1 files changed, 201 insertions, 0 deletions
diff --git a/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/canvas/BufferedCanvas.java b/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/canvas/BufferedCanvas.java
new file mode 100755
index 00000000000..b4f2778cef4
--- /dev/null
+++ b/visualizer/org.eclipse.cdt.visualizer.ui/src/org/eclipse/cdt/visualizer/ui/canvas/BufferedCanvas.java
@@ -0,0 +1,201 @@
+/*******************************************************************************
+ * Copyright (c) 2012 Tilera 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:
+ *     William R. Swanson (Tilera Corporation)
+ *******************************************************************************/
+
+package org.eclipse.cdt.visualizer.ui.canvas;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.ControlEvent;
+import org.eclipse.swt.events.ControlListener;
+import org.eclipse.swt.events.PaintEvent;
+import org.eclipse.swt.events.PaintListener;
+import org.eclipse.swt.graphics.GC;
+import org.eclipse.swt.graphics.Image;
+import org.eclipse.swt.graphics.Rectangle;
+import org.eclipse.swt.widgets.Canvas;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Display;
+
+
+// ---------------------------------------------------------------------------
+// BufferedCanvas
+// ---------------------------------------------------------------------------
+
+/** Canvas control with double-buffering support. */
+public class BufferedCanvas extends Canvas
+	implements PaintListener, ControlListener
+{
+	// --- members ---
+	
+	/** double-buffering image */
+	protected Image m_doubleBuffer = null;
+	
+	/** buffer GC */
+	protected GC m_doubleBufferGC = null;
+	
+	
+	// --- constructors/destructors ---
+	
+	/** Constructor. */
+	public BufferedCanvas(Composite parent) {
+        super(parent,
+        		SWT.NO_BACKGROUND |    // don't automatically clear background on paint event
+        		SWT.NO_REDRAW_RESIZE   // don't automatically repaint on resize event
+        	); 
+		initBufferedCanvas();
+	}
+	
+	/** Dispose method. */
+	public void dispose() {
+		super.dispose();
+		cleanupBufferedCanvas();
+	}
+	
+	// --- init methods ---
+
+	/** Initializes control. */
+	protected void initBufferedCanvas() {
+		addControlListener(this);
+		addPaintListener(this);
+	}
+	
+	/** Cleans up control. */
+	protected void cleanupBufferedCanvas() {
+		removePaintListener(this);
+		removeControlListener(this);
+		if (m_doubleBuffer != null) {
+			m_doubleBuffer.dispose();
+			m_doubleBuffer = null;
+		}
+	}
+	
+	
+	// --- event handlers ---
+	
+	/** Invoked when control is moved/resized */
+	public void controlMoved(ControlEvent e) {
+		// do nothing, we don't care
+	}
+
+	/** Invoked when control is resized */
+	public void controlResized(ControlEvent e) {
+		resized(getBounds());
+	}
+	
+	
+	// --- resize methods ---
+	
+	/** Invoked when control is resized.
+	 *  Default implementation does nothing,
+	 *  intended to be overridden by derived types.
+	 */
+	public void resized(Rectangle bounds) {
+		
+	}
+	
+	
+	// --- GC management ---
+	
+	/** Gets/creates GC for current background buffer.
+	 *  NOTE: The GC is disposed whenever the canvas size changes,
+	 *  so caller should not retain a reference to this GC.
+	 */
+	protected synchronized GC getBufferedGC() {
+		if (m_doubleBufferGC == null) {
+			
+			m_doubleBufferGC = new GC(m_doubleBuffer);
+		}
+		return m_doubleBufferGC;
+	}
+
+	/** Disposes of current background buffer GC. */
+	protected synchronized void disposeBufferedGC() {
+		if (m_doubleBufferGC != null) {
+			m_doubleBufferGC.dispose();
+			m_doubleBufferGC = null;
+		}
+	}
+
+	
+	// --- paint methods ---
+	
+	/** Invoked when control needs to be repainted */
+	public void paintControl(PaintEvent e) {
+		// Handle last paint event of a cluster.
+		if (e.count<=1) {
+			Display display = e.display;
+			GC gc = e.gc;
+			paintDoubleBuffered(display, gc);
+		}
+	}
+	
+	/** Internal -- handles double-buffering support, calls paintCanvas() */
+	// NOTE: need display to create image buffer, not for painting code
+	protected void paintDoubleBuffered(Display display, GC gc) {
+        // get/create background image buffer
+		Rectangle clientArea = getClientArea();
+		int width = clientArea.width;
+		int height = clientArea.height;
+		if (m_doubleBuffer == null
+            || m_doubleBuffer.getBounds().width  < width
+            || m_doubleBuffer.getBounds().height < height)
+		{
+			m_doubleBuffer = new Image(display, width, height);
+			disposeBufferedGC();
+        }
+
+        // create graphics context for buffer
+        GC bgc = getBufferedGC();
+        
+        // copy current GC properties into it as defaults
+        bgc.setBackground(gc.getBackground());
+        bgc.setForeground(gc.getForeground());
+        bgc.setFont(gc.getFont());
+        bgc.setAlpha(255);
+
+        // invoke paintCanvas() method to paint into the buffer
+        try {
+        	paintCanvas(bgc);
+        }
+        catch (Throwable t) {
+        	// Throwing an exception in painting code can hang Eclipse,
+        	// so catch any exceptions here.
+        	System.err.println("BufferedCanvas: Exception thrown in painting code: \n" + t);
+        }
+        
+        // then copy image buffer to actual canvas (reduces repaint flickering)
+        gc.drawImage(m_doubleBuffer, 0,0);
+	}
+	
+	/** Invoked when canvas repaint event is raised.
+	 *  Default implementation clears canvas to background color.
+	 */
+	public void paintCanvas(GC gc) {
+		clearCanvas(gc);
+	}
+
+	/** Clears canvas to background color. */
+	public void clearCanvas(GC gc) {
+		Rectangle bounds = getClientArea();
+		gc.fillRectangle(bounds);
+	}
+
+	
+	// --- update methods ---
+	
+	/** Redraws control */
+	public void update() {
+		// guard against update events that happen
+		// after app has shut down
+		if (! isDisposed()) {
+			redraw();
+		}
+	}
+}