Fix bug 2250457 - Open folder on home screen changes changes the behaviour of the home button

Now, home always goes to the center worksapce screen and back from an
app goes to all apps if it was open.

Getting that animations smooth took a little bit of work.

src/com/android/launcher2/Workspace.java

@@ -48,7 +48,7 @@ import java.util.ArrayList;
  * A workspace is meant to be used with a fixed width only.
  */
 public class Workspace extends ViewGroup implements DropTarget, DragSource, DragScroller {
-    //private static final String TAG = "Launcher.Workspace";
+    private static final String TAG = "Launcher.Workspace";
     private static final int INVALID_SCREEN = -1;
     
     /**
@@ -111,6 +111,8 @@ public class Workspace extends ViewGroup implements DropTarget, DragSource, Drag
     private Drawable mPreviousIndicator;
     private Drawable mNextIndicator;
 
+    private boolean mFading = true;
+
     /**
      * Used to inflate the Workspace from XML.
      *
@@ -474,8 +476,25 @@ public class Workspace extends ViewGroup implements DropTarget, DragSource, Drag
         }
     }
 
+    public void startFading(boolean dest) {
+        mFading = dest;
+        invalidate();
+    }
+
     @Override
     protected void dispatchDraw(Canvas canvas) {
+        final boolean allAppsOpaque = mLauncher.isAllAppsOpaque();
+        if (mFading == allAppsOpaque) {
+            invalidate();
+        } else {
+            mFading = !allAppsOpaque;
+        }
+        if (allAppsOpaque) {
+            // If the launcher is up, draw black.
+            canvas.drawARGB(0xff, 0, 0, 0);
+            return;
+        }
+
         if (Launcher.lastStartTime != 0) {
             int itemCount = 0;
             for (int i=0; i<getChildCount(); i++) {
@@ -790,6 +809,34 @@ public class Workspace extends ViewGroup implements DropTarget, DragSource, Drag
         return mTouchState != TOUCH_STATE_REST;
     }
 
+    /**
+     * If one of our descendant views decides that it could be focused now, only
+     * pass that along if it's on the current screen.
+     *
+     * This happens when live folders requery, and if they're off screen, they
+     * end up calling requestFocus, which pulls it on screen.
+     */
+    @Override
+    public void focusableViewAvailable(View focused) {
+        View current = getChildAt(mCurrentScreen);
+        View v = focused;
+        while (true) {
+            if (v == current) {
+                super.focusableViewAvailable(focused);
+                return;
+            }
+            if (v == this) {
+                return;
+            }
+            ViewParent parent = v.getParent();
+            if (parent instanceof View) {
+                v = (View)v.getParent();
+            } else {
+                return;
+            }
+        }
+    }
+
     void enableChildrenCache(int fromScreen, int toScreen) {
         if (fromScreen > toScreen) {
             fromScreen = toScreen;