/*
 * Copyright (C) 2006 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.
 */
/*
 * Revised 5/19/2010 by GORGES
 * Now supports two-dimensional view scrolling
 * http://GORGES.us
 */

package com.freerdp.freerdpcore.presentation;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.FocusFinder;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.animation.AnimationUtils;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.Scroller;

import com.freerdp.freerdpcore.R;
import android.widget.TextView;

import java.util.List;

/**
 * Layout container for a view hierarchy that can be scrolled by the user,
 * allowing it to be larger than the physical display.  A TwoDScrollView
 * is a {@link FrameLayout}, meaning you should place one child in it
 * containing the entire contents to scroll; this child may itself be a layout
 * manager with a complex hierarchy of objects.  A child that is often used
 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical
 * array of top-level items that the user can scroll through.
 * <p>
 * <p>The {@link TextView} class also
 * takes care of its own scrolling, so does not require a TwoDScrollView, but
 * using the two together is possible to achieve the effect of a text view
 * within a larger container.
 */
public class ScrollView2D extends FrameLayout
{

	static final int ANIMATED_SCROLL_GAP = 250;
	static final float MAX_SCROLL_FACTOR = 0.5f;
	private final Rect mTempRect = new Rect();
	private ScrollView2DListener scrollView2DListener = null;
	private long mLastScroll;
	private Scroller mScroller;
	private boolean scrollEnabled = true;
	/**
	 * Flag to indicate that we are moving focus ourselves. This is so the
	 * code that watches for focus changes initiated outside this TwoDScrollView
	 * knows that it does not have to do anything.
	 */
	private boolean mTwoDScrollViewMovedFocus;
	/**
	 * Position of the last motion event.
	 */
	private float mLastMotionY;
	private float mLastMotionX;
	/**
	 * True when the layout has changed but the traversal has not come through yet.
	 * Ideally the view hierarchy would keep track of this for us.
	 */
	private boolean mIsLayoutDirty = true;
	/**
	 * The child to give focus to in the event that a child has requested focus while the
	 * layout is dirty. This prevents the scroll from being wrong if the child has not been
	 * laid out before requesting focus.
	 */
	private View mChildToScrollTo = null;
	/**
	 * True if the user is currently dragging this TwoDScrollView around. This is
	 * not the same as 'is being flinged', which can be checked by
	 * mScroller.isFinished() (flinging begins when the user lifts his finger).
	 */
	private boolean mIsBeingDragged = false;
	/**
	 * Determines speed during touch scrolling
	 */
	private VelocityTracker mVelocityTracker;
	/**
	 * Whether arrow scrolling is animated.
	 */
	private int mTouchSlop;
	private int mMinimumVelocity;
	private int mMaximumVelocity;
	public ScrollView2D(Context context)
	{
		super(context);
		initTwoDScrollView();
	}

	public ScrollView2D(Context context, AttributeSet attrs)
	{
		super(context, attrs);
		initTwoDScrollView();
	}

	public ScrollView2D(Context context, AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);
		initTwoDScrollView();
	}

	@Override protected float getTopFadingEdgeStrength()
	{
		if (getChildCount() == 0)
		{
			return 0.0f;
		}
		final int length = getVerticalFadingEdgeLength();
		if (getScrollY() < length)
		{
			return getScrollY() / (float)length;
		}
		return 1.0f;
	}

	@Override protected float getBottomFadingEdgeStrength()
	{
		if (getChildCount() == 0)
		{
			return 0.0f;
		}
		final int length = getVerticalFadingEdgeLength();
		final int bottomEdge = getHeight() - getPaddingBottom();
		final int span = getChildAt(0).getBottom() - getScrollY() - bottomEdge;
		if (span < length)
		{
			return span / (float)length;
		}
		return 1.0f;
	}

	@Override protected float getLeftFadingEdgeStrength()
	{
		if (getChildCount() == 0)
		{
			return 0.0f;
		}
		final int length = getHorizontalFadingEdgeLength();
		if (getScrollX() < length)
		{
			return getScrollX() / (float)length;
		}
		return 1.0f;
	}

	@Override protected float getRightFadingEdgeStrength()
	{
		if (getChildCount() == 0)
		{
			return 0.0f;
		}
		final int length = getHorizontalFadingEdgeLength();
		final int rightEdge = getWidth() - getPaddingRight();
		final int span = getChildAt(0).getRight() - getScrollX() - rightEdge;
		if (span < length)
		{
			return span / (float)length;
		}
		return 1.0f;
	}

	/**
	 * Disable/Enable scrolling
	 */
	public void setScrollEnabled(boolean enable)
	{
		scrollEnabled = enable;
	}

