bundles/org.eclipse.draw2d/src/org/eclipse/draw2d/BufferedGraphicsSource.java

/*******************************************************************************
 * Copyright (c) 2000, 2010 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.draw2d;

import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTError;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Caret;
import org.eclipse.swt.widgets.Control;

import org.eclipse.draw2d.geometry.Rectangle;

class BufferedGraphicsSource implements GraphicsSource {
 
	private Image imageBuffer;
	private GC imageGC;
	private GC controlGC;
	private Control control;
	private Rectangle inUse;

	/**
	 * Constructs a new buffered graphics source using the given control.
	 * 
	 * @since 2.1
	 * @param c
	 *            the control
	 */
	public BufferedGraphicsSource(Control c) {
		control = c;
	}

	/**
	 * @see org.eclipse.draw2d.GraphicsSource#flushGraphics(org.eclipse.draw2d.geometry.Rectangle)
	 */
	public void flushGraphics(Rectangle region) {
		if (inUse.isEmpty())
			return;

		boolean restoreCaret = false;
		Canvas canvas = null;
		if (control instanceof Canvas) {
			canvas = (Canvas) control;
			Caret caret = canvas.getCaret();
			if (caret != null)
				restoreCaret = caret.isVisible();
			if (restoreCaret)
				caret.setVisible(false);
		}
		/*
		 * The imageBuffer may be null if double-buffering was not successful.
		 */
		if (imageBuffer != null) {
			imageGC.dispose();
			controlGC.drawImage(getImage(), 0, 0, inUse.width, inUse.height,
					inUse.x, inUse.y, inUse.width, inUse.height);
			imageBuffer.dispose();
			imageBuffer = null;
			imageGC = null;
		}
		if (controlGC != null) {
			controlGC.dispose();
		}
		controlGC = null;

		if (restoreCaret)
			canvas.getCaret().setVisible(true);
	}

	/**
	 * @see org.eclipse.draw2d.GraphicsSource#getGraphics(org.eclipse.draw2d.geometry.Rectangle)
	 */
	public Graphics getGraphics(Rectangle region) {
		if (control == null || control.isDisposed())
			return null;

		org.eclipse.swt.graphics.Point ptSWT = control.getSize();
		inUse = new Rectangle(0, 0, ptSWT.x, ptSWT.y);
		inUse.intersect(region);
		if (inUse.isEmpty())
			return null;

		  /*
		   * Bugzilla 53632 - Attempts to create large images on some platforms
		   * will fail. When this happens, do not use double-buffering for 
		   * painting.
		   */
		try {
//			imageBuffer = new Image(null, inUse.width, inUse.height);
		} catch (SWTError noMoreHandles) {
			imageBuffer = null;
		} catch (IllegalArgumentException tooBig) {
			imageBuffer = null;
		}

		controlGC = new GC(control, control.getStyle()
				& (SWT.RIGHT_TO_LEFT | SWT.LEFT_TO_RIGHT));
		Graphics graphics;
		if (imageBuffer != null) {
			imageGC = new GC(imageBuffer, control.getStyle()
					& (SWT.RIGHT_TO_LEFT | SWT.LEFT_TO_RIGHT));
			imageGC.setBackground(controlGC.getBackground());
			imageGC.setForeground(controlGC.getForeground());
			imageGC.setFont(controlGC.getFont());
			imageGC.setLineStyle(controlGC.getLineStyle());
			imageGC.setLineWidth(controlGC.getLineWidth());
			imageGC.setXORMode(controlGC.getXORMode());
			graphics = new SWTGraphics(imageGC);
			graphics.translate(inUse.getLocation().negate());
		} else {
			graphics = new SWTGraphics(controlGC);
		}

		graphics.setClip(inUse);
		return graphics;
	}

	/**
	 * Returns the current image buffer or <code>null</code>.
	 * 
	 * @since 2.1
	 * @return the current image buffer
	 */
	protected Image getImage() {
		return imageBuffer;
	}

	/**
	 * Returns the current GC used on the buffer or <code>null</code>.
	 * 
	 * @since 2.1
	 * @return the GC for the image buffer
	 */
	protected GC getImageGC() {
		return imageGC;
	}

}