Interpolate gesture preview trails (75028af2) · Commits · e / os / android_packages_inputmethods_LatinIME

java/src/com/android/inputmethod/keyboard/internal/GesturePreviewTrail.java

+16 −0

Original line number	Diff line number	Diff line
		@@ -44,6 +44,7 @@ final class GesturePreviewTrail {
		// The wall time of the zero value in {@link #mEventTimes}
		private long mCurrentTimeBase;
		private int mTrailStartIndex;
		private int mLastInterpolatedDrawIndex;

		static final class Params {
		public final int mTrailColor;
		@@ -96,6 +97,17 @@ final class GesturePreviewTrail {
		}
		final int[] eventTimes = mEventTimes.getPrimitiveArray();
		final int strokeId = stroke.getGestureStrokeId();
		// Because interpolation algorithm in {@link GestureStrokeWithPreviewPoints} can't determine
		// the interpolated points in the last segment of gesture stroke, it may need recalculation
		// of interpolation when new segments are added to the stroke.
		// {@link #mLastInterpolatedDrawIndex} holds the start index of the last segment. It may
		// be updated by the interpolation
		// {@link GestureStrokeWithPreviewPoints#interpolatePreviewStroke}
		// or by animation {@link #drawGestureTrail(Canvas,Paint,Rect,Params)} below.
		final int lastInterpolatedIndex = (strokeId == mCurrentStrokeId)
		? mLastInterpolatedDrawIndex : trailSize;
		mLastInterpolatedDrawIndex = stroke.interpolateStrokeAndReturnStartIndexOfLastSegment(
		lastInterpolatedIndex, mEventTimes, mXCoordinates, mYCoordinates);
		if (strokeId != mCurrentStrokeId) {
		final int elapsedTime = (int)(downTime - mCurrentTimeBase);
		for (int i = mTrailStartIndex; i < trailSize; i++) {
		@@ -216,6 +228,10 @@ final class GesturePreviewTrail {
		System.arraycopy(eventTimes, startIndex, eventTimes, 0, newSize);
		System.arraycopy(xCoords, startIndex, xCoords, 0, newSize);
		System.arraycopy(yCoords, startIndex, yCoords, 0, newSize);
		// The start index of the last segment of the stroke
		// {@link mLastInterpolatedDrawIndex} should also be updated because all array
		// elements have just been shifted for compaction.
		mLastInterpolatedDrawIndex = Math.max(mLastInterpolatedDrawIndex - startIndex, 0);
		}
		mEventTimes.setLength(newSize);
		mXCoordinates.setLength(newSize);

java/src/com/android/inputmethod/keyboard/internal/GestureStrokeWithPreviewPoints.java

+122 −16

Original line number	Diff line number	Diff line
		@@ -21,19 +21,32 @@ import com.android.inputmethod.latin.ResizableIntArray;
		public final class GestureStrokeWithPreviewPoints extends GestureStroke {
		public static final int PREVIEW_CAPACITY = 256;

		private static final boolean ENABLE_INTERPOLATION = true;

		private final ResizableIntArray mPreviewEventTimes = new ResizableIntArray(PREVIEW_CAPACITY);
		private final ResizableIntArray mPreviewXCoordinates = new ResizableIntArray(PREVIEW_CAPACITY);
		private final ResizableIntArray mPreviewYCoordinates = new ResizableIntArray(PREVIEW_CAPACITY);

		private int mStrokeId;
		private int mLastPreviewSize;
		private final HermiteInterpolator mInterpolator = new HermiteInterpolator();
		private int mLastInterpolatedPreviewIndex;

		private int mMinPreviewSampleLengthSquare;
		private int mMinPreviewSamplingDistanceSquared;
		private int mLastX;
		private int mLastY;
		private double mMinPreviewSamplingDistance;
		private double mDistanceFromLastSample;