	/**
	 * @return The maximum amount this scroll view will scroll in response to
	 * an arrow event.
	 */
	public int getMaxScrollAmountVertical()
	{
		return (int)(MAX_SCROLL_FACTOR * getHeight());
	}

	public int getMaxScrollAmountHorizontal()
	{
		return (int)(MAX_SCROLL_FACTOR * getWidth());
	}

	private void initTwoDScrollView()
	{
		mScroller = new Scroller(getContext());
		setFocusable(true);
		setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
		setWillNotDraw(false);
		final ViewConfiguration configuration = ViewConfiguration.get(getContext());
		mTouchSlop = configuration.getScaledTouchSlop();
		mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
		mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
	}

	@Override public void addView(View child)
	{
		if (getChildCount() > 0)
		{
			throw new IllegalStateException("TwoDScrollView can host only one direct child");
		}
		super.addView(child);
	}

	@Override public void addView(View child, int index)
	{
		if (getChildCount() > 0)
		{
			throw new IllegalStateException("TwoDScrollView can host only one direct child");
		}
		super.addView(child, index);
	}

	@Override public void addView(View child, ViewGroup.LayoutParams params)
	{
		if (getChildCount() > 0)
		{
			throw new IllegalStateException("TwoDScrollView can host only one direct child");
		}
		super.addView(child, params);
	}

	@Override public void addView(View child, int index, ViewGroup.LayoutParams params)
	{
		if (getChildCount() > 0)
		{
			throw new IllegalStateException("TwoDScrollView can host only one direct child");
		}
		super.addView(child, index, params);
	}

	/**
	 * @return Returns true this TwoDScrollView can be scrolled
	 */
	private boolean canScroll()
	{
		if (!scrollEnabled)
			return false;
		View child = getChildAt(0);
		if (child != null)
		{
			int childHeight = child.getHeight();
			int childWidth = child.getWidth();
			return (getHeight() < childHeight + getPaddingTop() + getPaddingBottom()) ||
			    (getWidth() < childWidth + getPaddingLeft() + getPaddingRight());
		}
		return false;
	}

	@Override public boolean onInterceptTouchEvent(MotionEvent ev)
	{
		/*
		 * This method JUST determines whether we want to intercept the motion.
		 * If we return true, onMotionEvent will be called and we do the actual
		 * scrolling there.
		 *
		 * Shortcut the most recurring case: the user is in the dragging
		 * state and he is moving his finger.  We want to intercept this
		 * motion.
		 */
		final int action = ev.getAction();
		if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged))
		{
			return true;
		}
		if (!canScroll())
		{
			mIsBeingDragged = false;
			return false;
		}
		final float y = ev.getY();
		final float x = ev.getX();
		switch (action)
		{
			case MotionEvent.ACTION_MOVE:
				/*
				 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check
				 * whether the user has moved far enough from his original down touch.
				 */
				/*
				 * Locally do absolute value. mLastMotionY is set to the y value
				 * of the down event.
				 */
				final int yDiff = (int)Math.abs(y - mLastMotionY);
				final int xDiff = (int)Math.abs(x - mLastMotionX);
				if (yDiff > mTouchSlop || xDiff > mTouchSlop)
				{
					mIsBeingDragged = true;
				}
				break;

			case MotionEvent.ACTION_DOWN:
				/* Remember location of down touch */
				mLastMotionY = y;
				mLastMotionX = x;

				/*
				 * If being flinged and user touches the screen, initiate drag;
				 * otherwise don't.  mScroller.isFinished should be false when
				 * being flinged.
				 */
				mIsBeingDragged = !mScroller.isFinished();
				break;

			case MotionEvent.ACTION_CANCEL:
			case MotionEvent.ACTION_UP:
				/* Release the drag */
				mIsBeingDragged = false;
				break;
		}

		/*
		 * The only time we want to intercept motion events is if we are in the
		 * drag mode.
		 */
		return mIsBeingDragged;
	}

	@Override public boolean onTouchEvent(MotionEvent ev)
	{

		if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0)
		{
			// Don't handle edge touches immediately -- they may actually belong to one of our
			// descendants.
			return false;
		}

		if (!canScroll())
		{
			return false;
		}

		if (mVelocityTracker == null)
		{
			mVelocityTracker = VelocityTracker.obtain();
		}
		mVelocityTracker.addMovement(ev);

		final int action = ev.getAction();
		final float y = ev.getY();
		final float x = ev.getX();

		switch (action)
		{
			case MotionEvent.ACTION_DOWN:
				/*
				 * If being flinged and user touches, stop the fling. isFinished
				 * will be false if being flinged.
				 */
				if (!mScroller.isFinished())
				{
					mScroller.abortAnimation();
				}

