How to get a different context-menu showing on a TreeViewers header - eclipse-rcp

Question

I wish to let users toggle column's visibility in a TreeViewer. I already have a context menu bound to the right-click of my TreeViewer using ..
MenuManager.addMenuListener( new IMenuListener() ... );
.. but I can find no way of detecting when the right click is on the header of the table, rather than on the currently selected node. Down at the SWT level this is all possible, as is demonstrated by this snippet: http://dev.eclipse.org/viewcvs/viewvc.cgi/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet312.java The JFace layer however may not expose it as far as I can see.
Your clues and other musings are most welcome
M.

Answer 1

Thanks for your example, it helped alot. Since I actually needed to know which column header was clicked, I built upon your code and came to the following solution (which also works in case the original column ordering was changed by dragging):
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.swt.events.MenuDetectEvent;
import org.eclipse.swt.events.MenuDetectListener;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Tree;
public class TreeColumnHeaderMenuDetectListener implements MenuDetectListener {
private Tree fTree;
private TreeViewer fTreeViewer;
public TreeColumnHeaderMenuDetectListener(TreeViewer treeViewer)
{
fTree = treeViewer.getTree();
fTreeViewer = treeViewer;
}
#Override
public void menuDetected(MenuDetectEvent event) {
Point curLoc = Display.getCurrent().map(null, fTreeViewer.getControl(), new Point(event.x, event.y));
Rectangle clientArea = fTree.getClientArea();
if (clientArea.y <= curLoc.y && curLoc.y < (clientArea.y + fTree.getHeaderHeight()) &&
clientArea.x <= curLoc.x && curLoc.x < (clientArea.x + clientArea.width)) {
int xOffset = 0; // Accumulates previous column widths
for (int colIdx : fTree.getColumnOrder()) {
int colWidth = fTree.getColumn(colIdx).getWidth();
// Check if cursor location lies within the current column
if (xOffset <= curLoc.x && curLoc.x < (xOffset + colWidth)) {
System.out.println("column header "+colIdx); // Your code goes here
break;
}
xOffset += colWidth;
}
}
}
}
Use it by registering with
tree.addMenuDetectListener(new TreeColumnHeaderMenuDetectListener(treeViewer))
for a given tree and corresponding treeViewer.

Answer 2

In the end, I wrote this class to listen to the underlying tree object, and tell me when the column headers had been clicked on ...
import org.eclipse.jface.viewers.TreeViewer;
public class HeaderClickDetector implements Listener
{
TreeViewer viewer;
private boolean headerClicked;
public HeaderClickDetector( TreeViewer viewer )
{
this.viewer = viewer;
}
public void handleEvent(Event event)
{
Point pt = Display.getCurrent().map(null, viewer.getControl(), new Point(event.x, event.y));
Rectangle clientArea = viewer.getTree().getClientArea();
headerClicked = (clientArea.y <= pt.y && pt.y < (clientArea.y + viewer.getTree().getHeaderHeight()));
}
public boolean isHeaderClicked()
{
return headerClicked;
}
}