Ported change from 7.7 to compatibility - ComboBox popup position while scrolling (#11055)

Fixes #5043

compatibility-client/src/main/java/com/vaadin/v7/client/ui/VFilterSelect.java

@@ -25,6 +25,8 @@ import java.util.Locale;
 import java.util.Set;
 import java.util.logging.Logger;
 
+import com.google.gwt.animation.client.AnimationScheduler;
+import com.google.gwt.animation.client.AnimationScheduler.AnimationCallback;
 import com.google.gwt.aria.client.Roles;
 import com.google.gwt.core.client.JavaScriptObject;
 import com.google.gwt.core.client.Scheduler;
@@ -56,6 +58,7 @@ import com.google.gwt.i18n.client.HasDirection.Direction;
 import com.google.gwt.user.client.Command;
 import com.google.gwt.user.client.DOM;
 import com.google.gwt.user.client.Event;
+import com.google.gwt.user.client.Event.NativePreviewEvent;
 import com.google.gwt.user.client.Timer;
 import com.google.gwt.user.client.Window;
 import com.google.gwt.user.client.ui.Composite;
@@ -355,8 +358,10 @@ public class VFilterSelect extends Composite
         private int popupOuterPadding = -1;
 
         private int topPosition;
+        private int leftPosition;
 
         private final MouseWheeler mouseWheeler = new MouseWheeler();
+        private boolean scrollPending = false;
 
         /**
          * Default constructor
@@ -444,12 +449,11 @@ public class VFilterSelect extends Composite
                     getElement().setId("VAADIN_COMBOBOX_OPTIONLIST");
 
                     menu.setSuggestions(currentSuggestions);
-                    final int x = VFilterSelect.this.getAbsoluteLeft();
+                    leftPosition = getDesiredLeftPosition();
 
-                    topPosition = tb.getAbsoluteTop();
-                    topPosition += tb.getOffsetHeight();
+                    topPosition = getDesiredTopPosition();
 
-                    setPopupPosition(x, topPosition);
+                    setPopupPosition(leftPosition, topPosition);
 
                     int nullOffset = (nullSelectionAllowed
                             && "".equals(lastFilter) ? 1 : 0);
@@ -496,6 +500,22 @@ public class VFilterSelect extends Composite
             });
         }
 
+        private native int toInt32(double val)
+        /*-{
+            return val | 0;
+        }-*/;
+
+        private int getDesiredTopPosition() {
+            return toInt32(WidgetUtil.getBoundingClientRect(tb.getElement())
+                    .getBottom()) + Window.getScrollTop();
+        }
+
+        private int getDesiredLeftPosition() {
+            return toInt32(WidgetUtil
+                    .getBoundingClientRect(VFilterSelect.this.getElement())
+                    .getLeft());
+        }
+
         /**
          * Should the next page button be visible to the user?
          *
@@ -682,6 +702,47 @@ public class VFilterSelect extends Composite
             handleMouseDownEvent(event);
         }
 
+        @Override
+        protected void onPreviewNativeEvent(NativePreviewEvent event) {
+            // Check all events outside the combobox to see if they scroll the
+            // page. We cannot use e.g. Window.addScrollListener() because the
+            // scrolled element can be at any level on the page.
+
+            // Normally this is only called when the popup is showing, but make
+            // sure we don't accidentally process all events when not showing.
+            if (!scrollPending && isShowing() && !DOM.isOrHasChild(
+                    SuggestionPopup.this.getElement(),
+                    Element.as(event.getNativeEvent().getEventTarget()))) {
+                if (getDesiredLeftPosition() != leftPosition
+                        || getDesiredTopPosition() != topPosition) {
+                    updatePopupPositionOnScroll();
+                }
+            }
+
+            super.onPreviewNativeEvent(event);
+        }
+
+        /**
+         * Make the popup follow the position of the ComboBox when the page is
+         * scrolled.
+         */
+        private void updatePopupPositionOnScroll() {
+            if (!scrollPending) {
+                AnimationScheduler.get()
+                        .requestAnimationFrame(new AnimationCallback() {
+                            public void execute(double timestamp) {
+                                if (isShowing()) {
+                                    leftPosition = getDesiredLeftPosition();
+                                    topPosition = getDesiredTopPosition();
+                                    setPopupPosition(leftPosition, topPosition);
+                                }
+                                scrollPending = false;
+                            }
+                        });
+                scrollPending = true;
+            }
+        }
+
         /**
          * Should paging be enabled. If paging is enabled then only a certain
          * amount of items are visible at a time and a scrollbar or buttons are