Introduce FastScrollGuardListView

This is a hack to work around androids stupid 48dip fast-scroll area: The framework will hijack any scroll events which happen
near (=48 dp) the fast scroll bar. We do not want this as it clashes with our expand buttons.

This class intercepts events in the problematic area and rewrites them to a fake event to pretend that the touch did not happen in the fastscroll area

res/layout/listview.xml

@@ -20,7 +20,7 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 -->
-<ListView
+<ch.blinkenlights.android.vanilla.FastScrollGuardedListView
 	xmlns:android="http://schemas.android.com/apk/res/android"
 	android:layout_width="fill_parent"
 	android:layout_height="fill_parent"

src/ch/blinkenlights/android/vanilla/FastScrollGuardedListView.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2016 Adrian Ulrich <adrian@blinkenlights.ch>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package ch.blinkenlights.android.vanilla;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.widget.ListView;
+
+
+public class FastScrollGuardedListView extends ListView {
+
+	/**
+	 * Start edgeProtection at width-start
+	 */
+	private static final int PROTECT_START_DP = 50; // AOSP has this set to 48dip in 5.x
+	/**
+	 * End protection at width-end
+	 */
+	private static final int PROTECT_END_DP = 12;
+	/**
+	 * The calculated start position in pixel
+	 */
+	private float mEdgeProtectStartPx = 0;
+	/**
+	 * The calculated end position in pixel
+	 */
+	private float mEdgeProtectEndPx = 0;
+
+
+	public FastScrollGuardedListView(Context context) {
+		super(context);
+	}
+	public FastScrollGuardedListView(Context context, AttributeSet attrs) {
+		super(context, attrs);
+	}
+	public FastScrollGuardedListView(Context context, AttributeSet attrs, int defStyleAttr) {
+		super(context, attrs, defStyleAttr);
+	}
+	public FastScrollGuardedListView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
+		super(context, attrs, defStyleAttr, defStyleRes);
+	}
+
+	/**
+	 * Intercepted touch event from ListView
+	 * We will use this callback to send fake X-coord events if
+	 * the actual event happened in the protected area (eg: the hardcoded fastscroll area)
+	 */
+	@Override
+	public boolean onInterceptTouchEvent(MotionEvent ev) {
+		if (mEdgeProtectStartPx == 0)
+			mEdgeProtectStartPx = getWidth() - PROTECT_START_DP * Resources.getSystem().getDisplayMetrics().density;
+		if (mEdgeProtectEndPx == 0)
+			mEdgeProtectEndPx = getWidth() - PROTECT_END_DP * Resources.getSystem().getDisplayMetrics().density;
+
+		if (ev.getX() > mEdgeProtectStartPx && ev.getX() < mEdgeProtectEndPx) {
+			// Cursor is in protected area: simulate an event with a faked x coordinate
+			ev = MotionEvent.obtain(ev.getDownTime(), ev.getEventTime(), ev.getAction(), mEdgeProtectStartPx, ev.getY(), ev.getMetaState());
+		}
+		return super.onInterceptTouchEvent(ev);
+	}
+
+}