Bug 708921 - Bounce back during overscroll when the magnitude of the …

…velocity vector exceeds the stopped threshold. r=kats
leto · Dec 9, 2011 · 0ae8295 · 0ae8295
1 parent 1d51cb7
commit 0ae8295
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Showing 2 changed files with 16 additions and 2 deletions.
diff --git a/mobile/android/base/gfx/PointUtils.java b/mobile/android/base/gfx/PointUtils.java
@@ -67,5 +67,10 @@ public static PointF interpolate(PointF startPoint, PointF endPoint, float weigh
        float y = FloatUtils.interpolate(startPoint.y, endPoint.y, weight);
        return new PointF(x, y);
    }
+
+   /* Computes the magnitude of the given vector. */
+   public static float distance(PointF point) {
+        return (float)Math.sqrt(point.x * point.x + point.y * point.y);
+   }
 }
 
diff --git a/mobile/android/base/ui/PanZoomController.java b/mobile/android/base/ui/PanZoomController.java
@@ -631,13 +631,17 @@ public void run() {
             if (flingingY)
                 mY.advanceFling();
 
-            /* If we're still flinging in any direction, update the origin and finish here. */
+            /* If we're still flinging in any direction, update the origin. */
             if (flingingX || flingingY) {
                 mX.displace(); mY.displace();
                 updatePosition();
-                return;
             }
 
+            /* If we're still flinging with an appreciable velocity, stop here. */
+            PointF velocityVector = new PointF(mX.getRealVelocity(), mY.getRealVelocity());
+            if (PointUtils.distance(velocityVector) >= STOPPED_THRESHOLD)
+                return;
+
             /*
              * Perform a bounce-back animation if overscrolled, unless panning is being overridden
              * (which happens e.g. when the user is panning an iframe).
@@ -747,6 +751,11 @@ public void applyEdgeResistance() {
                 velocity *= SNAP_LIMIT - excess / getViewportLength();
         }
 
+        /* Returns the velocity. If the axis is locked, returns 0. */
+        public float getRealVelocity() {
+            return locked ? 0.0f : velocity;
+        }
+
         public void startFling(boolean stopped) {
             if (!stopped) {
                 setFlingState(FlingStates.FLINGING);