javauis/eswt_qt/org.eclipse.swt/Eclipse SWT/qt/org/eclipse/swt/widgets/Canvas.java
/*******************************************************************************
* Copyright (c) 2000, 2006 IBM Corporation and others.
* Portion Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).
* 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
* Nokia Corporation - Qt implementation
*******************************************************************************/
package org.eclipse.swt.widgets;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.internal.qt.OS;
/**
* Instances of this class provide a surface for drawing
* arbitrary graphics.
* <dl>
* <dt><b>Styles:</b></dt>
* <dd>(none)</dd>
* <dt><b>Events:</b></dt>
* <dd>(none)</dd>
* </dl>
* <p>
* This class may be subclassed by custom control implementors
* who are building controls that are <em>not</em> constructed
* from aggregates of other controls. That is, they are either
* painted using SWT graphics calls or are handled by native
* methods.
* </p>
*
* @see Composite
*/
public class Canvas extends Composite {
Canvas () {}
/**
* Constructs a new instance of this class given its parent
* and a style value describing its behavior and appearance.
* <p>
* The style value is either one of the style constants defined in
* class <code>SWT</code> which is applicable to instances of this
* class, or must be built by <em>bitwise OR</em>'ing together
* (that is, using the <code>int</code> "|" operator) two or more
* of those <code>SWT</code> style constants. The class description
* lists the style constants that are applicable to the class.
* Style bits are also inherited from superclasses.
* </p>
*
* @param parent a composite control which will be the parent of the new instance (cannot be null)
* @param style the style of control to construct
*
* @exception IllegalArgumentException <ul>
* <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
* </ul>
* @exception SWTException <ul>
* <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
* </ul>
*
* @see SWT
* @see Widget#checkSubclass
* @see Widget#getStyle
*/
public Canvas (Composite parent, int style) {
super (parent, style);
}
/**
* Scrolls a rectangular area of the receiver by first copying
* the source area to the destination and then causing the area
* of the source which is not covered by the destination to
* be repainted. Children that intersect the rectangle are
* optionally moved during the operation. In addition, outstanding
* paint events are flushed before the source area is copied to
* ensure that the contents of the canvas are drawn correctly.
*
* @param destX the x coordinate of the destination
* @param destY the y coordinate of the destination
* @param x the x coordinate of the source
* @param y the y coordinate of the source
* @param width the width of the area
* @param height the height of the area
* @param all <code>true</code>if children should be scrolled, and <code>false</code> otherwise
*
* @exception SWTException <ul>
* <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
* <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
* </ul>
*/
public void scroll (int destX, int destY, int x, int y, int width, int height, boolean all) {
checkWidget();
if (width <= 0 || height <= 0)
return;
int deltaX = destX - x, deltaY = destY - y;
if (deltaX == 0 && deltaY == 0)
return;
if (!isVisible())
return;
_update();
if(isDisposed()) return;
OS.QWidget_scroll(handle, deltaX, deltaY, x, y, width, height);
if (all) {
Control[] children = _getChildren();
for (int i = 0; i < children.length; i++) {
Control child = children[i];
Rectangle rect = child.getBounds();
if (Math.min(x + width, rect.x + rect.width) >= Math.max(x, rect.x)
&& Math.min(y + height, rect.y + rect.height) >= Math.max(
y, rect.y)) {
child.setLocation(rect.x + deltaX, rect.y + deltaY);
}
}
}
}
void setTraversalFlags_pp(int type, int key, int modifier, int character) {
// Canvas by default doesn't traverse. This is the SWT behavior and it's
// there to better support custom controls. If Canvas would traverse then a
// custom control would have to explicitly undo all unwanted key handling.
traverseDoit = false;
traverseCancel = true;
return;
}
}