launcher3/celllayout/ReorderAlgorithm.java

/*
 * Copyright (C) 2023 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.launcher3.celllayout;

import android.graphics.Rect;
import android.view.View;

import com.android.launcher3.CellLayout;
import com.android.launcher3.util.CellAndSpan;
import com.android.launcher3.util.GridOccupancy;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Map.Entry;
import java.util.stream.Collectors;

/**
 * Contains the logic of a reorder.
 *
 * The content of this class was extracted from {@link CellLayout} and should mimic the exact
 * same behaviour.
 */
public class ReorderAlgorithm {

    CellLayout mCellLayout;

    public ReorderAlgorithm(CellLayout cellLayout) {
        mCellLayout = cellLayout;
    }

    /**
     * This method differs from closestEmptySpaceReorder and dropInPlaceSolution because this method
     * will move items around and will change the shape of the item if possible to try to find a
     * solution.
     * <p>
     * When changing the size of the widget this method will try first subtracting -1 in the x
     * dimension and then subtracting -1 in the y dimension until finding a possible solution or
     * until it no longer can reduce the span.
     * @param decX     whether it will decrease the horizontal or vertical span if it can't find a
     *                 solution for the current span.
     * @return the same solution variable
     */
    public ItemConfiguration findReorderSolution(ReorderParameters reorderParameters,
            boolean decX) {
        return findReorderSolution(reorderParameters, mCellLayout.mDirectionVector, decX);
    }

    /**
     * This method differs from closestEmptySpaceReorder and dropInPlaceSolution because this method
     * will move items around and will change the shape of the item if possible to try to find a
     * solution.
     * <p>
     * When changing the size of the widget this method will try first subtracting -1 in the x
     * dimension and then subtracting -1 in the y dimension until finding a possible solution or
     * until it no longer can reduce the span.
     * @param direction Direction to attempt to push items if needed
     * @param decX     whether it will decrease the horizontal or vertical span if it can't find a
     *                 solution for the current span.
     * @return the same solution variable
     */
    public ItemConfiguration findReorderSolution(ReorderParameters reorderParameters,
            int[] direction, boolean decX) {
        return findReorderSolutionRecursive(reorderParameters.getPixelX(),
                reorderParameters.getPixelY(), reorderParameters.getMinSpanX(),
                reorderParameters.getMinSpanY(), reorderParameters.getSpanX(),
                reorderParameters.getSpanY(), direction,
                reorderParameters.getDragView(), decX, reorderParameters.getSolution());
    }

    private ItemConfiguration findReorderSolutionRecursive(int pixelX, int pixelY, int minSpanX,
            int minSpanY, int spanX, int spanY, int[] direction, View dragView, boolean decX,
            ItemConfiguration solution) {
        // Copy the current state into the solution. This solution will be manipulated as necessary.
        mCellLayout.copyCurrentStateToSolution(solution);
        // Copy the current occupied array into the temporary occupied array. This array will be
        // manipulated as necessary to find a solution.
        mCellLayout.getOccupied().copyTo(mCellLayout.mTmpOccupied);

        // We find the nearest cell into which we would place the dragged item, assuming there's
        // nothing in its way.
        int[] result = new int[2];
        result = mCellLayout.findNearestAreaIgnoreOccupied(pixelX, pixelY, spanX, spanY, result);

        boolean success;
        // First we try the exact nearest position of the item being dragged,
        // we will then want to try to move this around to other neighbouring positions
        success = rearrangementExists(result[0], result[1], spanX, spanY, direction, dragView,
                solution);

        if (!success) {
            // We try shrinking the widget down to size in an alternating pattern, shrink 1 in
            // x, then 1 in y etc.
            if (spanX > minSpanX && (minSpanY == spanY || decX)) {
                return findReorderSolutionRecursive(pixelX, pixelY, minSpanX, minSpanY, spanX - 1,
                        spanY, direction, dragView, false, solution);
            } else if (spanY > minSpanY) {
                return findReorderSolutionRecursive(pixelX, pixelY, minSpanX, minSpanY, spanX,
                        spanY - 1, direction, dragView, true, solution);
            }
            solution.isSolution = false;
        } else {
            solution.isSolution = true;
            solution.cellX = result[0];
            solution.cellY = result[1];
            solution.spanX = spanX;
            solution.spanY = spanY;
        }
        return solution;
    }

    private boolean rearrangementExists(int cellX, int cellY, int spanX, int spanY, int[] direction,
            View ignoreView, ItemConfiguration solution) {
        // Return early if get invalid cell positions
        if (cellX < 0 || cellY < 0) return false;

