application/org.openjdk.jmc.ui/src/main/java/org/openjdk/jmc/ui/misc/ChartCanvas.java

*** 75,84 ****
--- 75,85 ----
  
  public class ChartCanvas extends Canvas {
          private int lastMouseX = -1;
          private int lastMouseY = -1;
          private List<Rectangle2D> highlightRects;
+         private Object hoveredItemData;
  
          private class Selector extends MouseAdapter implements MouseMoveListener, MouseTrackListener {
  
                  int selectionStartX = -1;
                  int selectionStartY = -1;
*** 150,159 ****
--- 151,161 ----
                  public void mouseEnter(MouseEvent e) {
                  }
  
                  @Override
                  public void mouseExit(MouseEvent e) {
+                         resetHoveredItemData();
                          clearHighlightRects();
                  }
  
                  @Override
                  public void mouseHover(MouseEvent e) {
*** 389,398 ****
--- 391,412 ----
           */
          private int translateDisplayToImageXCoordinates(int x) {
                  return (int) Math.round(x / xScale);
          }
  
+         public Object getHoveredItemData() {
+                 return this.hoveredItemData;
+         }
+ 
+         public void setHoveredItemData(Object data) {
+                 this.hoveredItemData = data;
+         }
+ 
+         public void resetHoveredItemData() {
+                 this.hoveredItemData = null;
+         }
+ 
          private void updateHighlightRects() {
                  List<Rectangle2D> newRects = new ArrayList<>();
                  infoAt(new IChartInfoVisitor.Adapter() {
                          @Override
                          public void visit(IBucket bucket) {
*** 418,427 ****
--- 432,448 ----
  
                          @Override
                          public void visit(ILane lane) {
                                  // FIXME: Do we want this highlighted?
                          }
+ 
+                         @Override
+                         public void hover(Object data) {
+                                 if (data != null) {
+                                         setHoveredItemData(data);
+                                 }
+                         }
                  }, lastMouseX, lastMouseY);
                  // Attempt to reduce flicker by avoiding unnecessary updates.
                  if (!newRects.equals(highlightRects)) {
                          highlightRects = newRects;
                          redraw();