Be a little more graceful when scrolling horizontally in a (vertical) scroll view.

Not quite to the point of diagonal scrolling, but hopefully closer.

src/com/fsck/k9/view/ToggleScrollView.java

@@ -2,16 +2,19 @@ package com.fsck.k9.view;
 
 import android.content.Context;
 import android.util.AttributeSet;
+import android.view.GestureDetector;
 import android.view.MotionEvent;
 import android.widget.ScrollView;
 
 public class ToggleScrollView extends ScrollView
 {
+    private GestureDetector mDetector;
     private boolean mScrolling = true;
 
     public ToggleScrollView(Context context, AttributeSet attrs)
     {
         super(context, attrs);
+        mDetector = new GestureDetector(new YScrollDetector());
     }
 
     public void setScrolling(boolean enable)
@@ -28,6 +31,43 @@ public class ToggleScrollView extends ScrollView
     @Override
     public boolean onInterceptTouchEvent(MotionEvent ev)
     {
-        return (mScrolling) ? super.onInterceptTouchEvent(ev) : false;
+        if(!mScrolling) {
+            return false;
+        }
+
+        // This doesn't quite get us to diagonal scrolling, but it's somewhat better than what we've
+        // currently got.  This is based on
+        // http://stackoverflow.com/questions/2646028/android-horizontalscrollview-within-scrollview-touch-handling
+        boolean result = super.onInterceptTouchEvent(ev);
+        if (mDetector.onTouchEvent(ev))
+        {
+            return result;
+        }
+
+        return false;
+    }
+
+    // Return false if we're scrolling in the x direction
+    class YScrollDetector extends GestureDetector.SimpleOnGestureListener
+    {
+        @Override
+        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
+        {
+            try
+            {
+                if (Math.abs(distanceY) > Math.abs(distanceX))
+                {
+                    return true;
+                }
+                else
+                {
+                    return false;
+                }
+            } catch (Exception e)
+            {
+                // nothing
+            }
+            return false;
+        }
     }
 }