        ArrayList<View> intersectingViews = new ArrayList<>();
        Rect occupiedRect = new Rect(cellX, cellY, cellX + spanX, cellY + spanY);

        // Mark the desired location of the view currently being dragged.
        if (ignoreView != null) {
            CellAndSpan c = solution.map.get(ignoreView);
            if (c != null) {
                c.cellX = cellX;
                c.cellY = cellY;
            }
        }
        Rect r0 = new Rect(cellX, cellY, cellX + spanX, cellY + spanY);
        Rect r1 = new Rect();
        // The views need to be sorted so that the results are deterministic on the views positions
        // and not by the views hash which is "random".
        // The views are sorted twice, once for the X position and a second time for the Y position
        // to ensure same order everytime.
        Comparator<View> comparator = Comparator.comparing(
                (View view) -> ((CellLayoutLayoutParams) view.getLayoutParams()).getCellX()
        ).thenComparing(
                (View view) -> ((CellLayoutLayoutParams) view.getLayoutParams()).getCellY()
        );
        List<View> views = solution.map.keySet().stream()
                .sorted(comparator)
                .collect(Collectors.toList());
        for (View child : views) {
            if (child == ignoreView) continue;
            CellAndSpan c = solution.map.get(child);
            CellLayoutLayoutParams lp = (CellLayoutLayoutParams) child.getLayoutParams();
            r1.set(c.cellX, c.cellY, c.cellX + c.spanX, c.cellY + c.spanY);
            if (Rect.intersects(r0, r1)) {
                if (!lp.canReorder) {
                    return false;
                }
                intersectingViews.add(child);
            }
        }

        solution.intersectingViews = intersectingViews;

        // First we try to find a solution which respects the push mechanic. That is,
        // we try to find a solution such that no displaced item travels through another item
        // without also displacing that item.
        if (attemptPushInDirection(intersectingViews, occupiedRect, direction, ignoreView,
                solution)) {
            return true;
        }

        // Next we try moving the views as a block, but without requiring the push mechanic.
        if (addViewsToTempLocation(intersectingViews, occupiedRect, direction, ignoreView,
                solution)) {
            return true;
        }

        // Ok, they couldn't move as a block, let's move them individually
        for (View v : intersectingViews) {
            if (!addViewToTempLocation(v, occupiedRect, direction, solution)) {
                return false;
            }
        }
        return true;
    }

    private boolean addViewToTempLocation(View v, Rect rectOccupiedByPotentialDrop, int[] direction,
            ItemConfiguration currentState) {
        CellAndSpan c = currentState.map.get(v);
        boolean success = false;
        mCellLayout.mTmpOccupied.markCells(c, false);
        mCellLayout.mTmpOccupied.markCells(rectOccupiedByPotentialDrop, true);

        int[] tmpLocation = findNearestArea(c.cellX, c.cellY, c.spanX, c.spanY, direction,
                mCellLayout.mTmpOccupied.cells, null, new int[2]);

        if (tmpLocation[0] >= 0 && tmpLocation[1] >= 0) {
            c.cellX = tmpLocation[0];
            c.cellY = tmpLocation[1];
            success = true;
        }
        mCellLayout.mTmpOccupied.markCells(c, true);
        return success;
    }

    private boolean pushViewsToTempLocation(ArrayList<View> views, Rect rectOccupiedByPotentialDrop,
            int[] direction, View dragView, ItemConfiguration currentState) {

        ViewCluster cluster = new ViewCluster(mCellLayout, views, currentState);
        Rect clusterRect = cluster.getBoundingRect();
        int whichEdge;
        int pushDistance;
        boolean fail = false;

