org.eclipse.handly.ui.viewer.ProblemLabelDecorator.java Source code

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Here is the source code for org.eclipse.handly.ui.viewer.ProblemLabelDecorator.java

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/*******************************************************************************
 * Copyright (c) 2014 1C LLC.
 * 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:
 *     Vladimir Piskarev (1C) - initial API and implementation
 *******************************************************************************/
package org.eclipse.handly.ui.viewer;

import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.resource.LocalResourceManager;
import org.eclipse.jface.resource.ResourceManager;
import org.eclipse.jface.viewers.DecorationOverlayIcon;
import org.eclipse.jface.viewers.IDecoration;
import org.eclipse.jface.viewers.ILabelDecorator;
import org.eclipse.jface.viewers.ILabelProviderListener;
import org.eclipse.swt.graphics.Image;
import org.eclipse.ui.ISharedImages;
import org.eclipse.ui.PlatformUI;

/**
 * Decorates an element's image with error and warning overlays.
 * Subclasses must implement {@link #computeProblemSeverity} method.
 */
public abstract class ProblemLabelDecorator implements ILabelDecorator {
    private ResourceManager resourceManager;

    @Override
    public Image decorateImage(Image image, Object element) {
        if (image == null)
            return null;

        Severity severity = computeProblemSeverity(element);
        if (severity == null)
            return null;

        return (Image) getResourceManager()
                .get(new DecorationOverlayIcon(image, getOverlayImage(severity), IDecoration.BOTTOM_LEFT));
    }

    @Override
    public String decorateText(String text, Object element) {
        return null;
    }

    @Override
    public void dispose() {
        if (resourceManager != null) {
            resourceManager.dispose();
            resourceManager = null;
        }
    }

    @Override
    public boolean isLabelProperty(Object element, String property) {
        return false;
    }

    @Override
    public void addListener(ILabelProviderListener listener) {
    }

    @Override
    public void removeListener(ILabelProviderListener listener) {
    }

    /**
     * Computes problem severity for the given element.
     *
     * @param element never <code>null</code>
     * @return problem severity, or <code>null</code> if there is no problem
     */
    protected abstract Severity computeProblemSeverity(Object element);

    private ImageDescriptor getOverlayImage(Severity severity) {
        switch (severity) {
        case ERROR:
            return PlatformUI.getWorkbench().getSharedImages()
                    .getImageDescriptor(ISharedImages.IMG_DEC_FIELD_ERROR);
        case WARNING:
            return PlatformUI.getWorkbench().getSharedImages()
                    .getImageDescriptor(ISharedImages.IMG_DEC_FIELD_WARNING);
        default:
            throw new AssertionError();
        }
    }

    private ResourceManager getResourceManager() {
        if (resourceManager == null)
            resourceManager = new LocalResourceManager(JFaceResources.getResources());
        return resourceManager;
    }

    /**
     * Indicates problem severity.
     */
    protected static enum Severity {
        ERROR, WARNING;

        /**
         * Returns the more severe of the two <code>Severity</code> values.
         *
         * @param a may be <code>null</code>
         * @param b may be <code>null</code>
         * @return the more severe of <code>a</code> and <code>b</code>. 
         *  Returns <code>null</code> iff both values are <code>null</code>
         */
        public static Severity max(Severity a, Severity b) {
            if (a == ERROR)
                return a;
            if (a == WARNING && b != ERROR)
                return a;
            return b;
        }
    }
}