JavaFX 8 TabPane-Tab按钮不断滚动到TabPane标头的视口之外

Question

I got a really weird issue with a TabPane that has its tab buttons on the left. The problem is only present during runtime of applications but not in the SceneBuilder (2.0) preview.

Every time the selected Tab changes (either by user click or by changing the selectedIndex via code) the tabs shift their position upwards and out of the viewport of the tab button area as you can see in the examplary picture below . The amount of pixels shifted seems to depend on the width of the TabPane (the lower the width, the more it shifts) and most of the time the buttons in my TabPane are shifted completely out of the viewport.

It is possible to get the tab buttons back to their normal position by focusing a different window or by scrolling upwards or downwards in the tab button area. Once they are back in their normal positions they're only shifted again when the selected tab changes again.

I tried to access the TabHeaderSkin objects (style class "tab") that seem to be the only runtime objects in the TabPane header area that change as result of the shifting. According to Scenic View, their localY value changes. However, myTabPane.lookupAll(".tab") finds nothing.

Except from that, there seems to be no possibility at all to access the auto scroll behavior or tab button positions or things like that.

Edit
Here's an MCVE-FXML

<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>


<HBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="20.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
   <children>
      <TabPane side="LEFT" tabClosingPolicy="UNAVAILABLE">
        <tabs>
          <Tab text="Untitled Tab 1">
            <content>
              <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
            </content>
          </Tab>
          <Tab text="Untitled Tab 2">
            <content>
              <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
            </content>
          </Tab>
            <Tab text="Untitled Tab">
              <content>
                <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
              </content>
            </Tab>
            <Tab text="Untitled Tab">
              <content>
                <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
              </content>
            </Tab>
        </tabs>
      </TabPane>
   </children>
</HBox>

Answer 1

This looks like a known bug affecting JavaFX 8u20. It appears to be fixed in the ea release of 8u40.