        // Determine the edge of the cluster that will be leading the push and how far
        // the cluster must be shifted.
        if (direction[0] < 0) {
            whichEdge = ViewCluster.LEFT;
            pushDistance = clusterRect.right - rectOccupiedByPotentialDrop.left;
        } else if (direction[0] > 0) {
            whichEdge = ViewCluster.RIGHT;
            pushDistance = rectOccupiedByPotentialDrop.right - clusterRect.left;
        } else if (direction[1] < 0) {
            whichEdge = ViewCluster.TOP;
            pushDistance = clusterRect.bottom - rectOccupiedByPotentialDrop.top;
        } else {
            whichEdge = ViewCluster.BOTTOM;
            pushDistance = rectOccupiedByPotentialDrop.bottom - clusterRect.top;
        }

        // Break early for invalid push distance.
        if (pushDistance <= 0) {
            return false;
        }

        // Mark the occupied state as false for the group of views we want to move.
        for (View v : views) {
            CellAndSpan c = currentState.map.get(v);
            mCellLayout.mTmpOccupied.markCells(c, false);
        }

        // We save the current configuration -- if we fail to find a solution we will revert
        // to the initial state. The process of finding a solution modifies the configuration
        // in place, hence the need for revert in the failure case.
        currentState.save();

        // The pushing algorithm is simplified by considering the views in the order in which
        // they would be pushed by the cluster. For example, if the cluster is leading with its
        // left edge, we consider sort the views by their right edge, from right to left.
        cluster.sortConfigurationForEdgePush(whichEdge);

        while (pushDistance > 0 && !fail) {
            for (View v : currentState.sortedViews) {
                // For each view that isn't in the cluster, we see if the leading edge of the
                // cluster is contacting the edge of that view. If so, we add that view to the
                // cluster.
                if (!cluster.views.contains(v) && v != dragView) {
                    if (cluster.isViewTouchingEdge(v, whichEdge)) {
                        CellLayoutLayoutParams lp = (CellLayoutLayoutParams) v.getLayoutParams();
                        if (!lp.canReorder) {
                            // The push solution includes the all apps button, this is not viable.
                            fail = true;
                            break;
                        }
                        cluster.addView(v);
                        CellAndSpan c = currentState.map.get(v);

                        // Adding view to cluster, mark it as not occupied.
                        mCellLayout.mTmpOccupied.markCells(c, false);
                    }
                }
            }
            pushDistance--;

            // The cluster has been completed, now we move the whole thing over in the appropriate
            // direction.
            cluster.shift(whichEdge, 1);
        }

        boolean foundSolution = false;
        clusterRect = cluster.getBoundingRect();

        // Due to the nature of the algorithm, the only check required to verify a valid solution
        // is to ensure that completed shifted cluster lies completely within the cell layout.
        if (!fail && clusterRect.left >= 0 && clusterRect.right <= mCellLayout.getCountX()
                && clusterRect.top >= 0 && clusterRect.bottom <= mCellLayout.getCountY()) {
            foundSolution = true;
        } else {
            currentState.restore();
        }

        // In either case, we set the occupied array as marked for the location of the views
        for (View v : cluster.views) {
            CellAndSpan c = currentState.map.get(v);
            mCellLayout.mTmpOccupied.markCells(c, true);
        }

        return foundSolution;
    }

    private void revertDir(int[] direction) {
        direction[0] *= -1;
        direction[1] *= -1;
    }

    // This method tries to find a reordering solution which satisfies the push mechanic by trying
    // to push items in each of the cardinal directions, in an order based on the direction vector
    // passed.
    private boolean attemptPushInDirection(ArrayList<View> intersectingViews, Rect occupied,
            int[] direction, View ignoreView, ItemConfiguration solution) {
        if ((Math.abs(direction[0]) + Math.abs(direction[1])) > 1) {
            // If the direction vector has two non-zero components, we try pushing
            // separately in each of the components.
            int temp;
            for (int j = 0; j < 2; j++) {
                for (int i = 1; i >= 0; i--) {
                    temp = direction[i];
                    direction[i] = 0;
                    if (pushViewsToTempLocation(intersectingViews, occupied, direction, ignoreView,
                            solution)) {
                        return true;
                    }
                    direction[i] = temp;
                }
                revertDir(direction);
            }
        } else {
            // If the direction vector has a single non-zero component, we push first in the
            // direction of the vector
            int temp;
            for (int j = 0; j < 2; j++) {
                for (int i = 0; i < 2; i++) {
                    if (pushViewsToTempLocation(intersectingViews, occupied, direction, ignoreView,
                            solution)) {
                        return true;
                    }
                    revertDir(direction);
                }
                // Swap the components
                temp = direction[1];
                direction[1] = direction[0];
                direction[0] = temp;
            }
        }
        return false;
    }

