Attachment 108796 Details for Bug 224692 – Decorator for eager -> lazy tree content provider

Some Eclipse Foundation services are deprecated, or will be soon. Please ensure you've read this important communication.

Decorator for eager -> lazy tree content provider

PseudoLazyTreeContentProvider.java (text/plain), 3.07 KB, created by Peter Centgraf

on 2008-07-30 17:50:36 EDT

(hide)

Description:

Filename:

MIME Type:

Creator: Peter Centgraf

Created: 2008-07-30 17:50:36 EDT

Size: 3.07 KB

patch

obsolete

>package org.eclipse.nebula.jface.galleryviewer;
>
>import org.eclipse.jface.viewers.ILazyTreeContentProvider;
>import org.eclipse.jface.viewers.ITreeContentProvider;
>import org.eclipse.jface.viewers.Viewer;
>import org.eclipse.swt.SWT;
>
>/**
> * Decorator that turns an eager {@link ITreeContentProvider} into an 
> * {@link ILazyTreeContentProvider} by delegating the appropriate calls.  This is 
> * guaranteed to have worse performance characteristics than using the delegate directly,
> * but it enables the use of {@link SWT#VIRTUAL} for rendering labels and images.  
> * For {@link GalleryTreeViewer}, this is a net win in most cases, since rendering images
> * is vastly slower than fetching the model objects.
> * 
> * NOTE: This class relies on the IElementComparer set on the viewer to determine
> * whether an element is equal to the viewer input.  This determines whether
> * {@link ITreeContentProvider#getChildren(Object)} or 
> * {@link ITreeContentProvider#getElements(Object)} is used for a particular request.
> * 
> * @author pcentgraf
> * @since Jul 30, 2008
> */
>public class PseudoLazyTreeContentProvider implements ILazyTreeContentProvider {
>	
>	final protected ITreeContentProvider delegate;
>	protected GalleryTreeViewer viewer;
>	protected Object input;
>	
>	public PseudoLazyTreeContentProvider(ITreeContentProvider delegate) {
>		this.delegate = delegate;
>	}
>
>	/* (non-Javadoc)
>	 * @see org.eclipse.jface.viewers.IContentProvider#inputChanged(org.eclipse.jface.viewers.Viewer, java.lang.Object, java.lang.Object)
>	 */
>	public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
>		delegate.inputChanged(viewer, oldInput, newInput);
>		viewer = (GalleryTreeViewer) viewer;
>		input = newInput;
>	}
>
>	/* (non-Javadoc)
>	 * @see org.eclipse.jface.viewers.ILazyTreeContentProvider#getParent(java.lang.Object)
>	 */
>	public Object getParent(Object element) {
>		return delegate.getParent(element);
>	}
>
>	/* (non-Javadoc)
>	 * @see org.eclipse.jface.viewers.ILazyTreeContentProvider#updateChildCount(java.lang.Object, int)
>	 */
>	public void updateChildCount(Object element, int currentChildCount) {
>		if (viewer.getComparer().equals(element, input)) {
>			viewer.setChildCount(element, delegate.getElements(element).length);
>		}
>		else {
>			viewer.setChildCount(element, delegate.getChildren(element).length);
>		}
>	}
>
>	/* (non-Javadoc)
>	 * @see org.eclipse.jface.viewers.ILazyTreeContentProvider#updateElement(java.lang.Object, int)
>	 */
>	public void updateElement(Object parent, int index) {
>		Object[] children; 
>		if (viewer.getComparer().equals(parent, input)) {
>			children = delegate.getElements(parent);
>			viewer.replace(parent, index, children[index]);
>			viewer.setChildCount(children[index], delegate.getChildren(children[index]).length);
>		}
>		else {
>			children = delegate.getChildren(parent);
>			viewer.replace(parent, index, children[index]);
>			viewer.setChildCount(children[index], 0);
>		}
>	}
>
>	/* (non-Javadoc)
>	 * @see org.eclipse.jface.viewers.IContentProvider#dispose()
>	 */
>	public void dispose() {
>		delegate.dispose();
>	}
>
>}

Actions: View

Attachments on bug 224692: 108725 | 108796 | 108797 | 108958