				// Remember where the motion event started
				mLastMotionY = y;
				mLastMotionX = x;
				break;
			case MotionEvent.ACTION_MOVE:
				// Scroll to follow the motion event
				int deltaX = (int)(mLastMotionX - x);
				int deltaY = (int)(mLastMotionY - y);
				mLastMotionX = x;
				mLastMotionY = y;

				if (deltaX < 0)
				{
					if (getScrollX() < 0)
					{
						deltaX = 0;
					}
				}
				else if (deltaX > 0)
				{
					final int rightEdge = getWidth() - getPaddingRight();
					final int availableToScroll =
					    getChildAt(0).getRight() - getScrollX() - rightEdge;
					if (availableToScroll > 0)
					{
						deltaX = Math.min(availableToScroll, deltaX);
					}
					else
					{
						deltaX = 0;
					}
				}
				if (deltaY < 0)
				{
					if (getScrollY() < 0)
					{
						deltaY = 0;
					}
				}
				else if (deltaY > 0)
				{
					final int bottomEdge = getHeight() - getPaddingBottom();
					final int availableToScroll =
					    getChildAt(0).getBottom() - getScrollY() - bottomEdge;
					if (availableToScroll > 0)
					{
						deltaY = Math.min(availableToScroll, deltaY);
					}
					else
					{
						deltaY = 0;
					}
				}
				if (deltaY != 0 || deltaX != 0)
					scrollBy(deltaX, deltaY);
				break;
			case MotionEvent.ACTION_UP:
				final VelocityTracker velocityTracker = mVelocityTracker;
				velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
				int initialXVelocity = (int)velocityTracker.getXVelocity();
				int initialYVelocity = (int)velocityTracker.getYVelocity();
				if ((Math.abs(initialXVelocity) + Math.abs(initialYVelocity) > mMinimumVelocity) &&
				    getChildCount() > 0)
				{
					fling(-initialXVelocity, -initialYVelocity);
				}
				if (mVelocityTracker != null)
				{
					mVelocityTracker.recycle();
					mVelocityTracker = null;
				}
		}
		return true;
	}

	/**
	 * Finds the next focusable component that fits in this View's bounds
	 * (excluding fading edges) pretending that this View's top is located at
	 * the parameter top.
	 *
	 * @param topFocus           look for a candidate is the one at the top of the bounds
	 *                           if topFocus is true, or at the bottom of the bounds if topFocus is
	 *                           false
	 * @param top                the top offset of the bounds in which a focusable must be
	 *                           found (the fading edge is assumed to start at this position)
	 * @param preferredFocusable the View that has highest priority and will be
	 *                           returned if it is within my bounds (null is valid)
	 * @return the next focusable component in the bounds or null if none can be
	 * found
	 */
	private View findFocusableViewInMyBounds(final boolean topFocus, final int top,
	                                         final boolean leftFocus, final int left,
	                                         View preferredFocusable)
	{
		/*
		 * The fading edge's transparent side should be considered for focus
		 * since it's mostly visible, so we divide the actual fading edge length
		 * by 2.
		 */
		final int verticalFadingEdgeLength = getVerticalFadingEdgeLength() / 2;
		final int topWithoutFadingEdge = top + verticalFadingEdgeLength;
		final int bottomWithoutFadingEdge = top + getHeight() - verticalFadingEdgeLength;
		final int horizontalFadingEdgeLength = getHorizontalFadingEdgeLength() / 2;
		final int leftWithoutFadingEdge = left + horizontalFadingEdgeLength;
		final int rightWithoutFadingEdge = left + getWidth() - horizontalFadingEdgeLength;

		if ((preferredFocusable != null) &&
		    (preferredFocusable.getTop() < bottomWithoutFadingEdge) &&
		    (preferredFocusable.getBottom() > topWithoutFadingEdge) &&
		    (preferredFocusable.getLeft() < rightWithoutFadingEdge) &&
		    (preferredFocusable.getRight() > leftWithoutFadingEdge))
		{
			return preferredFocusable;
		}
		return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, bottomWithoutFadingEdge,
		                                 leftFocus, leftWithoutFadingEdge, rightWithoutFadingEdge);
	}

	/**
	 * Finds the next focusable component that fits in the specified bounds.
	 * </p>
	 *
	 * @param topFocus look for a candidate is the one at the top of the bounds
	 *                 if topFocus is true, or at the bottom of the bounds if topFocus is
	 *                 false
	 * @param top      the top offset of the bounds in which a focusable must be
	 *                 found
	 * @param bottom   the bottom offset of the bounds in which a focusable must
	 *                 be found
	 * @return the next focusable component in the bounds or null if none can
	 * be found
	 */
	private View findFocusableViewInBounds(boolean topFocus, int top, int bottom, boolean leftFocus,
	                                       int left, int right)
	{
		List<View> focusables = getFocusables(View.FOCUS_FORWARD);
		View focusCandidate = null;

