1 files changed, 137 insertions, 0 deletions
diff --git a/bundles/org.eclipse.compare/compare/org/eclipse/compare/internal/ImageCanvas.java b/bundles/org.eclipse.compare/compare/org/eclipse/compare/internal/ImageCanvas.java
new file mode 100644
index 000000000..2d56fc406
--- /dev/null
+++ b/bundles/org.eclipse.compare/compare/org/eclipse/compare/internal/ImageCanvas.java
@@ -0,0 +1,137 @@
+/*
+ * Licensed Materials - Property of IBM,
+ * WebSphere Studio Workbench
+ * (c) Copyright IBM Corp 2000, 2001
+ */
+package org.eclipse.compare.internal;
+
+import org.eclipse.swt.*;
+import org.eclipse.swt.graphics.*;
+import org.eclipse.swt.widgets.*;
+
+/**
+ * A <code>Canvas</code> showing a single centered SWT <code>Image</code>.
+ * If the <code>Image</code> is larger than the <code>Canvas<code>,
+ * <code>Scrollbars</code> will appear.
+ */
+class ImageCanvas extends Canvas {
+
+	private Image fImage;
+
+	/**
+	 * Create a new ImageCanvas with the given SWT stylebits.
+	 * (SWT.H_SCROLL and SWT.V_SCROLL are automtically added).
+	 */
+	public ImageCanvas(Composite parent, int style) {
+		super(parent, style | SWT.H_SCROLL | SWT.V_SCROLL);
+
+		ScrollBar sb= getHorizontalBar();
+		sb.setIncrement(20);
+		sb.addListener(SWT.Selection, new Listener() {
+			public void handleEvent(Event e) {
+				repaint();
+			}
+		});
+
+		sb= getVerticalBar();
+		sb.setIncrement(20);
+		sb.addListener(SWT.Selection, new Listener() {
+			public void handleEvent(Event e) {
+				repaint();
+			}
+		});
+
+		addListener(SWT.Resize, new Listener() {
+			public void handleEvent(Event e) {
+				updateScrollbars();
+			}
+		});
+
+		addListener(SWT.Paint, new Listener() {
+			public void handleEvent(Event event) {
+				paint(event.gc);
+			}
+		});
+	}
+
+	/**
+	 * Set the SWT Image to use as the ImageCanvas contents.
+	 */
+	public void setImage(Image img) {
+		fImage= img;
+
+		if (!isDisposed()) {
+			getHorizontalBar().setSelection(0);
+			getVerticalBar().setSelection(0);
+			updateScrollbars();
+			getParent().layout();
+			redraw();
+		}
+	}
+
+	public void repaint() {
+		if (!isDisposed()) {
+			GC gc= new GC(this);
+			paint(gc);
+			gc.dispose();
+		}
+	}
+
+	/**
+	 * @private
+	 */
+	private void paint(GC gc) {
+		if (fImage != null) {
+			Rectangle bounds= fImage.getBounds();
+			Rectangle clientArea= getClientArea();
+
+			int x;
+			if (bounds.width < clientArea.width)
+				x= (clientArea.width - bounds.width) / 2;
+			else
+				x= -getHorizontalBar().getSelection();
+
+			int y;
+			if (bounds.height < clientArea.height)
+				y= (clientArea.height - bounds.height) / 2;
+			else
+				y= -getVerticalBar().getSelection();
+
+			gc.drawImage(fImage, x, y);
+		}
+	}
+
+	/**
+	 * @private
+	 */
+	private void updateScrollbars() {
+		Rectangle bounds= fImage != null ? fImage.getBounds() : new Rectangle(0, 0, 0, 0);
+		Point size= getSize();
+		Rectangle clientArea= getClientArea();
+
+		ScrollBar horizontal= getHorizontalBar();
+		if (bounds.width <= clientArea.width) {
+			horizontal.setVisible(false);
+			horizontal.setSelection(0);
+		} else {
+			horizontal.setPageIncrement(clientArea.width - horizontal.getIncrement());
+			int max= bounds.width + (size.x - clientArea.width);
+			horizontal.setMaximum(max);
+			horizontal.setThumb(size.x > max ? max : size.x);
+			horizontal.setVisible(true);
+		}
+
+		ScrollBar vertical= getVerticalBar();
+		if (bounds.height <= clientArea.height) {
+			vertical.setVisible(false);
+			vertical.setSelection(0);
+		} else {
+			vertical.setPageIncrement(clientArea.height - vertical.getIncrement());
+			int max= bounds.height + (size.y - clientArea.height);
+			vertical.setMaximum(max);
+			vertical.setThumb(size.y > max ? max : size.y);
+			vertical.setVisible(true);
+		}
+	}
+
+}