| /******************************************************************************* |
| * Copyright (c) 2000, 2017 IBM Corporation and others. |
| * |
| * This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License 2.0 |
| * which accompanies this distribution, and is available at |
| * https://www.eclipse.org/legal/epl-2.0/ |
| * |
| * SPDX-License-Identifier: EPL-2.0 |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.compare.internal; |
| |
| import org.eclipse.jface.util.Util; |
| import org.eclipse.swt.SWT; |
| import org.eclipse.swt.graphics.*; |
| import org.eclipse.swt.widgets.Canvas; |
| import org.eclipse.swt.widgets.Composite; |
| |
| /** |
| * A Canvas which reduces flicker by drawing in an off screen buffer. |
| */ |
| public abstract class BufferedCanvas extends Canvas { |
| |
| //private static final boolean USE_DOUBLE_BUFFER= !"carbon".equals(SWT.getPlatform()); //$NON-NLS-1$ |
| private static final boolean USE_DOUBLE_BUFFER= true; |
| |
| /** The drawable for double buffering */ |
| Image fBuffer; |
| |
| public BufferedCanvas(Composite parent, int flags) { |
| super(parent, flags | SWT.NO_BACKGROUND); |
| |
| addPaintListener( |
| event -> doubleBufferPaint(event.gc) |
| ); |
| |
| addDisposeListener( |
| e -> { |
| if (fBuffer != null) { |
| fBuffer.dispose(); |
| fBuffer= null; |
| } |
| } |
| ); |
| } |
| |
| public void repaint() { |
| if (!isDisposed()) { |
| GC gc= new GC(this); |
| doubleBufferPaint(gc); |
| gc.dispose(); |
| if (Util.isGtk()) { |
| redraw(); |
| } |
| } |
| } |
| |
| /* |
| * Double buffer drawing. |
| */ |
| void doubleBufferPaint(GC dest) { |
| |
| if (!USE_DOUBLE_BUFFER) { |
| doPaint(dest); |
| return; |
| } |
| |
| Point size= getSize(); |
| |
| if (size.x <= 1 || size.y <= 1) // we test for <= 1 because on X11 controls have initial size 1,1 |
| return; |
| |
| if (fBuffer != null) { |
| Rectangle r= fBuffer.getBounds(); |
| if (r.width != size.x || r.height != size.y) { |
| fBuffer.dispose(); |
| fBuffer= null; |
| } |
| } |
| if (fBuffer == null) |
| fBuffer= new Image(getDisplay(), size.x, size.y); |
| |
| GC gc= new GC(fBuffer); |
| try { |
| gc.setBackground(getBackground()); |
| gc.fillRectangle(0, 0, size.x, size.y); |
| doPaint(gc); |
| } finally { |
| gc.dispose(); |
| } |
| |
| dest.drawImage(fBuffer, 0, 0); |
| } |
| |
| abstract public void doPaint(GC gc); |
| } |