JViewport.
* ViewportLayout defines
* a policy for layout that should be useful for most applications.
* The viewport makes its view the same size as the viewport,
* however it will not make the view smaller than its minimum size.
* As the viewport grows the view is kept bottom justified until
* the entire view is visible, subsequently the view is kept top
* justified.
*
* Warning:
* Serialized objects of this class will not be compatible with
* future Swing releases. The current serialization support is
* appropriate for short term storage or RMI between applications running
* the same version of Swing. As of 1.4, support for long term storage
* of all JavaBeans™
* has been added to the java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*
* @author Hans Muller
*/
@SuppressWarnings("serial") // Same-version serialization only
public class ViewportLayout implements LayoutManager, Serializable
{
// Single instance used by JViewport.
static ViewportLayout SHARED_INSTANCE = new ViewportLayout();
/**
* Adds the specified component to the layout. Not used by this class.
* @param name the name of the component
* @param c the the component to be added
*/
public void addLayoutComponent(String name, Component c) { }
/**
* Removes the specified component from the layout. Not used by
* this class.
* @param c the component to remove
*/
public void removeLayoutComponent(Component c) { }
/**
* Returns the preferred dimensions for this layout given the components
* in the specified target container.
* @param parent the component which needs to be laid out
* @return a Dimension object containing the
* preferred dimensions
* @see #minimumLayoutSize
*/
public Dimension preferredLayoutSize(Container parent) {
Component view = ((JViewport)parent).getView();
if (view == null) {
return new Dimension(0, 0);
}
else if (view instanceof Scrollable) {
return ((Scrollable)view).getPreferredScrollableViewportSize();
}
else {
return view.getPreferredSize();
}
}
/**
* Returns the minimum dimensions needed to layout the components
* contained in the specified target container.
*
* @param parent the component which needs to be laid out
* @return a Dimension object containing the minimum
* dimensions
* @see #preferredLayoutSize
*/
public Dimension minimumLayoutSize(Container parent) {
return new Dimension(4, 4);
}
/**
* Called by the AWT when the specified container needs to be laid out.
*
* @param parent the container to lay out
*
* @throws AWTError if the target isn't the container specified to the
* BoxLayout constructor
*/
public void layoutContainer(Container parent)
{
JViewport vp = (JViewport)parent;
Component view = vp.getView();
Scrollable scrollableView = null;
if (view == null) {
return;
}
else if (view instanceof Scrollable) {
scrollableView = (Scrollable) view;
}
/* All of the dimensions below are in view coordinates, except
* vpSize which we're converting.
*/
Insets insets = vp.getInsets();
Dimension viewPrefSize = view.getPreferredSize();
Dimension vpSize = vp.getSize();
Dimension extentSize = vp.toViewCoordinates(vpSize);
Dimension viewSize = new Dimension(viewPrefSize);
if (scrollableView != null) {
if (scrollableView.getScrollableTracksViewportWidth()) {
viewSize.width = vpSize.width;
}
if (scrollableView.getScrollableTracksViewportHeight()) {
viewSize.height = vpSize.height;
}
}
Point viewPosition = vp.getViewPosition();
/* If the new viewport size would leave empty space to the
* right of the view, right justify the view or left justify
* the view when the width of the view is smaller than the
* container.
*/
if (scrollableView == null ||
vp.getParent() == null ||
vp.getParent().getComponentOrientation().isLeftToRight()) {
if ((viewPosition.x + extentSize.width) > viewSize.width) {
viewPosition.x = Math.max(0, viewSize.width - extentSize.width);
}
} else {
if (extentSize.width > viewSize.width) {
viewPosition.x = viewSize.width - extentSize.width;
} else {
viewPosition.x = Math.max(0, Math.min(viewSize.width - extentSize.width, viewPosition.x));
}
}
/* If the new viewport size would leave empty space below the
* view, bottom justify the view or top justify the view when
* the height of the view is smaller than the container.
*/
if ((viewPosition.y + extentSize.height) > viewSize.height) {
viewPosition.y = Math.max(0, viewSize.height - extentSize.height);
}
/* If we haven't been advised about how the viewports size
* should change wrt to the viewport, i.e. if the view isn't
* an instance of Scrollable, then adjust the views size as follows.
*
* If the origin of the view is showing and the viewport is
* bigger than the views preferred size, then make the view
* the same size as the viewport.
*/
if (scrollableView == null) {
if ((viewPosition.x == 0) && (vpSize.width > viewPrefSize.width)) {
viewSize.width = vpSize.width;
}
if ((viewPosition.y == 0) && (vpSize.height > viewPrefSize.height)) {
viewSize.height = vpSize.height;
}
}
vp.setViewPosition(viewPosition);
vp.setViewSize(viewSize);
}
}