    private boolean addViewsToTempLocation(ArrayList<View> views, Rect rectOccupiedByPotentialDrop,
            int[] direction, View dragView, ItemConfiguration currentState) {
        if (views.isEmpty()) return true;

        boolean success = false;
        Rect boundingRect = new Rect();
        // We construct a rect which represents the entire group of views passed in
        currentState.getBoundingRectForViews(views, boundingRect);

        // Mark the occupied state as false for the group of views we want to move.
        for (View v : views) {
            CellAndSpan c = currentState.map.get(v);
            mCellLayout.mTmpOccupied.markCells(c, false);
        }

        GridOccupancy blockOccupied = new GridOccupancy(boundingRect.width(),
                boundingRect.height());
        int top = boundingRect.top;
        int left = boundingRect.left;
        // We mark more precisely which parts of the bounding rect are truly occupied, allowing
        // for interlocking.
        for (View v : views) {
            CellAndSpan c = currentState.map.get(v);
            blockOccupied.markCells(c.cellX - left, c.cellY - top, c.spanX, c.spanY, true);
        }

        mCellLayout.mTmpOccupied.markCells(rectOccupiedByPotentialDrop, true);

        int[] tmpLocation = findNearestArea(boundingRect.left, boundingRect.top,
                boundingRect.width(), boundingRect.height(), direction,
                mCellLayout.mTmpOccupied.cells, blockOccupied.cells, new int[2]);

        // If we successfully found a location by pushing the block of views, we commit it
        if (tmpLocation[0] >= 0 && tmpLocation[1] >= 0) {
            int deltaX = tmpLocation[0] - boundingRect.left;
            int deltaY = tmpLocation[1] - boundingRect.top;
            for (View v : views) {
                CellAndSpan c = currentState.map.get(v);
                c.cellX += deltaX;
                c.cellY += deltaY;
            }
            success = true;
        }

        // In either case, we set the occupied array as marked for the location of the views
        for (View v : views) {
            CellAndSpan c = currentState.map.get(v);
            mCellLayout.mTmpOccupied.markCells(c, true);
        }
        return success;
    }

    /**
     * Returns a "reorder" if there is empty space without rearranging anything.
     *
     * @return the configuration that represents the found reorder
     */
    public ItemConfiguration dropInPlaceSolution(ReorderParameters reorderParameters) {
        int[] result = mCellLayout.findNearestAreaIgnoreOccupied(reorderParameters.getPixelX(),
                reorderParameters.getPixelY(), reorderParameters.getSpanX(),
                reorderParameters.getSpanY(), new int[2]);
        ItemConfiguration solution = new ItemConfiguration();
        mCellLayout.copyCurrentStateToSolution(solution);

        solution.isSolution = !isConfigurationRegionOccupied(
                new Rect(result[0], result[1], result[0] + reorderParameters.getSpanX(),
                        result[1] + reorderParameters.getSpanY()), solution,
                reorderParameters.getDragView());
        if (!solution.isSolution) {
            return solution;
        }
        solution.cellX = result[0];
        solution.cellY = result[1];
        solution.spanX = reorderParameters.getSpanX();
        solution.spanY = reorderParameters.getSpanY();
        return solution;
    }

    private boolean isConfigurationRegionOccupied(Rect region, ItemConfiguration configuration,
            View ignoreView) {
        return configuration.map
                .entrySet()
                .stream()
                .filter(entry -> entry.getKey() != ignoreView)
                .map(Entry::getValue)
                .anyMatch(cellAndSpan -> region.intersect(
                        cellAndSpan.cellX,
                        cellAndSpan.cellY,
                        cellAndSpan.cellX + cellAndSpan.spanX,
                        cellAndSpan.cellY + cellAndSpan.spanY
                        )
                );
    }

