Java tutorial
/******************************************************************************* * Copyright (c) 2002, 2016 Innoopract Informationssysteme GmbH 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: * Innoopract Informationssysteme GmbH - initial API and implementation * EclipseSource - ongoing development ******************************************************************************/ package org.eclipse.swt.widgets; import org.eclipse.rap.rwt.internal.lifecycle.WidgetLCA; import org.eclipse.swt.SWT; import org.eclipse.swt.SWTException; import org.eclipse.swt.events.PaintListener; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Point; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.internal.graphics.GCAdapter; import org.eclipse.swt.internal.widgets.canvaskit.CanvasLCA; /** * Instances of this class provide a surface for drawing * arbitrary graphics. * <dl> * <dt><b>Styles:</b></dt> * <dd>(none)</dd> * <dt><b>Events:</b></dt> * <dd>(none)</dd> * </dl> * <p> * This class may be subclassed by custom control implementors * who are building controls that are <em>not</em> constructed * from aggregates of other controls. That is, they are either * painted using SWT graphics calls or are handled by native * methods. * </p> * * @see Composite * @since 1.0 */ public class Canvas extends Composite { private transient GCAdapter gcAdapter; Canvas(Composite parent) { // prevent instantiation from outside this package super(parent); } /** * Constructs a new instance of this class given its parent * and a style value describing its behavior and appearance. * <p> * The style value is either one of the style constants defined in * class <code>SWT</code> which is applicable to instances of this * class, or must be built by <em>bitwise OR</em>'ing together * (that is, using the <code>int</code> "|" operator) two or more * of those <code>SWT</code> style constants. The class description * lists the style constants that are applicable to the class. * Style bits are also inherited from superclasses. * </p> * * @param parent a composite control which will be the parent of the new * instance (cannot be null) * @param style the style of control to construct * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the parent is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that * created the parent</li> * </ul> * * @see SWT * @see Widget#checkSubclass * @see Widget#getStyle */ public Canvas(Composite parent, int style) { super(parent, style); } @Override @SuppressWarnings("unchecked") public <T> T getAdapter(Class<T> adapter) { if (adapter == GCAdapter.class) { if (gcAdapter == null) { gcAdapter = new GCAdapter(); } return (T) gcAdapter; } if (adapter == WidgetLCA.class) { return (T) CanvasLCA.INSTANCE; } return super.getAdapter(adapter); } /** * Adds the listener to the collection of listeners who will * be notified when the receiver needs to be painted, by sending it * one of the messages defined in the <code>PaintListener</code> * interface. * * @param listener the listener which should be notified * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the listener is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> * </ul> * * @see PaintListener * @see #removePaintListener * @since 1.3 */ public void addPaintListener(PaintListener listener) { checkWidget(); if (listener == null) { error(SWT.ERROR_NULL_ARGUMENT); } TypedListener typedListener = new TypedListener(listener); addListener(SWT.Paint, typedListener); } /** * Removes the listener from the collection of listeners who will * be notified when the receiver needs to be painted. * * @param listener the listener which should no longer be notified * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the listener is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> * </ul> * * @see PaintListener * @see #addPaintListener * @since 1.3 */ public void removePaintListener(PaintListener listener) { checkWidget(); if (listener == null) { error(SWT.ERROR_NULL_ARGUMENT); } removeListener(SWT.Paint, listener); } ///////////// // repainting @Override void notifyResize(Point oldSize) { super.notifyResize(oldSize); if (!oldSize.equals(getSize())) { repaint(getClientArea()); } } @Override void internalSetRedraw(boolean redraw) { super.internalSetRedraw(redraw); if (redraw) { repaint(getClientArea()); } } @Override void internalSetRedraw(boolean redraw, int x, int y, int width, int height) { super.internalSetRedraw(redraw, x, y, width, height); if (redraw) { repaint(new Rectangle(x, y, width, height)); } } private void repaint(Rectangle paintRect) { if (gcAdapter != null) { gcAdapter.clearGCOperations(); gcAdapter.setForceRedraw(true); } GC gc = new GC(this); Event paintEvent = new Event(); paintEvent.gc = gc; paintEvent.setBounds(paintRect); notifyListeners(SWT.Paint, paintEvent); gc.dispose(); if (gcAdapter != null) { gcAdapter.setPaintRect(paintRect); } } }