		/*
		 * A fully contained focusable is one where its top is below the bound's
		 * top, and its bottom is above the bound's bottom. A partially
		 * contained focusable is one where some part of it is within the
		 * bounds, but it also has some part that is not within bounds.  A fully contained
		 * focusable is preferred to a partially contained focusable.
		 */
		boolean foundFullyContainedFocusable = false;

		int count = focusables.size();
		for (int i = 0; i < count; i++)
		{
			View view = focusables.get(i);
			int viewTop = view.getTop();
			int viewBottom = view.getBottom();
			int viewLeft = view.getLeft();
			int viewRight = view.getRight();

			if (top < viewBottom && viewTop < bottom && left < viewRight && viewLeft < right)
			{
				/*
				 * the focusable is in the target area, it is a candidate for
				 * focusing
				 */
				final boolean viewIsFullyContained = (top < viewTop) && (viewBottom < bottom) &&
				                                     (left < viewLeft) && (viewRight < right);
				if (focusCandidate == null)
				{
					/* No candidate, take this one */
					focusCandidate = view;
					foundFullyContainedFocusable = viewIsFullyContained;
				}
				else
				{
					final boolean viewIsCloserToVerticalBoundary =
					    (topFocus && viewTop < focusCandidate.getTop()) ||
					    (!topFocus && viewBottom > focusCandidate.getBottom());
					final boolean viewIsCloserToHorizontalBoundary =
					    (leftFocus && viewLeft < focusCandidate.getLeft()) ||
					    (!leftFocus && viewRight > focusCandidate.getRight());
					if (foundFullyContainedFocusable)
					{
						if (viewIsFullyContained && viewIsCloserToVerticalBoundary &&
						    viewIsCloserToHorizontalBoundary)
						{
							/*
							 * We're dealing with only fully contained views, so
							 * it has to be closer to the boundary to beat our
							 * candidate
							 */
							focusCandidate = view;
						}
					}
					else
					{
						if (viewIsFullyContained)
						{
							/* Any fully contained view beats a partially contained view */
							focusCandidate = view;
							foundFullyContainedFocusable = true;
						}
						else if (viewIsCloserToVerticalBoundary && viewIsCloserToHorizontalBoundary)
						{
							/*
							 * Partially contained view beats another partially
							 * contained view if it's closer
							 */
							focusCandidate = view;
						}
					}
				}
			}
		}
		return focusCandidate;
	}

	/**
	 * <p>Handles scrolling in response to a "home/end" shortcut press. This
	 * method will scroll the view to the top or bottom and give the focus
	 * to the topmost/bottommost component in the new visible area. If no
	 * component is a good candidate for focus, this scrollview reclaims the
	 * focus.</p>
	 *
	 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP}
	 *                  to go the top of the view or
	 *                  {@link android.view.View#FOCUS_DOWN} to go the bottom
	 * @return true if the key event is consumed by this method, false otherwise
	 */
	public boolean fullScroll(int direction, boolean horizontal)
	{
		if (!horizontal)
		{
			boolean down = direction == View.FOCUS_DOWN;
			int height = getHeight();
			mTempRect.top = 0;
			mTempRect.bottom = height;
			if (down)
			{
				int count = getChildCount();
				if (count > 0)
				{
					View view = getChildAt(count - 1);
					mTempRect.bottom = view.getBottom();
					mTempRect.top = mTempRect.bottom - height;
				}
			}
			return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom, 0, 0, 0);
		}
		else
		{
			boolean right = direction == View.FOCUS_DOWN;
			int width = getWidth();
			mTempRect.left = 0;
			mTempRect.right = width;
			if (right)
			{
				int count = getChildCount();
				if (count > 0)
				{
					View view = getChildAt(count - 1);
					mTempRect.right = view.getBottom();
					mTempRect.left = mTempRect.right - width;
				}
			}
			return scrollAndFocus(0, 0, 0, direction, mTempRect.top, mTempRect.bottom);
		}
	}

