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/*******************************************************************************
* Copyright (c) 2000, 2017 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.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, e -> repaint());
sb= getVerticalBar();
sb.setIncrement(20);
sb.addListener(SWT.Selection, e -> repaint());
addListener(SWT.Resize, e -> updateScrollbars());
addListener(SWT.Paint, 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();
}
}
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
*/
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);
}
}
}
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