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/*******************************************************************************
* Copyright (C) 2016, Thomas Wolf <thomas.wolf@paranor.ch>
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*******************************************************************************/
package org.eclipse.egit.ui.internal.commit;
import java.util.HashSet;
import java.util.Set;
import org.eclipse.jgit.annotations.NonNull;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Listener;
/**
* Utility class to track the focus of a set of {@link Control}s to determine
* the one that last had the focus.
*/
public class FocusTracker {
private final Set<Control> trackedControls = new HashSet<>();
private final Listener listener = event -> {
switch (event.type) {
case SWT.Dispose:
trackedControls.remove(event.widget);
break;
case SWT.FocusIn:
case SWT.FocusOut:
if (event.widget instanceof Control) {
lastFocusControl = (Control) event.widget;
}
break;
default:
break;
}
};
private Control lastFocusControl;
private void hookControl(@NonNull Control control) {
control.addListener(SWT.Dispose, listener);
control.addListener(SWT.FocusIn, listener);
control.addListener(SWT.FocusOut, listener);
}
private void unhookControl(@NonNull Control control) {
control.removeListener(SWT.FocusOut, listener);
control.removeListener(SWT.FocusIn, listener);
control.removeListener(SWT.Dispose, listener);
}
/**
* Registers the given {@link Control} for having focus changes being
* tracked. Has no effect if the control is already being tracked.
*
* @param control
* to track
*/
public void addToFocusTracking(@NonNull Control control) {
if (trackedControls.add(control)) {
hookControl(control);
}
}
/**
* Stops tracking focus changes for the given {@link Control}. Has no effect
* if the control is {@code null} or is not currently being tracked.
*
* @param control
* to remove from focus tracking
*/
public void removeFromFocusTracking(Control control) {
if (trackedControls.remove(control) && !control.isDisposed()) {
unhookControl(control);
}
}
/**
* Retrieves the last control to have had the focus.
*
* @return the control, or {@code null} if none determined yet.
*/
public Control getLastFocusControl() {
if (lastFocusControl != null && lastFocusControl.isDisposed()) {
trackedControls.remove(lastFocusControl);
lastFocusControl = null;
}
return lastFocusControl;
}
/**
* Dispose of this {@link FocusTracker}.
*/
public void dispose() {
for (Control tracked : trackedControls) {
if (!tracked.isDisposed()) {
unhookControl(tracked);
}
}
trackedControls.clear();
lastFocusControl = null;
}
}
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