Take body scrolling into account when deciding combobox popup position (#19162)

For standard standalone Vaadin apps, the body scroll is not scrollable. For
these this change should have no effect.

In embedded cases and when running as portlet, the body is scrollable. For
these cases, the popup is now correctly shown below the combo box when
there is space.

Change-Id: Ia183f4f2988e6593634f6e9735fd58abbd4a1da1

1 files changed, 24 insertions, 11 deletions

diff --git a/client/src/main/java/com/vaadin/client/ui/VFilterSelect.java b/client/src/main/java/com/vaadin/client/ui/VFilterSelect.java
index 8a6b442fb8..9fb6d18ac5 100644
--- a/client/src/main/java/com/vaadin/client/ui/VFilterSelect.java
+++ b/client/src/main/java/com/vaadin/client/ui/VFilterSelect.java
@@ -28,6 +28,7 @@ import com.google.gwt.aria.client.Roles;
 import com.google.gwt.core.client.JavaScriptObject;
 import com.google.gwt.core.client.Scheduler;
 import com.google.gwt.core.client.Scheduler.ScheduledCommand;
+import com.google.gwt.dom.client.Document;
 import com.google.gwt.dom.client.Element;
 import com.google.gwt.dom.client.NativeEvent;
 import com.google.gwt.dom.client.Style;
@@ -657,7 +658,7 @@ public class VFilterSelect extends Composite implements Field, KeyDownHandler,
             debug("VFS.SP: setPosition(" + offsetWidth + ", " + offsetHeight
                     + ")");
 
-            int top = topPosition;
+            int top;
             int left = getPopupLeft();
 
             // reset menu size and retrieve its "natural" size
@@ -705,19 +706,31 @@ public class VFilterSelect extends Composite implements Field, KeyDownHandler,
                 getContainerElement().getStyle().setWidth(rootWidth, Unit.PX);
             }
 
-            final int vfsHeight = VFilterSelect.this.getOffsetHeight();
-            final int spaceAvailableAbove = top - vfsHeight;
-            final int spaceAvailableBelow = Window.getClientHeight() - top;
-            if (spaceAvailableBelow < offsetHeight
-                    && spaceAvailableBelow < spaceAvailableAbove) {
+            final int textInputHeight = VFilterSelect.this.getOffsetHeight();
+            final int textInputTopOnPage = tb.getAbsoluteTop();
+            final int viewportOffset = Document.get().getScrollTop();
+            final int textInputTopInViewport = textInputTopOnPage
+                    - viewportOffset;
+            final int textInputBottomInViewport = textInputTopInViewport
+                    + textInputHeight;
+
+            final int spaceAboveInViewport = textInputTopInViewport;
+            final int spaceBelowInViewport = Window.getClientHeight()
+                    - textInputBottomInViewport;
+
+            if (spaceBelowInViewport < offsetHeight
+                    && spaceBelowInViewport < spaceAboveInViewport) {
                 // popup on top of input instead
-                top -= offsetHeight + vfsHeight;
-                if (top < 0) {
-                    offsetHeight += top;
-                    top = 0;
+                if (offsetHeight > spaceAboveInViewport) {
+                    // Shrink popup height to fit above
+                    offsetHeight = spaceAboveInViewport;
                 }
+                top = textInputTopOnPage - offsetHeight;
             } else {
-                offsetHeight = Math.min(offsetHeight, spaceAvailableBelow);
+                // Show below, position calculated in showSuggestions for some
+                // strange reason
+                top = topPosition;
+                offsetHeight = Math.min(offsetHeight, spaceBelowInViewport);
             }
 
             // fetch real width (mac FF bugs here due GWT popups overflow:auto )