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Bug 705114 - Filter velocity changes for kinetic panning. r=kats

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Certain devices, such as the HTC Flyer, deliver motion events with identical
coordinates before a touch-release event. This causes kinetic panning to fail,
as the calculated velocity is only based on the last two events.

Introduce a velocity change factor, so that the velocity can only change by a
certain amount per event. This has the effect of smoothing velocity changes
and fixes the bug on the HTC Flyer, at least.
This commit is contained in:
Chris Lord 2011-11-30 11:32:49 +00:00
parent 7a790c98ea
commit d7d5b2beab
1 changed files with 83 additions and 15 deletions
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98
mobile/android/base/ui/PanZoomController.java
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@ -87,11 +87,16 @@ public class PanZoomController
private static final float PAN_THRESHOLD = 4.0f;
// Angle from axis within which we stay axis-locked
private static final double AXIS_LOCK_ANGLE = Math.PI / 6.0; // 30 degrees
// The maximum velocity change factor between events, per ms, in %.
// Direction changes are excluded.
private static final float MAX_EVENT_ACCELERATION = 0.012f;
private Timer mFlingTimer;
private Axis mX, mY;
/* The zoom focus at the first zoom event (in page coordinates). */
private PointF mLastZoomFocus;
/* The time the last motion event took place. */
private long mLastEventTime;
private enum PanZoomState {
NOTHING, /* no touch-start events received */
@ -145,8 +150,13 @@ public class PanZoomController
case FLING:
case NOTHING:
mState = PanZoomState.TOUCHING;
mX.firstTouchPos = mX.touchPos = event.getX(0);
mY.firstTouchPos = mY.touchPos = event.getY(0);
mX.setFlingState(Axis.FlingStates.STOPPED);
mY.setFlingState(Axis.FlingStates.STOPPED);
mX.velocity = mY.velocity = 0.0f;
mX.locked = mY.locked = false;
mX.lastTouchPos = mX.firstTouchPos = mX.touchPos = event.getX(0);
mY.lastTouchPos = mY.firstTouchPos = mY.touchPos = event.getY(0);
mLastEventTime = event.getEventTime();
return false;
case TOUCHING:
case PANNING:
@ -246,33 +256,77 @@ public class PanZoomController
return (float)Math.sqrt(dx * dx + dy * dy);
}
private void track(MotionEvent event) {
float x = event.getX(0);
float y = event.getY(0);
private float clampByFactor(float oldValue, float newValue, float factor) {
float maxChange = Math.abs(oldValue * factor);
return Math.min(oldValue + maxChange, Math.max(oldValue - maxChange, newValue));
}
private void track(float x, float y, float lastX, float lastY, float timeDelta) {
if (mState == PanZoomState.PANNING_LOCKED) {
// check to see if we should break the axis lock
double angle = Math.atan2(y - mY.firstTouchPos, x - mX.firstTouchPos); // range [-pi, pi]
angle = Math.abs(angle); // range [0, pi]
if (angle < AXIS_LOCK_ANGLE || angle > (Math.PI - AXIS_LOCK_ANGLE)) {
// lock to x-axis
y = mY.firstTouchPos;
mX.locked = false;
mY.locked = true;
} else if (Math.abs(angle - (Math.PI / 2)) < AXIS_LOCK_ANGLE) {
// lock to y-axis
x = mX.firstTouchPos;
mX.locked = true;
mY.locked = false;
} else {
// break axis lock but log the angle so we can fine-tune this when people complain
mState = PanZoomState.PANNING;
mX.locked = mY.locked = false;
angle = Math.abs(angle - (Math.PI / 2)); // range [0, pi/2]
Log.i(LOGTAG, "Breaking axis lock at " + (angle * 180.0 / Math.PI) + " degrees");
}
}
float zoomFactor = 1.0f;//mController.getZoomFactor();
mX.velocity = (mX.touchPos - x) / zoomFactor;
mY.velocity = (mY.touchPos - y) / zoomFactor;
mX.touchPos = x;
mY.touchPos = y;
float newVelocityX = ((lastX - x) / timeDelta) * (1000.0f/60.0f);
float newVelocityY = ((lastY - y) / timeDelta) * (1000.0f/60.0f);
float maxChange = MAX_EVENT_ACCELERATION * timeDelta;
// If there's a direction change, or current velocity is very low,
// allow setting of the velocity outright. Otherwise, use the current
// velocity and a maximum change factor to set the new velocity.
if (Math.abs(mX.velocity) < 1.0f ||
(((mX.velocity > 0) != (newVelocityX > 0)) &&
!FloatUtils.fuzzyEquals(newVelocityX, 0.0f)))
mX.velocity = newVelocityX;
else
mX.velocity = clampByFactor(mX.velocity, newVelocityX, maxChange);
if (Math.abs(mY.velocity) < 1.0f ||
(((mY.velocity > 0) != (newVelocityY > 0)) &&
!FloatUtils.fuzzyEquals(newVelocityY, 0.0f)))
mY.velocity = newVelocityY;
else
mY.velocity = clampByFactor(mY.velocity, newVelocityY, maxChange);
}
private void track(MotionEvent event) {
mX.lastTouchPos = mX.touchPos;
mY.lastTouchPos = mY.touchPos;
for (int i = 0; i < event.getHistorySize(); i++) {
float x = event.getHistoricalX(0, i);
float y = event.getHistoricalY(0, i);
long time = event.getHistoricalEventTime(i);
float timeDelta = (float)(time - mLastEventTime);
mLastEventTime = time;
track(x, y, mX.touchPos, mY.touchPos, timeDelta);
mX.touchPos = x; mY.touchPos = y;
}
float timeDelta = (float)(event.getEventTime() - mLastEventTime);
mLastEventTime = event.getEventTime();
track(event.getX(0), event.getY(0), mX.touchPos, mY.touchPos, timeDelta);
mX.touchPos = event.getX(0);
mY.touchPos = event.getY(0);
if (stopped()) {
if (mState == PanZoomState.PANNING) {
@ -400,9 +454,11 @@ public class PanZoomController
BOTH, // Overscrolled in both directions (page is zoomed to smaller than screen)
}
public float firstTouchPos; /* Position of the first touch. */
public float touchPos; /* Position of the last touch. */
public float firstTouchPos; /* Position of the first touch event on the current drag. */
public float touchPos; /* Position of the most recent touch event on the current drag. */
public float lastTouchPos; /* Position of the touch event before touchPos. */
public float velocity; /* Velocity in this direction. */
public boolean locked; /* Whether movement on this axis is locked. */
private FlingStates mFlingState; /* The fling state we're in on this axis. */
private EaseOutAnimation mSnapAnim; /* The animation when the page is snapping back. */
@ -415,6 +471,10 @@ public class PanZoomController
public FlingStates getFlingState() { return mFlingState; }
public void setFlingState(FlingStates aFlingState) {
mFlingState = aFlingState;
}
public void setViewportLength(float viewportLength) { mViewportLength = viewportLength; }
public void setScreenLength(int screenLength) { mScreenLength = screenLength; }
public void setPageLength(float pageLength) { mPageLength = pageLength; }
@ -535,7 +595,15 @@ public class PanZoomController
}
// Performs displacement of the viewport position according to the current velocity.
public void displace() { viewportPos += velocity; }
public void displace() {
if (locked)
return;
if (mFlingState == FlingStates.SCROLLING)
viewportPos += velocity;
else
viewportPos += lastTouchPos - touchPos;
}
}
private static class EaseOutAnimation {