		// TODO: Move this to resource.
		private static final float MIN_PREVIEW_SAMPLE_LENGTH_RATIO_TO_KEY_WIDTH = 0.1f;
		// TODO: Move these constants to resource.
		// The minimum linear distance between sample points for preview in keyWidth unit.
		private static final float MIN_PREVIEW_SAMPLING_RATIO_TO_KEY_WIDTH = 0.1f;
		// The minimum trail distance between sample points for preview in keyWidth unit when using
		// interpolation.
		private static final float MIN_PREVIEW_SAMPLING_RATIO_TO_KEY_WIDTH_WITH_INTERPOLATION = 0.2f;
		// The angular threshold to use interpolation in radian. PI/12 is 15 degree.
		private static final double INTERPOLATION_ANGULAR_THRESHOLD = Math.PI / 12.0d;
		private static final int MAX_INTERPOLATION_PARTITION = 4;

		public GestureStrokeWithPreviewPoints(final int pointerId, final GestureStrokeParams params) {
		super(pointerId, params);
		@@ -44,6 +57,7 @@ public final class GestureStrokeWithPreviewPoints extends GestureStroke {
		super.reset();
		mStrokeId++;
		mLastPreviewSize = 0;
		mLastInterpolatedPreviewIndex = 0;
		mPreviewEventTimes.setLength(0);
		mPreviewXCoordinates.setLength(0);
		mPreviewYCoordinates.setLength(0);
		@@ -53,35 +67,49 @@ public final class GestureStrokeWithPreviewPoints extends GestureStroke {
		return mStrokeId;
		}

		public int getGestureStrokePreviewSize() {
		return mPreviewEventTimes.getLength();
		}

		@Override
		public void setKeyboardGeometry(final int keyWidth, final int keyboardHeight) {
		super.setKeyboardGeometry(keyWidth, keyboardHeight);
		final float sampleLength = keyWidth * MIN_PREVIEW_SAMPLE_LENGTH_RATIO_TO_KEY_WIDTH;
		mMinPreviewSampleLengthSquare = (int)(sampleLength * sampleLength);
		final float samplingRatioToKeyWidth = ENABLE_INTERPOLATION
		? MIN_PREVIEW_SAMPLING_RATIO_TO_KEY_WIDTH_WITH_INTERPOLATION
		: MIN_PREVIEW_SAMPLING_RATIO_TO_KEY_WIDTH;
		mMinPreviewSamplingDistance = keyWidth * samplingRatioToKeyWidth;
		mMinPreviewSamplingDistanceSquared = (int)(
		mMinPreviewSamplingDistance * mMinPreviewSamplingDistance);
		}

		private boolean needsSampling(final int x, final int y, final boolean isMajorEvent) {
		if (ENABLE_INTERPOLATION) {
		mDistanceFromLastSample += Math.hypot(x - mLastX, y - mLastY);
		mLastX = x;
		mLastY = y;
		if (mDistanceFromLastSample >= mMinPreviewSamplingDistance) {
		mDistanceFromLastSample = 0.0d;
		return true;
		}
		return false;
		}

		private boolean needsSampling(final int x, final int y) {
		final int dx = x - mLastX;
		final int dy = y - mLastY;
		return dx * dx + dy * dy >= mMinPreviewSampleLengthSquare;
		if (isMajorEvent \|\| dx * dx + dy * dy >= mMinPreviewSamplingDistanceSquared) {
		mLastX = x;
		mLastY = y;
		return true;
		}
		return false;
		}

		@Override
		public boolean addPointOnKeyboard(final int x, final int y, final int time,
		final boolean isMajorEvent) {
		final boolean onValidArea = super.addPointOnKeyboard(x, y, time, isMajorEvent);
		if (isMajorEvent \|\| needsSampling(x, y)) {
		if (needsSampling(x, y, isMajorEvent)) {
		mPreviewEventTimes.add(time);
		mPreviewXCoordinates.add(x);
		mPreviewYCoordinates.add(y);
		mLastX = x;
		mLastY = y;
		}
		return onValidArea;
		return super.addPointOnKeyboard(x, y, time, isMajorEvent);