    /**
     * Returns a "reorder" where we simply drop the item in the closest empty space, without moving
     * any other item in the way.
     *
     * @return the configuration that represents the found reorder
     */
    public ItemConfiguration closestEmptySpaceReorder(ReorderParameters reorderParameters) {
        ItemConfiguration solution = new ItemConfiguration();
        int[] result = new int[2];
        int[] resultSpan = new int[2];
        mCellLayout.findNearestVacantArea(reorderParameters.getPixelX(),
                reorderParameters.getPixelY(), reorderParameters.getMinSpanX(),
                reorderParameters.getMinSpanY(), reorderParameters.getSpanX(),
                reorderParameters.getSpanY(), result, resultSpan);
        if (result[0] >= 0 && result[1] >= 0) {
            mCellLayout.copyCurrentStateToSolution(solution);
            solution.cellX = result[0];
            solution.cellY = result[1];
            solution.spanX = resultSpan[0];
            solution.spanY = resultSpan[1];
            solution.isSolution = true;
        } else {
            solution.isSolution = false;
        }
        return solution;
    }

    /**
     * When the user drags an Item in the workspace sometimes we need to move the items already in
     * the workspace to make space for the new item, this function return a solution for that
     * reorder.
     *
     * @return returns a solution for the given parameters, the solution contains all the icons and
     * the locations they should be in the given solution.
     */
    public ItemConfiguration calculateReorder(ReorderParameters reorderParameters) {
        getDirectionVectorForDrop(reorderParameters, mCellLayout.mDirectionVector);

        ItemConfiguration dropInPlaceSolution = dropInPlaceSolution(reorderParameters);

        // Find a solution involving pushing / displacing any items in the way
        ItemConfiguration swapSolution = findReorderSolution(reorderParameters, true);

        // We attempt the approach which doesn't shuffle views at all
        ItemConfiguration closestSpaceSolution = closestEmptySpaceReorder(reorderParameters);

        // If the reorder solution requires resizing (shrinking) the item being dropped, we instead
        // favor a solution in which the item is not resized, but
        if (swapSolution.isSolution && swapSolution.area() >= closestSpaceSolution.area()) {
            return swapSolution;
        } else if (closestSpaceSolution.isSolution) {
            return closestSpaceSolution;
        } else if (dropInPlaceSolution.isSolution) {
            return dropInPlaceSolution;
        }
        return null;
    }

    /*
     * Returns a pair (x, y), where x,y are in {-1, 0, 1} corresponding to vector between
     * the provided point and the provided cell
     */
    private void computeDirectionVector(float deltaX, float deltaY, int[] result) {
        double angle = Math.atan(deltaY / deltaX);

        result[0] = 0;
        result[1] = 0;
        if (Math.abs(Math.cos(angle)) > 0.5f) {
            result[0] = (int) Math.signum(deltaX);
        }
        if (Math.abs(Math.sin(angle)) > 0.5f) {
            result[1] = (int) Math.signum(deltaY);
        }
    }

    /**
     * This seems like it should be obvious and straight-forward, but when the direction vector
     * needs to match with the notion of the dragView pushing other views, we have to employ
     * a slightly more subtle notion of the direction vector. The question is what two points is
     * the vector between? The center of the dragView and its desired destination? Not quite, as
     * this doesn't necessarily coincide with the interaction of the dragView and items occupying
     * those cells. Instead we use some heuristics to often lock the vector to up, down, left
     * or right, which helps make pushing feel right.
     */
    public void getDirectionVectorForDrop(ReorderParameters reorderParameters,
            int[] resultDirection) {

        //TODO(adamcohen) b/151776141 use the items visual center for the direction vector
        int[] targetDestination = new int[2];

        mCellLayout.findNearestAreaIgnoreOccupied(reorderParameters.getPixelX(),
                reorderParameters.getPixelY(), reorderParameters.getSpanX(),
                reorderParameters.getSpanY(), targetDestination);
        Rect dragRect = new Rect();
        mCellLayout.cellToRect(targetDestination[0], targetDestination[1],
                reorderParameters.getSpanX(), reorderParameters.getSpanY(), dragRect);
        dragRect.offset(reorderParameters.getPixelX() - dragRect.centerX(),
                reorderParameters.getPixelY() - dragRect.centerY());

