Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit c574b68c authored by Jeff Brown's avatar Jeff Brown
Browse files

Fix trackball interpretation of precision. 

The trackball to dpad synthesis was using the MotionEvent's precision
field to determine a threshold for movement but the calculations
involved did not actually make sense for any value of precision
less than 2.0.  This worked fine before since the InputReader
hardcodes the trackball's precision to 6.

Injected trackball events may have a different precision which can
result in the thresholds being set inappropriately.  For example,
it was not possible to move focus by one unit at a time when
the precision was set to 1.0.

The old code was probably using precision as a way to set a
threshold based on the trackball moving by some minimum number
of physical ticks, in this case 2.  But the code will work just
as well if we set an absolute threshold based on distance
traveled given that the input system is already expected to
normalize the trackball movements before delivering them to the
application.

So stop using precision.

Bug: 8473020
Change-Id: I3c6f7fb1b507f8cf5608b47550e7345fea3352fa
parent f9e989d5

core/java/android/view/ViewRootImpl.java

+13 −15
Original line number Diff line number Diff line
@@ -3990,7 +3990,7 @@ public final class ViewRootImpl implements ViewParent, 
            int movement = 0;

            float accel = 1;

            if (xOff > yOff) {

                movement = x.generate((2/event.getXPrecision()));

                movement = x.generate();

                if (movement != 0) {

                    keycode = movement > 0 ? KeyEvent.KEYCODE_DPAD_RIGHT

                            : KeyEvent.KEYCODE_DPAD_LEFT;
@@ -3998,7 +3998,7 @@ public final class ViewRootImpl implements ViewParent, 
                    y.reset(2);

                }

            } else if (yOff > 0) {

                movement = y.generate((2/event.getYPrecision()));

                movement = y.generate();

                if (movement != 0) {

                    keycode = movement > 0 ? KeyEvent.KEYCODE_DPAD_DOWN

                            : KeyEvent.KEYCODE_DPAD_UP;
@@ -5515,8 +5515,11 @@ public final class ViewRootImpl implements ViewParent, 
         */

        static final float ACCEL_MOVE_SCALING_FACTOR = (1.0f/40);



        static final float FIRST_MOVEMENT_THRESHOLD = 0.5f;

        static final float SECOND_CUMULATIVE_MOVEMENT_THRESHOLD = 2.0f;

        static final float SUBSEQUENT_INCREMENTAL_MOVEMENT_THRESHOLD = 1.0f;



        float position;

        float absPosition;

        float acceleration = 1;

        long lastMoveTime = 0;

        int step;
@@ -5593,21 +5596,18 @@ public final class ViewRootImpl implements ViewParent, 
                }

            }

            position += off;

            return (absPosition = Math.abs(position));

            return Math.abs(position);

        }



        /**

         * Generate the number of discrete movement events appropriate for

         * the currently collected trackball movement.

         *

         * @param precision The minimum movement required to generate the

         * first discrete movement.

         *

         * @return Returns the number of discrete movements, either positive

         * or negative, or 0 if there is not enough trackball movement yet

         * for a discrete movement.

         */

        int generate(float precision) {

        int generate() {

            int movement = 0;

            nonAccelMovement = 0;

            do {
@@ -5617,7 +5617,7 @@ public final class ViewRootImpl implements ViewParent, 
                    // to do this as soon as possible instead of waiting for

                    // a full movement, in order to make things look responsive.

                    case 0:

                        if (absPosition < precision) {

                        if (Math.abs(position) < FIRST_MOVEMENT_THRESHOLD) {

                            return movement;

                        }

                        movement += dir;
@@ -5628,13 +5628,12 @@ public final class ViewRootImpl implements ViewParent, 
                    // to wait for the second complete trackball motion before

                    // generating the second discrete movement.

                    case 1:

                        if (absPosition < 2) {

                        if (Math.abs(position) < SECOND_CUMULATIVE_MOVEMENT_THRESHOLD) {

                            return movement;

                        }

                        movement += dir;

                        nonAccelMovement += dir;

                        position += dir > 0 ? -2 : 2;

                        absPosition = Math.abs(position);

                        position -= SECOND_CUMULATIVE_MOVEMENT_THRESHOLD * dir;

                        step = 2;

                        break;

                    // After the first two, we generate discrete movements
@@ -5645,12 +5644,11 @@ public final class ViewRootImpl implements ViewParent, 
                    // a longer increasing acceleration to continuous movement

                    // in one direction.

                    default:

                        if (absPosition < 1) {

                        if (Math.abs(position) < SUBSEQUENT_INCREMENTAL_MOVEMENT_THRESHOLD) {

                            return movement;

                        }

                        movement += dir;

                        position += dir >= 0 ? -1 : 1;

                        absPosition = Math.abs(position);

                        position -= dir * SUBSEQUENT_INCREMENTAL_MOVEMENT_THRESHOLD;

                        float acc = acceleration;

                        acc *= 1.1f;

                        acceleration = acc < MAX_ACCELERATION ? acc : acceleration;