		}

		public void appendPreviewStroke(final ResizableIntArray eventTimes,
		@@ -95,4 +123,82 @@ public final class GestureStrokeWithPreviewPoints extends GestureStroke {
		yCoords.append(mPreviewYCoordinates, mLastPreviewSize, length);
		mLastPreviewSize = mPreviewEventTimes.getLength();
		}

		/**
		* Calculate interpolated points between the last interpolated point and the end of the trail.
		* And return the start index of the last interpolated segment of input arrays because it
		* may need to recalculate the interpolated points in the segment if further segments are
		* added to this stroke.
		*
		* @param lastInterpolatedIndex the start index of the last interpolated segment of
		* <code>eventTimes</code>, <code>xCoords</code>, and <code>yCoords</code>.
		* @param eventTimes the event time array of gesture preview trail to be drawn.
		* @param xCoords the x-coordinates array of gesture preview trail to be drawn.
		* @param yCoords the y-coordinates array of gesture preview trail to be drawn.
		* @return the start index of the last interpolated segment of input arrays.
		*/
		public int interpolateStrokeAndReturnStartIndexOfLastSegment(final int lastInterpolatedIndex,
		final ResizableIntArray eventTimes, final ResizableIntArray xCoords,
		final ResizableIntArray yCoords) {
		if (!ENABLE_INTERPOLATION) {
		return lastInterpolatedIndex;
		}
		final int size = mPreviewEventTimes.getLength();
		final int[] pt = mPreviewEventTimes.getPrimitiveArray();
		final int[] px = mPreviewXCoordinates.getPrimitiveArray();
		final int[] py = mPreviewYCoordinates.getPrimitiveArray();
		mInterpolator.reset(px, py, 0, size);
		// The last segment of gesture stroke needs to be interpolated again because the slope of
		// the tangent at the last point isn't determined.
		int lastInterpolatedDrawIndex = lastInterpolatedIndex;
		int d1 = lastInterpolatedIndex;
		for (int p2 = mLastInterpolatedPreviewIndex + 1; p2 < size; p2++) {
		final int p1 = p2 - 1;
		final int p0 = p1 - 1;
		final int p3 = p2 + 1;
		mLastInterpolatedPreviewIndex = p1;
		lastInterpolatedDrawIndex = d1;
		mInterpolator.setInterval(p0, p1, p2, p3);
		final double m1 = Math.atan2(mInterpolator.mSlope1Y, mInterpolator.mSlope1X);
		final double m2 = Math.atan2(mInterpolator.mSlope2Y, mInterpolator.mSlope2X);
		final double dm = Math.abs(angularDiff(m2, m1));
		final int partition = Math.min((int)Math.ceil(dm / INTERPOLATION_ANGULAR_THRESHOLD),
		MAX_INTERPOLATION_PARTITION);
		final int t1 = eventTimes.get(d1);
		final int dt = pt[p2] - pt[p1];
		d1++;
		for (int i = 1; i < partition; i++) {
		final float t = i / (float)partition;
		mInterpolator.interpolate(t);
		eventTimes.add(d1, (int)(dt * t) + t1);
		xCoords.add(d1, (int)mInterpolator.mInterpolatedX);
		yCoords.add(d1, (int)mInterpolator.mInterpolatedY);
		d1++;
		}
		eventTimes.add(d1, pt[p2]);
		xCoords.add(d1, px[p2]);
		yCoords.add(d1, py[p2]);
		}
		return lastInterpolatedDrawIndex;
		}

		private static final double TWO_PI = Math.PI * 2.0d;

