org.freedesktop.dbus.annotations.PropertiesEmitsChangedSignal Maven / Gradle / Ivy

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Improved version of the DBus-Java library provided by freedesktop.org (https://dbus.freedesktop.org/doc/dbus-java/).

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package org.freedesktop.dbus.annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * From DBUS Specification:

 * If set to false, the org.freedesktop.DBus.Properties.PropertiesChanged signal,

 * see the section called “org.freedesktop.DBus.Properties” is not guaranteed to be emitted if the property changes.

 * 

 * If set to const the property never changes value during the lifetime of the object it belongs to, 

 * and hence the signal is never emitted for it. 

 * 

 * If set to invalidates the signal is emitted but the value is not included in the signal.

 * 

 * If set to true the signal is emitted with the value included. 

 * The value for the annotation defaults to true if the enclosing interface element does not specify the annotation.
 * Otherwise it defaults to the value specified in the enclosing interface element.

 * 

 * This annotation is intended to be used by code generators to implement client-side caching of property values. 

 * For all properties for which the annotation is set to const, invalidates or true the client may unconditionally 

 * cache the values as the properties don't change or notifications are generated for them if they do.
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@DBusInterfaceName("org.freedesktop.DBus.Property.EmitsChangedSignal")
public @interface PropertiesEmitsChangedSignal {

    EmitChangeSignal value();

    /**
     * The different values which are supported for emitting a signal.
     */
    enum EmitChangeSignal {
        /** The signal is emitted with the value included. */
        TRUE,
        /** The signal is emitted but the value is not included in the signal. */
        INVALIDATES,
        /** The property never changes value during the lifetime of the object it belongs to, and hence the signal is never emitted for it. */
        CONST,
        /** It is not guaranteed to emit a signal if the property changes. */
        FALSE;

        @Override
        public String toString() {
            return name().toLowerCase();
        }
    }
}