org.eclipse.jface.databinding.swt.IWidgetValueProperty.java Source code

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Here is the source code for org.eclipse.jface.databinding.swt.IWidgetValueProperty.java

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/*******************************************************************************
 * Copyright (c) 2009, 2015 Matthew Hall and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     Matthew Hall - initial API and implementation (bug 264286)
 *******************************************************************************/

package org.eclipse.jface.databinding.swt;

import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.core.databinding.observable.value.IVetoableValue;
import org.eclipse.core.databinding.observable.value.ValueChangingEvent;
import org.eclipse.core.databinding.property.value.IValueProperty;
import org.eclipse.swt.widgets.Widget;

/**
 * {@link IValueProperty} for observing an SWT Widget
 *
 * @param <S> type of the source widget
 * @param <T> type of the value of the property
 *
 * @since 1.3
 * @noimplement This interface is not intended to be implemented by clients.
 */
public interface IWidgetValueProperty<S extends Widget, T> extends IValueProperty<S, T> {
    /**
     * Returns an {@link ISWTObservableValue} observing this value property on
     * the given widget
     *
     * @param widget
     *            the source widget
     * @return an observable value observing this value property on the given
     *         widget
     */
    @Override
    public ISWTObservableValue<T> observe(S widget);

    /**
     * Returns an {@link ISWTObservableValue} observing this value property on the
     * given widget, which delays notification of value changes until at least
     * <code>delay</code> milliseconds have elapsed since that last change event, or
     * until a FocusOut event is received from the widget (whichever happens first).
     * <p>
     * This observable helps to boost performance in situations where an observable
     * has computationally expensive listeners (e.g. changing filters in a viewer)
     * or many dependencies (master fields with multiple detail fields). A common
     * use of this observable is to delay validation of user input until the user
     * stops typing in a UI field.
     * <p>
     * To notify about pending changes, the returned observable fires a stale event
     * when the wrapped observable value fires a change event, and remains stale
     * until the delay has elapsed and the value change is fired. A call to
     * {@link IObservableValue#getValue} while a value change is pending will fire
     * the value change immediately, short-circuiting the delay.
     * <p>
     * Only updates resulting from the observed widget are delayed. Calls directly
     * to {@link IObservableValue#setValue} are not, and they cancel pending delayed
     * values.
     * <p>
     * Note that this observable will not forward {@link ValueChangingEvent} events
     * from a wrapped {@link IVetoableValue}.
     * <p>
     * This method is equivalent to
     * <code>SWTObservables.observeDelayedValue(delay, observe(widget))</code>.
     *
     * @param delay  the delay in milliseconds.
     * @param widget the source widget
     * @return an observable value observing this value property on the given
     *         widget, and which delays change notifications for <code>delay</code>
     *         milliseconds.
     */
    public ISWTObservableValue<T> observeDelayed(int delay, S widget);
}