	/**
	 * <p>Scrolls the view to make the area defined by <code>top</code> and
	 * <code>bottom</code> visible. This method attempts to give the focus
	 * to a component visible in this area. If no component can be focused in
	 * the new visible area, the focus is reclaimed by this scrollview.</p>
	 *
	 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP}
	 *                  to go upward
	 *                  {@link android.view.View#FOCUS_DOWN} to downward
	 * @param top       the top offset of the new area to be made visible
	 * @param bottom    the bottom offset of the new area to be made visible
	 * @return true if the key event is consumed by this method, false otherwise
	 */
	private boolean scrollAndFocus(int directionY, int top, int bottom, int directionX, int left,
	                               int right)
	{
		boolean handled = true;
		int height = getHeight();
		int containerTop = getScrollY();
		int containerBottom = containerTop + height;
		boolean up = directionY == View.FOCUS_UP;
		int width = getWidth();
		int containerLeft = getScrollX();
		int containerRight = containerLeft + width;
		boolean leftwards = directionX == View.FOCUS_UP;
		View newFocused = findFocusableViewInBounds(up, top, bottom, leftwards, left, right);
		if (newFocused == null)
		{
			newFocused = this;
		}
		if ((top >= containerTop && bottom <= containerBottom) ||
		    (left >= containerLeft && right <= containerRight))
		{
			handled = false;
		}
		else
		{
			int deltaY = up ? (top - containerTop) : (bottom - containerBottom);
			int deltaX = leftwards ? (left - containerLeft) : (right - containerRight);
			doScroll(deltaX, deltaY);
		}
		if (newFocused != findFocus() && newFocused.requestFocus(directionY))
		{
			mTwoDScrollViewMovedFocus = true;
			mTwoDScrollViewMovedFocus = false;
		}
		return handled;
	}

	/**
	 * Handle scrolling in response to an up or down arrow click.
	 *
	 * @param direction The direction corresponding to the arrow key that was
	 *                  pressed
	 * @return True if we consumed the event, false otherwise
	 */
	public boolean arrowScroll(int direction, boolean horizontal)
	{
		View currentFocused = findFocus();
		if (currentFocused == this)
			currentFocused = null;
		View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);
		final int maxJump =
		    horizontal ? getMaxScrollAmountHorizontal() : getMaxScrollAmountVertical();

		if (!horizontal)
		{
			if (nextFocused != null)
			{
				nextFocused.getDrawingRect(mTempRect);
				offsetDescendantRectToMyCoords(nextFocused, mTempRect);
				int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
				doScroll(0, scrollDelta);
				nextFocused.requestFocus(direction);
			}
			else
			{
				// no new focus
				int scrollDelta = maxJump;
				if (direction == View.FOCUS_UP && getScrollY() < scrollDelta)
				{
					scrollDelta = getScrollY();
				}
				else if (direction == View.FOCUS_DOWN)
				{
					if (getChildCount() > 0)
					{
						int daBottom = getChildAt(0).getBottom();
						int screenBottom = getScrollY() + getHeight();
						if (daBottom - screenBottom < maxJump)
						{
							scrollDelta = daBottom - screenBottom;
						}
					}
				}
				if (scrollDelta == 0)
				{
					return false;
				}
				doScroll(0, direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta);
			}
		}
		else
		{
			if (nextFocused != null)
			{
				nextFocused.getDrawingRect(mTempRect);
				offsetDescendantRectToMyCoords(nextFocused, mTempRect);
				int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
				doScroll(scrollDelta, 0);
				nextFocused.requestFocus(direction);
			}
			else
			{
				// no new focus
				int scrollDelta = maxJump;
				if (direction == View.FOCUS_UP && getScrollY() < scrollDelta)
				{
					scrollDelta = getScrollY();
				}
				else if (direction == View.FOCUS_DOWN)
				{
					if (getChildCount() > 0)
					{
						int daBottom = getChildAt(0).getBottom();
						int screenBottom = getScrollY() + getHeight();
						if (daBottom - screenBottom < maxJump)
						{
							scrollDelta = daBottom - screenBottom;
						}
					}
				}
				if (scrollDelta == 0)
				{
					return false;
				}
				doScroll(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta, 0);
			}
		}
		return true;
	}

	/**
	 * Smooth scroll by a Y delta
	 *
	 * @param delta the number of pixels to scroll by on the Y axis
	 */
	private void doScroll(int deltaX, int deltaY)
	{
		if (deltaX != 0 || deltaY != 0)
		{
			smoothScrollBy(deltaX, deltaY);
		}
	}

	/**
	 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
	 *
	 * @param dx the number of pixels to scroll by on the X axis
	 * @param dy the number of pixels to scroll by on the Y axis
	 */
	public final void smoothScrollBy(int dx, int dy)
	{
		long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll;
		if (duration > ANIMATED_SCROLL_GAP)
		{
			mScroller.startScroll(getScrollX(), getScrollY(), dx, dy);
			awakenScrollBars(mScroller.getDuration());
			invalidate();
		}
		else
		{
			if (!mScroller.isFinished())
			{
				mScroller.abortAnimation();
			}
			scrollBy(dx, dy);
		}
		mLastScroll = AnimationUtils.currentAnimationTimeMillis();
	}

