyleProperty);
_styleClass = value;
if (_styleClass != null) {
_classStyleProperties = new List<BindableProperty> ();
foreach (var styleClass in _styleClass) {
var classStyleProperty = BindableProperty.Create ("ClassStyle", typeof(IList<Style>), typeof(VisualElement), default(IList<Style>),
propertyChanged: (bindable, oldvalue, newvalue) => ((VisualElement)bindable)._mergedStyle.OnClassStyleChanged());
_classStyleProperties.Add (classStyleProperty);
Target.OnSetDynamicResource (classStyleProperty, Forms.Style.StyleClassPrefix + styleClass);
}
}
}
}
public BindableObject Target { get; }
IList<Style> ClassStyles
{
get { return _classStyles; }
set { SetStyle(ImplicitStyle, value, Style); }
}
IStyle ImplicitStyle
{
get { return _implicitStyle; }
set { SetStyle(value, ClassStyles, Style); }
}
public void Apply(BindableObject bindable)
{
ImplicitStyle?.Apply(bindable);
if (ClassStyles != null)
foreach (var classStyle in ClassStyles)
((IStyle)classStyle)?.Apply(bindable);
Style?.Apply(bindable);
}
public Type TargetType { get; }
public void UnApply(BindableObject bindable)
{
Style?.UnApply(bindable);
if (ClassStyles != null)
foreach (var classStyle in ClassStyles)
((IStyle)classStyle)?.UnApply(bindable);
ImplicitStyle?.UnApply(bindable);
}
void OnClassStyleChanged()
{
ClassStyles = _classStyleProperties.Select (p => (Target.GetValue (p) as IList<Style>)?.FirstOrDefault (s => s.CanBeAppliedTo (TargetType))).ToList ();
}
void OnImplicitStyleChanged()
{
var first = true;
foreach (BindableProperty implicitStyleProperty in _implicitStyles)
{
var implicitStyle = (Style)Target.GetValue(implicitStyleProperty);
if (implicitStyle != null)
{
if (first || implicitStyle.ApplyToDerivedTypes)
{
ImplicitStyle = implicitStyle;
return;
}
}
first = false;
}
}
void RegisterImplicitStyles()
{
Type type = TargetType;
while (true) {
BindableProperty implicitStyleProperty = BindableProperty.Create("ImplicitStyle", typeof(Style), typeof(VisualElement), default(Style),
propertyChanged: (bindable, oldvalue, newvalue) => OnImplicitStyleChanged());
_implicitStyles.Add(implicitStyleProperty);
Target.SetDynamicResource(implicitStyleProperty, type.FullName);
type = type.GetTypeInfo().BaseType;
if (s_stopAtTypes.Contains(type))
return;
}
}
void SetStyle(IStyle implicitStyle, IList<Style> classStyles, IStyle style)
{
bool shouldReApplyStyle = implicitStyle != ImplicitStyle || classStyles != ClassStyles || Style != style;
bool shouldReApplyClassStyle = implicitStyle != ImplicitStyle || classStyles != ClassStyles;
bool shouldReApplyImplicitStyle = implicitStyle != ImplicitStyle && (Style as Style == null || ((Style)Style).CanCascade);
if (shouldReApplyStyle)
Style?.UnApply(Target);
if (shouldReApplyClassStyle && ClassStyles != null)
foreach (var classStyle in ClassStyles)
((IStyle)classStyle)?.UnApply(Target);
if (shouldReApplyImplicitStyle)
ImplicitStyle?.UnApply(Target);
_implicitStyle = implicitStyle;
_classStyles = classStyles;
_style = style;
if (shouldReApplyImplicitStyle)
ImplicitStyle?.Apply(Target);
if (shouldReApplyClassStyle && ClassStyles != null)
foreach (var classStyle in ClassStyles)
((IStyle)classStyle)?.Apply(Target);
if (shouldReApplyStyle)
Style?.Apply(Target);
}
}
}
}
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