org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/breadcrumb/BreadcrumbViewer.java

/*******************************************************************************
 * Copyright (c) 2008, 2009 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
 *     Pawel Piech (Wind River) - adapted breadcrumb for use in Debug view (Bug 252677)
 *******************************************************************************/
package org.eclipse.debug.internal.ui.viewers.breadcrumb;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.ListenerList;
import org.eclipse.jface.viewers.DoubleClickEvent;
import org.eclipse.jface.viewers.IContentProvider;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.ITreePathContentProvider;
import org.eclipse.jface.viewers.ITreePathLabelProvider;
import org.eclipse.jface.viewers.OpenEvent;
import org.eclipse.jface.viewers.SelectionChangedEvent;
import org.eclipse.jface.viewers.StructuredViewer;
import org.eclipse.jface.viewers.TreePath;
import org.eclipse.jface.viewers.TreeSelection;
import org.eclipse.jface.viewers.ViewerLabel;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.events.MenuDetectEvent;
import org.eclipse.swt.events.MenuDetectListener;
import org.eclipse.swt.events.TraverseEvent;
import org.eclipse.swt.events.TraverseListener;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Widget;


/**
 * A breadcrumb viewer shows a the parent chain of its input element in a list. Each breadcrumb item
 * of that list can be expanded and a sibling of the element presented by the breadcrumb item can be
 * selected.
 * <p>
 * Content providers for breadcrumb viewers must implement the <code>ITreePathContentProvider</code>
 * interface.
 * </p>
 * <p>
 * Label providers for breadcrumb viewers must implement the <code>ITreePathLabelProvider</code> interface.
 * </p>
 *
 * @since 3.5
 */
public abstract class BreadcrumbViewer extends StructuredViewer {

	private static final boolean IS_GTK= "gtk".equals(SWT.getPlatform()); //$NON-NLS-1$

	private final int fStyle;
	private final Composite fContainer;
	private final ArrayList fBreadcrumbItems;
	private final ListenerList fMenuListeners;

	private Image fGradientBackground;
	private BreadcrumbItem fSelectedItem;
	
	/**
	 * Create a new <code>BreadcrumbViewer</code>.
	 * <p>
	 * Style is one of:
	 * <ul>
	 * <li>SWT.NONE</li>
	 * <li>SWT.VERTICAL</li>
	 * <li>SWT.HORIZONTAL</li>
     * <li>SWT.BOTTOM</li>
     * <li>SWT.RIGHT</li>
	 * </ul>
	 *
	 * @param parent the container for the viewer
	 * @param style the style flag used for this viewer
	 */
	public BreadcrumbViewer(Composite parent, int style) {
	    fStyle = style;
		fBreadcrumbItems= new ArrayList();
		fMenuListeners= new ListenerList();

		fContainer= new Composite(parent, SWT.NONE);
		GridData layoutData= new GridData(SWT.FILL, SWT.TOP, true, false);
		fContainer.setLayoutData(layoutData);
		fContainer.addTraverseListener(new TraverseListener() {
			public void keyTraversed(TraverseEvent e) {
				e.doit= true;
			}
		});
		fContainer.setBackgroundMode(SWT.INHERIT_DEFAULT);

		fContainer.addListener(SWT.Resize, new Listener() {
            public void handleEvent(Event event) {
                int height= fContainer.getClientArea().height;

                if (fGradientBackground == null || fGradientBackground.getBounds().height != height) {
                    Image image= createGradientImage(height, event.display);
                    fContainer.setBackgroundImage(image);

                    if (fGradientBackground != null)
                        fGradientBackground.dispose();
                    fGradientBackground= image;
                }
            }
        });

		
		fContainer.addDisposeListener(new DisposeListener() {
			public void widgetDisposed(DisposeEvent e) {
			    if (fGradientBackground != null) {
			        fGradientBackground.dispose();
			        fGradientBackground = null;
			    }
			}
		});

		hookControl(fContainer);

		int columns= 1000;
		if ((SWT.VERTICAL & style) != 0) {
			columns= 2;
		}

		GridLayout gridLayout= new GridLayout(columns, false);
		gridLayout.marginWidth= 0;
		gridLayout.marginHeight= 0;
		gridLayout.verticalSpacing= 0;
		gridLayout.horizontalSpacing= 0;
		fContainer.setLayout(gridLayout);

		fContainer.addListener(SWT.Resize, new Listener() {
			public void handleEvent(Event event) {
			    updateSize();
			    fContainer.layout(true, true);
			}
		});
	}

	int getStyle() {
	    return fStyle;
	}
	
    /**
     * Configure the given drop down viewer. The given input is used for the viewers input. Clients
     * must at least set the label and the content provider for the viewer.
     *
     * @param viewer the viewer to configure
     * @param input the input for the viewer
     */
	protected abstract Control createDropDown(Composite parent, IBreadcrumbDropDownSite site, TreePath path);
	
