Adds the ability to lock the scroll direction of the Escalator (#13334)

Change-Id: I8e20ce971e313495941059a869d4db826bfa903b

client/src/com/vaadin/client/ui/grid/Escalator.java

@@ -4623,4 +4623,49 @@ public class Escalator extends Widget {
         }
         return null;
     }
+
+    /**
+     * Sets whether a scroll direction is locked or not.
+     * <p>
+     * If a direction is locked, the escalator will refuse to scroll in that
+     * direction.
+     * 
+     * @param direction
+     *            the orientation of the scroll to set the lock status
+     * @param locked
+     *            <code>true</code> to lock, <code>false</code> to unlock
+     */
+    public void setScrollLocked(ScrollbarBundle.Direction direction,
+            boolean locked) {
+        switch (direction) {
+        case HORIZONTAL:
+            horizontalScrollbar.setLocked(locked);
+            break;
+        case VERTICAL:
+            verticalScrollbar.setLocked(locked);
+            break;
+        default:
+            throw new UnsupportedOperationException("Unexpected value: "
+                    + direction);
+        }
+    }
+
+    /**
+     * Checks whether or not an direction is locked for scrolling.
+     * 
+     * @param direction
+     *            the direction of the scroll of which to check the lock status
+     * @return <code>true</code> iff the direction is locked
+     */
+    public boolean isScrollLocked(ScrollbarBundle.Direction direction) {
+        switch (direction) {
+        case HORIZONTAL:
+            return horizontalScrollbar.isLocked();
+        case VERTICAL:
+            return verticalScrollbar.isLocked();
+        default:
+            throw new UnsupportedOperationException("Unexpected value: "
+                    + direction);
+        }
+    }
 }

client/src/com/vaadin/client/ui/grid/ScrollbarBundle.java

@@ -39,6 +39,13 @@ import com.google.gwt.user.client.Timer;
  */
 abstract class ScrollbarBundle {
 
+    /**
+     * The orientation of the scrollbar.
+     */
+    public enum Direction {
+        VERTICAL, HORIZONTAL;
+    }
+
     private class TemporaryResizer extends Object {
         private static final int TEMPORARY_RESIZE_DELAY = 1000;
 
@@ -188,6 +195,11 @@ abstract class ScrollbarBundle {
                 root.getStyle().clearOverflowY();
             }
         }
+
+        @Override
+        public Direction getDirection() {
+            return Direction.VERTICAL;
+        }
     }
 
     /**
@@ -252,6 +264,11 @@ abstract class ScrollbarBundle {
                 root.getStyle().clearOverflowX();
             }
         }
+
+        @Override
+        public Direction getDirection() {
+            return Direction.HORIZONTAL;
+        }
     }
 
     protected final Element root = DOM.createDiv();
@@ -263,6 +280,8 @@ abstract class ScrollbarBundle {
 
     private boolean scrollHandleIsVisible = false;
 
+    private boolean isLocked = false;
+
     /** @deprecarted access via {@link #getHandlerManager()} instead. */
     @Deprecated
     private HandlerManager handlerManager;
@@ -369,6 +388,10 @@ abstract class ScrollbarBundle {
      *            the new scroll position in pixels
      */
     public final void setScrollPos(double px) {
+        if (isLocked()) {
+            return;
+        }
+
         double oldScrollPos = scrollPos;
         scrollPos = Math.max(0, Math.min(maxScrollPos, truncate(px)));
 
@@ -577,7 +600,13 @@ abstract class ScrollbarBundle {
      * the DOM.
      */
     private final void updateScrollPosFromDom() {
-        scrollPos = internalGetScrollPos();
+        int newScrollPos = internalGetScrollPos();
+        if (!isLocked()) {
+            scrollPos = newScrollPos;
+        } else if (scrollPos != newScrollPos) {
+            // we need to actually undo the setting of the scroll.
+            internalSetScrollPos(toInt32(scrollPos));
+        }
     }
 
     protected HandlerManager getHandlerManager() {
@@ -636,4 +665,33 @@ abstract class ScrollbarBundle {
     private static boolean pixelValuesEqual(final double num1, final double num2) {
         return Math.abs(num1 - num2) <= PIXEL_EPSILON;
     }
+
+    /**
+     * Locks or unlocks the scrollbar bundle.
+     * <p>
+     * A locked scrollbar bundle will refuse to scroll, both programmatically
+     * and via user-triggered events.
+     * 
+     * @param isLocked
+     *            <code>true</code> to lock, <code>false</code> to unlock
+     */
+    public void setLocked(boolean isLocked) {
+        this.isLocked = isLocked;
+    }
+
+    /**
+     * Checks whether the scrollbar bundle is locked or not.
+     * 
+     * @return <code>true</code> iff the scrollbar bundle is locked
+     */
+    public boolean isLocked() {
+        return isLocked;
+    }
+
+    /**
+     * Returns the scroll direction of this scrollbar bundle.
+     * 
+     * @return the scroll direction of this scrollbar bundle
+     */
+    public abstract Direction getDirection();
 }