Setting Metadata to Influence Layout

When a property of an element has an effect on the size of the element or the ordering of its children, appropriate metadata has to be added to its declaration as a dependency property to trigger the appropriate stage of the layout process.

• AffectsLayout: Specifies that the property triggers a change in the ordering of child elements. Used to trigger a layout update whenever the property changes.

• InvalidatesLayout: Used in the old layout system to invalidate the layout of an element when the property value changes.

• AffectMeasure: Specifies that the property triggers a change in the size of the element. Used to trigger a layout update whenever the property changes.

• AffectsArrange: Equivalent to AffectsLayout.

The example code below shows a RightToLeft dependency property with the AffectsLayout and InvalidatesLayout included in the call to RadPropertyRegister.

Adding metadata

• C#
• VB.NET

public static RadProperty RTLProperty = RadProperty.Register(
    "RTL", typeof(bool), typeof(BoxLayout), new RadElementPropertyMetadata(
    false, ElementPropertyOptions.AffectsLayout | ElementPropertyOptions.InvalidatesLayout));

Public Shared RTLProperty As RadProperty = RadProperty.Register("RTL", GetType(Boolean), GetType(BoxLayout), New RadElementPropertyMetadata(False, ElementPropertyOptions.AffectsLayout Or ElementPropertyOptions.InvalidatesLayout))

The metadata is consumed when the RadElement OnPropertyChanged method is fired, the RadElement RadPropertyMetaData is evaluated and methods are called based on the type of metadata present.