	/*
	 * @see org.eclipse.jface.viewers.Viewer#getControl()
	 */
	public Control getControl() {
		return fContainer;
	}

	/*
	 * @see org.eclipse.jface.viewers.StructuredViewer#reveal(java.lang.Object)
	 */
	public void reveal(Object element) {
		//all elements are always visible
	}

	/**
	 * Transfers the keyboard focus into the viewer.
	 */
	public void setFocus() {
		fContainer.setFocus();

		if (fSelectedItem != null) {
			fSelectedItem.setFocus(true);
		} else {
			if (fBreadcrumbItems.size() == 0)
				return;

			BreadcrumbItem item= (BreadcrumbItem) fBreadcrumbItems.get(fBreadcrumbItems.size() - 1);
			item.setFocus(true);
		}
	}

	/**
	 * @return true if any of the items in the viewer is expanded
	 */
	public boolean isDropDownOpen() {
		for (int i= 0, size= fBreadcrumbItems.size(); i < size; i++) {
			BreadcrumbItem item= (BreadcrumbItem) fBreadcrumbItems.get(i);
			if (item.isMenuShown())
				return true;
		}

		return false;
	}

	/**
	 * The shell used for the shown drop down or <code>null</code>
	 * if no drop down is shown at the moment.
	 *
	 * @return the drop downs shell or <code>null</code>
	 */
	public Shell getDropDownShell() {
		for (int i= 0, size= fBreadcrumbItems.size(); i < size; i++) {
			BreadcrumbItem item= (BreadcrumbItem) fBreadcrumbItems.get(i);
			if (item.isMenuShown())
				return item.getDropDownShell();
		}

		return null;
	}

	/**
	 * Add the given listener to the set of listeners which will be informed
	 * when a context menu is requested for a breadcrumb item.
	 *
	 * @param listener the listener to add
	 */
	public void addMenuDetectListener(MenuDetectListener listener) {
		fMenuListeners.add(listener);
	}

	/**
	 * Remove the given listener from the set of menu detect listeners.
	 * Does nothing if the listener is not element of the set.
	 *
	 * @param listener the listener to remove
	 */
	public void removeMenuDetectListener(MenuDetectListener listener) {
		fMenuListeners.remove(listener);
	}

	/*
	 * @see org.eclipse.jface.viewers.StructuredViewer#assertContentProviderType(org.eclipse.jface.viewers.IContentProvider)
	 */
	protected void assertContentProviderType(IContentProvider provider) {
		super.assertContentProviderType(provider);
		Assert.isTrue(provider instanceof ITreePathContentProvider);
	}

	/*
	 * @see org.eclipse.jface.viewers.Viewer#inputChanged(java.lang.Object, java.lang.Object)
	 */
	protected void inputChanged(final Object input, Object oldInput) {
		if (fContainer.isDisposed())
			return;

		disableRedraw();
		try {
		    preservingSelection(new Runnable() {
		        public void run() {
		            buildItemChain(input);
		        }
		    });
		} finally {
			enableRedraw();
		}
	}

	/*
	 * @see org.eclipse.jface.viewers.StructuredViewer#doFindInputItem(java.lang.Object)
	 */
	protected Widget doFindInputItem(Object element) {
		if (element == null)
			return null;

		if (element == getInput() || element.equals(getInput()))
			return doFindItem(element);

		return null;
	}

	/*
	 * @see org.eclipse.jface.viewers.StructuredViewer#doFindItem(java.lang.Object)
	 */
	protected Widget doFindItem(Object element) {
		if (element == null)
			return null;

		for (int i= 0, size= fBreadcrumbItems.size(); i < size; i++) {
			BreadcrumbItem item= (BreadcrumbItem) fBreadcrumbItems.get(i);
			if (item.getData() == element || element.equals(item.getData()))
				return item;
		}

		return null;
	}

	/*
	 * @see org.eclipse.jface.viewers.StructuredViewer#doUpdateItem(org.eclipse.swt.widgets.Widget, java.lang.Object, boolean)
	 */
	protected void doUpdateItem(Widget widget, Object element, boolean fullMap) {
		myDoUpdateItem(widget, element, fullMap);
	}
	
	private boolean myDoUpdateItem(Widget widget, Object element, boolean fullMap) {
		if (widget instanceof BreadcrumbItem) {
			final BreadcrumbItem item= (BreadcrumbItem) widget;