	/**
	 * Like {@link #scrollTo}, but scroll smoothly instead of immediately.
	 *
	 * @param x the position where to scroll on the X axis
	 * @param y the position where to scroll on the Y axis
	 */
	public final void smoothScrollTo(int x, int y)
	{
		smoothScrollBy(x - getScrollX(), y - getScrollY());
	}

	/**
	 * <p>The scroll range of a scroll view is the overall height of all of its
	 * children.</p>
	 */
	@Override protected int computeVerticalScrollRange()
	{
		int count = getChildCount();
		return count == 0 ? getHeight() : (getChildAt(0)).getBottom();
	}

	@Override protected int computeHorizontalScrollRange()
	{
		int count = getChildCount();
		return count == 0 ? getWidth() : (getChildAt(0)).getRight();
	}

	@Override
	protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec)
	{
		ViewGroup.LayoutParams lp = child.getLayoutParams();
		int childWidthMeasureSpec;
		int childHeightMeasureSpec;

		childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,
		                                            getPaddingLeft() + getPaddingRight(), lp.width);
		childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);

		child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
	}

	@Override
	protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,
	                                       int parentHeightMeasureSpec, int heightUsed)
	{
		final MarginLayoutParams lp = (MarginLayoutParams)child.getLayoutParams();
		final int childWidthMeasureSpec =
		    MeasureSpec.makeMeasureSpec(lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED);
		final int childHeightMeasureSpec =
		    MeasureSpec.makeMeasureSpec(lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED);

		child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
	}

	@Override public void computeScroll()
	{
		if (mScroller.computeScrollOffset())
		{
			// This is called at drawing time by ViewGroup.  We don't want to
			// re-show the scrollbars at this point, which scrollTo will do,
			// so we replicate most of scrollTo here.
			//
			//         It's a little odd to call onScrollChanged from inside the drawing.
			//
			//         It is, except when you remember that computeScroll() is used to
			//         animate scrolling. So unless we want to defer the onScrollChanged()
			//         until the end of the animated scrolling, we don't really have a
			//         choice here.
			//
			//         I agree.  The alternative, which I think would be worse, is to post
			//         something and tell the subclasses later.  This is bad because there
			//         will be a window where mScrollX/Y is different from what the app
			//         thinks it is.
			//
			int oldX = getScrollX();
			int oldY = getScrollY();
			int x = mScroller.getCurrX();
			int y = mScroller.getCurrY();
			if (getChildCount() > 0)
			{
				View child = getChildAt(0);
				scrollTo(
				    clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth()),
				    clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(),
				          child.getHeight()));
			}
			else
			{
				scrollTo(x, y);
			}
			if (oldX != getScrollX() || oldY != getScrollY())
			{
				onScrollChanged(getScrollX(), getScrollY(), oldX, oldY);
			}

			// Keep on drawing until the animation has finished.
			postInvalidate();
		}
	}

	/**
	 * Scrolls the view to the given child.
	 *
	 * @param child the View to scroll to
	 */
	private void scrollToChild(View child)
	{
		child.getDrawingRect(mTempRect);
		/* Offset from child's local coordinates to TwoDScrollView coordinates */
		offsetDescendantRectToMyCoords(child, mTempRect);
		int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
		if (scrollDelta != 0)
		{
			scrollBy(0, scrollDelta);
		}
	}

	/**
	 * If rect is off screen, scroll just enough to get it (or at least the
	 * first screen size chunk of it) on screen.
	 *
	 * @param rect      The rectangle.
	 * @param immediate True to scroll immediately without animation
	 * @return true if scrolling was performed
	 */
	private boolean scrollToChildRect(Rect rect, boolean immediate)
	{
		final int delta = computeScrollDeltaToGetChildRectOnScreen(rect);
		final boolean scroll = delta != 0;
		if (scroll)
		{
			if (immediate)
			{
				scrollBy(0, delta);
			}
			else
			{
				smoothScrollBy(0, delta);
			}
		}
		return scroll;
	}

	/**
	 * Compute the amount to scroll in the Y direction in order to get
	 * a rectangle completely on the screen (or, if taller than the screen,
	 * at least the first screen size chunk of it).
	 *
	 * @param rect The rect.
	 * @return The scroll delta.
	 */
	protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect)
	{
		if (getChildCount() == 0)
			return 0;
		int height = getHeight();
		int screenTop = getScrollY();
		int screenBottom = screenTop + height;
		int fadingEdge = getVerticalFadingEdgeLength();
		// leave room for top fading edge as long as rect isn't at very top
		if (rect.top > 0)
		{
			screenTop += fadingEdge;
		}