		/**
		* Calculate the angular of rotation from <code>a0</code> to <code>a1</code>.
		*
		* @param a1 the angular to which the rotation ends.
		* @param a0 the angular from which the rotation starts.
		* @return the angular rotation value from a0 to a1, normalized to [-PI, +PI].
		*/
		private static double angularDiff(final double a1, final double a0) {
		double deltaAngle = a1 - a0;
		while (deltaAngle > Math.PI) {
		deltaAngle -= TWO_PI;
		}
		while (deltaAngle < -Math.PI) {
		deltaAngle += TWO_PI;
		}
		return deltaAngle;
		}
		}

java/src/com/android/inputmethod/keyboard/internal/HermiteInterpolator.java

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		/*
		* Copyright (C) 2013 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.inputmethod.keyboard.internal;

		import com.android.inputmethod.annotations.UsedForTesting;

		/**
		* Interpolates XY-coordinates using Cubic Hermite Curve.
		*/
		public final class HermiteInterpolator {
		private int[] mXCoords;
		private int[] mYCoords;
		private int mMinPos;
		private int mMaxPos;

		// Working variable to calculate interpolated value.
		/** The coordinates of the start point of the interval. */
		public int mP1X, mP1Y;
		/** The coordinates of the end point of the interval. */
		public int mP2X, mP2Y;
		/** The slope of the tangent at the start point. */
		public float mSlope1X, mSlope1Y;
		/** The slope of the tangent at the end point. */
		public float mSlope2X, mSlope2Y;
		/** The interpolated coordinates.
		* The return variables of {@link #interpolate(float)} to avoid instantiations.
		*/
		public float mInterpolatedX, mInterpolatedY;

		public HermiteInterpolator() {
		// Nothing to do with here.
		}

		/**
		* Reset this interpolator to point XY-coordinates data.
		* @param xCoords the array of x-coordinates. Valid data are in left-open interval
		* <code>[minPos, maxPos)</code>.
		* @param yCoords the array of y-coordinates. Valid data are in left-open interval
		* <code>[minPos, maxPos)</code>.
		* @param minPos the minimum index of left-open interval of valid data.
		* @param maxPos the maximum index of left-open interval of valid data.
		*/
		@UsedForTesting
		public void reset(final int[] xCoords, final int[] yCoords, final int minPos,
		final int maxPos) {
		mXCoords = xCoords;
		mYCoords = yCoords;
		mMinPos = minPos;
		mMaxPos = maxPos;
		}

		/**
		* Set interpolation interval.
		* <p>
		* The start and end coordinates of the interval will be set in {@link #mP1X}, {@link #mP1Y},
		* {@link #mP2X}, and {@link #mP2Y}. The slope of the tangents at start and end points will be
		* set in {@link #mSlope1X}, {@link #mSlope1Y}, {@link #mSlope2X}, and {@link #mSlope2Y}.
		*
		* @param p0 the index just before interpolation interval. If <code>p1</code> points the start
		* of valid points, <code>p0</code> must be less than <code>minPos</code> of
		* {@link #reset(int[],int[],int,int)}.
		* @param p1 the start index of interpolation interval.
		* @param p2 the end index of interpolation interval.
		* @param p3 the index just after interpolation interval. If <code>p2</code> points the end of
		* valid points, <code>p3</code> must be equal or greater than <code>maxPos</code> of
		* {@link #reset(int[],int[],int,int)}.
		*/
		@UsedForTesting
		public void setInterval(final int p0, final int p1, final int p2, final int p3) {
		mP1X = mXCoords[p1];
		mP1Y = mYCoords[p1];
		mP2X = mXCoords[p2];
		mP2Y = mYCoords[p2];
		// A(ax,ay) is the vector p1->p2.
		final int ax = mP2X - mP1X;
		final int ay = mP2Y - mP1Y;

