Improvements to relative layout move and delete operations

This changeset improves the way the RelativeLayout editing support in
the layout editor handles deletions and moves.

First, during a move, if the move is simply within the same layout,
then the layout constraints are left alone such that if you for
example have

      A
      v
      B < C < D

and you move B up to be next to A, you end up with

      A < B < C < D

(It will however remove cycles if the move would result in them.)

Second, it now handles deletion better where deleting a view will
cause all references to any deleted views to be replaced by transitive
constraints.

For example, if you hve

     A < B < C < D

and you delete B and C, you end up with

     A < D

Change-Id: Icb9d3552e60aee20192f7941fe52be71ba52557f

2 files changed, 41 insertions, 28 deletions

diff --git a/rule_api/src/com/android/ide/common/api/AbstractViewRule.java b/rule_api/src/com/android/ide/common/api/AbstractViewRule.java
index 7f05809..068580f 100644
--- a/rule_api/src/com/android/ide/common/api/AbstractViewRule.java
+++ b/rule_api/src/com/android/ide/common/api/AbstractViewRule.java
@@ -47,8 +47,6 @@ public class AbstractViewRule implements IViewRule {
         return null;
     }
 
-    // ==== Selection ====
-
     @Override
     @Nullable
     public List<String> getSelectionHint(@NonNull INode parentNode, @NonNull INode childNode) {
@@ -69,12 +67,10 @@ public class AbstractViewRule implements IViewRule {
             @NonNull List<? extends INode> childNodes, @Nullable Object view) {
     }
 
-    // ==== Drag & drop support ====
-
-    // By default Views do not accept drag'n'drop.
     @Override
     @Nullable
-    public DropFeedback onDropEnter(@NonNull INode targetNode, @Nullable Object targetView, @Nullable IDragElement[] elements) {
+    public DropFeedback onDropEnter(@NonNull INode targetNode, @Nullable Object targetView,
+            @Nullable IDragElement[] elements) {
         return null;
     }
 
@@ -86,7 +82,8 @@ public class AbstractViewRule implements IViewRule {
     }
 
     @Override
-    public void onDropLeave(@NonNull INode targetNode, @NonNull IDragElement[] elements, @Nullable DropFeedback feedback) {
+    public void onDropLeave(@NonNull INode targetNode, @NonNull IDragElement[] elements,
+            @Nullable DropFeedback feedback) {
         // ignore
     }
 
@@ -101,39 +98,42 @@ public class AbstractViewRule implements IViewRule {
 
 
     @Override
-    public void onPaste(@NonNull INode targetNode, @Nullable Object targetView, @NonNull IDragElement[] pastedElements) {
+    public void onPaste(@NonNull INode targetNode, @Nullable Object targetView,
+            @NonNull IDragElement[] pastedElements) {
     }
 
-    // ==== Create/Remove hooks ====
-
     @Override
-    public void onCreate(@NonNull INode node, @NonNull INode parent, @NonNull InsertType insertType) {
+    public void onCreate(@NonNull INode node, @NonNull INode parent,
+            @NonNull InsertType insertType) {
     }
 
     @Override
-    public void onChildInserted(@NonNull INode child, @NonNull INode parent, @NonNull InsertType insertType) {
+    public void onChildInserted(@NonNull INode child, @NonNull INode parent,
+            @NonNull InsertType insertType) {
     }
 
     @Override
-    public void onRemovingChildren(@NonNull List<INode> deleted, @NonNull INode parent) {
+    public void onRemovingChildren(@NonNull List<INode> deleted, @NonNull INode parent,
+            boolean moved) {
     }
 
-    // ==== Resizing ====
-
     @Override
     @Nullable
-    public DropFeedback onResizeBegin(@NonNull INode child, @NonNull INode parent, @Nullable SegmentType horizontalEdge,
-            @Nullable SegmentType verticalEdge, @Nullable Object childView, @Nullable Object parentView) {
+    public DropFeedback onResizeBegin(@NonNull INode child, @NonNull INode parent,
+            @Nullable SegmentType horizontalEdge,
+            @Nullable SegmentType verticalEdge, @Nullable Object childView,
+            @Nullable Object parentView) {
         return null;
     }
 
     @Override
-    public void onResizeUpdate(@Nullable DropFeedback feedback, @NonNull INode child, @NonNull INode parent, @NonNull Rect newBounds,
+    public void onResizeUpdate(@Nullable DropFeedback feedback, @NonNull INode child,
+            @NonNull INode parent, @NonNull Rect newBounds,
             int modifierMask) {
     }
 
     @Override
-    public void onResizeEnd(@Nullable DropFeedback feedback, @NonNull INode child, final @NonNull INode parent,
-            final @NonNull Rect newBounds) {
+    public void onResizeEnd(@Nullable DropFeedback feedback, @NonNull INode child,
+            @NonNull INode parent, @NonNull Rect newBounds) {
     }
 }
diff --git a/rule_api/src/com/android/ide/common/api/IViewRule.java b/rule_api/src/com/android/ide/common/api/IViewRule.java
index c115795..b16df26 100644
--- a/rule_api/src/com/android/ide/common/api/IViewRule.java
+++ b/rule_api/src/com/android/ide/common/api/IViewRule.java
@@ -298,19 +298,32 @@ public interface IViewRule {
             @NonNull InsertType insertType);
 
     /**
-     * Called when one or more children are about to be deleted by the user. Note that
-     * children deleted programmatically from view rules (via
+     * Called when one or more children are about to be deleted by the user.
+     * Note that children deleted programmatically from view rules (via
      * {@link INode#removeChild(INode)}) will not notify about deletion.
      * <p>
-     * Note that this method will be called under an edit lock, so rules can directly
-     * add/remove nodes and attributes as part of the deletion handling (and their
-     * actions will be part of the same undo-unit.)
+     * Note that this method will be called under an edit lock, so rules can
+     * directly add/remove nodes and attributes as part of the deletion handling
+     * (and their actions will be part of the same undo-unit.)
+     * <p>
+     * Note that when children are moved (such as when you drag a child within a
+     * LinearLayout to move it from one position among the children to another),
+     * that will also result in a
+     * {@link #onChildInserted(INode, INode, InsertType)} (with the
+     * {@code InsertType} set to {@link InsertType#MOVE_WITHIN}) and a remove
+     * via this {@link #onRemovingChildren(List, INode, boolean)} method. When
+     * the deletion is occurring as part of a local move (insert + delete), the
+     * {@code moved} parameter to this method is set to true.
      *
      * @param deleted a nonempty list of children about to be deleted
-     * @param parent the parent of the deleted children (which still contains the children
-     *            since this method is called before the deletion is performed)
+     * @param parent the parent of the deleted children (which still contains
+     *            the children since this method is called before the deletion
+     *            is performed)
+     * @param moved when true, the nodes are being deleted as part of a local
+     *            move (where copies are inserted elsewhere)
      */
-    void onRemovingChildren(@NonNull List<INode> deleted, @NonNull INode parent);
+    void onRemovingChildren(@NonNull List<INode> deleted, @NonNull INode parent,
+            boolean moved);
 
     /**
      * Called by the IDE on the parent layout when a child widget is being resized. This