| /******************************************************************************* |
| * Copyright (c) 2005, 2006 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.jface.internal.databinding.provisional.swt; |
| |
| import org.eclipse.jface.internal.databinding.internal.swt.SWTUtil; |
| import org.eclipse.jface.internal.databinding.provisional.observable.IChangeListener; |
| import org.eclipse.jface.internal.databinding.provisional.observable.IObservable; |
| import org.eclipse.jface.internal.databinding.provisional.observable.ObservableTracker; |
| import org.eclipse.swt.events.DisposeEvent; |
| import org.eclipse.swt.events.DisposeListener; |
| import org.eclipse.swt.events.PaintEvent; |
| import org.eclipse.swt.events.PaintListener; |
| import org.eclipse.swt.widgets.Control; |
| |
| /** |
| * A ControlUpdater updates an SWT control in response to changes in the model. |
| * By wrapping a block of code in a ControlUpdater, clients can rely on the fact |
| * that the block of code will be re-executed whenever anything changes in the |
| * model that might affect its behavior. |
| * |
| * <p> |
| * ControlUpdaters only execute when their controls are visible. If something changes |
| * in the model while the control is invisible, the updator is flagged as dirty and |
| * the updator stops listening to the model until the next time the control repaints. |
| * This saves CPU cycles by deferring UI updates to widgets that are currently invisible. |
| * </p> |
| * |
| * <p> |
| * Clients should subclass this when copying information from the model to |
| * a control. Typical usage: |
| * </p> |
| * |
| * <ul> |
| * <li>Override updateControl. It should do whatever is necessary to display |
| * the contents of the model in the control.</li> |
| * <li>In the constructor, attach listeners to the model. The listeners should |
| * call markDirty whenever anything changes in the model that affects |
| * updateControl. Note: this step can be omitted when calling any method |
| * tagged with "@TrackedGetter" since ControlUpdater will automatically attach |
| * a listener to any object if a "@TrackedGetter" method is called in |
| * updateControl.</li> |
| * <li>(optional)Extend dispose() to remove any listeners attached in the constructor</li> |
| * </ul> |
| * |
| * <p> |
| * Example: |
| * </p> |
| * |
| * <code> |
| * // Displays an updatable value in a label and keeps the label in synch with changes |
| * // in the value. |
| * IReadableValue someValue = ... |
| * final Label myLabel = new Label(parent, SWT.NONE); |
| * new ControlUpdater(myLabel) { |
| * protected void updateControl() { |
| * myLabel.setText(someValue.getValue().toString); |
| * } |
| * } |
| * // myLabel will display the value of someValue the next time it repaints, and will automatically |
| * // be updated whenever someValue changes and the label is visible |
| * </code> |
| * |
| * @since 1.0 |
| */ |
| public abstract class ControlUpdater { |
| |
| private class PrivateInterface implements PaintListener, |
| DisposeListener, Runnable, IChangeListener { |
| |
| // PaintListener implementation |
| public void paintControl(PaintEvent e) { |
| updateIfNecessary(); |
| } |
| |
| // DisposeListener implementation |
| public void widgetDisposed(DisposeEvent e) { |
| ControlUpdater.this.dispose(); |
| } |
| |
| // Runnable implementation. This method runs at most once per repaint whenever the |
| // value gets marked as dirty. |
| public void run() { |
| if (theControl != null && !theControl.isDisposed() && theControl.isVisible()) { |
| updateIfNecessary(); |
| } |
| } |
| |
| // IChangeListener implementation (listening to the ComputedValue) |
| public void handleChange(IObservable source) { |
| // Whenever this updator becomes dirty, schedule the run() method |
| makeDirty(); |
| } |
| |
| } |
| |
| private Runnable updateRunnable = new Runnable() { |
| public void run() { |
| updateControl(); |
| } |
| }; |
| |
| private PrivateInterface privateInterface = new PrivateInterface(); |
| private Control theControl; |
| private IObservable[] dependencies = new IObservable[0]; |
| private boolean dirty = false; |
| |
| /** |
| * Creates an updator for the given control. |
| * |
| * @param toUpdate control to update |
| */ |
| public ControlUpdater(Control toUpdate) { |
| theControl = toUpdate; |
| |
| theControl.addDisposeListener(privateInterface); |
| theControl.addPaintListener(privateInterface); |
| makeDirty(); |
| } |
| |
| private void updateIfNecessary() { |
| if (dirty) { |
| dependencies = ObservableTracker.runAndMonitor(updateRunnable, privateInterface, null); |
| dirty = false; |
| } |
| } |
| |
| /** |
| * This is called automatically when the control is disposed. It may also |
| * be called explicitly to remove this updator from the control. Subclasses |
| * will normally extend this method to detach any listeners they attached |
| * in their constructor. |
| */ |
| public void dispose() { |
| theControl.removeDisposeListener(privateInterface); |
| theControl.removePaintListener(privateInterface); |
| |
| stopListening(); |
| } |
| |
| private void stopListening() { |
| // Stop listening for dependency changes |
| for (int i = 0; i < dependencies.length; i++) { |
| IObservable observable = dependencies[i]; |
| |
| observable.removeChangeListener(privateInterface); |
| } |
| } |
| |
| /** |
| * Updates the control. This method will be invoked once after the |
| * updator is created, and once before any repaint during which the |
| * control is visible and dirty. |
| * |
| * <p> |
| * Subclasses should overload this method to provide any code that |
| * changes the appearance of the widget. |
| * </p> |
| */ |
| protected abstract void updateControl(); |
| |
| /** |
| * Marks this updator as dirty. Causes the updateControl method to |
| * be invoked before the next time the control is repainted. |
| */ |
| protected final void makeDirty() { |
| if (!dirty) { |
| dirty = true; |
| stopListening(); |
| SWTUtil.runOnce(theControl.getDisplay(), privateInterface); |
| } |
| } |
| |
| } |