/** Returns the cost of children only, not including the {@linkplain #tile} in this node. */
private long childrenCost() {
long c = 0;
SelectedNode child = (SelectedNode) firstChildren();
while (child != null) {
c += child.cost;
child = (SelectedNode) child.nextSibling();
}
assert cost >= c;
return c;
}
/** Removes all children. */
@Override
public void removeChildren() {
final long removed = childrenCost();
if (removed != 0) {
SelectedNode parent = this;
do {
parent.cost -= removed;
} while ((parent = (SelectedNode) parent.getParent()) != null);
}
super.removeChildren();
}
/**
* Removes all children from the given map. Note that we do not removes this node directly because
* the corresponding Map.Entry is presumed already used by an other node.
*/
private void removeFrom(final Map<Rectangle, SelectedNode> overlaps) {
SelectedNode child = (SelectedNode) firstChildren();
while (child != null) {
child.removeFrom(overlaps);
final SelectedNode existing = overlaps.remove(child);
if (existing != null && existing != child) {
overlaps.put(existing, existing);
}
child = (SelectedNode) child.nextSibling();
}
}
/**
* Adds the given tile as a child of this tile.
*
* @throws ClassCastException if the given child is not an instance of {@code SelectedNode}. This
* is an intentional restriction in order to avoid more subtile bugs later.
*/
@Override
public void addChild(final TreeNode child) throws ClassCastException {
super.addChild(child);
if (child != null) {
final long added = ((SelectedNode) child).cost;
if (added != 0) {
SelectedNode parent = this;
do {
parent.cost += added;
} while ((parent = (SelectedNode) parent.getParent()) != null);
}
}
}
/** Returns {@code true} if this node has a lower cost than the specified one. */
public final boolean isCheaperThan(final SelectedNode other) {
if (cost < other.cost) {
return true;
}
if (cost == other.cost) {
return getTileCount() < other.getTileCount();
}
return false;
}
/**
* Removes the nodes having the same bounding box than this tile, then process recursively for
* children. If such matchs are found, they are probably tiles at a different resolution. Retains
* the one which minimize the disk reading, and discards the other ones.
*
* <p>This check is not generic since we search for an exact match, but this case is common
* enough. Handling it with a {@link java.util.HashMap} will help to reduce the amount of tiles to
* handle in a more costly way later.
*
* <p>As a side effect, this method trims the bounding box of selected nodes to the tiles that
* they contain.
*
* @param overlaps An initially empty map. Will be filled through recursive invocation of this
* method while we iterate down the tree.
*/
final void removeTrivialOverlaps(final Map<Rectangle, SelectedNode> overlaps) {
/*
* Must process children first because if any of them are removed, it will lower
* the cost and consequently can change the decision taken at the end of this method.
*/
SelectedNode child = (SelectedNode) firstChildren();
while (child != null) {
// Must ask for next sibling before to filter since the later
// may set it to null if the child is removed from the tree.
final SelectedNode next = (SelectedNode) child.nextSibling();
child.removeTrivialOverlaps(overlaps);
child = next;
}
/*
* If this node is just a container for other nodes, trims the bounding box to the tiles
* that it contains. We would not need to do that if the size of parent nodes was always
* a multiple of child nodes. But sometime they are not, in which case some child nodes
* may live on the boundary between two parent nodes. It is not easy to predict in which
* parent such child will end up and what will be its bounding box since the computation
* involves intersection, but the end result is that two parents may have identical bbox
* while their child do not overlaps at all.
*
* We don't perform this computation if this node contains a tile, because in such case
* we assume that the bounding box was carefully choosen by the user. This is different
* than a null tile in which case the bounding box was calculated by our code.
*/
if (tile == null) {
child = (SelectedNode) firstChildren();
if (child != null) {
int xmin = x, ymin = y, w = width, h = height;
width = height = -1;
do {
assert !child.isEmpty() : child;
add(child);
child = (SelectedNode) child.nextSibling();
} while (child != null);
if (x < xmin) {
w -= (xmin - x);
x = xmin;
}
if (y < ymin) {
h -= (ymin - y);
y = ymin;
}
if (width > w) width = w;
if (height > h) height = h;
}
}
/*
* Now searchs for overlaps.
*/
SelectedNode existing = overlaps.put(this, this);
if (existing != null && existing != this) {
if (!isCheaperThan(existing)) {
/*
* A cheaper tiles existed for the same bounds. Reinsert the previous tile in the
* map. We will delete this node from the tree later, except if the previous node
* is a children of this node. In the later case, we can't remove completly this
* node since it would remove its children as well, so we just nullify the tile.
*/
if (existing.getParent() == this) {
if (tile != null) {
tile = null;
cost = childrenCost();
}
return;
}
overlaps.put(existing, existing);
existing = this;
}
existing.remove();
existing.removeFrom(overlaps);
assert overlaps.get(existing) != existing;
}
}
