services/accessibility/java/com/android/server/accessibility/GestureUtils.java

package com.android.server.accessibility;

import android.util.MathUtils;
import android.view.MotionEvent;

/**
 * Some helper functions for gesture detection.
 */
final class GestureUtils {

    private GestureUtils() {
        /* cannot be instantiated */
    }

    public static boolean isTap(MotionEvent down, MotionEvent up, int tapTimeSlop,
            int tapDistanceSlop, int actionIndex) {
        return eventsWithinTimeAndDistanceSlop(down, up, tapTimeSlop, tapDistanceSlop, actionIndex);
    }

    public static boolean isMultiTap(MotionEvent firstUp, MotionEvent secondUp,
            int multiTapTimeSlop, int multiTapDistanceSlop, int actionIndex) {
        return eventsWithinTimeAndDistanceSlop(firstUp, secondUp, multiTapTimeSlop,
                multiTapDistanceSlop, actionIndex);
    }

    private static boolean eventsWithinTimeAndDistanceSlop(MotionEvent first, MotionEvent second,
            int timeout, int distance, int actionIndex) {
        if (isTimedOut(first, second, timeout)) {
            return false;
        }
        final double deltaMove = computeDistance(first, second, actionIndex);
        if (deltaMove >= distance) {
            return false;
        }
        return true;
    }

    public static double computeDistance(MotionEvent first, MotionEvent second, int pointerIndex) {
         return MathUtils.dist(first.getX(pointerIndex), first.getY(pointerIndex),
                 second.getX(pointerIndex), second.getY(pointerIndex));
    }

    public static boolean isTimedOut(MotionEvent firstUp, MotionEvent secondUp, int timeout) {
        final long deltaTime = secondUp.getEventTime() - firstUp.getEventTime();
        return (deltaTime >= timeout);
    }

    public static boolean isSamePointerContext(MotionEvent first, MotionEvent second) {
        return (first.getPointerIdBits() == second.getPointerIdBits()
                && first.getPointerId(first.getActionIndex())
                        == second.getPointerId(second.getActionIndex()));
    }

    /**
     * Determines whether a two pointer gesture is a dragging one.
     *
     * @param event The event with the pointer data.
     * @return True if the gesture is a dragging one.
     */
    public static boolean isDraggingGesture(float firstPtrDownX, float firstPtrDownY,
            float secondPtrDownX, float secondPtrDownY, float firstPtrX, float firstPtrY,
            float secondPtrX, float secondPtrY, float maxDraggingAngleCos) {

        // Check if the pointers are moving in the same direction.
        final float firstDeltaX = firstPtrX - firstPtrDownX;
        final float firstDeltaY = firstPtrY - firstPtrDownY;

        if (firstDeltaX == 0 && firstDeltaY == 0) {
            return true;
        }

        final float firstMagnitude =
            (float) Math.sqrt(firstDeltaX * firstDeltaX + firstDeltaY * firstDeltaY);
        final float firstXNormalized =
            (firstMagnitude > 0) ? firstDeltaX / firstMagnitude : firstDeltaX;
        final float firstYNormalized =
            (firstMagnitude > 0) ? firstDeltaY / firstMagnitude : firstDeltaY;

        final float secondDeltaX = secondPtrX - secondPtrDownX;
        final float secondDeltaY = secondPtrY - secondPtrDownY;

        if (secondDeltaX == 0 && secondDeltaY == 0) {
            return true;
        }

        final float secondMagnitude =
            (float) Math.sqrt(secondDeltaX * secondDeltaX + secondDeltaY * secondDeltaY);
        final float secondXNormalized =
            (secondMagnitude > 0) ? secondDeltaX / secondMagnitude : secondDeltaX;
        final float secondYNormalized =
            (secondMagnitude > 0) ? secondDeltaY / secondMagnitude : secondDeltaY;

        final float angleCos =
            firstXNormalized * secondXNormalized + firstYNormalized * secondYNormalized;

        if (angleCos < maxDraggingAngleCos) {
            return false;
        }

        return true;
    }
}