        Rect region = new Rect(targetDestination[0], targetDestination[1],
                targetDestination[0] + reorderParameters.getSpanX(),
                targetDestination[1] + reorderParameters.getSpanY());
        Rect dropRegionRect = mCellLayout.getIntersectingRectanglesInRegion(region,
                reorderParameters.getDragView());
        if (dropRegionRect == null) dropRegionRect = new Rect(region);

        int dropRegionSpanX = dropRegionRect.width();
        int dropRegionSpanY = dropRegionRect.height();

        mCellLayout.cellToRect(dropRegionRect.left, dropRegionRect.top, dropRegionRect.width(),
                dropRegionRect.height(), dropRegionRect);

        int deltaX = (dropRegionRect.centerX() - reorderParameters.getPixelX())
                / reorderParameters.getSpanX();
        int deltaY = (dropRegionRect.centerY() - reorderParameters.getPixelY())
                / reorderParameters.getSpanY();

        if (dropRegionSpanX == mCellLayout.getCountX()
                || reorderParameters.getSpanX() == mCellLayout.getCountX()) {
            deltaX = 0;
        }
        if (dropRegionSpanY == mCellLayout.getCountY()
                || reorderParameters.getSpanY() == mCellLayout.getCountY()) {
            deltaY = 0;
        }

        if (deltaX == 0 && deltaY == 0) {
            // No idea what to do, give a random direction.
            resultDirection[0] = 1;
            resultDirection[1] = 0;
        } else {
            computeDirectionVector(deltaX, deltaY, resultDirection);
        }
    }

    /**
     * Find a vacant area that will fit the given bounds nearest the requested
     * cell location, and will also weigh in a suggested direction vector of the
     * desired location. This method computers distance based on unit grid distances,
     * not pixel distances.
     *
     * @param cellX         The X cell nearest to which you want to search for a vacant area.
     * @param cellY         The Y cell nearest which you want to search for a vacant area.
     * @param spanX         Horizontal span of the object.
     * @param spanY         Vertical span of the object.
     * @param direction     The favored direction in which the views should move from x, y
     * @param occupied      The array which represents which cells in the CellLayout are occupied
     * @param blockOccupied The array which represents which cells in the specified block (cellX,
     *                      cellY, spanX, spanY) are occupied. This is used when try to move a group
     *                      of views.
     * @param result        Array in which to place the result, or null (in which case a new array
     *                      will
     *                      be allocated)
     * @return The X, Y cell of a vacant area that can contain this object,
     * nearest the requested location.
     */
    public int[] findNearestArea(int cellX, int cellY, int spanX, int spanY, int[] direction,
            boolean[][] occupied, boolean[][] blockOccupied, int[] result) {
        // Keep track of best-scoring drop area
        final int[] bestXY = result != null ? result : new int[2];
        float bestDistance = Float.MAX_VALUE;
        int bestDirectionScore = Integer.MIN_VALUE;

        final int countX = mCellLayout.getCountX();
        final int countY = mCellLayout.getCountY();

        for (int y = 0; y < countY - (spanY - 1); y++) {
            inner:
            for (int x = 0; x < countX - (spanX - 1); x++) {
                // First, let's see if this thing fits anywhere
                for (int i = 0; i < spanX; i++) {
                    for (int j = 0; j < spanY; j++) {
                        if (occupied[x + i][y + j] && (blockOccupied == null
                                || blockOccupied[i][j])) {
                            continue inner;
                        }
                    }
                }

                float distance = (float) Math.hypot(x - cellX, y - cellY);
                int[] curDirection = new int[2];
                computeDirectionVector(x - cellX, y - cellY, curDirection);
                // The direction score is just the dot product of the two candidate direction
                // and that passed in.
                int curDirectionScore =
                        direction[0] * curDirection[0] + direction[1] * curDirection[1];
                if (Float.compare(distance, bestDistance) < 0 || (Float.compare(distance,
                        bestDistance) == 0 && curDirectionScore > bestDirectionScore)) {
                    bestDistance = distance;
                    bestDirectionScore = curDirectionScore;
                    bestXY[0] = x;
                    bestXY[1] = y;
                }
            }
        }

        // Return -1, -1 if no suitable location found
        if (bestDistance == Float.MAX_VALUE) {
            bestXY[0] = -1;
            bestXY[1] = -1;
        }
        return bestXY;
    }
}