/*******************************************************************************
* Copyright (c) 2006, 2008 IBM Corporation and others.
* 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
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.help;
import org.eclipse.core.expressions.EvaluationContext;
import org.eclipse.core.expressions.IEvaluationContext;
import org.eclipse.core.runtime.Platform;
import org.eclipse.help.internal.HelpPlugin;
/**
* <p>
* This class provides the ability to filter out user assistance model elements
* that support filtering (e.g. <code>IToc</code>, <code>ITopic</code>, ...).
* Implementations that display such elements should consult this class before
* attempting to display them.
* </p>
*
* @since 3.2
*/
public class UAContentFilter {
private static final String VARIABLE_PLATFORM = "platform"; //$NON-NLS-1$
private static IEvaluationContext defaultContext;
/**
* <p>
* Returns whether or not the given object should be filtered out. This
* applies to any user assistance component's elements where filters apply
* (e.g. help tocs, topics, intro elements, context help topics). If the
* element is <code>null</code> or is not filterable, this method returns
* <code>false</code>.
* </p>
* <p>
* This method is for use in non-UI environments, when serving help outside
* the workbench. If filtering from the UI, use the <code>isFiltered</code>
* method that accepts the evaluation context as well.
* </p>
*
* @param element the element to check
* @return whether or not the element should be filtered out
*/
public static boolean isFiltered(Object element) {
if (defaultContext == null) {
defaultContext = createDefaultContext();
}
return isFiltered(element, defaultContext);
}
private static IEvaluationContext createDefaultContext() {
EvaluationContext context = new EvaluationContext(null, Platform.class);
context.addVariable(VARIABLE_PLATFORM, Platform.class);
return context;
}
/**
* <p>
* Returns whether or not the given object should be filtered out. This
* applies to any user assistance component's elements where filters apply
* (e.g. help tocs, topics, intro elements, context help topics). If the
* element is <code>null</code> or is not filterable, this method returns
* <code>false</code>. The evaluation context provides the default object
* to test on and a set of variables that can be accessed.
* </p>
*
* @param element the element to check
* @param context the evaluation context for evaluating expressions
* @return whether or not the element should be filtered out
*/
public static boolean isFiltered(Object element, IEvaluationContext context) {
if (element instanceof IUAElement) {
try {
return !((IUAElement)element).isEnabled(context);
}
catch (Throwable t) {
String msg = "Error while checking element filter"; //$NON-NLS-1$
HelpPlugin.logError(msg, t);
}
}
return false;
}
}
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