			// remember element we are showing
			if (fullMap) {
				associate(element, item);
			} else {
				Object data= item.getData();
				if (data != null) {
					unmapElement(data, item);
				}
				item.setData(element);
				mapElement(element, item);
			}

			refreshItem(item);
		}
		return false;
	}

   /**
     * This implementation of getSelection() returns an instance of
     * ITreeSelection.
     */
    public ISelection getSelection() {
        Control control = getControl();
        if (control == null || control.isDisposed()) {
            return TreeSelection.EMPTY;
        }
        if (fSelectedItem != null) {
            TreePath path = getTreePathFromItem(fSelectedItem);
            if (path != null) {
                return new TreeSelection(new TreePath[] { path });
            }
        }
        return TreeSelection.EMPTY;
    }

    protected TreePath getTreePathFromItem(BreadcrumbItem item) {
        List elements = new ArrayList(fBreadcrumbItems.size());
        for (int i = 0; i < fBreadcrumbItems.size(); i++) {
            elements.add( ((BreadcrumbItem)fBreadcrumbItems.get(i)).getData() );
            if (fBreadcrumbItems.get(i).equals(item)) {
                return new TreePath(elements.toArray());
            }
        }
        return null;
    }
    
	/*
 	 * @see org.eclipse.jface.viewers.StructuredViewer#getSelectionFromWidget()
	 */
	protected List getSelectionFromWidget() {
		if (fSelectedItem == null)
			return Collections.EMPTY_LIST;

		if (fSelectedItem.getData() == null)
			return Collections.EMPTY_LIST;

		ArrayList result= new ArrayList();
		result.add(fSelectedItem.getData());
		return result;
	}

	/*
	 * @see org.eclipse.jface.viewers.StructuredViewer#internalRefresh(java.lang.Object)
	 */
	protected void internalRefresh(Object element) {

		disableRedraw();
		try {
		    boolean layoutChanged = false;
		    
			BreadcrumbItem item= (BreadcrumbItem) doFindItem(element);
			if (item == null || element != null && element.equals(getInput())) {
				for (int i= 0, size= fBreadcrumbItems.size(); i < size; i++) {
					BreadcrumbItem item1= (BreadcrumbItem) fBreadcrumbItems.get(i);
					layoutChanged = refreshItem(item1) || layoutChanged;
				}
			} else {
			    layoutChanged = refreshItem(item) || layoutChanged;
			}
			
			if (layoutChanged) {
			    updateSize();
			    fContainer.layout(true, true);
			}
		} finally {
			enableRedraw();
		}
	}

	/*
	 * @see org.eclipse.jface.viewers.StructuredViewer#setSelectionToWidget(java.util.List, boolean)
	 */
	protected void setSelectionToWidget(List l, boolean reveal) {
		BreadcrumbItem focusItem= null;

		// Unselect the currently selected items, and remember the focused item.  
		for (int i= 0, size= fBreadcrumbItems.size(); i < size; i++) {
			BreadcrumbItem item= (BreadcrumbItem) fBreadcrumbItems.get(i);
			if (item.hasFocus())
				focusItem= item;

			item.setSelected(false);
		}

		if (l == null) {
		    l = Collections.EMPTY_LIST;
		}

		// Set the new selection to items.
		fSelectedItem = null;
		for (Iterator iterator= l.iterator(); iterator.hasNext();) {
			Object element= iterator.next();
			BreadcrumbItem item= (BreadcrumbItem) doFindItem(element);
			if (item != null) {
				item.setSelected(true);
				fSelectedItem= item;
				if (item == focusItem) {
					focusItem = null;
				}
			}
		}
		
		// If there is a new selection, and it does not overlap the old selection, 
		// remove the focus marker from the old focus item.
		if (fSelectedItem != null && focusItem != null) {
		    focusItem.setFocus(false);
		}
	}

