New edge effects for scrolling widgets (overscroll)

TODO: Currently disabled for WebView. Assets used for the glow effect
need to be themable/styleable. Overscroll effect should take place
even when the user did not grab the widget within actual content.

Change-Id: I68277d14d37dc5bcdb9254eaddf6e4998b3f2bf4

1 files changed, 31 insertions, 0 deletions

diff --git a/core/java/android/view/ViewConfiguration.java b/core/java/android/view/ViewConfiguration.java
index acdfc2829da9..aa9fe76374c2 100644
--- a/core/java/android/view/ViewConfiguration.java
+++ b/core/java/android/view/ViewConfiguration.java
@@ -140,6 +140,16 @@ public class ViewConfiguration {
      */
     private static float SCROLL_FRICTION = 0.015f;
 
+    /**
+     * Max distance to overscroll for edge effects
+     */
+    private static final int OVERSCROLL_DISTANCE = 4;
+
+    /**
+     * Max distance to overfling for edge effects
+     */
+    private static final int OVERFLING_DISTANCE = 8;
+
     private final int mEdgeSlop;
     private final int mFadingEdgeLength;
     private final int mMinimumFlingVelocity;
@@ -150,6 +160,8 @@ public class ViewConfiguration {
     private final int mDoubleTapSlop;
     private final int mWindowTouchSlop;
     private final int mMaximumDrawingCacheSize;
+    private final int mOverscrollDistance;
+    private final int mOverflingDistance;
 
     private static final SparseArray<ViewConfiguration> sConfigurations =
             new SparseArray<ViewConfiguration>(2);
@@ -170,6 +182,8 @@ public class ViewConfiguration {
         mWindowTouchSlop = WINDOW_TOUCH_SLOP;
         //noinspection deprecation
         mMaximumDrawingCacheSize = MAXIMUM_DRAWING_CACHE_SIZE;
+        mOverscrollDistance = OVERSCROLL_DISTANCE;
+        mOverflingDistance = OVERFLING_DISTANCE;
     }
 
     /**
@@ -198,6 +212,9 @@ public class ViewConfiguration {
 
         // Size of the screen in bytes, in ARGB_8888 format
         mMaximumDrawingCacheSize = 4 * metrics.widthPixels * metrics.heightPixels;
+
+        mOverscrollDistance = (int) (density * OVERSCROLL_DISTANCE + 0.5f);
+        mOverflingDistance = (int) (density * OVERFLING_DISTANCE + 0.5f);
     }
 
     /**
@@ -455,6 +472,20 @@ public class ViewConfiguration {
     }
 
     /**
+     * @return The maximum distance a View should overscroll by when showing edge effects.
+     */
+    public int getScaledOverscrollDistance() {
+        return mOverscrollDistance;
+    }
+
+    /**
+     * @return The maximum distance a View should overfling by when showing edge effects.
+     */
+    public int getScaledOverflingDistance() {
+        return mOverflingDistance;
+    }
+
+    /**
      * The amount of time that the zoom controls should be
      * displayed on the screen expressed in milliseconds.
      *