Minor fixes/clarifications for previous patch.

Change-Id: Ib44f6de570064b3f3ddf70b6727b479a09ae5d7a

Author: adamp

core/java/android/view/ScaleGestureDetector.java

@@ -213,8 +213,7 @@ public boolean onTouchEvent(MotionEvent event) {
         for (int i = 0; i < count; i++) {
             if (skipIndex == i) continue;
 
-            // touchMajor/Minor are axes of an ellipse; average them together and
-            // convert the resulting 'diameter' into a radius.
+            // Average touch major and touch minor and convert the resulting diameter into a radius.
             final float touchSize = (event.getTouchMajor(i) + event.getTouchMinor(i)) / 4;
             devSumX += Math.abs(event.getX(i) - focusX) + touchSize;
             devSumY += Math.abs(event.getY(i) - focusY) + touchSize;
@@ -245,7 +244,7 @@ public boolean onTouchEvent(MotionEvent event) {
             mPrevSpanY = mCurrSpanY = spanY;
             mInitialSpan = mPrevSpan = mCurrSpan = span;
         }
-        if (!mInProgress && span > mMinSpan &&
+        if (!mInProgress && span >= mMinSpan &&
                 (wasInProgress || Math.abs(span - mInitialSpan) > mSpanSlop)) {
             mPrevSpanX = mCurrSpanX = spanX;
             mPrevSpanY = mCurrSpanY = spanY;

core/res/res/values/config.xml

@@ -927,8 +927,14 @@
     <integer name="config_multiuserMaximumUsers">1</integer>
 
     <!-- Minimum span needed to begin a touch scaling gesture.
+         If the span is equal to or greater than this size, a scaling gesture
+         will begin, where supported. (See android.view.ScaleGestureDetector)
+
          This also takes into account the size of any active touch points.
          Devices with screens that deviate too far from their assigned density
-         bucket should consider tuning this value in a device-specific overlay. -->
+         bucket should consider tuning this value in a device-specific overlay.
+         For best results, care should be taken such that this value remains
+         larger than the minimum reported touchMajor/touchMinor values
+         reported by the hardware. -->
     <dimen name="config_minScalingSpan">25mm</dimen>
 </resources>