	/**
	 * Set a single selection to the given item. <code>null</code> to deselect all.
	 *
	 * @param item the item to select or <code>null</code>
	 */
	void selectItem(BreadcrumbItem item) {
		if (fSelectedItem != null)
			fSelectedItem.setSelected(false);

		fSelectedItem= item;
		setSelectionToWidget(getSelection(), false);
		setFocus();

		fireSelectionChanged(new SelectionChangedEvent(this, getSelection()));
	}

	/**
	 * Returns the item count.
	 *
	 * @return number of items shown in the viewer
	 */
	int getItemCount() {
		return fBreadcrumbItems.size();
	}

	/**
	 * Returns the item for the given item index.
	 *
	 * @param index the index of the item
	 * @return the item ad the given <code>index</code>
	 */
	BreadcrumbItem getItem(int index) {
		return (BreadcrumbItem) fBreadcrumbItems.get(index);
	}

	/**
	 * Returns the index of the given item.
	 *
	 * @param item the item to search
	 * @return the index of the item or -1 if not found
	 */
	int getIndexOfItem(BreadcrumbItem item) {
		for (int i= 0, size= fBreadcrumbItems.size(); i < size; i++) {
			BreadcrumbItem pItem= (BreadcrumbItem) fBreadcrumbItems.get(i);
			if (pItem == item)
				return i;
		}

		return -1;
	}

	/**
	 * Notifies all double click listeners.
	 */
	void fireDoubleClick() {
		fireDoubleClick(new DoubleClickEvent(this, getSelection()));
	}

	/**
	 * Notifies all open listeners.
	 */
	void fireOpen() {
		fireOpen(new OpenEvent(this, getSelection()));
	}

	/**
	 * The given element was selected from a drop down menu.
	 *
	 * @param element the selected element
	 */
	void fireMenuSelection(ISelection selection) {
		fireOpen(new OpenEvent(this, selection));
	}

	/**
	 * A context menu has been requested for the selected breadcrumb item.
	 *
	 * @param event the event issued the menu detection
	 */
	void fireMenuDetect(MenuDetectEvent event) {
		Object[] listeners= fMenuListeners.getListeners();
		for (int i= 0; i < listeners.length; i++) {
			((MenuDetectListener)listeners[i]).menuDetected(event);
		}
	}

	/**
	 * Set selection to the next or previous element if possible.
	 *
	 * @param next <code>true</code> if the next element should be selected, otherwise the previous
	 *            one will be selected
	 */
	void doTraverse(boolean next) {
		if (fSelectedItem == null)
			return;

		int index= fBreadcrumbItems.indexOf(fSelectedItem);
		if (next) {
			if (index == fBreadcrumbItems.size() - 1) {
				BreadcrumbItem current= (BreadcrumbItem) fBreadcrumbItems.get(index);

				current.openDropDownMenu();
				current.getDropDownShell().setFocus();
			} else {
				BreadcrumbItem nextItem= (BreadcrumbItem) fBreadcrumbItems.get(index + 1);
				selectItem(nextItem);
			}
		} else {
			if (index == 0) {
				BreadcrumbItem root= (BreadcrumbItem) fBreadcrumbItems.get(index);
				root.openDropDownMenu();
				root.getDropDownShell().setFocus();
			} else {
				selectItem((BreadcrumbItem) fBreadcrumbItems.get(index - 1));
			}
		}
	}

	/**
	 * Generates the parent chain of the given element.
	 *
	 * @param element element to build the parent chain for
	 * @return the first index of an item in fBreadcrumbItems which is not 
	 *         part of the chain
	 */
	private void buildItemChain(Object input) {
		if (fBreadcrumbItems.size() > 0) {
			BreadcrumbItem last= (BreadcrumbItem) fBreadcrumbItems.get(fBreadcrumbItems.size() - 1);
			last.setIsLastItem(false);
		}
		
        int index = 0;
        boolean updateLayout = false;
		if (input != null) {
	        ITreePathContentProvider contentProvider= (ITreePathContentProvider) getContentProvider();
	        TreePath path = new TreePath(new Object[0]);
	
	        // Top level elements need to be retrieved using getElements(), rest 
	        // using getChildren().
	        Object[] children = contentProvider.getElements(input);
	        Object element = children != null && children.length != 0 ? children[0] : null;
	        while (element != null) {
	            path = path.createChildPath(element);
	            