		// leave room for bottom fading edge as long as rect isn't at very bottom
		if (rect.bottom < getChildAt(0).getHeight())
		{
			screenBottom -= fadingEdge;
		}
		int scrollYDelta = 0;
		if (rect.bottom > screenBottom && rect.top > screenTop)
		{
			// need to move down to get it in view: move down just enough so
			// that the entire rectangle is in view (or at least the first
			// screen size chunk).
			if (rect.height() > height)
			{
				// just enough to get screen size chunk on
				scrollYDelta += (rect.top - screenTop);
			}
			else
			{
				// get entire rect at bottom of screen
				scrollYDelta += (rect.bottom - screenBottom);
			}

			// make sure we aren't scrolling beyond the end of our content
			int bottom = getChildAt(0).getBottom();
			int distanceToBottom = bottom - screenBottom;
			scrollYDelta = Math.min(scrollYDelta, distanceToBottom);
		}
		else if (rect.top < screenTop && rect.bottom < screenBottom)
		{
			// need to move up to get it in view: move up just enough so that
			// entire rectangle is in view (or at least the first screen
			// size chunk of it).

			if (rect.height() > height)
			{
				// screen size chunk
				scrollYDelta -= (screenBottom - rect.bottom);
			}
			else
			{
				// entire rect at top
				scrollYDelta -= (screenTop - rect.top);
			}

			// make sure we aren't scrolling any further than the top our content
			scrollYDelta = Math.max(scrollYDelta, -getScrollY());
		}
		return scrollYDelta;
	}

	@Override public void requestChildFocus(View child, View focused)
	{
		if (!mTwoDScrollViewMovedFocus)
		{
			if (!mIsLayoutDirty)
			{
				scrollToChild(focused);
			}
			else
			{
				// The child may not be laid out yet, we can't compute the scroll yet
				mChildToScrollTo = focused;
			}
		}
		super.requestChildFocus(child, focused);
	}

	/**
	 * When looking for focus in children of a scroll view, need to be a little
	 * more careful not to give focus to something that is scrolled off screen.
	 * <p>
	 * This is more expensive than the default {@link android.view.ViewGroup}
	 * implementation, otherwise this behavior might have been made the default.
	 */
	@Override
	protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect)
	{
		// convert from forward / backward notation to up / down / left / right
		// (ugh).
		if (direction == View.FOCUS_FORWARD)
		{
			direction = View.FOCUS_DOWN;
		}
		else if (direction == View.FOCUS_BACKWARD)
		{
			direction = View.FOCUS_UP;
		}

		final View nextFocus = previouslyFocusedRect == null
		                           ? FocusFinder.getInstance().findNextFocus(this, null, direction)
		                           : FocusFinder.getInstance().findNextFocusFromRect(
		                                 this, previouslyFocusedRect, direction);

		if (nextFocus == null)
		{
			return false;
		}

		return nextFocus.requestFocus(direction, previouslyFocusedRect);
	}

	@Override
	public boolean requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate)
	{
		// offset into coordinate space of this scroll view
		rectangle.offset(child.getLeft() - child.getScrollX(), child.getTop() - child.getScrollY());
		return scrollToChildRect(rectangle, immediate);
	}

	@Override public void requestLayout()
	{
		mIsLayoutDirty = true;
		super.requestLayout();
	}

	private int lastCenterContentH = -1;
	private int lastCenterTop = 0;

	@Override protected void onLayout(boolean changed, int l, int t, int r, int b)
	{
		super.onLayout(changed, l, t, r, b);
		mIsLayoutDirty = false;
		// Give a child focus if it needs it
		if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this))
		{
			scrollToChild(mChildToScrollTo);
		}
		mChildToScrollTo = null;

		// Center the content area (excluding touch-pointer padding) within the viewport.
		// This keeps the RDP surface visually centered regardless of pointer padding changes.
		if (getChildCount() > 0)
		{
			View child = getChildAt(0);
			SessionView sv = findViewById(R.id.sessionView);
			int ptw = sv != null ? sv.getTouchPointerPaddingWidth() : 0;
			int pth = sv != null ? sv.getTouchPointerPaddingHeight() : 0;
			int contentW = child.getMeasuredWidth() - ptw;
			int contentH = child.getMeasuredHeight() - pth;
			int usableW = getWidth() - getPaddingLeft() - getPaddingRight();
			int usableH = getHeight() - getPaddingTop() - getPaddingBottom();
			int left = getPaddingLeft() + Math.max(0, (usableW - contentW) / 2);
			int top;
			if (contentH == lastCenterContentH)
			{
				// viewport-only change (e.g. keyboard): keep position, don't re-center
				top = lastCenterTop;
			}
			else
			{
				top = getPaddingTop() + Math.max(0, (usableH - contentH) / 2);
				lastCenterContentH = contentH;
				lastCenterTop = top;
			}
			child.layout(left, top, left + child.getMeasuredWidth(),
			             top + child.getMeasuredHeight());
		}