		// Calculate the slope of the tangent at p1.
		if (p0 >= mMinPos) {
		// p1 has previous valid point p0.
		// The slope of the tangent is half of the vector p0->p2.
		mSlope1X = (mP2X - mXCoords[p0]) / 2.0f;
		mSlope1Y = (mP2Y - mYCoords[p0]) / 2.0f;
		} else if (p3 < mMaxPos) {
		// p1 has no previous valid point, but p2 has next valid point p3.
		// B(bx,by) is the slope vector of the tangent at p2.
		final float bx = (mXCoords[p3] - mP1X) / 2.0f;
		final float by = (mYCoords[p3] - mP1Y) / 2.0f;
		final float crossProdAB = ax * by - ay * bx;
		final float dotProdAB = ax * bx + ay * by;
		final float normASquare = ax * ax + ay * ay;
		final float invHalfNormASquare = 1.0f / normASquare / 2.0f;
		// The slope of the tangent is the mirror image of vector B to vector A.
		mSlope1X = invHalfNormASquare * (dotProdAB * ax + crossProdAB * ay);
		mSlope1Y = invHalfNormASquare * (dotProdAB * ay - crossProdAB * ax);
		} else {
		// p1 and p2 have no previous valid point. (Interval has only point p1 and p2)
		mSlope1X = ax;
		mSlope1Y = ay;
		}

		// Calculate the slope of the tangent at p2.
		if (p3 < mMaxPos) {
		// p2 has next valid point p3.
		// The slope of the tangent is half of the vector p1->p3.
		mSlope2X = (mXCoords[p3] - mP1X) / 2.0f;
		mSlope2Y = (mYCoords[p3] - mP1Y) / 2.0f;
		} else if (p0 >= mMinPos) {
		// p2 has no next valid point, but p1 has previous valid point p0.
		// B(bx,by) is the slope vector of the tangent at p1.
		final float bx = (mP2X - mXCoords[p0]) / 2.0f;
		final float by = (mP2Y - mYCoords[p0]) / 2.0f;
		final float crossProdAB = ax * by - ay * bx;
		final float dotProdAB = ax * bx + ay * by;
		final float normASquare = ax * ax + ay * ay;
		final float invHalfNormASquare = 1.0f / normASquare / 2.0f;
		// The slope of the tangent is the mirror image of vector B to vector A.
		mSlope2X = invHalfNormASquare * (dotProdAB * ax + crossProdAB * ay);
		mSlope2Y = invHalfNormASquare * (dotProdAB * ay - crossProdAB * ax);
		} else {
		// p1 and p2 has no previous valid point. (Interval has only point p1 and p2)
		mSlope2X = ax;
		mSlope2Y = ay;
		}
		}

		/**
		* Calculate interpolation value at <code>t</code> in unit interval <code>[0,1]</code>.
		* <p>
		* On the unit interval [0,1], given a starting point p1 at t=0 and an ending point p2 at t=1
		* with the slope of the tangent m1 at p1 and m2 at p2, the polynomial of cubic Hermite curve
		* can be defined by
		* p(t) = (1+2t)(1-t)(1-t)p1 + t(1-t)(1-t)m1 + (3-2t)t^2p2 + (t-1)t^2m2
		* where t is an element of [0,1].
		* <p>
		* The interpolated XY-coordinates will be set in {@link #mInterpolatedX} and
		* {@link #mInterpolatedY}.
		*
		* @param t the interpolation parameter. The value must be in close interval <code>[0,1]</code>.
		*/
		@UsedForTesting
		public void interpolate(final float t) {
		final float omt = 1.0f - t;
		final float tm2 = 2.0f * t;
		final float k1 = 1.0f + tm2;
		final float k2 = 3.0f - tm2;
		final float omt2 = omt * omt;
		final float t2 = t * t;
		mInterpolatedX = (k1 * mP1X + t * mSlope1X) * omt2 + (k2 * mP2X - omt * mSlope2X) * t2;
		mInterpolatedY = (k1 * mP1Y + t * mSlope1Y) * omt2 + (k2 * mP2Y - omt * mSlope2Y) * t2;
		}
		}

tests/src/com/android/inputmethod/keyboard/internal/HermiteInterpolatorTests.java

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