	            // All but last item are hidden if the viewer is in a vertical toolbar.
	            children = contentProvider.getChildren(path);
	            if ((getStyle() & SWT.VERTICAL) == 0 || children == null || children.length == 0) {
	                updateLayout = updateOrCreateItem(index++, path, element) || updateLayout;
	            }
	            
	            if (children != null && children.length != 0) {
	                element = children[0];
	            } else {
	                break;
	            }
	                
	        }	
		}
		
        BreadcrumbItem last = null;
        if (index <= fBreadcrumbItems.size()) {
        	last = ((BreadcrumbItem)fBreadcrumbItems.get(index - 1));
        	last.setIsLastItem(true);
        }
        
		while (index < fBreadcrumbItems.size()) {
			updateLayout = true;
			BreadcrumbItem item= (BreadcrumbItem) fBreadcrumbItems.remove(fBreadcrumbItems.size() - 1);
            if (item.hasFocus() && last != null) {
                last.setFocus(true);
            }
			if (item == fSelectedItem) {
				selectItem(null);
			}
			if (item.getData() != null)
				unmapElement(item.getData());
			item.dispose();
		}

		if (updateLayout) {
			updateSize();
			fContainer.layout(true, true);
		}
	}

	/** 
	 * @param item Item to refresh.
	 * @return returns whether the item's size and layout needs to be updated.
	 */
	private boolean refreshItem(BreadcrumbItem item) {
	    boolean layoutChanged = false;
	    
	    TreePath path = getTreePathFromItem(item);

	    ViewerLabel label = new ViewerLabel(item.getText(), item.getImage());
	    ((ITreePathLabelProvider)getLabelProvider()).updateLabel(label, path);

	    if (label.hasNewText()) {
	        item.setText(label.getText());
	        layoutChanged = true;
	    }
	    if (label.hasNewImage()) {
	        item.setImage(label.getImage());
	        layoutChanged = true;
	    }
	    if (label.hasNewTooltipText()) {
	        item.setToolTip(label.getTooltipText());
	    }
	    return layoutChanged;
	}
	
	/**
	 * Creates or updates a breadcrumb item.
	 *
	 * @return whether breadcrumb layout needs to be updated due to this change
	 */
	private boolean updateOrCreateItem(int index, TreePath path, Object element) {
	    BreadcrumbItem item;
	    if (fBreadcrumbItems.size() > index) {
	        item = (BreadcrumbItem)fBreadcrumbItems.get(index);
	        if (item.getData() != null) {
	            unmapElement(item.getData());
	        }
	    } else {
	        item = new BreadcrumbItem(this, fContainer);
	        fBreadcrumbItems.add(item);
	    }

		boolean updateLayout = false;
		
	    if (equals(element, item.getData())) {
	        item.setPath(path);
            updateLayout = myDoUpdateItem(item, element, false);
        } else {
            item.setData(element);
            item.setPath(path);
    	    mapElement(element, item);
            updateLayout = refreshItem(item);
        }
	    
        return updateLayout;
	}

	/**
	 * Update the size of the items such that all items are visible, if possible.
	 *
	 * @return <code>true</code> if any item has changed, <code>false</code> otherwise
	 */
	private boolean updateSize() {
		int width= fContainer.getClientArea().width;

		int currentWidth= getCurrentWidth();

		boolean requiresLayout= false;

		if (currentWidth > width) {
			int index= 0;
			while (currentWidth > width && index < fBreadcrumbItems.size() - 1) {
				BreadcrumbItem viewer= (BreadcrumbItem) fBreadcrumbItems.get(index);
				if (viewer.isShowText()) {
					viewer.setShowText(false);
					currentWidth= getCurrentWidth();
					requiresLayout= true;
				}

				index++;
			}

		} else if (currentWidth < width) {

			int index= fBreadcrumbItems.size() - 1;
			while (currentWidth < width && index >= 0) {