		// Calling this with the present values causes it to re-clamp them
		scrollTo(getScrollX(), getScrollY());
	}

	@Override protected void onSizeChanged(int w, int h, int oldw, int oldh)
	{
		super.onSizeChanged(w, h, oldw, oldh);

		View currentFocused = findFocus();
		if (null == currentFocused || this == currentFocused)
			return;

		// If the currently-focused view was visible on the screen when the
		// screen was at the old height, then scroll the screen to make that
		// view visible with the new screen height.
		currentFocused.getDrawingRect(mTempRect);
		offsetDescendantRectToMyCoords(currentFocused, mTempRect);
		int scrollDeltaX = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
		int scrollDeltaY = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
		doScroll(scrollDeltaX, scrollDeltaY);
	}

	/**
	 * Return true if child is an descendant of parent, (or equal to the parent).
	 */
	private boolean isViewDescendantOf(View child, View parent)
	{
		if (child == parent)
		{
			return true;
		}

		final ViewParent theParent = child.getParent();
		return (theParent instanceof ViewGroup) && isViewDescendantOf((View)theParent, parent);
	}

	/**
	 * Fling the scroll view
	 *
	 * @param velocityY The initial velocity in the Y direction. Positive
	 *                  numbers mean that the finger/curor is moving down the screen,
	 *                  which means we want to scroll towards the top.
	 */
	public void fling(int velocityX, int velocityY)
	{
		if (getChildCount() > 0)
		{
			int height = getHeight() - getPaddingBottom() - getPaddingTop();
			int bottom = getChildAt(0).getHeight();
			int width = getWidth() - getPaddingRight() - getPaddingLeft();
			int right = getChildAt(0).getWidth();

			mScroller.fling(getScrollX(), getScrollY(), velocityX, velocityY, 0, right - width, 0,
			                bottom - height);

			final boolean movingDown = velocityY > 0;
			final boolean movingRight = velocityX > 0;

			View newFocused = findFocusableViewInMyBounds(
			    movingRight, mScroller.getFinalX(), movingDown, mScroller.getFinalY(), findFocus());
			if (newFocused == null)
			{
				newFocused = this;
			}

			if (newFocused != findFocus() &&
			    newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP))
			{
				mTwoDScrollViewMovedFocus = true;
				mTwoDScrollViewMovedFocus = false;
			}

			awakenScrollBars(mScroller.getDuration());
			invalidate();
		}
	}

	/**
	 * {@inheritDoc}
	 * <p>
	 * <p>This version also clamps the scrolling to the bounds of our child.
	 */
	public void scrollTo(int x, int y)
	{
		// we rely on the fact the View.scrollBy calls scrollTo.
		if (getChildCount() > 0)
		{
			View child = getChildAt(0);
			x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth());
			y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight());
			if (x != getScrollX() || y != getScrollY())
			{
				super.scrollTo(x, y);
			}
		}
	}

	private int clamp(int n, int my, int child)
	{
		if (my >= child || n < 0)
		{
			/* my >= child is this case:
			 *                    |--------------- me ---------------|
			 *     |------ child ------|
			 * or
			 *     |--------------- me ---------------|
			 *            |------ child ------|
			 * or
			 *     |--------------- me ---------------|
			 *                                  |------ child ------|
			 *
			 * n < 0 is this case:
			 *     |------ me ------|
			 *                    |-------- child --------|
			 *     |-- mScrollX --|
			 */
			return 0;
		}
		if ((my + n) > child)
		{
			/* this case:
			 *                    |------ me ------|
			 *     |------ child ------|
			 *     |-- mScrollX --|
			 */
			return child - my;
		}
		return n;
	}

	public void setScrollViewListener(ScrollView2DListener scrollViewListener)
	{
		this.scrollView2DListener = scrollViewListener;
	}

	@Override protected void onScrollChanged(int x, int y, int oldx, int oldy)
	{
		super.onScrollChanged(x, y, oldx, oldy);
		if (scrollView2DListener != null)
		{
			scrollView2DListener.onScrollChanged(this, x, y, oldx, oldy);
		}
	}

	// interface to receive notifications when the view is scrolled
	public interface ScrollView2DListener {
		void onScrollChanged(ScrollView2D scrollView, int x, int y, int oldx, int oldy);
	}
}
