com.sun.javafx.scene.traversal.TraversalEngine Maven / Gradle / Ivy
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package com.sun.javafx.scene.traversal;
import com.sun.javafx.application.PlatformImpl;
import com.sun.javafx.scene.NodeHelper;
import javafx.geometry.BoundingBox;
import javafx.geometry.Bounds;
import javafx.scene.Node;
import javafx.scene.Parent;
import java.util.ArrayList;
import java.util.List;
/**
* This is abstract class for a traversal engine. There are 2 types : {@link com.sun.javafx.scene.traversal.ParentTraversalEngine}
* to be used in {@link Parent#setTraversalEngine(ParentTraversalEngine)} to override default behavior
* and {@link com.sun.javafx.scene.traversal.TopMostTraversalEngine} that is the default traversal engine for scene and subscene.
*
* Every engine is basically a wrapper of an algorithm + some specific parent (or scene/subscene), which define engine's root.
*/
public abstract class TraversalEngine{
/**
* This is the default algorithm for the running platform. It's the algorithm that's used in TopMostTraversalEngine
*/
static final Algorithm DEFAULT_ALGORITHM = PlatformImpl.isContextual2DNavigation() ? new Hueristic2D() : new ContainerTabOrder();
private final TraversalContext context = new EngineContext(); // This is the context used in calls to this engine's algorithm
// This is a special context that's used when invoking select "callbacks" to default algorithm in other contexts
private final TempEngineContext tempEngineContext = new TempEngineContext();
protected final Algorithm algorithm;
private final Bounds initialBounds = new BoundingBox(0, 0, 1, 1);
private final ArrayList listeners = new ArrayList<>();
/**
* Creates engine with the specified algorithm
* @param algorithm
*/
protected TraversalEngine(Algorithm algorithm) {
this.algorithm = algorithm;
}
/**
* Creates engine with no algorithm. This makes all the select* calls invalid.
* @see #canTraverse()
*/
protected TraversalEngine() {
this.algorithm = null;
}
/**
* Add a listener to traversal engine. The listener is notified whenever focus is changed by traversal inside the associated scene or parent.
* This can be used with ParentTraversalEngine that has no algorithm to observe changes to the focus inside the parent.
* @param listener
*/
public final void addTraverseListener(TraverseListener listener) {
listeners.add(listener);
}
/**
* Fire notifications for listeners. This is called from the TopMostTraversalEngine
* @param newNode the node which has been focused
*/
final void notifyTraversedTo(Node newNode) {
for (TraverseListener l : listeners) {
l.onTraverse(newNode, getLayoutBounds(newNode, getRoot()));
}
}
/**
* Returns the node that is in the direction {@code dir} starting from the Node {@code from} using the engine's algorithm.
* Null means there is no Node in that direction
* @param from the node to start traversal from
* @param dir the direction of traversal
* @return the subsequent node in the specified direction or null if none
* @throws java.lang.NullPointerException if there is no algorithm
*/
public final Node select(Node from, Direction dir) {
return algorithm.select(from, dir, context);
}
/**
* Returns the first node in this engine's context (scene/parent) using the engine's algorithm.
* This can be null only if there are no traversable nodes
* @return The first node or null if none exists
* @throws java.lang.NullPointerException if there is no algorithm
*/
public final Node selectFirst() {
return algorithm.selectFirst(context);
}
/**
* Returns the last node in this engine's context (scene/parent) using the engine's algorithm.
* This can be null only if there are no traversable nodes
* @return The last node or null if none exists
* @throws java.lang.NullPointerException if there is no algorithm
*/
public final Node selectLast() {
return algorithm.selectLast(context);
}
/**
* The root of this engine's context. This is the node that is the root of the tree that is traversed by this engine.
* @return This engine's root
*/
protected abstract Parent getRoot();
/**
* Returns true only if there's specified algorithm for this engine. Otherwise, this engine cannot be used for traversal.
* The engine might be still useful however, e.g. for listening on traversal changes.
* @return
*/
public final boolean canTraverse() {
return algorithm != null;
}
/**
* Gets the appropriate bounds for the given node, transformed into
* the scene's or the specified node's coordinates.
* @return bounds of node in {@code forParent} coordinates or scene coordinates if {@code forParent} is null
*/
private Bounds getLayoutBounds(Node n, Parent forParent) {
final Bounds bounds;
if (n != null) {
if (forParent == null) {
bounds = n.localToScene(n.getLayoutBounds());
} else {
bounds = forParent.sceneToLocal(n.localToScene(n.getLayoutBounds()));
}
} else {
bounds = initialBounds;
}
return bounds;
}
// This is the engine context passed algorithm on select calls
private final class EngineContext extends BaseEngineContext {
@Override
public Parent getRoot() {
return TraversalEngine.this.getRoot();
}
}
// This is the engine context passed to algorithm on select callbacks from other contexts.
// It can change the root to the node defined in "selectFirstInParent", "selectLastInParent" or
// "selectInSubtree" methods
private final class TempEngineContext extends BaseEngineContext {
private Parent root;
@Override
public Parent getRoot() {
return root;
}
public void setRoot(Parent root) {
this.root = root;
}
}
/**
* The base class for all engine contexts
*/
private abstract class BaseEngineContext implements TraversalContext {
/**
* Returns all traversable nodes in the context's (engine's) root
*/
@Override
public List getAllTargetNodes() {
final List targetNodes = new ArrayList<>();
addFocusableChildrenToList(targetNodes, getRoot());
return targetNodes;
}
@Override
public Bounds getSceneLayoutBounds(Node n) {
return getLayoutBounds(n, null);
}
private void addFocusableChildrenToList(List list, Parent parent) {
List parentsNodes = parent.getChildrenUnmodifiable();
for (Node n : parentsNodes) {
if (n.isFocusTraversable() && !n.isFocused() && NodeHelper.isTreeVisible(n) && !n.isDisabled()) {
list.add(n);
}
if (n instanceof Parent) {
addFocusableChildrenToList(list, (Parent)n);
}
}
}
// All of the methods below are callbacks from traversal context to the default algorithm.
// They can be used to obtain "default" result for the specified subtree.
// This is useful when there is some algorithm that overrides behavior for a Parent but parent's children
// should be again traversed by default algorithm.
@Override
public Node selectFirstInParent(Parent parent) {
tempEngineContext.setRoot(parent);
return DEFAULT_ALGORITHM.selectFirst(tempEngineContext);
}
@Override
public Node selectLastInParent(Parent parent) {
tempEngineContext.setRoot(parent);
return DEFAULT_ALGORITHM.selectLast(tempEngineContext);
}
@Override
public Node selectInSubtree(Parent subTreeRoot, Node from, Direction dir) {
tempEngineContext.setRoot(subTreeRoot);
return DEFAULT_ALGORITHM.select(from, dir, tempEngineContext);
}
}
}
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