				BreadcrumbItem viewer= (BreadcrumbItem) fBreadcrumbItems.get(index);
				if (!viewer.isShowText()) {
					viewer.setShowText(true);
					currentWidth= getCurrentWidth();
					if (currentWidth > width) {
						viewer.setShowText(false);
						index= 0;
					} else {
						requiresLayout= true;
					}
				}

				index--;
			}
		}

		return requiresLayout;
	}

	/**
	 * Returns the current width of all items in the list.
	 *
	 * @return the width of all items in the list
	 */
	private int getCurrentWidth() {
		int result= 0;
		for (int i= 0, size= fBreadcrumbItems.size(); i < size; i++) {
			BreadcrumbItem viewer= (BreadcrumbItem) fBreadcrumbItems.get(i);
			result+= viewer.getWidth();
		}

		return result;
	}

	/**
	 * Enables redrawing of the breadcrumb.
	 */
	private void enableRedraw() {
		if (IS_GTK) //flickers on GTK
			return;

		fContainer.setRedraw(true);
	}

	/**
	 * Disables redrawing of the breadcrumb.
	 *
	 * <p>
	 * <strong>A call to this method must be followed by a call to {@link #enableRedraw()}</strong>
	 * </p>
	 */
	private void disableRedraw() {
		if (IS_GTK) //flickers on GTK
			return;

		fContainer.setRedraw(false);
	}

	   /**
     * The image to use for the breadcrumb background as specified in
     * https://bugs.eclipse.org/bugs/show_bug.cgi?id=221477
     *
     * @param height the height of the image to create
     * @param display the current display
     * @return the image for the breadcrumb background
     */
    private Image createGradientImage(int height, Display display) {
        int width= 50;

        Image result= new Image(display, width, height);

        GC gc= new GC(result);

        Color colorC= createColor(SWT.COLOR_WIDGET_BACKGROUND, SWT.COLOR_LIST_BACKGROUND, 35, display);
        Color colorD= createColor(SWT.COLOR_WIDGET_BACKGROUND, SWT.COLOR_LIST_BACKGROUND, 45, display);
        Color colorE= createColor(SWT.COLOR_WIDGET_BACKGROUND, SWT.COLOR_LIST_BACKGROUND, 80, display);
        Color colorF= createColor(SWT.COLOR_WIDGET_BACKGROUND, SWT.COLOR_LIST_BACKGROUND, 70, display);
        Color colorG= createColor(SWT.COLOR_WIDGET_BACKGROUND, SWT.COLOR_WHITE, 45, display);
        Color colorH= createColor(SWT.COLOR_WIDGET_NORMAL_SHADOW, SWT.COLOR_LIST_BACKGROUND, 35, display);

        try {
            drawLine(width, 0, colorC, gc);
            drawLine(width, 1, colorC, gc);

            gc.setForeground(colorD);
            gc.setBackground(colorE);
            gc.fillGradientRectangle(0, 2, width, 2 + 8, true);

            gc.setBackground(colorE);
            gc.fillRectangle(0, 2 + 9, width, height - 4);

            drawLine(width, height - 3, colorF, gc);
            drawLine(width, height - 2, colorG, gc);
            drawLine(width, height - 1, colorH, gc);

        } finally {
            gc.dispose();

            colorC.dispose();
            colorD.dispose();
            colorE.dispose();
            colorF.dispose();
            colorG.dispose();
            colorH.dispose();
        }

        return result;
    }

    private void drawLine(int width, int position, Color color, GC gc) {
        gc.setForeground(color);
        gc.drawLine(0, position, width, position);
    }

    private Color createColor(int color1, int color2, int ratio, Display display) {
        RGB rgb1= display.getSystemColor(color1).getRGB();
        RGB rgb2= display.getSystemColor(color2).getRGB();

        RGB blend= blend(rgb2, rgb1, ratio);

        return new Color(display, blend);
    }

	/**
	 * Blends c1 and c2 based in the provided ratio.
	 * 
	 * @param c1
	 *            first color
	 * @param c2
	 *            second color
	 * @param ratio
	 *            percentage of the first color in the blend (0-100)
	 * @return the RGB value of the blended color
	 * @since 3.1
	 */
	public static RGB blend(RGB c1, RGB c2, int ratio) {
		int r = blend(c1.red, c2.red, ratio);
		int g = blend(c1.green, c2.green, ratio);
		int b = blend(c1.blue, c2.blue, ratio);
		return new RGB(r, g, b);
	}
	
	/**
	 * Blends two primary color components based on the provided ratio.
	 * 
	 * @param v1
	 *            first component
	 * @param v2
	 *            second component
	 * @param ratio
	 *            percentage of the first component in the blend
	 * @return
	 */
	private static int blend(int v1, int v2, int ratio) {
		int b = (ratio * v1 + (100 - ratio) * v2) / 100;
		return Math.min(255, b);
	}	
}